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Group 1: six-spined shortfin gobies 1
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Group 3: seven-spined shortfin gobies
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Group 4: longfin gobies
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Group 5: divided pelvic-fin gobies
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allied family Ptereleotridae
allied family Eleotridae
allied family Microdesmidae

Group 2: The short-fin gobies pt. 2 (six-spined, fused)

Coryphopterus and Lythrypnus

 

These two large genera include many of the abundant small gobies ubiquitous on and around Caribbean reefs. They share six first-dorsal-fin spines and 9, 10, or 11 dorsal and anal-fin elements. The larvae of these gobies are typically small and lightly marked, usually with only a ventral midline series of melanophores (at the isthmus, pelvic-fin base, anal-fin base and caudal peduncle). The larvae of this group and the seven-spined short-fin gobies (Group 3) can appear similar; although, with the characters discussed here, they should all be able to be identified, at least to genus.

The large genus Coryphopterus dominates this group of gobies and accounts for the vast majority of gobies one sees on a Caribbean coral reef. The largest group within Coryphopterus are the sand gobies. These fishes can be found perching on the bottom along the sandy edges of hard substrate, seemingly everywhere except in the most turbid or muddy environments. The sand gobies are particularly difficult to identify to the species level in the field and, even when in the hand, careful examination of marking patterns is required to distinguish the species. This becomes even more difficult for smaller juveniles that have not developed their species-specific marking patterns. The other group of Coryphopterus, the hovering masked and glass gobies, are also very abundant, although more reef-associated. They are found in large groups just off the bottom on almost every coral reef in the region.

The Lythrypnus gobies are much less conspicuous, but may also be quite abundant on reefs. Their larvae can be difficult to separate from those of Coryphopterus

The small lightly-marked goby larvae account for a major fraction of larval collections in the region. They are superficially quite similar, sharing the ventral midline markings and an otherwise unremarkable appearance. Before counting fin rays, the basic appearance of the larvae can distinguish the three most common genera. The larvae below are from a typical collection: Coryphopterus personatus in the middle, Lythrypnus nesiotes below, and Microgobius signatus above. The body shape of each is distinctive: Coryphopterus larvae tend to be hunched-over, Lythrypnus are usually not hunched-over and have a slightly wider body with a shorter caudal peduncle, and larval Microgobius are long and straight with a blunted upward-facing mouth and a sharply-tapering caudal peduncle.

Note: fin-ray counts for the second dorsal fin and the anal fin are total elements (spines plus rays).
 
Coryphopterus taxonomy
The large goby genus Coryphopterus contains numerous species in the Caribbean, several of which are particularly difficult to distinguish, sometimes even as adults. The results of my barcode (mtDNA) sequencing for this group show that many of the important characters used to separate adults do not apply to larvae or juveniles. Since the basic markings and morphology of the early stages are shared by many of the species in the group, DNA sequencing is likely the only reliable way to distinguish species for most larvae and some juveniles.
One of the primary causes of the difficulty in identifying juveniles and adults of Coryphopterus species in the western Atlantic is the extreme variability in the degree of dark markings with habitat. All of the sand gobies have lightly-marked forms on white sand in clear water and heavily-marked forms on darker sediments in more turbid waters, particularly along continental coastlines. This variation can become extreme in several species (C. tortugae, C. bol, C. eidolon, and C. thrix), with some individuals showing almost no dark markings at all. These super-pallid individuals can be impossible to identify to species without DNA sequencing. On the other hand, heavily-marked populations of some typically pallid species, for example C. eidolon, have not been recognized as conspecific and are typically assigned to other species in museum collections.
An additional problem when using the literature and field-guides for identifications is the presence of heretofore cryptic species in the common 10/10 sand-perching bridled-goby group, i.e. the recently twice-redescribed "pallid" bridled goby C. tortugae and a new more-offshore species C. bol (Victor 2008). These species are presently lumped by most observers as variants of the bridled goby C. glaucofraenum. To avoid confusion, I propose that C. glaucofraenum retain the original "bridled goby" common name, while C. tortugae should be called the "patch-reef goby" and C. bol should be called the "sand-canyon goby", after their distinctive habitats.
Most of the characters traditionally used to separate sand gobies do not apply to juvenile or larval stages. For example, the morphology of the pelvic fin is one of the more important taxonomic characters separating the regional Coryphopterus species. The degree of joining of the pelvic fins, the relative length of the innermost ray, and the presence or absence of the pelvic frenum are diagnostic for some adult Coryphopterus (the pelvic-fin frenum is the anterior membrane running from spine to spine that forms the fin into a sucking disk). My DNA barcoding results, however, reveal that pelvic-fin characters do not apply to larvae, recruits, or even small juveniles of several species. For example, the species with divided pelvic fins have fused pelvic fins as larvae and small juveniles (i.e. C. alloides, C. personatus, C. hyalinus, and C. lipernes). The pelvic frenum can be present in juveniles of species that later do not have one (C. dicrus) and the innermost pelvic-fin rays do not become distinctly shorter or longer until well after the transitional stage.
Transitional sand gobies can develop their metamorphic melanophores in differing sequences, leading to a proliferation of transitional larval types that certainly represent the same species. At least some of this variation may reflect the marked variability in the degree of markings with habitat types, with lightly-marked juveniles living on white sand and those on darker backgrounds or more turbid waters being heavily-marked. The light marking may occur in larvae as well, where a significant portion of individuals are missing the melanophores on the caudal-fin base and/or the dorsal caudal peduncle. If these patterns prove to occur within the same species, it raises a very interesting question whether larvae have pre-determined which habitat to settle onto or the trait is flexible.
 
The reported fin-ray counts for the genus Coryphopterus in the literature:

species: #dorsal/#anal-fin elements #pectoral rays (pelvic-fin form), sand or other goby

 
The Sand Gobies
10/10 group
(widespread and abundant species)

C. glaucofraenum: Randall: 10/10 pect 17-20 Bohlke: 10/10, rare 9 pect 17-20 usu 19

C. tortugae: Acero: 10/10 pect 18-20

C. bol: Victor 2008: 10/10 pect 18-20

C. eidolon: Randall: 10 (11 is a typo)/9-10, mode 10 pect 19-20, rare 18 Bohlke: 10/10, rare 9 pect 19-20

C. thrix: Bohlke: 9-10/10 pect 17-19

C. dicrus: Randall: 10/10 pect 18-20 Bohlke: 10/10 pect 18-20

11 group
(localized endemics)

C. punctipectophorus: Bohlke: 11/10 pect 18-20 (South Carolina to the Gulf of Mexico)

C. venezuelae: Cervigon: 11/11 pect 18-20 (NE Venezuela: Cubagua, Isla Margarita, and Cumana)

fewer than 10
(widespread, but notably uncommon)

C. kuna: 9/9 pect 15

C. alloides: 10/9 Bohlke: 10, rare 9/9, rare 8 pect 16-17 (divided pelvic fins)

The Reef Gobies

C. lipernes: 10/10 pect 16-18 (divided pelvic fins)

C. hyalinus: 10/10 pect 14-16 (divided pelvic fins)

C. personatus: Randall: 11/11 pect 14-16 (occ. 10/10) Bohlke: 10-11, mode 11/10-11, mode 11 pect 14-16 (divided pelvic fins)

Coryphopterus larvae

the "sand gobies"
 
Most of the Coryphopterus species are sand gobies, i.e. small sand-perching gobies with pale bodies and a set of dark stripes and spots. There are numerous species and larvae cannot confidently be identified to the species level without DNA sequencing. Fin-ray counts can distinguish the sand goby species with fewer or more than 10 dorsal and anal-fin elements, but many of the species and the vast majority of specimens share the 10/10 fin-ray count. The non-sand species comprise C. lipernes, a colorful coral-dwelling species, and C. personatus and C. hyalinus, both colorful hovering gobies that school in groups over corals and sponges. The sand and non-sand species are similar as larvae and share a suite of larval characters, but can be distinguished.

Analogues: (VMS4: jaw angle, thorax, anal fin, caudal peduncle) The basic larval melanophore patterns on the sand gobies are shared with a number of other gobies, although, in general, these others do not have equal numbers of dorsal and anal-fin elements as do most of the sand goby species. Coryphopterus personatus larvae do have the equal numbers of fin elements, but are missing the melanophores at the jaw angle and at the caudal-fin base and have a larger eye. Larval Lythrypnus appear quite similar, but have 10/9, are shorter and wider, have fewer procurrent caudal-fin rays, and transition at a smaller size. Lophogobius cyprinoides may share the VMS4 pattern, but have 10/9 and fewer procurrent caudal-fin rays. Bathygobius larvae have 10/9 and VMS4, but have distinctive internal melanophores not present on larval Coryphopterus The seven-spined gobies with similar larvae do not have the jaw angle melanophores and the caudal peduncle streak extends only halfway to the caudal fin.

Description: Body relatively thin, long and narrow with a large eye and a terminal mouth. Paired fins medium to long at transition, dorsal and anal-fin bases relatively short, caudal peduncle long and narrow, procurrent caudal-fin rays 7-10 (7-8 spindly). Lightly marked mostly along the lower body: melanophores on the ventral midline at the isthmus and the pelvic-fin insertion (usually streaks). Rare variants have a melanophore on the abdominal midline promontory just forward of the vent. There is a row of melanophores along the anal-fin base, usually five, paired and one per side between the third and eighth element (often merged into a streak on each side). Then, after a space, there is a row of midline melanophores, usually seven or eight unpaired (but often merged into a streak) extending along the ventral caudal peduncle ending near the start of the procurrent caudal-fin rays. Melanophores are typically present on the base of several (usually 4 or 5) of the lower segmented caudal-fin rays extending up to halfway out along the rays. The majority of larvae have one (often none or two, occasionally three or four) melanophores on the dorsal midline just after the last dorsal-fin ray (proportions vary greatly between collections). Some have an additional small melanophore off-center of the dorsal midline near the base of some of the mid-soft-dorsal-fin rays. Many (all?) have melanophores on the distal membranes between the anal-fin rays, usually between the second and sixth elements. Internal melanophores are present at the base of the saccule and often above the saccule and sometimes several around the rear braincase, along the dorsal surface of the swim bladder, and around the gut near the vent. Most individuals have a melanophore at the angle of the jaw, however less-developed larvae are often missing them (but they do have caudal-fin melanophores, separating them from C. personatus).
Early-stage larvae before the completion of all of the fin elements have a dorsal and ventral indentation in the iris, with some later-stage larvae retaining a dorsal indentation in the iris. Series of transitional larvae show development of the eye from a moderately-narrowed vertical oval, often somewhat squared-off, with a small posterior-inferior extension of the iris, to round. The extension has no surface melanophores overlying it, or, at most, a single small melanophore at the dorsal edge (vs. C. personatus, see comparative photograph under C. personatus). Rare individuals show abnormal enlargements of this extension (interestingly, often several in the same collection). There is often a prominently speckled "eyebrow" membrane over the upper half and posterior of the eyeball that appears detached from the pigmented iris below.
Although the length of the pelvic rays are an important character as adults, larvae and juveniles typically have the innermost pelvic-fin ray slightly shorter or about equal in length to the next ray. The pelvic frenum is not usually visible, but may develop on all juveniles in the group (see C. dicrus). Larvae have fused pelvic fins, and the species with divided pelvic fins likely develop the division after transition (unknown for C. alloides, but confirmed for C. lipernes and C. personatus).
 
Coryphopterus sp. 10/10 larva
4.2 mm SL
early-stage with rounded eye
San Blas, Panama, SB86-927
coryphopterus larvae
Coryphopterus sp. 10/10 larva
6.5 mm SL
early stage with narrow eye
and dorsal iris indentation
San Blas, Panama, SB86-512
Coryphopterus sp. 10/10 larva
7.2 mm SL
with slightly narrowed eye
San Blas, Panama, SB86-426
coryphopterus glaucofraenum larvae
 
Coryphopterus sp. 10/10 larva
7.4 mm SL
with round eye
San Blas, Panama, SB86-426
 
Coryphopterus sp. 10/10 larva
7.2 mm SL
squarish eye, membrane above eyeball,
braincase melanophores (left-sided visible)
San Blas, Panama, SB87-219
 
Coryphopterus sp. 10/10 larva
7.3 mm SL
speckled membrane above eyeball
San Blas, Panama, SB86-1103
Coryphopterus sp. 10/10 larva
7.5 mm SL
with anal-fin ray membrane melanophores
San Blas, Panama, SB86-1124
Coryphopterus sp. 10/10 larva
6.6 mm SL
innermost pelvic-fin ray equal to next,
with abdominal promontory melanophore
San Blas, Panama, SB86-1103
Coryphopterus sp. 10/10 larva
5.9 mm SL
internal melanophores
San Blas, Panama, SB86-404
Coryphopterus sp. 10/10 larva
6.3 mm SL
small and thin, but with round eye
San Blas, Panama, SB84-522
 
Coryphopterus sp. 10/10 larva
7.0 mm SL
Barbados, HV 8-04-02 SB86-805
Coryphopterus sp. 10/10 larva
6.6 mm SL
San Blas, Panama, SB86-805
 
Coryphopterus sp. 10/10 larva
8.6 mm SL
large-sized, extreme one percent
San Blas, Panama, SB86-805
Coryphopterus sp. 10/10 larva
7.0 mm SL and 7.1 mm SL
variant with melanophore on promontory
forward of vent, pect-18
San Blas, Panama, SB86-1004
 
 
Coryphopterus sp. 10/10 transitional larva
6.3 mm SL
San Blas, Panama, SB83-151
Coryphopterus sp. 10/10 transitional larva
6.6 mm SL
transitional variant? no anal-fin base or caudal-fin melanophores:
D-VI,10 A-10 Pect-18
Banco Chinchorro, Mexico, coll. D. Jones
Coryphopterus sp. 10/10 transitional larva
7.6 mm SL
San Blas, Panama, SB86-426
 
 
 
 
Coryphopterus sp. 10/10 transitional larva
7.2 mm SL
San Blas, Panama, SB86-424
Coryphopterus sp. 10/10 transitional larva
6.6 mm SL
typical type, head iridophore pattern
San Blas, Panama, SB86-416
Coryphopterus sp. 10/10 transitional larva
6.6 mm SL
note head neuromasts developing
San Blas, Panama, SB86-1010
Coryphopterus sp. 10/10 transitional larva
8.6 mm SL
transitional variant, the only dorsal body
melanophores along first-dorsal-fin spine
D-VI,10 A-10 Pect-19
San Blas, Panama, SB86-627a
Coryphopterus sp. 10/10 larva
abnormal posterior extension of the iris
San Blas, Panama, SB83-151
Coryphopterus glaucofraenum
 
Diagnosis: Modal fin-ray counts of D-VI,10 A-10 and Pect-18-20 with fused pelvic fins indicate the 10/10 Coryphopterus sand gobies, i.e. Coryphopterus glaucofraenum, C. tortugae, C. bol, C. dicrus, C. eidolon, and C. thrix. Some of the the distinguishing features of adult C. glaucofraenum are not present on recruits and small juveniles.
Analogues: The 10/10 sand goby clade share fin-ray counts, morphology, and most markings as larvae and new recruits. C. glaucofraenum and the other head-striped sand gobies develop short stripes on top of the head very early in transition, separating them from the spotted-head gobies (i.e. C. eidolon, C. thrix, C. alloides, C. kuna, and the non-sand Coryphopterus species). C. glaucofraenum diverge early from the other head-striped gobies (C. tortugae, C. bol, and C. dicrus) when they develop colon-like rounded spots at the base of the caudal fin. In addition, they develop melanophores at about 7-8 o'clock on the orbital rim extending straight forward in a stripe (not obliquely down) across the upper jaw vs. a cluster at 6-7 o'clock in C. tortugae and C. bol. In Venezuela, C. venezuelae develops almost identical markings to C. glaucofraenum (but have 11/11 fin elements), diverging only in the juvenile stage.
Description: Transitional recruits develop three short stripes behind the eye with the lowest stripe extending forward of the eye to the tip of the jaw, but notably not continuous under the eyeball (until larger juveniles). Lightly-marked transitional recruits can have only a single melanophore or two at the 7-8 o'clock position on the orbital rim (they have all of the stripes behind the eye). Pigmentation of the body develops more slowly, as a lateral midline row of spots, then an upper body row. The midline spots become X-shaped later. The two colon-like rounded spots at the base of the caudal fin are present early and typically have a linear trail of melanophores onto the fin rays. A chain-like pattern of large deep melanophores develop within the musculature of the tail.
NOTE: Pre-transitional larvae are described above as the 10/10 Coryphopterus spp.
Coryphopterus glaucofraenum recruits
8.1 and 7.0 mm SL, DNA confirmed ID
Colon, Panama, N7527b
Coryphopterus glaucofraenum recruits
8.4, 9.0, 10.2 mm SL, DNA confirmed ID
Colon, Panama, N7527b
Coryphopterus glaucofraenum recruit
7.0 mm SL, DNA confirmed ID
Colon, Panama, N7527b
Coryphopterus glaucofraenum juvenile
8.1 mm SL, DNA confirmed ID
Colon, Panama, N7527b
Coryphopterus glaucofraenum recruit
9.2 mm SL, 10/10 fin elements
Cumana, Venezuela, GCRL 15947
 
Coryphopterus glaucofraenum juveniles
12.6 and 13.7 mm SL
basicaudal colon spots, bridging
Colon, Panama, N7527b
Coryphopterus glaucofraenum recruit
13.1 mm SL, DNA confirmed ID
pallid, lower-eye stripe, 8 o'clock spot
St. Thomas, USVI, ST307
Coryphopterus glaucofraenum juvenile
12.9 mm SL
San Blas, Panama, SB82-054
Coryphopterus tortugae
 
Diagnosis: Modal fin-ray counts of D-VI,10 A-10 and Pect-18-20 with fused pelvic fins indicate the 10/10 Coryphopterus sand gobies, i.e. Coryphopterus tortugae, C. glaucofraenum, C. dicrus, C. eidolon, and C. thrix. The distinguishing features of adult C. tortugae are mostly not present on recruits and small juveniles.
Analogues: The 10/10 sand goby clade share fin-ray counts, morphology, and most markings as larvae and new recruits. C. tortugae and the other head-striped sand gobies develop short stripes on top of the head very early in transition, separating them from the spotted-head gobies (i.e. C. eidolon, C. thrix, C. alloides, C. kuna, and the non-sand Coryphopterus species). C. tortugae begin to diverge when they develop a cluster of melanophores below the eye at 6-7 o'clock on the orbital rim (i.e. under the anterior pupil) vs. at 7-8 o'clock (and then continuing as a line across the upper jaw to the tip) on C. glaucofraenum. C. bol share the cluster under the eye and only diverge from C. tortugae when they develop melanophores on the lower third of the pectoral-fin base (absent on C. tortugae) and then a complete long upper eye-stripe (broken on C. tortugae); note that these long surface eye stripes overlie the short eye stripes of the transitional stage. C. tortugae develop a basicaudal bar, notably without the rounded colon-like spots on the base of the caudal fin as seen on C. glaucofraenum.
Description:
NOTE: Pre-transitional larvae are described above as the 10/10 Coryphopterus spp.
   
Coryphopterus bol
 
Diagnosis: Modal fin-ray counts of D-VI,10 A-10 and Pect-18-20 with fused pelvic fins indicate the 10/10 Coryphopterus sand gobies, i.e. Coryphopterus bol, C. glaucofraenum, C. tortugae, C. dicrus, C. eidolon, and C. thrix. The distinguishing features of adult C. bol are mostly not present on recruits and small juveniles.
Analogues: The 10/10 sand goby clade share fin-ray counts, morphology, and most markings as larvae and new recruits. C. bol and the other head-striped sand gobies develop short stripes on top of the head very early in transition, separating them from the spotted-head gobies (i.e. C. eidolon, C. thrix, C. alloides, C. kuna, and the non-sand Coryphopterus species). C. bol begin to diverge when they develop a cluster of melanophores below the eye at 6-7 o'clock on the orbital rim (i.e. under the anterior pupil) vs. at 7-8 o'clock (and then continuing as a line across the upper jaw to the tip) on C. glaucofraenum. C. tortugae share the cluster under the eye, and C. bol only diverge from C. tortugae when they develop melanophores on the lower third of the pectoral-fin base (absent on C. tortugae) and then a complete long upper eye-stripe (broken on C. tortugae); note that these long surface eye stripes overlie the short eye stripes of the transitional stage. C. bol develops a basicaudal bar, notably without the rounded colon-like spots on the base of the caudal fin as seen on C. glaucofraenum.
Description: Transitional stage C. bol first develop short head stripes at the dorsal interorbital midline and behind the upper eye and mid-eye. The body is mostly unmarked and the larval melanophores at the jaw angle, thoracic ventral midline, and caudal fin disappear. The larval melanophores along the base of the anal fin and the ventral midline of the caudal peduncle persist through transition. Melanophores develop along the bases of the dorsal-fin spines and speckle the membranes of the dorsal and anal fins. The pectoral, pelvic, and caudal fins are unmarked.Internal melanophores are present over the dorsal peritoneum.
NOTE: Pre-transitional larvae are described above as the 10/10 Coryphopterus spp.
Coryphopterus bol transitional recruit
7.7 mm SL
short head stripes of the transitional stage
La Parguera, Puerto Rico, PR785a
Coryphopterus bol transitional recruits
7.7, 8.0, 9.3 mm SL
short head stripes of the transitional stage
La Parguera, Puerto Rico, PR785a
Coryphopterus bol recruit
8.0 mm SL, DNA confirmed ID
cluster at 7 o'clock, under pupil
Colon, Panama, N7530a
Coryphopterus bol recruits
11.0-11.9 mm SL, DNA confirmed ID
stripe to 6-7 o'clock,not linear to jaw tip
lower pectoral base spot
complete upper eye stripe
Colon, Panama, N7530a
 
Coryphopterus bol transitional recruits
9.0 and 9.5 mm SL, DNA confirmed ID
innermost pelvic-fin ray equal to next
Noronha, Brazil, FN01
 
Coryphopterus bol
late transitional recruit
7.4 mm SL
Barbados, V05-R20, coll. H. Valles
Coryphopterus bol
7.9 mm SL
San Blas, Panama, SB82-050
Coryphopterus bol juvenile
12.5 mm SL, DNA confirmed ID
Noronha, Brazil FN01
Coryphopterus bol juveniles
12.5 to 15.1 mm SL, DNA confirmed ID
no stripe on lower cheek and
equal innermost and next pelvic-fin rays
Noronha, Brazil FN01
 
 
Coryphopterus bol juvenile
22.5 mm SL, DNA confirmed ID
lower pectoral base spot, complete upper-eye stripe, no 7-8 o'clock bar or stripe
Panama, n7530a
   
Coryphopterus dicrus
 
Diagnosis: Modal fin-ray counts of D-VI,10 A-10 and Pect-18-20 with fused pelvic fins indicate the 10/10 Coryphopterus sand gobies, i.e. Coryphopterus dicrus, C. glaucofraenum, C. tortugae, C. bol, C. eidolon, and C. thrix. The distinguishing features of adult C. dicrus are mostly not present on recruits and small juveniles.
Analogues: The 10/10 sand goby clade share fin-ray counts, morphology, and most markings as larvae and new recruits. C. dicrus and the other head-striped sand gobies develop short stripes on top of the head very early in transition, separating them from the spotted-head gobies (i.e. C. eidolon, C. thrix, C. alloides, C. kuna, and the non-sand Coryphopterus species). Transitional C. dicrus diverge
Description:
NOTE: Pre-transitional larvae are described above as the 10/10 Coryphopterus spp.
Coryphopterus dicrus juvenile, DNA ID
11.0 mm SL
distinct frenum present
Barbados, HV 8-02-02
Coryphopterus dicrus juvenile
14.5 mm SL
stripe on lower cheek
colon-like spots on pectoral axil
San Blas, Panama, SB82-058
 
Coryphopterus eidolon
 
Diagnosis: Modal fin-ray counts of D-VI,10 A-10 and Pect-18-20 with fused pelvic fins indicate the 10/10 Coryphopterus sand gobies, i.e. Coryphopterus eidolon, C. glaucofraenum, C. tortugae, C. bol , C. dicrus, and C. thrix. The distinguishing features of adult C. eidolon are mostly not present on recruits and small juveniles.
Analogues: The 10/10 sand goby clade share fin-ray counts, morphology, and most markings as larvae and new recruits. Transitional C. eidolon and C. thrix develop scattered spots on the top of the head vs. short stripes on most other sand gobies, as well as a prominent melanophore(s) at the 7-8 o'clock position on the orbital rim, often early in transition. Both species have no jaw angle melanophores, at least as recruits (larval pattern uncertain). C. thrix juveniles larger than about 12 mm SL diverge from C. eidolon as they develop the characteristic speckling of small patches of melanophores (some 0.05-0.1 mm) over the dorsal aspect of the eye vs. a few large round and comma-shaped patches (0.3-0.5 mm) in C. eidolon (and other sand gobies). An additional difference between the small juveniles (>10 mm SL) of these two very similar species is the uniform size of the head melanophores in C. eidolon vs. C. thrix, where the lowest melanophores, just behind the eye, are larger than the adjacent sets of dorsal melanophores. Transitional recruits of the hovering gobies Coryphopterus personatus, C. hyalinus, and C. lipernes also do not have the stripes on the head at transition; nevertheless they can be distinguished from transitional sand gobies by developing melanophores around the vent and in a wide band from the eye to the maxilla.

Description: Based on transitional recruits, the larvae of C. eidolon may or may not have the jaw-angle or thoracic midline melanophores characteristic of other sand goby larvae. The caudal fin of transitional recruits have melanophores at the base of the central fin rays, and not at the lowest two or three segmented rays. Otherwise the larvae would look similar to other sand goby larvae: body relatively thin, long and narrow with a large eye and a terminal mouth. Pectoral fins long, dorsal and anal-fin bases relatively short, caudal peduncle long and narrow, procurrent caudal-fin rays 8-9 (7-8 spindly). Melanophores in a paired row along the anal-fin base, usually between the third and eighth element (often merged into a streak on each side). Then, after a space, there are several midline melanophores extending along the ventral caudal peduncle ending near the start of the procurrent caudal-fin rays. Internal melanophores are present at the base of the saccule and often above the saccule and sometimes several around the rear braincase, along the dorsal surface of the swim bladder, and around the gut near the vent. Transitional recruits develop a scattering of melanophores on the dorsal aspect of the head, not forming stripes. There is usually a conspicuous one or two large melanophores at 7-8 o'clock on the orbital rim and two or three oblong and comma-shaped collections of melanophores on the membrane overlying the dorsal aspect of the eyeball. The pelvic fins have not developed the short innermost fin rays and notched outline (rays equal in length). The lower portion of the head and the thorax are unmarked, as is the base of the pectoral fin. Melanophores cover the membranes of both dorsal fins and the anal fin. A bar of melanophores develops at the base of the caudal fin, concentrated at the base of the central caudal-fin rays. Fine melanophores speckle the distal portions of the lower segmented caudal-fin rays and, to a lesser extent, the central and upper rays.

NOTE: Pre-transitional larvae are described above as the 10/10 Coryphopterus spp.
Coryphopterus eidolon transitional recruit
9.9 mm SL, DNA confirmed ID
melanophore at 8 o'clock on orbital rim
equal innermost pelvic-fin rays
Colon, Panama, n7530a
 
 
 
 
 
Coryphopterus thrix (top) vs. eidolon
 
Colon, Panama, n7530a
Coryphopterus thrix (top) vs. eidolon
 
Colon, Panama, n7530a
Coryphopterus thrix
 
Diagnosis: Modal fin-ray counts of D-VI,10 A-10 and Pect-18-20 with fused pelvic fins indicate the 10/10 Coryphopterus sand gobies, i.e. Coryphopterus thrix, C. glaucofraenum, C. tortugae, C. bol, C. dicrus, and C. eidolon. The distinguishing features of adult C. thrix are mostly not present on recruits and small juveniles.
Analogues: The 10/10 sand goby clade share fin-ray counts, morphology, and most markings as larvae and new recruits. C. thrix and C. eidolon diverge during transition as they develop scattered spots on the top of the head vs. stripes on most other sand gobies, as well as a prominent melanophore(s) at the 7-8 o'clock position on the orbital rim (on the majority of individuals), often early in transition. Both species have no jaw angle melanophores, at least as recruits (larval pattern uncertain). C. thrix juveniles larger than about 12 mm SL begin to develop the characteristic speckling of small patches of melanophores (some 0.05-0.1 mm) over the dorsal aspect of the eye vs. a few large round and comma-shaped patches (0.3-0.5 mm) in C. eidolon and other sand gobies. An additional difference between the small juveniles (>10 mm SL) of these two very similar species is the uniform size of the head melanophores in C. eidolon vs. C. thrix, where the lowest melanophores, just behind the eye, are distinctly larger than the adjacent sets of dorsal melanophores. Recruits of the hovering gobies Coryphopterus personatus, C. hyalinus, and C. lipernes also do not have stripes on the head at transition; nevertheless they can be distinguished from transitional C. thrix by developing melanophores around the vent and in a wide band from the eye to the maxilla.
Description:
NOTE: Pre-transitional larvae are described above as the 10/10 Coryphopterus spp.
Coryphopterus thrix transitional recruit
10.0 mm SL,
melanophores at 8 o'clock on orbital rim
Colon, Panama, n7530a
Coryphopterus thrix juvenile
14.1 mm SL, DNA confirmed ID
speckled upper eye, variably-sized melanophores behind eye
La Parguera, Puerto Rico, PR785a
 
   
   
   
   
Coryphopterus punctipectophorus
 
Diagnosis: Modal fin-ray counts of D-VI,11 A-10 and Pect-18-20 indicate Coryphopterus punctipectophorus. Most other sand-goby congeners have 10/10, with only a rare individual with 11 second-dorsal-fin elements. The distinguishing features of adult C. punctipectophorus are mostly not present on recruits and small juveniles.
Analogues: The sand goby clade share morphology and most markings as larvae and new recruits. C. punctipectophorus can best be separated by fin-ray counts (11/10) at these early stages. C. punctipectophorus and the other head-striped sand gobies develop short stripes on top of the head very early in transition, separating them from the spotted-head gobies (i.e. C. eidolon, C. thrix, C. alloides, C. kuna, and the non-sand Coryphopterus species).
Description:
 
 
 
 
 
   
Coryphopterus venezuelae
 
Diagnosis: Modal fin-ray counts of D-VI,11 A-11 and Pect-18-20 indicate Coryphopterus venezuelae. Most other sand-goby congeners have 10/10, with only a rare individual with 11 fin elements. C. venezuelae has 11 elements in both the second dorsal and anal fins. The distinguishing features of adult C. venezuelae are mostly not present on recruits and small juveniles.
Analogues: The sand goby clade share morphology and most markings as larvae and new recruits. C. venezuelae can best be separated by fin-ray counts (11/11) at these early stages. C. venezuelae and the other head-striped sand gobies develop short stripes on top of the head very early in transition, separating them from the spotted-head gobies (i.e. C. eidolon, C. thrix, C. alloides, C. kuna, and the non-sand Coryphopterus species). Recruits of C. venezuelae appear almost identical to C. glaucofraenum; they diverge in transition when C. venezuelae have a long streak at the base of the first anal-fin rays, usually over 5-6 rays, while on C. glaucofraenum the streak is short and covers about 3 rays. C. glaucofraenum (and C. venezuelae) diverge from the other head-striped gobies (C. tortugae, C. bol, and C. dicrus) as early recruits when they develop colon-like rounded spots at the base of the caudal fin and as melanophores form at about 7-8 o'clock on the orbital rim extending forward in a stripe (not obliquely down) across the upper jaw vs. at 6-7 o'clock down to the angle of the jaw in C. tortugae and C. bol.
Description: Recruits develop three stripes behind the eye with the lowest stripe extending in a straight line across the jaw, not continuous under the eyeball until about 14 mm SL. Notably, recruits have no melanophores extending down from the orbital rim at 6-7 o'clock toward the corner of the jaw. A row of melanophores develop at the lower base of the pectoral fin after transition and the median-fins are heavily speckled. Two colon-like rounded spots are present at the base of the caudal fin and rows of X-shaped markings develop along the sides of the body.
Coryphopterus venezuelae recruit
11.6 mm SL, 11/11
Cumana, Venezuela, GCRL 15947
vs. Coryphopterus glaucofraenum recruit
11.5 mm SL, 10/10
Cumana, Venezuela, , GCRL 15947
   
   
Coryphopterus alloides
 
Diagnosis: Modal fin-ray counts of D-VI,10 A-8-9 and Pect-16-17 match Coryphopterus alloides, along with a number of other regional gobies. Some Lythrypnus species can have as many as 16 pectoral-fin rays, but only rare individuals would have 17 (17 is frequent in C. alloides). Bathygobius curacao can overlap the fin-ray count but larvae have prominent internal melanophores. Coryphopterus kuna has D-VI,9 A-9 and pect-15. Other gobies which share the median-fin-ray count have more pectoral-fin rays: Lophogobius cyprinoides with 17-19 (16-20), Priolepis hipoliti (17-19), Bathygobius mystacium and B. soporator (both with mode 19-20). The only seven-spined goby with a similar modal fin-ray count is Gobiosoma grosvenori (16-18). Some distinguishing features of adult C. alloides are present on recruits and small juveniles, such as the characteristic mid-body bar and dorsal-fin spot, however recruits do not have the diagnostic divided pelvic fins. (DNA)
Analogues: (VMS4: jaw angle, thorax, anal fin, caudal peduncle) Based on the appearance of transitional recruits, larval C. alloides likely share the VSM4 melanophore pattern. The reduced anal-fin-ray count separates larvae from the other sand gobies. Transitional C. alloides share a spotted head pattern with C. thrix and C. eidolon vs. stripes on most other sand gobies, as well as a prominent melanophore(s) at the 8 o'clock position on the orbital rim (on the majority of individuals), often early in transition. C. alloides diverge early from C. thrix and C. eidolon, having the jaw angle melanophores and the mid-body bar.
Description:
Coryphopterus alloides transitional recruit
8 mm SL
bar through mid-body and spinous dorsal
Colon, Panama, n7530
   
   
   
   
Coryphopterus kuna
 

Diagnosis: Modal fin-ray counts of D-VI,9 A-9 and Pect-15 indicate the newly-described species Coryphopterus kuna (Victor 2007), found widely in the Caribbean Sea: so far recorded from Yucatan (Banco Chinchorro), Belize, Honduras (Utila), Panama, San Andres, Guadeloupe and Florida. The distinguishing features of later juvenile and adult C. kuna are mostly not present on recruits and small juveniles. (DNA)

Analogues:

Description: Body relatively thin, long and narrow with a large eye and a terminal relatively small mouth. Pectoral fins long, reaching to the level of the vent. Pelvic fins fused at transition with no apparent frenum, innermost pelvic-fin ray about equal to next ray. Dorsal and anal-fin bases relatively short, caudal peduncle long and narrowing rapidly, 5-7 procurrent caudal-fin rays (5-6 spindly). Melanophores on the ventral midline at the isthmus and the pelvic-fin insertion and then a row along the anal-fin base, paired and one per side between the third and ninth element, followed by a space and then a row of melanophores extending along the ventral midline of the caudal peduncle ending near the start of the procurrent caudal-fin rays. Internal melanophores are present around the sacculus, at the dorsal surface of the swim bladder, and around the gut near the vent. Along the dorsal midline, there are melanophores along the base of the dorsal fins: one at the first and last dorsal spines and then at the base of each soft dorsal-fin element. One or two melanophores are on the body just lateral to the midline near the base of the soft dorsal fin. Internal melanophores are present on the head at the base of the saccule and a deep pair at the rear of the braincase, and then along the dorsal surface of the swim bladder and around the gut near the vent. Transitional larvae have a large round eye. They develop a pattern of large discrete melanophores on the dorsal aspect of the body, most notably three or four large melanophores overlying the eyeball, a triangle of three with the vertex at the anterior midline between the eyes, several around the back of the braincase and then a row of sometimes paired melanophores along the dorsal midline of the body back to the soft-dorsal-fin base. A large stripe of iridophores extends backward on the head from the upper eye. Melanophores develop along the first dorsal spine and at the base of the second-dorsal-fin elements. Note that in this larva there are no melanophores at the angle of the jaw or on the caudal-fin rays.

Coryphopterus kuna larva
7.0 mm SL
Yucatan, Mexico, 240306
coll. by Lourdes Vasquez et al.
Coryphopterus kuna transitional larva
7.3 mm SL, DNA confirmed ID
Banco Chinchorro, Mexico
courtesy Dave Jones
 
coryphopterus kuna
 
 
 
 
Coryphopterus lipernes
 
Diagnosis: Modal fin-ray counts of D-VI,10 A-10 and Pect-16-18 indicate Coryphopterus lipernes. The distinguishing features of later juvenile and adult C. lipernes are mostly not present on recruits and small juveniles. (DNA)
Analogues:
Description: Body relatively thin, long and narrow with a large eye and a terminal mouth. Paired fins medium to long at transition, dorsal and anal-fin bases relatively short, caudal peduncle long and narrow, procurrent caudal-fin rays 7-10 (7-9 spindly).
Coryphopterus lipernes + larva
7.7 mm SL
speckled membrane above eye
San Blas, Panama, SB86-825
 
   
   
   
   
Coryphopterus personatus
 
Diagnosis: Modal fin-ray counts of D-VI,11 A-11 and Pect-15 indicate Coryphopterus personatus. The distinguishing features of later juvenile and adult C. personatus are mostly not present on recruits and small juveniles. (DNA)
Analogues: (VMS3: thorax, anal fin, caudal peduncle) Larval C. personatus look much like larvae of the typical sand goby, but are missing the melanophores at the jaw angle and on the caudal fin. Occasional individuals with 10/10 can be similar to rare unmarked variants of the sand gobies; only the low pectoral-fin ray count would be definitive. Larval C. personatus have a larger eye than many of the sand goby larvae with more extensive dorsal membrane stippling, although these characters may be subtle. Transitional stage C. personatus diverge from the two other non-sand Coryphopterus species as follows: from C. hyalinus by developing spots scattered on the top of the head (vs. an unmarked central region) and having rows of melanophores along the posterior dorsal quadrant (1 to 2 o'clock) of the ocular rim (vs. an unmarked area); from C. lipernes by developing a prominent patch of melanophores along the abdomen to the vent (vs. a simple ring around the vent). As larger recruits, C. personatus diverge from the two other species by retaining a mostly unmarked body (vs. speckling on the posterior half of the body).
Description: Body relatively thin, long and narrow with a large eye and a terminal mouth. Paired fins medium to long at transition, dorsal and anal-fin bases relatively short, caudal peduncle long and narrow, procurrent caudal-fin rays 7-10 (7-9 spindly). Lightly marked mostly along the lower body: melanophores on the ventral midline at the isthmus and the pelvic-fin insertion (usually streaks). Then there is a row along the anal-fin base, usually six or often seven, paired and one per side between the third and ninth element (often merged into a streak on each side). Then after a space there is a row of midline melanophores, usually seven, sometimes eight, unpaired (but often merged into a streak), extending along the caudal peduncle ending near the start of the procurrent caudal-fin rays. Internal melanophores are present at the dorsal surface of the swim bladder and around the gut near the vent (none on the head). Series of transitional larvae show development of the eye from a slightly narrowed vertical oval slightly tilted forward with a small posterior-inferior extension of the iris to round and notably larger. The extension has several surface melanophores overlying it (vs. C. glaucofraenum, comparative photograph below). Rare individuals show abnormal enlargements of this extension. There is often a prominently speckled "eyebrow" membrane over the upper half and posterior of the eyeball that appears detached from the pigmented iris below. Transitional larvae develop a scattering of iridophores between the eyes and in a stripe behind the upper eye. Melanophores start as a few scattered on top of the head developing into a loose cluster on the dorsal surface of the head behind the eye (not a stripe). Melanophores later develop in a tight group on the abdominal wall forward of the vent.
Coryphopterus personatus + larva
7.7 mm SL
speckled membrane above eye
San Blas, Panama, SB86-825
coryphopterus personatus
 
 
 
 
Coryphopterus personatus + larva
6.5 mm SL (upper)
vs. C. glaucofraenum 6.7 mm SL (lower)
note eye larger top to bottom vs. head depth
San Blas, Panama, SB86-805
 
Coryphopterus personatus + larva
7.0 mm SL (upper)
vs. C. glaucofraenum 7.0 mm SL (lower)
note melanophores over iris extension
San Blas, Panama, SB86-1103
Coryphopterus personatus + larva
7.6 mm SL,
fused pelvic fins, note uniting membrane
San Blas, Panama, SB86-805
 
Coryphopterus personatus pelagic larva
5.4 mm SL
DNA ID
USA
 
Coryphopterus personatus + larva
7.4 mm SL
round eye and lightly marked
San Blas, Panama, SB84-522
 
Coryphopterus personatus + larva
7.3 mm SL
deeper-bodied variant
San Blas, Panama, SB84-527a
 
Coryphopterus personatus + larva
7.2 mm SL
iris extension abnormality
San Blas, Panama, SB87-119
C. personatus + early transitional larva
7.9 mm SL
iridescent head stripe
San Blas, Panama, SB84-624a
C. personatus + transitional larva
8.1 mm SL
diagnostic abdominal melanophore patch
San Blas, Panama, SB83-151
 
C. personatus + transitional larva
7.8 mm SL
melanophores on membrane over eyeball
San Blas, Panama, SB86-1031
C. personatus transitional recruit (above)
C. hyalinus transitional recruit (below)
7.9 and 7.0 mm SL, DNA confirmed ID
St. Thomas, USVI, ST506
Utila, Honduras, U8703
C. personatus transitional recruit (above)
C. hyalinus transitional recruit (below)
8.0 and 8.4 mm SL, DNA confirmed ID
St. Thomas, USVI, ST506
Utila, Honduras, U8703
C. personatus transitional recruit (above)
C. hyalinus transitional recruit (below)
8.0 and 8.4 mm SL, DNA confirmed ID
St. Thomas, USVI, ST-506
Utila, Honduras, U8703
C. personatus transitional recruit (above)
C. hyalinus transitional recruit (below)
8.0 and 8.4 mm SL, DNA confirmed ID
St. Thomas, USVI, ST-506
Utila, Honduras, U8703
Coryphopterus personatus recruit
8.6 mm SL
St. Thomas, USVI,
Coryphopterus hyalinus
 
Diagnosis: Modal fin-ray counts of D-VI,10 A-10 and Pect-15 indicate Coryphopterus hyalinus. The distinguishing features of later juvenile and adult C. hyalinus are mostly not present on recruits and small juveniles. (DNA)
Analogues: (VMS3: thorax, anal fin, caudal peduncle) Larval C. hyalinus look much like larvae of the typical sand goby, but are missing the melanophores at the jaw angle and on the caudal fin. They can be similar to rare unmarked variants of the sand gobies; only the low pectoral-fin ray count would be definitive. Larval C. hyalinus have a larger eye than many of the sand goby larvae with more extensive dorsal membrane stippling, although these characters may be subtle. C. hyalinus diverge from congeners at transition when they develop an unmarked central region on the top of the head vs. a collection of spots or stripes on the others. They diverge later in transition from the two other non-sand Coryphopterus species as follows: from C. personatus by developing no rows of melanophores along the posterior dorsal quadrant (1 to 2 o'clock) of the ocular rim and from C. lipernes by developing a prominent patch of melanophores along the abdomen to the vent (vs. a simple ring around the vent). As larger recruits, C. hyalinus diverge from the former by developing extensive speckling on the posterior half of the body (vs. little to none) and from the latter by having the speckling somewhat equal above and below the lateral line (vs. mostly above the line).
Description: Body relatively thin, long and narrow with a large eye and a terminal mouth. Paired fins medium to long at transition, dorsal and anal-fin bases relatively short, caudal peduncle long and narrow, procurrent caudal-fin rays 7-10 (7-9 spindly). Lightly marked mostly along the lower body: melanophores on the ventral midline at the isthmus and the pelvic-fin insertion (usually streaks). Then there is a row along the anal-fin base, usually six or often seven, paired and one per side between the third and ninth element (often merged into a streak on each side). Then after a space there is a row of midline melanophores, usually seven, sometimes eight, unpaired (but often merged into a streak), extending along the caudal peduncle ending near the start of the procurrent caudal-fin rays. Internal melanophores are present at the dorsal surface of the swim bladder and around the gut near the vent (none on the head). Series of transitional larvae show development of the eye from a slightly narrowed vertical oval slightly tilted forward with a small posterior-inferior extension of the iris to round and notably larger. The extension has several surface melanophores overlying it (vs. C. glaucofraenum, comparative photograph below). Rare individuals show abnormal enlargements of this extension. There is often a prominently speckled "eyebrow" membrane over the upper half and posterior of the eyeball that appears detached from the pigmented iris below. Transitional larvae develop a scattering of iridophores between the eyes and in a stripe behind the upper eye. Melanophores start as a few scattered on top of the head developing into a loose cluster on the dorsal surface of the head behind the eye (not a stripe). Melanophores later develop in a tight group on the abdominal wall forward of the vent.
Coryphopterus hyalinus transitional recruits
7.0, 6.9, and 7.3 mm SL
Utila, Honduras, U8703
Coryphopterus hyalinus transitional recruits
7.0 and 6.9 mm SL
note eye membrane stippling at transition
Utila, Honduras, U8703
Coryphopterus hyalinus recruit
8.4 mm SL
Utila, Honduras, U8703
Lythrypnus vs.
Coryphopterus
 
The larvae of the two most common genera in this group, Lythrypnus and Coryphopterus, are quite similar and the two sets of species can be difficult to distinguish. Nevertheless, it is possible to separate the larvae of the two genera by fin-ray counts, melanophore patterns, and, to a lesser degree, morphology and size at transition.
fin-ray counts: One distinctive difference between the two genera is that most Lythrypnus have one fewer anal-fin ray than dorsal-fin ray, while most Coryphopterus have equal numbers (C. alloides and C. punctipectophorus are exceptions). In addition, Lythrypnus have 9, sometimes 8, anal-fin elements, lower than for all Coryphopterus except for C. kuna, C. alloides and a rare C. eidolon. Lastly, Lythrypnus have only 14-16 pectoral-fin rays, fewer than all of the Coryphopterus other than C. kuna and Coryphopterus personatus/hyalinus (both of which share the count of 15) and C. alloides, which often have 16.
On close examination, there are generally fewer procurrent caudal-fin rays in larval Lythrypnus: 5 or 6 vs. 8 or 9 in most larval Coryphopterus The photograph below shows 5-6 procurrent caudal-fin rays in a 6.1 mm SL larval Lythrypnus sp. The procurrent rays are small, spindly, and not segmented, the other rays are thickened and have vertical breaks dividing the rays into segments (square-ended rays are broken at a segment division).
Size and Morphology: If the collection consists of only late-stage larvae (as do collections made over the reef), the most useful practical method of separation is body length: the Lythrypnus larvae transform at a smaller size, about 5.5 to 6.2 mm SL (vs. 6.3 to 8.0 mm SL in Coryphopterus ). There is certainly some overlap in size when large series of larvae are compared, but the larvae at the small end of the range for Coryphopterus are typically more narrow-bodied than the Lythrypnus larvae of the same size. The body-width difference is most pronounced at the level of the vent (the photograph below shows a narrow-bodied 5.1 mm SL larval Coryphopterus sand goby above a wider-bodied 5.6 mm SL laval Lythrypnus sp.) For larger "average-sized" larvae there are illustrations below in the species descriptions. Note, however, that this paragraph considers only the species thus far identified; the addition of other species may obscure the size difference.
A useful difference that applies most of the time is that the larvae of Coryphopterus tend to be hunched-over while most Lythrypnus larvae are straight. In general, if one extends the midline of the tail region forward, the eye is mostly below the line in Coryphopterus and mostly above the line in Lythrypnus larvae. Hunched-over Lythrypnus larvae do occur (see below). On closer examination, Lythrypnus larvae tend to be wider-bodied, especially at the level of the vent and the caudal peduncle, and have a shorter tail; i.e. the distance from the last dorsal ray to the base of the caudal fin is relatively shorter.
Melanophore Patterns: Fortunately, the most common larval types mostly separate out by a simple algorithm. Larval Lythrypnus have a melanophore at the angle of the jaw but no melanophores at the caudal-fin base. Larval Coryphopterus sand-gobies usually have both, while larval C. personatus have neither. For example, the photograph below shows the typical ventral melanophore pattern of Lythrypnus (upper two, small and large specimens), Coryphopterus sand gobies (third from top, with caudal-fin melanophores) and C. personatus (lowest, with neither). Lastly, larval Lythrypnus have a characteristic deep thoracic melanophore beneath the pelvic girdle. Although not always visible, it often manifests itself as a deep extension of the surface melanophore at the pelvic-fin base. A few individuals of Lythrypnus will have a midline melanophore just after the last dorsal-fin ray or on the base of the lower caudal-fin rays (markings typical of Coryphopterus sand-goby larvae), however the morphological differences and fin-ray counts should then be able to differentiate between the two.
Six vs. Seven-Spined Gobies: There are many similarities in markings between the two common genera of six-spined gobies discussed here and the Elacatinus/Gobiosoma group of seven-spined gobies. The simplest and most easily visible difference is that the streak or row of melanophores on the ventral caudal peduncle of these six-spined gobies extends almost to the start of the procurrent caudal-fin rays, while the seven-spined gobies have only one spot or have a streak or row ending well before the procurrent caudal-fin rays (photograph below of the streak extending full length on a 7.7 mm SL larval Coryphopterus personatus larva). In addition, most of the six-spined larvae have a melanophore at the angle of the jaw, which I have not found (so far) in any of the Elacatinus/Gobiosoma group. Some uncommon forms of Lythrypnus larvae with reduced caudal peduncle melanophores, e.g. forms C and D, can resemble Elacatinus/Gobiosoma larvae, but still have six first-dorsal-fin spines and the melanophore at the angle of the jaw, which is present on all larval Lythrypnus I have examined.
Lythrypnus nesiotes +
Diagnosis: Modal fin-ray counts of D-VI,10 A-9 and Pect-15 (often 16) match Lythrypnus as well as several other goby species. Bathygobius curacao can overlap the fin-ray counts but has a heavily-marked larval stage. Coryphopterus alloides shares the median-fin-ray count but has an equal incidence of 16 and 17 pectoral-fin rays (adults have divided pelvic fins with no frenum, but that is likely not apparent on larvae). C. kuna shares the 15 pectoral-fin rays but has equal numbers of dorsal and anal soft rays (D-VI,9 A-9) and often dorsal head and body markings. Other gobies which share the median-fin-ray count but have more pectoral-fin rays include Lophogobius cyprinoides 17-19 (16-20), Priolepis hipoliti (17-19), Bathygobius mystacium and B. soporator (both with mode 19-20). The only seven-spined goby coming close to the fin-ray count is Gobiosoma grosvenori (16-18).
There are many regional Lythrypnus species and their ranges are not well-understood and they may include geographic variants of the widespread L. nesiotes. It is likely that these species all appear similar or identical as larvae. Up to seven species could be present at most locations, making DNA sequencing necessary to reliably identify larvae to species. L. phorellus is primarily found from Florida northwards and L. mowbrayi was first described as the Bermuda sibling of L. nesiotes. L. nesiotes and L. crocodilus are widespread, co-occur with some habitat isolation, and differ only slightly in markings (L. nesiotes has dark bars wider than light bars). Other species with a mode of 15 pectoral-fin rays (but often having 14) include L. heterochroma, L. elasson, and the tiny and elusive L. minimus. L. okapia has fewer rays, i.e. a mode of 9 dorsal-fin elements, 8 anal-fin elements and 14 pectoral-fin rays (but rare individuals of the other species also have this fin-ray count). L. spilus has a mode of 16 pectoral-fin rays.
Note: There is extensive variation in body shape and melanophore patterns in this laval type. Since all fin-ray counts can overlap extensively in this genus, it is unclear whether this variation indicates different species or variation during transition. There are three basic forms of these larvae, but intermediates occur and I cannot separate them as larval types. The most common form has four or five melanophores in the row along the anal-fin base and about seven melanophores in the row along the ventral midline of the caudal peduncle. The anal-fin row is about half the length of the caudal peduncle row. Less common is a "short anal" variant with a shorter row of anal-fin base melanophores, two or three, but often just a short streak that is clearly less than half the length of the caudal peduncle row. The caudal peduncle row is also often reduced in this type. Lastly, there is a "five spot" variant with only about five total melanophores along the anal fin and the caudal peduncle, and the anal-fin base melanophores are widely-spaced. Some of these have typical medium-sized round eyes but some are hunched-over and have larger eyes. It is possible that the reduction in melanophores is part of transition, but it does not seem to correlate with the development of metamorphic melanophores (however this would not be unusual in larval gobies).
Analogues: Tail with full ventral streak
Description: Body relatively thin, long and narrow with a medium to large eye and a terminal mouth. Pectoral and pelvic fins long, reaching beyond the vent as transition approaches, dorsal and anal-fin bases relatively short, caudal peduncle long and narrowing rapidly, procurrent caudal-fin rays 5-7 (5, sometimes 6, spindly). Lightly marked mostly along the lower body: melanophores on the ventral midline at the isthmus and the pelvic-fin insertion (usually streaks). The latter melanophore often appears to extend deep into the body. Then there is a row along the anal-fin base, usually four or five, paired and one per side, between the third and eighth element, often merged into a streak on each side (less common forms have only two or three melanophores along the anal-fin base, but there are intermediate individuals). Then, after a space, there is a row of midline melanophores, usually seven unpaired (but often merged into a streak), extending along the caudal peduncle ending near the start of the procurrent caudal-fin rays (the reduced-melanophore forms have only three or four). In addition, all individuals have a melanophore at the angle of the jaw, at very least on one side. Rare individuals have a single midline melanophore just after the last dorsal-fin ray or a single melanophore on the base of the lower segmented caudal-fin rays. Internal melanophores are present in the head at the base of the saccule and at the dorsal surface of the swim bladder and around the gut near the vent. There is a characteristic deep thoracic melanophore beneath the base of the pelvic fin, often merged into the surface melanophore at the pelvic-fin base. Series of transitional larvae show development of the eye from a markedly narrowed vertical oval, often tilted forward and often with a dorsal indentation in the iris, with a small posterior-inferior extension of the iris (usually covered with surface melanophores) to medium-sized and round and then becoming much larger at the end of transition. On the oval eyes, there is often a small speckled "eyebrow" membrane over the anterior-superior lobe of the eyeball that appears detached from the pigmented iris below. Unlike several other goby larval types, this membrane is not obvious on the later rounded eyeball. The pectoral and pelvic fins become distinctly longer through transition. Transitional larvae develop seven bars of melanophores radiating outwards from the orbit, beginning with the bar to the mid-upper jaw.
Lythrypnus sp. larvae
6.0 mm SL (top), 6.4 mm SL (middle)
vs. C. glaucofraenum 6.5 mm SL (below)
San Blas, Panama, SB86-805
 
Lythrypnus sp. larvae
6.0 and 6.4 mm SL
transitional eye changes
San Blas, Panama, SB86-805
Lythrypnus sp. larva
5.6 mm SL
San Blas, Panama, SB86-1103
Lythrypnus sp. larva
6.5 mm SL
variant with melanophore only
at lower eye extension
San Blas, Panama, SB86-825
Lythrypnus sp. larva
5.9 mm SL
internal melanophores
San Blas, Panama, SB86-000
Lythrypnus sp. larva
5.9 mm SL
note deep thoracic melanophore
San Blas, Panama, SB86-1029
 
Lythrypnus sp. larva
6.0 mm SL
D-VI,10 A-9 Pect-16, deep thoracic
melanophore, 5 procurrent caudal rays
San Blas, Panama, SB86-516
 
Lythrypnus sp. larva
5.5 mm SL
five spot variant
San Blas, Panama, SB86-806
lythrypnus nesiotes larvae
 
 
Lythrypnus sp. transitional larva
5.7 mm SL
five spot variant
San Blas, Panama, SB86-1121
 
Lythrypnus sp. larva
5.5 mm SL
five spot variant, large eye
San Blas, Panama, SB84-624a
 
Lythrypnus sp. larva
6.1 mm SL
variant with melanophore after the last
dorsal-fin ray; D-VI,10 A-9 Pect-16
San Blas, Panama, SB86-426
 
Lythrypnus nesiotes transitional recruit
6.7 mm SL
San Blas, Panama, SB80-095
 
Lythrypnus cf nesiotes juvenile
12.4 mm SL
does not key to any in Greenfield 1988
Noronha, Brazil, FN-01
 
Lythrypnus sp. 223
Diagnosis: An individual larva with the fin-ray count of D-VI,11 A-9 and Pect-15 does not fit the typical count on any Caribbean goby, but there are many species with 10/9. Most of those, however, have many more than 15 pectoral-fin rays. Only Lythrypnus, a few Coryphopterus, and Bathygobius curacao have as few as 15 pectoral-fin rays (the latter has a very different larva and can be excluded). This larva resembles Lythrypnus and Coryphopterus larvae in form and markings, in particular the melanophore at the angle of the jaw and the ventral caudal peduncle row of melanophores extending to the start of the procurrent caudal-fin rays. Coryphopterus kuna has 15 pectoral-fin rays, but usually 9/9, and different larval markings. C. alloides can rarely have 15 pectoral fin rays (usually 16-17, with 10/9) and cannot be excluded. C. personatus and C. hyalinus also have15 pectoral-fin rays, but almost always equal numbers of second dorsal and anal-fin elements (11/11 or sometimes 10/10, not 11/9). Furthermore, this larva has a prominent melanophore at the angle of the jaw that is characteristically missing in all larval C. personatus and C. hyalinus. This larva has 6-8 procurrent caudal-fin rays, intermediate between the usual Lythrypnus and Coryphopterus. Rare individuals of otherwise typical Lythrypnus larvae described above can have 11/9 elements and some individuals have deep extensions of the midline melanophore around the pelvic-fin base, although not in the same location as in this larva. A linear internal melanophore above the pelvic girdle, perhaps along the ventral postcleithrum, is characteristic of some eleotrids (Eleotris and Erotelis smaragdus), but no other larval gobies. Given the co-occurrence of the unusual fin-ray count, the linear cleithral melanophore, and the large size of this larva compared to the other Lythrypnus larvae (7.9 mm SL vs. never more than 7.0 mm SL in a large sample), it is assigned to its own larval type.
Analogues:
Description: Body relatively thin, long and narrow with a large eye and a terminal mouth. Paired fins medium length, dorsal and anal-fin bases relatively short and unequal (dorsal-fin base about 50% longer than anal-fin base), caudal peduncle long and narrowing sharply, procurrent caudal-fin rays 6-8 (6-7 spindly). Lightly marked mostly along the lower body: melanophores on the ventral midline at the isthmus and forward of the pelvic-fin insertion, in a short row along the anal-fin base, two or three (paired and one per side) between the third and sixth element, and then a streak of seven or eight unpaired melanophores along the ventral midline of the caudal peduncle ending near the start of the lower procurrent caudal-fin rays. Head melanophores are present only at the angle of the jaw. Internal melanophores are present around the sacculus and along the dorsal surface of the swim bladder and around the gut near the vent. In this larva there is a prominent linear internal melanophore along the ventral postcleithrum (above the pelvic girdle). The eye is round in this specimen.
Goby 223 larva
7.9 mm SL
San Blas, Panama, SB87-223
gobiidae larvae
 
 
 
 

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