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Sub-family Ptereleotrinae
Ptereleotris
Sub-family Microdesminae
Cerdale
Microdesmus
The wormfishes are tiny and rarely-seen relatives of the gobies. There are only two Caribbean genera: Cerdale floridana and the genus Microdesmus with five regional species. Fortunately, fin-ray counts clearly distinguish the regional species, which share almost all other larval characters and markings. Despite the small size of the adults, the larvae are large and not uncommon in larval collections.
The dartfishes of the family Ptereleotridae have been taxonomically mobile in recent years and some taxonomists now include them in the wormfish family Microdesmidae. I place them here alongside the family Eleotridae because they are also gobioids and share the clearly-divided pelvic fins of the eleotrids. Larval ptereleotrids most closely resemble the "long" larvae of my Group 4 gobies. There are only two dartfishes in the region, a pair of sibling species that vary only slightly in color: their larvae are likely identical.
 
Larval microdesmids are long and worm-like with a prominent mid-body swim bladder. They have a characteristically blunt, hooked, and protruding lower jaw and more, usually many more, than 35 elements in the dorsal fin and 23 in the anal fin. These features easily distinguish them from the gobies and other gobioids. Wormfish larvae are morphologically similar to the larval pikeblennies of Chaenopsis, but the latter have long and thread-like pelvic fins while larval wormfishes have inconspicuous pelvic fins. Transforming eel larvae of many families may superficially resemble larval microdesmids, but the eels do not have a normal caudal fin as do the microdesmids and chaenopsids.
Ptereleotris helenae
 
Diagnosis: Modal fin-ray counts of D-VI,23 A-22 Pect-21 indicate Ptereleotris helenae or P. calliurus. The fin-ray counts are unique to this genus in the region, where no other gobioid exceeds 22 second-dorsal-fin elements (some Microgobius signatus individuals can occasionally reach 22 elements and larval Palatogobius have up to 21). In addition, these other candidates have seven dorsal-fin spines and do not have obviously separated pelvic fins. There are ony two regional species: P. helenae throughout most of the Caribbean and the sibling species P. calliurus from Florida and the Northern Gulf of Mexico. (U)g21
Analogues: (long goby with long dorsal and anal fins) Larval Ptereleotris helenae have unique markings for the gobioids, especially a long row of melanophores along the base of the dorsal fins in a pre-transitional larva. Their body form is similar to larval Microgobius, but the melanophore patterns are quite different. The markings of larval Ptereleotris helenae are similar to those found in some larval labrisomids or chaenopsids, but larvae of those families do not have the distinctive separate and short spinous dorsal fins of the gobioids.
Description: Body thin, long and narrow with a large eye and a large terminal mouth. Pectoral fins short, pelvic fins medium-length, extending less than halfway to the vent, clearly separate with no frenum. Dorsal and anal-fin bases very long, caudal peduncle very short and narrow, procurrent caudal-fin rays 7-9 (7-8 spindly). Lightly marked along the dorsal and ventral midlines: melanophores in rows on the body near the base of the spinous dorsal fin, variably paired and offset from the midline, then in rows near the base of the second dorsal fin, one offset pair per fin element, then extending onto the dorsal midline at the caudal peduncle ending at the start of the procurrent caudal-fin rays. Melanophores are present on some of the central and lower segmented caudal-fin rays. There is a row of melanophores along the anal-fin base (variably paired, one per side, a few larger ones starting at the fifth or sixth element that are fewer than one per ray, then becoming small and usually one per ray around the tenth element), and then a streak along the ventral midline of the very short caudal peduncle ending at the start of the procurrent caudal-fin rays. There are no melanophores at the isthmus or at the pelvic-fin insertion. On the head there is a pair of large melanophores at the rear of the braincase on each side of the dorsal midline. Internal melanophores are present around the sacculus, along the dorsal surface of the swim bladder and around the gut near the vent. The eye is large and round.
Ptereleotris helenae larva
12.2 mm SL
note separated pelvic fins
San Blas, Panama, SB82-016
 
 
 
 
Cerdale floridana
 
Diagnosis: The modal fin-ray count of D-XIII,31-32 (XII-XIV,30-34) A-30-31 (28-33) indicates Cerdale floridana. (U) md2
Analogues:
Description: Body somewhat thick, very long and narrow with a small head and round medium-sized eye and mouth with a blunt, hooked, and protruding lower jaw. Pectoral fins short and pelvic fins separate and short. Dorsal and anal fin bases very long, caudal peduncle very short and relatively wide. The caudal fin has a distinct vertical row and three lateral rows of caudal fin neuromasts (sensory papillae) and there are 5-7 procurrent caudal fin rays (5-6 spindly). Very lightly marked, mostly along the ventral midline: a melanophore at the pelvic fin base (often missing), followed by a pair of short rows of melanophores diverging from the pelvic fin base along the side of the abdominal gut strip. There is a row of melanophores along the base of the anal fin rays after the first three (paired and one per ray), becoming more disassociated from the anal fin base and more variable in number and depth at the last several rays and continuing into the ventral caudal peduncle ending at the start of the lower procurrent caudal fin rays. A few scattered melanophores sometimes extend out along the lower segmented caudal fin rays. A rare individual has a surface melanophore on the lateral aspect of the caudal peduncle (a characteristic of larval Microdesmus spp.), although it is off-center from the lateral midline. Dorsal markings consist of a few off-center and variably-paired melanophores at the base of some posterior dorsal fin rays continuing onto the dorsal caudal peduncle ending at the start of the upper procurrent caudal fin rays. Some larvae have a melanophore at the angle of the jaw. Internal melanophores occur around the saccule and along the dorsal surface of the swim bladder (not at the vent).
Cerdale floridana larva
18.9 mm SL
San Blas, Panama, SB86-1001
 
 
 
Cerdale floridana larva
19.0 mm SL
head neuromasts
San Blas, Panama, SB86-1001
Cerdale floridana larvae
19.0 and 18.9 mm SL
dorsal view of caudal peduncle (below)
San Blas, Panama, SB86-1001
 
Cerdale floridana larva
19.4 mm SL
lateral caudal peduncle melanophore
San Blas, Panama, SB87-101
Microdesmus bahianus
Diagnosis: The fin-ray count range of D-IX-XII,26-30 A-24-28 indicates Microdesmus bahianus. (U)
Analogues:
Description: Body somewhat thick, very long and narrow with a small head and round medium eye and mouth with a hook-like protruding lower jaw with a bulbous tip.
Microdesmus carri
 
Diagnosis: The fin-ray count range of D-XXV-XXVII,43-45 A-36-37 indicates Microdesmus carri. This is the only Caribbean microdesmid with more than 23 dorsal fin spines. (U)
Analogues:
Description: Body somewhat thick, very long and narrow with a small head and small to medium-sized round eye and a large mouth with a hook-like protruding lower jaw with a bulbous tip. Pectoral fins short and pelvic fins separate and short. Dorsal and anal fin bases very long, caudal peduncle very short and relatively wide, 5-6 procurrent caudal fin rays (5 spindly). Lightly marked, mostly along the ventral midline: melanophores at the isthmus, a short row of about four just forward of the pelvic fin base continuing as a short row behind the pelvic fin base then diverging into a pair of rows along the sides of the abdominal gut strip. There is a row of melanophores along the base of all of the anal fin rays (paired and one per ray) continuing as a short row of about three melanophores along the ventral caudal peduncle midline ending before the procurrent caudal fin rays. There are melanophores along the base of some of the last dorsal fin rays (paired, off-center, and one per ray) continuing along the dorsal caudal peduncle midline ending before the procurrent caudal fin rays. There is a short row of about three melanophores along the lateral midline of the caudal peduncle. Melanophores line the proximal third of the lower central caudal fin rays and the mid- and distal portion of the several lowest segmented caudal fin rays. Melanophores on the head are limited to a pair at the angles of the jaw. Internal melanophores occur around the saccule and along the dorsal surface of the swim bladder (not at the vent).
Microdesmus carri larva
30.3 mm SL
San Blas, Panama, SB86-1103
 
 
Microdesmus carri larva
30.4 mm SL
San Blas, Panama, SB86-701
Microdesmus lanceolatus
Diagnosis: The fin-ray count range of D-XI-XIII,51-61 A-48-56 indicates Microdesmus lanceolatus .(U)
Analogues: Content goes here
Description: Body somewhat thick, long and narrow with a small head and round eye, small mouth and hook-like protruding lower jaw with a bulbous tip.
Microdesmus longipinnis
Diagnosis: The fin-ray count range of D-XIX-XXIII, 51-52 (40-58) A-44 (36-52) indicates Microdesmus longipinnis. (U)
Analogues:
Description: Body somewhat thick, long and narrow with a small head and round eye, small mouth and hook-like protruding lower jaw with a bulbous tip.
Microdesmus luscus
 
Diagnosis: The fin-ray count range of D-XII-XIII,37-38 A-35 indicates Microdesmus luscus. md5(U)
Analogues:
Description: Body somewhat thick, very long and narrow with a small head and small round eye and medium-sized mouth with only a slightly protruding lower jaw. Pectoral fins short and pelvic fins separate and short. Dorsal and anal fin bases very long, caudal peduncle very short and relatively wide, 5-6 procurrent caudal fin rays (5 spindly). Lightly marked, mostly along the ventral midline: melanophores at the isthmus, just forward of the pelvic fin base and just behind the pelvic fin base diverging into a pair of short rows along the side of the abdominal gut strip. There is a row of melanophores along the base of all of the anal fin rays (paired and one per ray), becoming more disassociated from the anal fin base and more variable in number and depth at the last several rays and continuing along the ventral caudal peduncle midline ending under the first lower procurrent caudal fin ray. There are melanophores along the base of the last two dorsal fin rays (paired, off-center, and one per ray), and continuing along the dorsal caudal peduncle midline ending under the first upper procurrent caudal fin ray. There are one or two discrete large melanophores along the lateral midline of the caudal peduncle. Melanophores line the proximal third of the lower central caudal fin rays and the full length of the several lowest segmented caudal fin rays. Melanophores on the head are limited to a pair at the angles of the jaw. Internal melanophores occur around the saccule and along the dorsal surface of the swim bladder (not at the vent).
Microdesmus luscus larva
22.3 mm SL
San Blas, Panama, SB87-101
 

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