The chaenopsids comprise a particularly
speciose group of specialized blennies including
the flag, tube, sailfin, arrow, and pike-blennies.
They tend to be tiny fishes and are rarely
noticed underwater, although they occur
in most habitats around Caribbean reefs,
including around corals, algae, sand, grassbeds,
rocks, tidepools, and pilings. They form
a large New World family with numerous genera
and identifications can be difficult. A
number of ill-defined species and species-complexes
with many cryptic species and lineages are
being discovered as DNA-sequencing of the
group progresses. Many species are hole-dwelling
with precise habitat requirements and sometimes
narrow geographic ranges and, perhaps as
a result, chaenopsid larvae are relatively
uncommon and mostly undescribed.
Larval chaenopsids can be recognized by
their long thin body, large round eyes,
(usually) pointed snout, a long and continuous
dorsal fin with numerous slender spines,
a very short and narrow caudal peduncle,
long strand-like pelvic fins (mostly straight,
not markedly curled-up over the body), no
obvious head spines, no silvery peritoneal
lining, and light markings. The markings
vary little and typically comprise a row
of melanophores along the anal-fin base.
These larval characters are shared with
the larvae of the closely-related scaled
blennies of the family Labrisomidae,
which vastly outnumber chaenopsids in larval
collections. The common labrisomid larvae
are very similar in general appearance to
larval chaenopsids and are distinguished
mainly by having fewer dorsal-fin rays (although
there is a small overlap): regional labrisomids
have 12 or fewer dorsal-fin soft rays (with
a rare 13) and rarely have more than 32
total dorsal-fin elements, while most chaenopsids
have more than 31 dorsal-fin elements, often
with 13 or more soft rays. The Caribbean
chaenopsids that overlap in fin-ray counts
with labrisomids comprise
Coralliozetus cardonae, the Emblemariopsis species complex, and the rare Emblemaria
vitta. The larvae of these chaenopsids
can be distinguished from labrisomid larvae
by their somewhat different morphology and
mostly differing modes and combinations
of fin-ray counts. The taxonomic features
separating the two families, i.e. scales
on labrisomids and scales absent on chaenopsids
and a set of osteological characters, are
useless for larval stages.
The genus Stathmonotus
is still considered chaenopsid even though
their dorsal fin is made up of all spines
(and they can have scales). Some labrisomids
of Paraclinus
also have a dorsal fin made up
of all spines; fortunately the larvae of
the two genera are easily distinguished
by their morphological differences.
Chaenopsid larvae generally resemble those
of the other blennioid families of reef
fishes; nevertheless, they can be distinguished
easily from larvae of the true blennies
(family Blenniidae),
which have fewer dorsal-fin spines than
soft rays and blunt snouts at all stages
(chaenopsids have many more dorsal-fin spines
than rays and most have pointed snouts).
Larvae of the blennioid triplefins (Family
Tripterygiidae)
have three separate dorsal fins (and distinctive
markings) and the related stargazers (Family
Dactyloscopidae)
have relatively foreshortened anterior bodies
and curled-up pelvic fins.
Larval chaenopsids are superficially similar
to the larvae of labrids,
scarids,
and gobies,
which are also common in collections and
can be the same size as chaenopsid larvae
and also often share the anal-fin row of
melanophores. However, those larvae notably
have many fewer fin spines, short and/or
fused pelvic fins, and narrowed or oddly-shaped
eyes, while late-stage chaenopsids usually
have long thread-like pelvic fins and large
round eyes.
Fin-ray counts: The
taxonomic features used to distinguish chaenopsid genera
are not apparent on larvae. Since fin-ray counts are
one of the few characters that are readily assessed
on larvae and since most related species share counts
to some degree, it is useful to present species in order
of increasing fin-ray counts. The list is in general
order of total dorsal-fin elements, but with genera
and clades grouped together. Note, however, that recent
evidence indicates that local cryptic populations (lineages
or species) can have slightly variant modes and, unfortunately,
many counts are based on relatively few specimens.
Counts are generally from the literature and my own
collections: Useful sources are J. S. Stephens' "Seven
new chaenopsid blennies..." (1970);
(note: fin-ray counts in
parentheses are ranges, modes at right in bold, and two
anal-fin spines not listed)
Chaenopsis
resh: mode D-IXX,35-36 A-36-37 P-13; NE Venezuela
54-55-56
Emblemariopsis signifera
Diagnosis: The
modal fin-ray count of D-XX-XXI,11-12 A-II,19-20
P-13 with a mode of 31 total dorsal-fin elements
indicates Emblemariopsis signifera and
some congeners in the E. occidentalis clade
as well as the 20-spined
Labrisomus. Many other L and M can
overlap this fin-ray count, but tend to have one
or two more pectoral-fin rays and often more anal-fin
rays and
Description: Body
long, narrow, and thin with a particularly small
head, small round eye, small terminal mouth, and
a short pointed snout (becoming more blunted at
transition). Pectoral and pelvic fins very short,
dorsal fin long and continuous with numerous short
spines and anal fin long with numerous short rays,
the membranes merging with the caudal fin well
above the base of the caudal-fin rays. Lightly
marked with melanophores mainly along the ventral
midline: at the isthmus and pelvic-fin insertion
and then along the base of the anal fin, typically
with a melanophore at the base of each anal-fin
soft ray, variably missing a few of the series.
Internal melanophores occur subsurface at the
midline at the rear of the braincase, around the
otic capsule, and along the dorsal aspect of the
swim bladder and around the hindgut near the vent
(often contracted into two spots). ((As transition
approaches two irregular rows of large deep melanophores
develops in the musculature below the dorsal and
anal fins (diff species?)). Series of transitional
larvae show that the eye remains round. Transitional
larvae lose the anal-fin row of melanophores ((starting
at the front and develop a patch of melanophores
at the base of the central caudal fin rays. A
fine uniform speckling appears over the body and
the fins. Patches of fine melanophores develops
on the top of the head and behind the eye and
in a bar below the eye, as well as over the mandibular
and angle of the jaw)).
S. hemphilli is
separated from the other two species by not having
head cirri and having more dorsal spines and fewer
pectoral fin rays (45-53 dorsal spines, 25-31
anal-fin elements and only 4-5 pectoral fin rays).
Stathmonotus
sp. larva,
7.9 mm SL
(San Blas, Panama, SB86-401)
Stathmonotus
sp. transitional larva
7.5 mm SL
(San Blas, Panama,
SB86-729)
Stathmonotus
sp. transitional larva
7.6 mm SL
(San Blas, Panama,
SB86-826)
Stathmonotus stahli
Diagnosis: The
modal fin-ray count of D-XLI-XLIII A-II,23-25
indicates either Stathmonotus
stahli or S.
gymnodermis. The two species are morphologically
very similar; adults are easily separated since
S. stahli
have scales and S.
gymnodermis are scaleless. S.
stahli also have the dorsal and anal-fin
membranes merging with the caudal fin about halfway
up the fin vs. only at the base in S.
gymnodermis. Two regional (sub)species
are recognized: S.
stahli tekla west of the Mona Passage (between
Hispaniola and Puerto Rico) including Florida
and the Bahamas across the Western Caribbean down
to Panama and S.
stahli stahli limited to the Lesser Antilles
down to Venezuela (the former with a mode of 11
segmented caudal-fin rays vs. 12 in the latter
(sub)species).
Description: Body
long, narrow, and thin with a particularly small
head, small round eye, small terminal mouth, and
a short pointed snout (becoming more blunted at
transition). Pectoral and pelvic fins very short,
dorsal fin long and continuous with numerous short
spines and anal fin long with numerous short rays,
the membranes merging with the caudal fin well
above the base of the caudal-fin rays. Lightly
marked with melanophores mainly along the ventral
midline: at the isthmus and pelvic-fin insertion
and then along the base of the anal fin, typically
with a melanophore at the base of each anal-fin
soft ray, variably missing a few of the series.
Internal melanophores occur subsurface at the
midline at the rear of the braincase, around the
otic capsule, and along the dorsal aspect of the
swim bladder and around the hindgut near the vent
(often contracted into two spots). ((As transition
approaches two irregular rows of large deep melanophores
develops in the musculature below the dorsal and
anal fins (diff species?)). Series of transitional
larvae show that the eye remains round. Transitional
larvae lose the anal-fin row of melanophores ((starting
at the front and develop a patch of melanophores
at the base of the central caudal fin rays. A
fine uniform speckling appears over the body and
the fins. Patches of fine melanophores develops
on the top of the head and behind the eye and
in a bar below the eye, as well as over the mandibular
and angle of the jaw)).
S. hemphilli is
separated from the other two species by not having
head cirri and having more dorsal spines and fewer
pectoral fin rays (45-53 dorsal spines, 25-31
anal-fin elements and only 4-5 pectoral fin rays).
