A Photographic GUIDE to the Late-Stage LARVAE of CORAL REEF FISHES
Under construction with daily additions, corrections, and refinements/June 2006
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Chaenopsids, or the flag, tube, and pipe-blennies, tend to be tiny fishes and rarely noticed on and around Caribbean reefs. Nevertheless, they form a large family with numerous genera and identifications can be difficult. Many species have precise habitat requirements and peculiarly narrow geographic ranges and thus most species' larvae are relatively uncommon and mostly undescribed.
Larval chaenopsids can be recognized by their often pointed snout, long and continuous dorsal and anal fins with flexible spines, a very short and narrow caudal peduncle, long strand-like pelvic fins (usually straight, not curled up over the body), the absence of spines on the head, and light markings (basically a row of melanophores along the anal fin base). Larval chaenopsids usually have large round eyes, in contrast to larval scarids, labrids, and gobiids in which the eye is often smaller or narrowed.
Chaenopsids and labrisomids can share fin ray counts; nevertheless, most chaenopsids have more than 13 dorsal fin soft rays and 34 or more total dorsal fin elements while regional labrisomids always have 13 or fewer dorsal fin soft rays and fewer than 34 total dorsal fin elements. The only Caribbean chaenopsids that share the low dorsal fin soft ray count with labrisomids are Coralliozetus cardonae, Emblemaria vitta, Acanthemblemaria johnsoni (Tobago only?), A. rivasi (from the SW Caribbean) and the Emblemariopsis spp.
The genus Stathmonotus is still considered chaenopsid even though their dorsal fin is made up of all spines.
Other similar-appearing families include dactyloscopids (very similar larvae, but with curled pelvic fins), blenniids with blunt snouts and fewer dorsal fin spines than soft rays (chaenopsids other than Chaenopsis spp. have more spines than rays), and tripterygiids with three separated dorsal fins. Many larval gobies fit the general labrisomid gestalt, but have separate and very short spinous dorsal fins with spindly spines, and often a pelvic fin disk as well.
Diagnosis: Modal fin ray counts of D-XLIII-XLIV A-II,24-25 indicate Stathmonotus stahli. S. stahli has from 39-45 dorsal fin spines, 23-28 anal fin elements and 8-9 pectoral fin rays. S. gymnodermis is separated from the other two species by having slightly fewer anal fin rays (A-II,22-24) and having the dorsal and anal fin membranes merging only with the base of the caudal fin, not halfway up the fin. Later in development there is an easy separation since S. gymnodermis is scaleless. S. hemphilli is separated from the other two species by not having head cirrhi 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). (U)
Description: Body thin long and narrow with a medium eye and a short pointed snout (becoming blunted at transition). Pectoral and pelvic fins very short, dorsal and anal fin bases very long, the membranes merging with the caudal fin well above the base of the caudal rays. Lightly marked: melanophores on the ventral midline at the isthmus and the pelvic fin insertion and along the base of the anal fin, typically one for each anal fin soft ray. Internal melanophores occur at the rear of the brain just below the surface and around the sacculus, along the dorsal surface of the swim bladder and around the gut near the vent. ((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)).
Stathmonotus sp. larva, 7.9 mm SL (San Blas, Panama, SB86-401)
Stathmonotus sp. larva, 6.8 mm SL (internal melanophore pattern)(San Blas, Panama, SB86-827)
Stathmonotus sp. early transitional larvae, 7.3 and 7.7 mm SL (note caudal fin melanophores and rows of deep body melanophores)(San Blas, Panama, SB86-426)
Stathmonotus sp. early transitional larva, 7.5 mm SL (internal melanophore pattern)(San Blas, Panama, SB86-729)
Stathmonotus sp. transitional larva, 7.6 mm SL (San Blas, Panama, SB86-826)
Chaenopsis sp.larva, 15.7 mm SL (melanophores faint)(San Blas, Panama, SB84-523a)
Chaenopsis sp. larva, 17.1 mm SL (San Blas, Panama, SB86-406)
Acanthemblemaria rivasi - in panama- 21,13 2,22
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