AHLSTROM: FISH LAR\AE IN EASTERN TROPICAL PACIFIC 



pardlnus (Giinther), and B. constellatus (Jor- 

 dan) — he notes that the latter is very doubtfully 

 distinct from B. leopardinns. Based on larval 

 material, there appears to be only one common, 

 widely distributed species in the eastern Pacific 

 (Fig. 10), which is referred to B. leopardimis. 

 It lacks pigmentation, except for a dorsal and 

 ventral finfold spot near the end of the noto- 

 chord. This finfold pigment has been observed 

 on a number of species of Bothus, hence may 

 be a generic character. Bothus larvae are read- 

 ily separable from other bothid flatfish larvae 

 in the EASTROPAC area by a number of char- 

 acteristics. Young-stage larvae possess a single 

 elongated anterior dorsal ray, which becomes in- 

 conspicuous in older larvae. Older larvae are 

 very deep bodied, usually lack pigmentation and 

 lack head spination. The pelvic fin base on the 

 left side originates mostly anterior to the cleith- 

 rum, not posterior as in Syacium, Engyophrys, 

 Cyclopsetta, or Citharichthys, and the fin on 

 the ventral midline is much broader based than 

 in these genera. Almost 100 specimens of 

 Bothtis larvae from the tropical eastern Pacific 

 have been cleared and stained (based in part 

 on EASTROPAC material, in part on previous 

 expeditions). The modal number of vertebrae 

 was 10 -I- 28 = 38. 



Several specimens of flatfish larvae were taken 

 on EASTROPAC I, and on previous expeditions, 

 that had an exceptionally heavy, elongated, 

 single anterior dorsal ray, such as have been 

 described for several genera of bothid flatfish 

 of the subfamily Bothinae. However, the pelvic 

 fins formed behind the cleithrum and the fin 

 on the ventral margin was not much wider 

 based than its recessed partner. These intrigu- 

 ing larvae appear to be those of Monolene. 

 Two difl'erent kinds have been obtained from the 

 eastern tropical Pacific, one form has 10 + 35 

 vertebrae, the other has 10 +28 vertebrae. The 

 latter may be the larva of Monolene asaedai 

 (Perkins, 1963). 



genera. Larvae of both genera develop marked 

 opercular spination as well as a sphenotic spine 

 on either side of the head. Cyclopsetta larvae 

 develop 8 to 11 elongated anterior dorsal rays, 

 rather than 5 to 8 as in Syacium. Cyclopsetta 

 larvae also attain a larger size before transfor- 

 mation; larval specimens as large as 32 mm 

 have been observed in the EASTROPAC area. 

 In late-stage larvae of Cyclopsetta the anterior 

 group of dorsal rays is quite elongated, but a 

 more striking feature is the marked develop- 

 ment of three rays of the left pelvic fin which 

 may extend almost to the base of the caudal fin. 

 The Cyclopsetta larvae have a larger number 

 of vertebrae — usually 10 + 29, as compared 

 to 10 + 25 for larvae of Syacium ovale (Giin- 

 ther) . Three species of Cyclopsetta have been 

 described from the tropical eastern Pacific — 

 C. quema (Jordan and Bollman), C. panamensis 

 (Steindachner), and C. maculifera (Carman), 

 but only C. querna has been collected with any 

 frequency as juveniles and adults. The usual 

 count of vertebrae in C. quema and C. pana- 

 mensis is 10 + 29; the vertebral count of C. 

 maculifera is not known. 



Engyrophrys sancti-laurentii Jordan and Bollman 

 ( 8 occurrences, 9 larvae ) 



Larvae of Engyophrys are about as deep 

 bodied as those of Bothus. They possess heavy 

 serrations on the ventral edge of the body both 

 fore and aft of the cleithrum; three small spines 

 also develop on the otic region of the head. The 

 pelvic fins develop immediately posterior to the 

 cleithrum and anterior to the posterior group 

 of ventral serrations. A cleared and stained 

 specimen, 18 mm long, from station 13.040 had 

 10 + 31 vertebrae, 86 dorsal rays, 71 anal rays, 

 and 17 caudal rays. 



Syacium ovale (Giinther) ( 24 occurrences, 

 84 larvae) 



Cyclopsetta sp. (3 occurrences, 4 specimens) 



Larvae of Cyclopsetta are more closely re- 

 lated to those of Syacium than to other bothid 



A larval stage of Syacium was first illustrated 

 by Kyle (1913) ss"Ancylopsettasx>." Syacium 

 has a distinctive larva with heavy opercular 

 spination, a sphenotic spine on either side of 



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