640 



ONTOGENY AND SYSTEMATICS OF FISHES-AHLSTROM SYMPOSIUM 



several hours after hatching and during preflexion stages, most 

 species of caliionymid larvae have snout-to-vent lengths <50% 

 of standard length, while gobiesocids have snout-to- vent lengths 

 >50%. Both callionymids and gobiesocid larvae have swim- 

 bladders which are lost during metamorphosis, a characteristic 

 common to many teleost families. Caliionymid preflexion larvae 

 are small and laterally compressed. They have low myomere/ 

 vertebral numbers (19 to 23). Gobiesocid larvae are relatively 

 large, basically cylindrical in shape, with high myomere/verte- 

 bral counts (24 to 37) (Allen, this volume). The various species 

 of caliionymid larvae differ little from each other but they can 

 be identified by distinctive pigment patterns and median fin ray 

 counts (Demir, 1972; Miller et al., 1979: Takai and Yoshioka, 

 1979; Takita, 1980, 1983; Olney and Sedberry, in press). There 



has been no attempt yet to relate larval characters or differences 

 among larvae to the generic characters proposed by Nakabo 

 (1982b). There are no descriptions of eggs or larvae of Draco- 

 nettidae, adults of which bear close resemblance to Calliony- 

 midae (Davis, 1966). The discovery and description of larval 

 draconettids might resolve the systematic uncertainties among 

 gobiesociform fishes. A careful, comparative analysis of cal- 

 iionymid larval development may clarify the generic relation- 

 ships among species within Callionymidae. 



University of Maryland, Center for Environmental and 

 EsTUARiNE Studies, Chesapeake Biological Laboratory, 

 Solomons, Maryland 20688. 



Pleuronectiformes: Development 

 E. H. Ahlstrom, K. Amaoka, D. A. Hensley, 



H. G. MOSER AND B. Y. SUMIDA 



PLEURONECTIFORM fishes have both eyes on one side of 

 the head in juveniles and adults. The eyes are symmetrical 

 in larvae, and migration of either the left or right eye occurs 

 during metamorphosis. In some flatfish groups the eyes are on 

 the left side (sinistral) while in others they are on the right side 

 (dextral); relatively few species are indiscriminate. In some flat- 

 fishes the ocular nerve of the migrating eye usually lies dorsal 

 to the other nerve in the optic chiasma; in other groups the 

 nerve of the migrating eye is dorsal or ventral in the chiasma 

 with about equal frequency. In most groups the nasal organ of 

 the blind side also migrates to a position near the dorsal midline. 

 Features of the dentition and cranial osteology may also show 

 asymmetry. Flatfishes are highly compressed with the underside 

 of the body usually unpigmented. The lateral line may be lacking 

 on the blind side; the pectoral fin is often shorter on the blind 

 side and has fewer rays; the pelvic fin on the blind side is often 

 shorter, smaller and diflierently placed with respect to the ventral 

 midline compared with the pelvic fin on the ocular side; squa- 

 mation may be different on the two sides of the body. The dorsal 

 and anal fins are long-based; the dorsal extends anteriad to at 

 least the eye in all flatfishes except Psettodes and the anal fin 

 extends well forward of the first haemal spine. The caudal fin 

 is typically rounded or truncate with few or no secondary rays. 

 Pleuronectiforms are benthic carnivores, occurring worldwide, 

 primarily in shallow to moderate depths, with some represen- 

 tatives in brackish and fresh water habitats. Nelson (1976) notes 

 a total of 520 species. 



The classification presented below is based on the works of 

 Regan (1910, 1929) and Norman (1934, 1966) with modifica- 

 tions by Hubbs (1945), Amaoka (1969), Hensley (1977), and 

 Futch ( 1 977). Our removal of Perissias from the Paralichthyidae 

 and placement in the Bothidae are based on previously unpub- 

 lished information. Those genera marked with an asterisk are 

 misplaced in this classification and are discussed in this paper 

 and in Hensley and Ahlstrom (this volume). 



Order Pleuronectiformes 

 Suborder Psettodoidei 



Family Psettodidae (Indo-Pacific, West Africa) 

 Pseltodes 

 Suborder Pleuronectoidei 

 Family Citharidae 

 Subfamily Brachypleurinae (Indo-Pacific) 



Brachyplcura* Lepidohlepharon 

 Subfamily Citharinae (Indo-Pacific, Mediterranean, 

 West Africa) 

 Citharoides, Euatharus 

 Family Scophthalmidae (North Atlantic, Mediterranean, 

 Black Sea) 



Lepidorhombus. Phrynorhombus, Scophthalmus, 

 Zeugoplerus 

 Family Paralichthyidae (Western and Eastern Atlantic, 

 Eastern Pacific, Indo-Pacific) 

 Ancylopsetta, Cephalopsctta, Cithanchthys, Cyclop- 



Fig. 341. Eggs of Pleuronectiformes. Captions in each illustration indicate the species and diameter of the egg in mm. Scophthalmus maeoticus 

 maeoticus. from Dekhnik, 1973; Paralichthys oltvaceus. from Mito, 1963; Bothidae, from Mito, 1963; Limanda aspera. from Pertseva-Ostroumova, 

 1954; Hippoglossotdes duhius, from Pertseva-Ostroumova, 1961; Microstomus pacijicus. onginal, CalCOFI; Pleuronichlhys cornutus. from Mito. 

 1963; PehlretisJIavilalus. from Robertson. 1975a; Pellorhamphus novaezeelandiae. from Robertson. 1975a; Tnnecles maculalus. from Hildebrand 

 and Cable, 1938; Pegusa lascans nasula. from Dekhnik, 1973; Cynoglossus robuslus. from Fujita and Uchida, 1957. 



