LARVAL DEVELOPMENT OF CITHARICHTHYS CORNUTUS, 



C. GYMNORHINUS, C SPILOPTERUS, AND 



ETROPUS CROSSOTUS (BOTHIDAE), WITH NOTES ON 



LARVAL OCCURRENCE 1 2 



John W. Tucker, Jr. 3 



ABSTRACT 



Developmental series of 4 of the 12 species of Citharickthys and Etropus known from the western 

 North Atlantic and Gulf of Mexico are illustrated and described. The series consist of C. cornutus 

 (preflexion to nearly transformed, 2.2-17.4 mm body length. BL), C. gymnorhinus (preflexion to 

 late transformation, 4.4-12.9 mm BL), C. spilopterus (preflexion to juvenile, 3.7-25.4 mm BL), and 

 E. crossotus (preflexion to nearly transformed, 4.6-10.8 mm BL). 



Data from this study and that for 2 species previously described permit identification of larvae of 6 

 of the 12 species. For the species investigated, caudal fin formula (4-5-4-4) is the most reliable indi- 

 cator for the group of genera Citharichthys, Cyclopsetta, Etropus, and Syacium. Number of elongate 

 dorsal rays, degree of cephalic spination, and pigmentation are most useful for determining genus 

 for known forms. Number of elongate dorsal rays, number of caudal vertebrae, pigmentation, mor- 

 phology, and number of gill rakers are most useful for identification of Citharichthys and Etropus 

 larvae that have been described. 



Citharichthys cornutus larvae have no pectoral melanophore, little notochordal pigmentation, 

 heavy lateral pigmentation, 3 elongate dorsal rays, and develop 6 left pelvic rays and 25-26 caudal 

 vertebrae. Flexion is complete at 9-10 mm SL and transformation at about 18 mm SL. Larvae have 

 been collected during all seasons. Caudal fin development in C. cornutus is typical of the four species 

 described here. Citharichthys gymnorhinus larvae have no pectoral melanophore, little notochordal 

 pigmentation, light lateral pigmentation except for a caudal band, 3 elongate dorsal rays, and de- 

 velop only 5 left pelvic rays and 23-24 caudal vertebrae. Flexion is complete at 7-8 mm SL and trans- 

 formation probably at about 18 mm SL. Larvae have been collected during all seasons. Citharichthys 

 spilopterus larvae have no pectoral melanophore, little notochordal pigmentation, light lateral pig- 

 mentation, a blunt snout, a deep body, 2 elongate dorsal rays, and develop 6 left pelvic rays and 23-24 

 (rarely 25) caudal vertebrae. Flexion is complete at 7-8 mm SL and transformation at 9-11 mm SL. 

 Larvae have been collected from September through April. Etropus crossotus larvae have a melano- 

 phore at the base of the pectoral fin, heavy notochordal pigmentation, heavy lateral pigmentation, 2 

 elongate dorsal rays, and develop 6 left pelvic rays and 25-26 (very rarely 24) caudal vertebrae. 

 Flexion is complete at 9-10 mm SL and transformation at 10-12 mm SL. Larvae have been collected 

 in May and August and probably occur from March to August. 



Twelve species of the flatfish genera Citharich- 

 thys and Etropus (subfamily Paralichthyinae, 

 family Bothidae) are recognized from the west- 

 ern North Atlantic (Table 1). Because of their 

 small size at maturity, these fishes are presently 

 used only by the petfood and fish meal industries 

 (Topp and Hoff 1972). However, the abundance 

 of larvae (Richardson and Joseph 1973; Smith et 



"Contribution No. 1037, Virginia Institute of Marine Sci- 

 ence, Gloucester Point, VA 23062. 



2 Derived from a thesis submitted to North Carolina State 

 University in partial fulfillment of the requirements for the 

 Master of Science degree. 



3 School of Marine Science of the College of William and 

 Mary. Virginia Institute of Marine Science, Gloucester Point, 

 VA 23062. 



Manuscript accepted October 1981. 

 FISHERY BULLETIN: VOL. 80. NO. 1. 1982. 



al. 1975; Dowd 1978) and adults (Dawson 1969; 

 Topp and Hoff 1972; Christmas and Waller 1973) 

 indicates that some species may represent sig- 

 nificant components of estuarine and marine 

 food webs. 



Larvae in the Citharichthys-Etropus complex 

 are difficult to distinguish and are often ignored 

 or classified as "unidentified bothids" in species 

 composition analyses (e.g., Fahay 1975). Of the 

 12 western North Atlantic species, only C. arcti- 

 frcms and E. microstomas have been described in 

 detail (Richardson and Joseph 1973). Citharich- 

 thys cornutus, C. gymnorhinus, C. macrops, and 

 E. rimosus have been briefly described by Dowd 

 (1978). Larvae of the remaining species have not 

 been reported previously. Hsiao (1940) mis- 



35 



