TUCKER: LARVAL DEVELOPMENT OF CITHARICHTHYS AND KTROPUS 



arichthys arctifrons, C. cornutus, C. gymno- 

 rhinus, C. spiloptems, Cyclopsetta fimbriata, C. 

 ch ittendeni, E. crossotus, E. microstomus, and S. 

 papillosum). Caudal formula, pelvic fin place- 

 ment, shape, and pigmentation of larvae in the 

 four series corresponded to this group. 



Cyclopsetta spp. have 26-28 caudal vertebrae 

 (Gutherz 1967). Larvae of C. fimbriata, C. chit- 

 tendeni, and S. papillosum have 5-10 elongate 

 dorsal rays and well-developed preopercular and 

 frontal-sphenotic spines (Gutherz 1971; Futch 

 and Hoff 1971; Evseenko 1979). Futch and Hoff 

 (1971) listed Syacium generic larval characters. 

 Other Cyclopsetta and Syacium larvae are prob- 

 ably similar. Larvae in the four developmental 

 series had lower caudal vertebral count ranges 

 than Cyclopsetta spp., only 2-3 elongate dorsal 

 rays, and relatively small preopercular and fron- 

 tal-sphenotic spines. Therefore, these two genera 

 were ruled out, leaving Citharichthys and 

 Etropus. Identification to species is described in 

 the individual species accounts. 



For aid in determining species of Citharich- 

 thys and Etropus, frequency distributions of cau- 

 dal vertebral, anal ray, and dorsal ray counts 

 were tabulated from the literature, and from 

 radiographs of juveniles and adults from the 

 Atlantic off the southeastern United States 

 (Append. Tables 1-3). Ranges of gill raker counts 

 were tabulated from the literature (Append. 

 Table 4). Number of caudal vertebrae (Append. 

 Table 1) was the count most useful for distin- 

 guishing larvae. Vertebral counts can be made 

 before ossification during early or midflexion, 

 and overlap is not excessive. However, care is 

 necessary to avoid inaccurate counts because of 

 fused centra. Caudal neural spines and hemal 

 spines, both of which number one less than cau- 

 dal vertebrae, will stain with alizarin and some- 

 times can be counted before caudal vertebrae, 

 during early or midflexion. The number of gill 

 rakers on the lower limb of the first arch (Ap- 

 pend. Table 4) can be counted in most specimens 

 during transformation and can be very useful for 

 identification of older larvae. The number of 

 anal rays (Append. Table 2) is next in usefulness, 

 followed by the number of dorsal rays (Append. 

 Table 3); however, the overlaps for these counts 

 are great. Efficiency can be gained by plotting 

 individual anal versus dorsal counts on a graph, 

 so that the counts can be used simultaneously. 

 The adult complements of anal and dorsal rays 

 are present by the end of transformation. 



After the largest specimens in each series were 



identified, the identities of successively smaller 

 larvae were verified. The most useful characters 

 for untransformed specimens were lateral, pec- 

 toral, and notochordal pigment; number of elon- 

 gate dorsal rays; number of caudal vertebrae; 

 number and size of left pelvic rays; and head 

 shape. 



DESCRIPTION OF 

 DEVELOPMENTAL STAGES 



Citharichthys cornutus 

 (Figs. 1-5) 



Identification 



Larvae approaching transformation had com- 

 plete complements of countable characters. 

 Those specimens were identified by comparing 

 the following larval counts with known adult 

 counts. Number of specimens is given in paren- 

 theses. 



Caudal fin formula = 4-5-4-4 (27) 



Caudal vertebrae = 25(11)-26(16) 



Gill rakers (lower limb, first left) = 12 (1) 



Left pelvic rays = 6 (17) 



Anal rays = 60-66(11) 



Dorsal rays = 78-84 (11) 



Of the potential species listed in Table 1, only C. 

 cornutus has counts that agree with these. In 

 addition, larvae were captured over the outer 

 shelf, slightly farther offshore than C. gymnorhi- 

 nus (Fig. 1). This is consistent with bathymetric 

 distribution of adults. 



Distinguishing Characters 



Citharichthys cornutus larvae have no pectoral 

 melanophore, and notochordal pigment is re- 

 stricted to the caudal region. Three elongate 

 dorsal rays are present from preflexion (about 4 

 mm) through transformation. Caudal vertebrae 

 (25-26) can be counted by early flexion (6 mm). 

 Lateral pigment is relatively heavy. Flexion is 

 complete at 9-10 mm SL. The larval mouth and 

 eye are large. Morphology is similar to that of C. 

 gymnorhinus. However, the left pelvic fin of C. 

 cornutus has a full complement of six rays, and in 

 larvae the first ray is not reduced in size. The left 

 pelvic fin of C. gymnorhinus has only five rays, 

 and in larvae the first ray is much reduced com- 

 pared with that of C. cornutus. Length of C. 



39 



