TUCKER: LARVAL DEVELOPMENT OF CITHARICHTHYS AND KTROPUS 



Citharichthys spilopterus 

 (Figs. 8, 9) 



Identification 



Most specimens had complete complements of 

 countable characters. They were identified by 

 comparing the following larval and juvenile 

 counts with known adult counts. Number of 

 specimens is given in parentheses. 



Caudal fin formula = 4-5-4-4 (40) 

 Caudal vertebrae = 23(16), 24(38), 25(6) 

 Gill rakers (lower limb, first left) = 11-14 (9) 

 Left pelvic rays = 6 (24) 

 Anal rays = 55-62 (53) 

 Dorsal rays = 74-82 (53) 



Of the potential species listed in Table 1, only 3 

 have 23-24 caudal vertebrae (Append. Table 1). 

 Citharichthys gymnorhinus has only five left pel- 

 vic rays, and lower anal and dorsal fin ray 

 counts. Etropus rimosus has 3-7 gill rakers and 

 usually only 24-25 caudal vertebrae. In addition, 

 most larvae were caught in an estuary, which is 

 consistent with C. spilopterus adult distribution. 



Distinguishing Characters 



Citharichthys spilopterus larvae have no pec- 

 toral melanophore, and notochordal pigment is 

 restricted to the caudal region. Two elongate 

 dorsal rays are present from preflexion (3.7 mm) 

 through transformation. Caudal vertebrae (23- 

 24, rarely 25) can be counted by late flexion (5.7 

 mm). Lateral larval pigmentation is relatively 

 light, but juvenile pigmentation is heavy. Flex- 

 ion is complete at 7-8 mm SL. The larval snout is 

 very blunt and the body is deep. Relative snout to 

 anus length is small. The left pelvic fin has a full 

 complement of six rays. Length at transforma- 

 tion is 9-11 mm. Larvae usually appear in collec- 

 tions from September through April. 



Pigmentation 



Pigmentation of C. spilopterus larvae is rela- 

 tively light, but it becomes heavy in juveniles. 

 Gas bladder, lower gut, and lateral tail pigment 

 are the most striking. 



By about 3.7 mm (early caudal formation, 

 Fig. 8A) and throughout larval development, 

 the left side of the gas bladder is fairly heavily 

 pigmented, usually with one or two distinct 



melanophores. No pigment is evident on the 

 right side of the gas bladder. Additional melano- 

 phores sometimes appear later in development, 

 but are usually larger and fewer in number than 

 in the preceding two species. The only other pig- 

 ment apparent in the 3.7 mm specimen is a small 

 amount along the ventral surface of the gut loop. 



During late flexion (6.7 mm, Fig. 8B), two 

 dashlike melanophores are present on the ven- 

 tral body margin between the anus and the 

 caudal fin base. A few melanophores appear on 

 each side of the symphysis of the lower jaw. A 

 melanophore is on the posterior margin of the 

 articular. Pigment along the ventral surface of 

 the gut loop increases. Some pigment may occur 

 on the ventral body margin anterior to the clei- 

 thrum. A stellate melanophore is present at the 

 junction of left and right branchiostegal mem- 

 branes, just forward of the isthmus. A series of 

 small melanophores usually is present along the 

 distal tips of anal pterygiophores. 



During postflexion, one to five (usually one or 

 two) melanophores are present on the left side of 

 the gas bladder. Additional dashlike clusters of 

 pigment (up to four total) appear on the ventral 

 body margin along the anal fin base, but the first 

 two remain the most distinct (8.7 mm). Similar 

 clusters of pigment appear on the dorsal body 

 margin along the dorsal fin base (up to six from 

 above the hindbrain to the caudal fin base). 

 Heavy pigment is present along the ventral body 

 margin anterior to the cleithrum. The area im- 

 mediately around the anus is usually densely 

 pigmented internally. Several external melano- 

 phores are present on the body below the pectoral 

 fin base and along the ventral and lateral sur- 

 faces of the abdomen. Internal melanophores are 

 present along the hindgut. Visible internal noto- 

 chordal pigment is restricted to a small area just 

 forward of the caudal peduncle. This appears as 

 fine dashes along the dorsal surfaces of one to a 

 few centra in the area of caudal vertebrae 15-16. 

 Some internal pigment is present near the pec- 

 toral fin base and just forward of the cleithrum 

 beneath the angle of the last gill arch (visible 

 through the opercle). The left pelvic fin becomes 

 pigmented, mostly around the first to third rays. 

 Clusters of melanophores appear on the dorsal 

 and anal fins. Often, melanophores occur along 

 the sides of the middle caudal rays. By about 9 

 mm, lateral melanophores appear on the snout, 

 jaws, and posterior part of the head. One or two 

 internal melanophores appear above the brain. 



Gas bladder pigment becomes diffuse after 



57 



