MATARESE and MARLIAVE: LARVAL DEVELOPMENT OF ROSYLIP SCULPIN 



ent, some differences are found among the gen- 

 era in degree of gut pigmentation, head spina- 

 tion, number and position of postanal ventral 

 melanophores, and myomere counts. 



In degree of gut pigmentation, A. rhodorus 

 larvae have a moderate intensity of melano- 

 phores; the gut is not as dark as Pa ricelinus but is 

 darker than Chito>wtus. Ascelichthys rhodorus 

 do not have as many head spines as some mem- 

 bers of Group 2 (e.g., Triglops and Paricelinus), 

 possessing only parietal and nuchal spines and 

 lacking spines in regions of the postocular, post- 

 temporal-supracleithrum, opercle, and cleith- 

 rum. There is much variation among Group 2 

 genera in the number of ventral melanophores 

 ranging from none in some species of Triglops to 

 over 40 in Chitonotus( Richardson and Washing- 

 ton 1980). Larvae of A. rhodorus are most similar 

 to larvae of Paricelinus in ventral pigmentation 

 by having approximately 20-30 melanophores in 

 preflexion larvae and approximately 15-20 me- 

 lanophores in postflexion larvae. Myomere 

 counts may also be useful in distinguishing A. 

 rhodorus larvae. Myomere counts for A. rhodorus 

 are most similar to those reported for Chitonotus 

 and Icelinus«40). Triglops, Icelus, and Pariceli- 

 nus have >40 myomeres (Howe and Richardson 

 footnote 3). 



The absence of pelvic fins in A. rhodorus does 

 not distinguish the early larvae since in most cot- 

 tids the pelvic fins are the last fins to develop. 

 However, in larger postflexion specimens the 

 lack of pelvic fins does help to distinguish the 

 species. 



DEVELOPMENT OF 

 ASCELICHTHYS RHODORUS 



Pigment Patterns 



A total of 35 larvae was examined for changes 

 in larval pigmentation (Fig. 1). The following 

 discussion describes general trends in melano- 

 phore distribution. 



In the head region, pigment on early preflex- 

 ion larvae is usually scattered dorsally over the 

 head and nape; posterior to the eye, heavy inter- 

 nal pigment occurs at the base of the brain (Fig. 

 1 A). With development, pigment increases in the 

 area of the head, snout, mouth, operculum, and 

 internally around the brain (Fig. 1B-E). A dis- 

 tinct patch of melanophores occurs at the jaw 

 angle, first appearing between 6.0 and 8.0 mm 

 SL and then becoming less prominent as larvae 



begin to transform (>12.0 mm SL). After 6.0 mm 

 SL, pigment appears on the underside of the 

 mouth along the median cartilage between the 

 dentaries and urohyal (Fig. 1C). In the abdomi- 

 nal region, early larvae have a distinctly pig- 

 mented gut with large, stellate melanophores 

 covering most of the abdominal cavity (Fig. 1A- 

 C). Melanophores are also present on the isthmus 

 and pectoral fin base of early larvae (Fig. IB, C). 

 With development, the external pigment cover- 

 ing the gut becomes more internal than external 

 with only a few melanophores visible on the over- 

 lying skin (Fig. ID). 



An average of about 15 melanophores ( N = 12, 

 range 11-22) line the ventral body midline in 0-8 d 

 (6.1-7.9 mm SL) A. rhodorus larvae, beginning 

 well posterior to the anus at about myomeres 11- 

 15 (Fig. 1A-C). These ventral melanophores 

 show much variation in size and spacing among 

 individual specimens. In general, the spacing be- 

 tween melanophores decreases from anterior to 

 posterior with the last few spots appearing close 

 together. The size of melanophores does not fol- 

 low any pattern although usually the first 2 or 3 

 anterior spots are larger than the posterior ones. 

 In preflexion larvae between 22 and 36 d (8.8-9.5 

 mm SL), the ventral melanophores extend fur- 

 ther forward beginning at about the fifth myo- 

 mere posterior to the anus and increase in 

 number to over 20 (N= 11, range 23-28). Melano- 

 phores in the anterior half of the ventral midline 

 pigment (about the first 12 spots) are more 

 widely spaced and occur in the area where the 

 anal fin is forming. In larger postflexion larvae 

 at 44 d ( 10.2 mm SL), 15-20 (N = 25, range 9-22) 

 ventral midline melanophores are present with 

 the pigment beginning just posterior to the anus 

 (Fig. ID, E). The anterior melanophores along 

 the developing anal fin are larger and are be- 

 coming more diffuse as they extend into the fin. 

 Transforming specimens have fewer ventral 

 spots, usually about 10 (N — 23, range 8-13), with 

 most of them more internal than external (Fig. 

 IF). In these specimens, melanophores posterior 

 to the completely developed anal fin appear more 

 or less as a single row whereas those along the 

 anal fin are aligned in a double row. In the tail 

 region posterior to the ventral midline row of 

 melanophores a group of caudal melanophores 

 occurs near the tail tip on the early larvae (Fig. 

 1A). As the caudal fin develops, these melano- 

 phores begin to align in the area where the hy- 

 pural bones are forming and in some specimens 

 mav extend onto the caudal fin (Fig. IB, D). 



347 



