MOSER: DEVELOPMENT OF ROCKFISH 



8 + 7 principal rays is present in an 8.2-mm 

 larva of the stained series. Also, the initial pro- 

 current rays are ossifying in this specimen. Os- 

 sification of these rays proceeds anteriad in both 

 superior and inferior series. The largest larva 

 (15.9 mm) has 10 superior and 11 inferior ossi- 

 fied rays, but the full complement of 11 to 13 

 superior and 13 to 15 inferior rays is attained 

 in pelagic juveniles. 



The dorsal and anal fins are the last to appear. 

 The bases of the fins appear in larvae 5.3 to 7.0 

 mm long (Figures IB, C). Cartilaginous radial 

 elements start to differentiate when the larvae 

 are about 7.0 mm and the full complements of 

 these elements are present in larvae 8.0 to 8.5 

 mm. Initial ossification of the spinous rays of 

 these fins is visible in an 8.2-mm specimen in 

 which the three anal spines and the anterior 

 seven dorsal spines are stained. A larger, but 

 apparently less advanced specimen, 8.7 mm long 

 has only four stained dorsal spines and shows 

 no stain on the anal spines. A 9.2-mm faintly 

 stained larva has seven spinous and eight soft 

 dorsal rays but shows no stain on the anal rays. 

 The next larva in the stained series, 9.4 mm long, 

 has the adult complement of III-7 anal and 

 XIII-13 dorsal rays. The remaining larvae in the 

 stained series, with the exception of one speci- 

 men, also have III-7 anal and XIII-13 dorsal rays. 



PIGMENTATION 



Newly hatched S. macdonaldi larvae have a 

 melanophore pattern similar to that of S. paii- 

 cispinis. The gut is covered with a mantle of 

 melanophores that is solid on the dorsal surface 

 and more sparsely distributed on the lateral and 

 ventral surfaces (Figure lA). A line of mel- 

 anistic dashes on the ventral midline of the tail 

 extends posteriad from the third or fourth post- 

 anal myomere. In a sample of 60 newborn larvae 

 of S. macdonaldi the number of melanophores 

 in the ventral midline series ranged from 6 to 14 

 with a median of 8. Thus, this species has fewer 

 ventral midline melanophores than any eastern 

 Pacific species of Sebastes studied to date (see 

 Morris, 1956; DeLacy et al., 1964; Moser, 1967). 

 Head pigmentation in newborn larvae consists 



of a series of melanophores that line the anterior 

 region of the lower jaw and one to several mel- 

 anophores that form a blotch on the nape. The 

 pectoral fins also are pigmented; the inner sur- 

 face of each fin base is covered solidly with mel- 

 anophores while the lateral surface is pigment- 

 less. The future rayed portion of the fin has 

 sparsely distributed melanophores on both lat- 

 eral and inner surfaces. 



Melanophores are added throughout the larval 

 period so that large larvae of S. rnacdonaldi are 

 among the most heavily pigmented of all rock- 

 fish species (Figures 1, 2, 3) . Much of the mel- 

 anistic pigment is added in the head region. One 

 or two melanophores appear over each optic lobe 

 of the brain in 4- to 5-mm larvae. Similarly 

 one or two melanophores appear above each side 

 of the cerebellum in larvae of the same size. 

 Melanophores are added continuously to the 

 dorsal surface of the brain so that it is covered 

 completely when the larvae reach 8.0 mm. Be- 

 ginning in larvae about 7.0 mm long, isolated 

 melanophores form anterior to the cleithra and 

 eventually form a small patch that is covered 

 by the opercle. When the larvae reach about 

 10.0 mm, considerably more pigment is added 

 to the head. Patches of melanophores form 

 around the external nares and along the an- 

 terior rim of the upper jaw; gradually the en- 

 tire dorsal region of the snout becomes covered. 

 Also, a conspicuous melanophore patch appears 

 at the ventroposterior margin of the orbit and 

 on the dorsal surface of the opercle. 



Pigmentation on the gut, particularly on the 

 dorsal and lateral surfaces, becomes more ex- 

 tensive during larval development. Beginning 

 in larvae of about 5.0-mm length, melanophores 

 are added in the region dorsal to the pectoral fin 

 base and eventually a continuous band of melano- 

 phores extends from the gut to the enlarging 

 melanistic blotch at the nape. 



The number of melanophores in the series at 

 the ventral midline of the tail appears to di- 

 minish as development proceeds; this may be an 

 apparent reduction since the melanophores be- 

 come embedded in the developing hypaxial mus- 

 culature and later become obscured by the de- 

 veloping anal fin. Typically, in larvae larger 

 than 8.0 mm the three posterior melanophores 



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