FISHERY BULLETIN: VOL. 70, NO. 3 



Table 2. — Meristic characters of cleared and stained larvae of Scopelopsis multipunetatus. 



PIGMENTATION 



Scopelopsis larvae develop a distinct pattern 

 of melanophores. The smallest larva in our ser- 

 ies (5.4 mm) has a prominent median melano- 

 phore at the nape and a smaller melanophore em- 

 bedded in the otic region at each side of the head. 

 Another large melanophore is embedded at the 

 ventral midline, just below the bases of the pec- 

 toral fins. An equally prominent melanophore 

 lies above the gut, at the point where the free 

 terminal section diverges from the body. An el- 

 liptical shield of melanophores lies above the de- 

 veloping gas bladder but is partially masked by 

 the body wall musculature. A series of six even- 

 ly spaced melanophores is embedded along the 

 ventral midline of the tail. All the melanophores 

 that constitute this initial pattern remain 

 throughout the larval period. The series at the 

 ventral midline of the tail usually contains five 

 or six melanophores in older larvae; specimens 

 with fewer than three or more than eight were 

 not found. 



Another major area of pigmentation is visible 

 in a 6.2-mm larva, which has two melanophores 

 in the dorsal midline posterior to the adipose fin. 

 In larger larvae this series extends anterior to 

 the dorsal fin, with the usual condition being a 

 series of three, four, or five melanophores on, 

 or on either side of, the midline. An 11.3-mm 

 larva has the maximum number of 10 melano- 

 phores in this series, with several of the melano- 

 phores positioned along the base of the dorsal fin. 



Final additions to the melanophore pattern are 

 in the head and caudal fin. In specimens 10.8 

 mm and larger, a melanophore is embedded an- 

 terior to the base of each pectoral fin, and speci- 

 mens 11.3 mm and larger have one to several 

 melanophores above the posterior region of the 

 brain. Larvae 10.8 mm and larger have one to 

 several melanophores embedded in the hypural 

 region of the tail; these melanophores may lie 

 over the superior hypurals, the inferior elements, 

 or both. Similarly, in specimens 12.3 mm and 

 larger, one to several melanophores may be found 

 at the base of the caudal rays, either at the su- 

 perior group, the inferior group, or both. Some 

 specimens lack these caudal ray melanophores. 

 A few larvae have an additional median melano- 

 phore at the junction of the hypural elements 

 and the rays. 



PHOTOPHORE DEVELOPMENT 



A number of photophores develop in larvae 

 of Scopelopsis in a prescribed sequence.^ As in 

 most other myctophids the Br2 are the first to 

 form. They are just visible in our smallest spe- 

 cimen (5.4 mm) and are well formed in a 10.8- 

 mm specimen. The next to appear is the poster- 

 iormost PO pair which is just visible in the 10.8- 

 mm larva but is well formed, although small, in 



^ For clarity, a diagram of the characteristic photo- 

 phore groups of adult myctophids is shown in Figure 4. 



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