FISHERY BULLETIN: VOL. 70. NO. 3 



elude Scopelopsis and 20 other genera. He pro- 

 vided the first substantial description of the 

 photophore pattern of Scopelopsis and, in his il- 

 lustration, differentiated the more conspicuous 

 "primary" photophores from the minute "sec- 

 ondary" organs. Further, he recognized two 

 major evolutionary lineages among these 21 ge- 

 nera and placed Scopelopsis among the group 

 which included Lampanyctiis and its relatives. 

 Authors since Smith (1949) have afforded full 

 family status to the neoscopelines, separating 

 the three genera from the Myctophidae. Re- 

 cently, Paxton (1968) reviewed the osteology of 

 the Myctophidae and constructed a higher classi- 

 fication to reflect generic relationships within the 

 family. His views have been stimulative and 

 complementary to our studies of larval myctoph- 

 ids (Moser and Ahlstrom, 1970). Our recent 

 discovery of the larvae of Scopelopsis has served 

 to crystallize our views of relationships within 

 that part of the family which contains Lampa- 

 nyctiis and its allies. These ideas, based chiefly 

 on larval morphology and sequence of photophore 

 development, are set forth herein, following the 

 description of Scopelopsis larvae. 



MATERIALS AND METHODS 



The developmental series of Scopelopsis used 

 in this study was obtained chiefly from the 

 R.R.S. Discovery plankton collections, housed at 

 the British Museum (Natural History) , A total 

 of 29 specimens was taken off South Africa at 

 stations 412, 413, 416, 418, 419, and 438 in Au- 

 gust-September 1930. An additional five larvae 

 were found on station 2352, occupied oflf South 

 Africa in July 1938. A single transforming spe- 

 cimen came from station 2280 of the U.S. Ant- 

 arctic Project ship Eltanin. Although adult spe- 

 cimens of Scopelopsis were obtained on EAS- 

 TROPAC surveys, larvae were not taken. 



A series of 25 specimens, from smallest larva 

 to juveniles, was measured according to the 

 method described in Moser and Ahlstrom (1970) , 

 to produce the table of morphometries essential 

 for description of the changes in body propor- 

 tions. These specimens also were used for de- 

 scribing the development of the melanophore 



pattern and of photophores. A second series of 

 11 larvae was cleared with KOH and stained with 

 Alizarin Red-S; a table of meristics was con- 

 structed from counts made on these specimens. 

 For purposes of discussion we have included 

 information and illustrations of nine genera re- 

 lated to Scopelopsis. These specimens and data, 

 accumulated over an extended period of time, 

 have come largely from the plankton collections 

 of the California Cooperative Oceanic Fisheries 

 Investigations, the NORPAC Expedition, the 

 EASTROPAC Expedition, and the Danish 

 Oceanographic Expedition, in addition to the two 

 sources mentioned above. Where specimens^ 

 from these and other sources are illustrated, 

 appropriate station data are included in the cap- 

 tion accompanying the figure. 



DESCRIPTION OF DEVELOPMENT 

 OF SCOPELOPSIS MULTIPUNCTATUS 



(Figures 1-3) 



LITERATURE 



Regan (1916) described the species Lampa- 

 nyctus longipinnis from a 15-mm larval speci- 

 men. Judging from the fin counts given in the 

 description and from the somewhat illegible 

 drawing, the specimen was a larva of Scopelopsis 

 multipunctatus. 



MORPHOLOGY 



Larvae of Scopelopsis are moderately slender. 

 Body depth at the pectoral fin base is 18-19% 

 of the body length in larvae undergoing noto- 

 chord flexion and is 20-24 9r (mean of 22%) in 

 later larval stages and transforming specimens 

 ( Table 1 ) . The gut is of moderate length in spe- 

 cimens undergoing notochord flexion; snout- 

 anus length is 44-45% of body length. The gut 

 is conical in these specimens and gradually arch- 

 es posteriad to the short terminal section. Snout- 

 anus distance increases slightly in later larval 

 and transforming specimens, which have a snout- 

 anus length of 50-54% (mean of 52%) of body 

 length. In these, the gut is covered by trunk 

 musculature. 



542 



