FISHERY BULLETIN: VOL. 70. NO. 3 



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Figure 15. — Dendrogram showing the 

 generic relationships and tribal division 

 of the subfamily Lampanyctinae as sug- 

 gested by larval characters. 



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Whatever were the adaptive forces that marsh- 

 alled the light organs of myctophids into specific 

 patterns, we believe that the ancestral myctoph- 

 ids had unspecialized photophores distributed 

 over the head and body (one at the margin of 

 each scale pocket) and that the specific patterns 

 were derived by enhancement of some photo- 

 phores and the concomitant deletion of others. 

 Among the 28 known genera of myctophids are 

 six (Scopelopsis, Hintonia, Lampichthys, Bolin- 

 ichthys, Lepidophanes, and Lampanyctus) in 

 which at least some species have minute photo- 

 phores on the body, in addition to the typical 

 pattern of primary photophores. The minute 

 photophores may occur at every scale pocket 

 (e.g., Scopelopsis) or may be restricted to a cer- 

 tain region of the body (e.g., Hintonia). Typi- 



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cally, those species with such minute photophores 

 also have one or more head photophores that are 

 lacking in most other myctophids. Previous 

 workers have considered the minute photophores 

 of these genera to be secondary structures, which 

 have evolved after the primary organs; how- 

 ever, we believe that they reflect an ancestral 

 stage in the evolution of photophore pattern. 

 We believe that Scopelopsis most closely approx- 

 imates the photophore pattern of ancestral myc- 

 tophids since the distinction between "primary" 

 and "secondary" organs is less apparent than in 

 the other genera retaining secondary photo- 

 phores. Moreover, every photophore position 

 described for lanternfishes has its counterpart 

 in Scopelopsis, and we find that every known 

 myctophid photophore pattern can be generated 



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