MOSER ET AL.: MYCTOPHIDAE 



229 



subfamilies have large fins and fin bases. In Symbolophorus the 

 fin base is uniquely shaped and in Lobianchia the fin blade has 

 a unique shape. In two genera (Loweina. Tarletonbeania) the 

 lowermost pectoral ray is elongate and ornamented. The finfold 

 is enlarged in many myctophine genera and greatly enlarged in 

 one myctophine tribe, the Gonichthyini. 



Myctophids, with the exception of Notolychnus and Taan- 

 ingichthys, develop the middle branch iostegal photophore (Br,) 

 during the larval period. It is located posteroventral to the orbit 

 but during transformation assumes a position beneath the orbit 

 on the branchiostegal membrane. Three myctophine genera and 

 1 1 lampanyctine genera develop additional photophores during 

 the larval period; however, the Br, is always the first to develop. 

 The larval photophore complements and the sequence of ap- 

 pearance of constituent photophores are useful characters. 



Myctophid species have distinct melanophore patterns, with 

 the exception of the large genus Diaphus, for which only a few 

 specific patterns have been identified. Most genera may be sep- 

 arated by overall similarity of pattern among their species and 

 some have unique melanophore loci. There are no clear patterns 

 for tribes or subfamilies although certain pigment loci are per- 

 sistent in some tribes (e.g., caudal fin base spots in diaphines; 

 dorsal midline series in gymnoscopelines). 



In the following summary of key larval characters, the genera 

 are listed for convenience as in Moser and Ahlstrom (1970. 

 1972, 1974) and the sequence does not necessarily imply rela- 

 tionship. Likewise, the species groups serve only to identify 

 phenotypically similar larval types. Larvae of a majority of myc- 

 tophid genera have a moderately slender body, a head of mod- 

 erate size, with a slightly convex dorsal profile and a pointed 

 snout of moderate length. Body and head shape are noted only 

 when they depart from this morph. In Myctophinae eye shape 

 is noted when it is markedly elliptical and size is noted only 

 when larger or smaller than typical. In Lampanyctinae eye shape 

 is noted only when it departs from the round condition and eye 

 size only when larger or smaller than typical. Choroid tissue is 

 described only when it is present. Gut length and shape are 

 described only if there is a departure from the typical morph — 

 a slightly S-shaped gut that extends to about midbody. The most 

 persistent pigment locus in myctophid larvae is above or to the 

 side of the free terminal section of the gut, thus only the lack 

 of this pigment is noted. Larval photophores, in addition to the 

 Br,, and their sequence of appearance are shown in Table 62. 



Myctophinae 



Krefflichthys. — Fig. 1 15 A; head small with short snout; conical 

 choroid tissue; gut straight, extending beyond midbody; dorsal 

 fin displaced posteriad; lateral gut and postanal median ventral 

 melanophore series; large lateral hypural pigment patch. 



Protomyctophum. — ¥\%. 1 15B, C; two subgenera; head small to 

 moderate in size; gut short, wide space between anus and anal 

 fin; head pigment lacking except in otic region of P. Heirops 

 chilensis; some species may have melanophores on lateral gut, 

 above gut on trunk, above gas bladder, in postanal ventral mid- 

 line series, prominent pigment on lateral hypural region. P. 

 Heirops: Fig. 1 1 5C; characters similar to P. Protomyctophum 

 except eye narrower. 



Eleclrona— Fig. 1 15D, E; body moderately slender to moder- 

 atey deep; head moderately large; snout blunt or pointed; gut 

 short, somewhat saccular, strongly S-shaped; space between anus 

 and anal fin not as large as in Protomyctophum; three morphs. 

 E. subaspera-E. carlsbergi: eye slightly elliptical, small lunate 

 choroid mass in E. carlsbergi; pigment above gut; E. subaspera 

 has pigment lateral to cleithrum. E. rissoi: Fig. 1 1 5D; head large, 

 broad; eye very narrow; pigment at lower jaw symphysis, on 

 pectoral fin blade. E. antarctica: Fig. 1 1 5E; body and head lat- 

 erally compressed; gut mass protrudes ventrally from body pro- 

 file; eye small, narrow, with bicolored elongate conical choroid 

 mass; pigment on upper jaw, pectoral fin blade, lateral gut, 

 lateral hypural region. 



Metelectrona. — Fig. 1 1 5F; body and head laterally compressed; 

 dorsal finfold enlarged with fin base initially separated from 

 body; lunate choroid mass; anterior gut section with small di- 

 ameter, opening dorsally into somewhat saccular posterior sec- 

 tion; pigment below lower jaw and on isthmus. 



Benthosema. — Fig. 1 16A-D; two morphs; photophores (Table 

 62). B. glaciale-B. sitborbitale: Fig. 1 16A, B; eyes narrow, with 

 small lunate choroid mass; gut moderately short in preflexion 

 larvae with space between anus and anal fin; pigment on snout, 

 lower jaw, hindbrain, lateral and ventral cleithral region; pig- 

 ment above gut in B. glaciate. B. pterota-B. fibulatum: Fig. 1 I6C. 

 D; eyes less narrow than in above morph, with sliver of choroid 

 tissue or none; gut extends to about midbody with no space 

 between anus and anal fin; preflexion larvae with melanophore 

 series on lateral gut and on postanal ventral midline, coalescing 

 to a single melanophore; lateral cleithral pigment; lower jaw 

 pigment in B. pterota. 



Diogenichthys. — Fig. I16E, F; eyes very narrow in preflexion 

 stage, less so in postflexion; photophores (Table 62); pigment 

 series on lateral gut and on postanal ventral midline, increasing 

 with development; spot at caudal fin base; pigment on tip of 

 lower jaw in D. laternatus; D. atlanticus has spot on trunk above 

 terminal gut flexure and pigment on symphyseal barbel. 



Fig. 1 18. Larvae of Myctophum. (A) M. phengodes. 9.8 mm; (B) M. asperum. 6.8 mm; (C) M. brachygnathum. 7.5 mm; (D) M. selenops. 7.8 

 mm; (E) A/, spinosum, 9.0 mm. From Moser and Ahlstrom (1974). 



Fig. 1 19. Larvae of Gonichthyini. (A) Loweina rara. 17.6 mm; (B) Tarletonbeania crenularis. 18.9 mm; (C) Gomchthys tenutculus. 1.1 mm; 

 (D) Centrobranchus choerocephalus. 7.3 mm. From Moser and Ahlstrom (1970). 



Fig. 120. Larvae of Lampanyctinae. (A) Notolychnus valdiviae. 8.7 mm; (B) Lobianchia dojleini. 8.2 mm; (C) L. gemellari. 6.7 mm; (D) 

 Diaphus theta. 6.9 mm; (E) D. pacificus. 5.2 mm; (F) Gymnoscopelus nicholsi. 23.5 mm. A-E from Moser and Ahlstrom (1974); F from Moser 

 and Ahlstrom (1972). 



Fig. 121. Larvae of Lampanyctinae. (A) Lampanyctodes hectoris. 1 3.0 mm; (B) Scopelopsis muttipunctatus. 1 3.4 mm; (C) Lampichthys procerus, 

 1 4.5 mm; (D) Notoscopelus resplendens. 11.2 mm; (E) Lampadena lununosa. 1 2.8 mm; (F) Taanmgichthys minimus. 1 4.4 mm. A from Ahlstrom 

 et al. (1976); B, C. F from Moser and Ahlstrom (1972); D and E from Moser and Ahlstrom (1974). 



