FISHERY BULLETIN: VOL. 72. NO. 2 

 Table 3. — Sequence of photophore formation in larvae of two species of Diaphus. 



Species 



Size 

 larva 



(mm) 



Photophores 



No. of 



photophore 



pairs 



Smallest 



luvenile 



(mm) 



deep-bodied, have large broad heads, and are eas- 

 ily identified by their unique wing-shaped pec- 

 toral fins (Figure 9C-E). The larvae of all three 

 species are heavily pigmented and develop the 

 Br2, POi , and PO5 photophores sequentially. In L. 

 urolampus (Figure 9C) and L. gemellari (Figure 

 9D) the eyes are large and nearly round and the 

 lower pectoral rays are delayed in developing. In 

 L. dofleini the lower pectoral rays develop along 

 with the produced upper rays and the eye is com- 

 pletely different (Figure 9E). With its narrow el- 

 liptical shape and unique squarish mass of choroid 

 tissue, it is the single obvious exception to the rule 

 of narrow eyes in the subfamily Myctophinae and 

 rounded eyes in the Lampanyctinae. All other lar- 

 val characters identify this species as a Lobian- 

 chia, and we conclude that the narrowing of the 

 eye in this species occurred independently as a 

 secondary adaptation. 



In our view the tribe Lampanyctini contains the 

 genera Lampanyctus, Triphoturus, Steno- 

 brachius, and Paruilux. As recently as Fraser- 

 Brunner's (1949) review of the family Myc- 

 toi)hidae, Lampanyctus was still a catchall genus 

 with a number of disparate subgenera. Since then 

 the subgenera Stenobrachius, Triphoturus, and 

 Lepidophanes have been removed from Lam- 

 panyctus and afforded generic status. Lepido- 

 phanes has been further split into the genera 

 Lepidophanes and Bolinichthys. All of the 

 separated genera have distinctive larval morphs. 

 With their removal, the species oi Lampanyctus 

 form a more coherent assemblage of 40-50 species, 

 and despite the diversity of larval specializations 

 encountered in the genus, there is a central morph 

 and pattern of larval development. 



Lampanyctus larvae are deep-bodied and 

 bigheaded. In older larvae characteristic pigment 

 can develop at a variety of locations such as the tip 

 of the lower jaw, between the eyes, the back of the 

 head, the side of the head, the adipose fin, the 



pectoral fin, internally in the region of the 

 cleithra, and along the myosepta. The pigment 

 patterns are of prime importance in identifying 

 the larvae to species. 



There are several rather distinct larval types in 

 Lampanyctus. One of these consists of a group of 

 species whose adults are characterized by having 

 the pectoral fins much reduced or even absent, and 

 has been separated recently as a distinct genus 

 Paralampanyctus by Kotthaus (1972) with P. 

 niger as type. Previously, Giinther (1887) had 

 proposed the generic name Nannobrachium for 

 this species and this has priority over Paralam- 

 panyctus (John Paxton, pers. commun.). There is a 

 remarkable trend of jaw specialization in the lar- 

 vae of this group (Figure 10). The larva of L. ritteri 

 has jaws of moderate length and the other species 

 shown have progressively longer jaws with more 

 prominent teeth, particularly anteriorly. This 

 trend culminates in the larva of Lampanyctus sp. 

 (possibly achirus) which somewhat resembles a 

 larval billfish. This species will lack the pectoral 

 fin in juveniles and adults, even though it is well 

 developed in the larvae. The pectoral fins are also 

 large inL. regalis andL. niger larvae, but will be 

 small and weakly developed in adults. This dis- 

 parity is even more apparent in another eastern 

 Pacific species, which lacks pectoral fins as an 

 adult, but whose larvae have the largest pectoral 

 fins with the highest number of rays that we have 

 encountered among Lampanyctus larvae. Other 

 less spectacular specializations appear in the 

 other subgroups 0^ Lampanyctus, but it appears 

 that the larval characters will be helpful in 

 defining the species composition of the several 

 subgenera. 



Representatives of other genera of Lampanyc- 

 tini, Triphoturus, Stenobrachius, andParvilux are 

 illustrated in Figure llA-C. Small larvae of 

 Triphoturus and Stenobrachius have a row of 

 melanophores along the ventral margin of the tail 



406 



