Diaphus termophilus 



(Taning, 1928) 



Fig. 86 — Diaphus termophilus, female, 48.0 mm. 



Description 



D. 13-14; A. 15-16; P. 12-13; AO 5-6 4- 4-5, total 10 (9-11); gill rakers 7 (6-8) + 1 + 12-13 

 (14), total 20-21 (19-22); vertebrae 35. 



PLO about over pectoral origin, or slightly behind, and much nearer that origin than to 

 lateral line. VLO variously over bases of inner pelvic rays or on a point between there and base 

 of outer ray. SAO series usually straight, occasionally slightly curved or angulate, and evenly 

 spaced; SAO2.3 interspace usually no more than a half (rarely a full) photophore diameter 

 wider than that between SAO, ;... SAd about half its diameter above level of VO-,. First and 

 last AOa elevated above level of adjacent AOa by about half their diameters, seldom by more. 



Dn usually smaller than Vn, not deeply embedded. Vn variable in form (see Discussion ); 

 several tiny dots of luminous (?) tissue are lightly embedded in a thin streak of dark tissue 

 anterior to Vn along anteroventral margin of orbit. Luminous scale at PLO small, somewhat 

 elongate, weakly formed, the tissue in almost vertical, slightly wavy lines. 



Size: To about 50 mm. 



Least depth of capture: To 100 m at night. 



Distribution: In the eastern Pacific Ocean D. termophilus appears to be confined to the 

 equatorial region (Fig. 87). Clarke (1973) did not report the species from near Hawaii. Appa- 

 rently D. termophilus occurs near Australia, for J. R. Paxton (personal communication) stated 

 that specimens at the Sydney Museum were D. termophilus rather than the related species D. 

 trachops and D. similis. 

 Discussion 



Specimens of Diaphus termophilus from the eastern Pacific Ocean agree rather well with 

 the diagnosis of the species given by Nafpaktitis (1968), based on North Atlantic material, 

 except in numbers of gill rakers; that author listed 8 (rarely 9 or 7) + 15 (14-16), total 23-25 

 (rarely 26). The somewhat higher count of gill rakers for the North Atlantic material may 

 indicate a specific difference, but until further studies are made, the name termophilus is 

 retained for these specimens from the eastern Pacific Ocean. 



In addition to the possible interocean differences, there is an interesting variation in 

 structure of the Vn in Pacific specimens. Two basic forms of Vn occur: One (Fig. 88, Form A) is 

 rather full bodied and horizontally elliptical, the tissue in rather coarse horizontal striations, 

 the general aspect closely resembling the Vn shown by Nafpaktitis (1968, p. 56, fig. 32). A 

 second type of Vn (Fig. 88, Form B) is vertically elliptical, finely striated horizontally, and does 

 not fill the total space in the outline of the organ, the posterior area usually being covered with 

 a thin layer of reflective tissue. Specimens with the Vn as in Form A were taken in the eastern 



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