Myctophum nitidulum 



Garman, 1899 



Fig. 57 — Myctophum nitidulum. female, 68.5 mm. 



Description 



D. 13 (12-14); A. 19 (18-20); P. 14 (13-15); AO 8 (6-10) -h 5 (4-7), total 13 -14(10-17); gill 

 rakers 6 (5-8) + 1 + 15 (12-18), total 20-22 (18-27— see discussion of variation); vertebrae 38 

 (37-39). 



SAO series in an essentially straight, steeply oblique line; SAO, over or slightly behind 

 VO4. Pol nearly under or slightly before end of adipose base. Exposed margins of scales smooth; 

 posterodorsal margin of operculum distinctly angulate, often more or less recurved; this angu- 

 lation is discernible in specimens as small as 20 mm. 



Supracaudal glands of males with 5 to 8 (3-6 in eastern tropical Pacific area) rather 

 triangular, overlapping luminous scales; infracaudal glands of females with 2 to 6 small, 

 round to oblong spots; in each sex the luminous scales are evident at about 35 mm. 



Size: To about 75 mm. 



Least depth of capture: At surface at night. 



Distribution: Myctophum nitidulum is widespread throughout the warmer waters of the 

 Pacific Ocean, and perhaps in the Atlantic and Indian Oceans. The localities shown in Fig. 58 

 represent only those specimens examined by me, for reasons discussed below. The southern 

 parts of the Pacific are too poorly collected to warrant firm statements of occurrence of the 

 species. Whitley (1968) did not include the species in his checklist of fishes from the New 

 Zealand area. Craddock and Mead ( 1970) reported two adults taken off Chile, at 30°59' S, 

 92°28' W. 



A hiatus in the distribution of M. nitidulum occurs in the eastern Pacific Ocean westward 

 of the coasts of Mexico and Central America, from about 25°-05° N and about 120°-125° W (Fig. 

 58). This broad area has been repeatedly collected with surface and subsurface nets without 

 taking the species. The area corresponds roughly with the region of very low oxygen concen- 

 trations (0.25 to 0.50 ml/1) as delineated by Wyrtki ( 1967), 



Discussion 



For at least the past 50 years the name Myctophum affine has been applied by most 

 authors to the species herein referred to as M. nitidulum. The following brief account is 

 intended as an aid in clarifying the current status of that name. 



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