Based on the criteria provided by Gibbs and Bolin, I have found only M. nitidulum among 

 hundreds of specimens from throughout the Pacific Ocean and from much of the Indian Ocean. 

 Becker (1967b), however, reported one occurrence of M. affine from the southwestern Pacific, 

 at Lord Howe Island, and at the same time indicated the occurrence of M. nitidulum in the 

 tropical Pacific. As the south-central and southwestern Pacific Ocean is still rather in- 

 adequately collected or reported on, it is not certain that the true M. affine (as restricted by 

 both Gibbs and Bolin) does not occur here, or perhaps elsewhere in the Pacific. For this reason 

 the localities for M. nitidulum shown in Fig. 58 represent only specimens examined by me. 



Variation: The numbers of total gill rakers (Table 10) indicate the existence of several 

 populations (or one highly variable population) of M. nitidulum in the Pacific Ocean, and 

 particularly the eastern equatorial area. Specimens from this area, bounded roughly by about 

 05° S to 10° N, 70° to 150° W, have significantly higher numbers of total gill rakers than those 

 from other areas of the Pacific and from the Indian and Atlantic Oceans. Also, in the eastern 

 equatorial region many specimens bear both supracaudal and infracaudal luminous glands, 

 the scales in the supracaudal glands of all males from the area being fewer (3-5) than in other 

 areas (5-9). Corollary to the higher numbers of gill rakers is an increase in numbers of AO 

 photophores and vertebrae, but to a lesser degree of significance. 



Table 10. Numbers of Total Gill Rakers for Myctophum nitidulum from Selected 

 Areas of the Pacific Ocean and from the Indian and Atlantic Oceans 



Area 17 18 19 20 21 22 23 24 25 26 27 N Mean 



Pacific Ocean 

 07°-28° S, 



Coast to 1 14° W 1 



IS'-SS" N, 



Coast to 1 22° W - 



10° -40° N, 



135°-170° W 

 Japan area — 



Equatorial area 

 05°-08° N 



75°-85°W _ _ _ 1 24 24 11 8 1 — — 69 22.06 



86°-99°W _ _ _ 1 4 16 52 72 29 2 2 178 23.66 



100°-129°W _ _ _ _ 1 8 22 58 49 30 2 170 24.44 



130°-150°W ___ 2 20 8 — — — — — 30 21.20 



South-Central Pacific 

 27°-28° S, 

 157°-159°W 3 5 3 ________ n 18.00 



Indian Ocean — — 1 7 42 20 — — — — — 70 21.16 



Atlantic Ocean — 18 31 12 8 — — — — — — 69 19.14 



64 



