GOPALAKRISHNAN: ZOOGEOGRAPHY OF NEMATOSCELIS 



APRIL 16 - OCTOBER 15 

 (NIGHT STATIONS) 



Number of ADULTS per ca. 200m' ' 



Nematoscelis gracilis 

 old form" "new form" "intermediate form* 



• 1-24 © 1-24 <^ 1-24 



• 25-224 25-74 

 ^ >225 



N mega/ops 



■f-J^W 



20" 3CP 40* W 60' 



80* 90" 100" 



10* l?0* 150- -40* ISO* 



Figure 5. — Locality records and nighttime abundance oi Nematoscelis gracilis and N. megalops adults in the Indian Ocean: b - SW 

 Monsoon period. (Solid lines represent approximate boundaries of distribution o{N. gracilis "old form," broken lines represent those of 

 "new form," and wavy lines those of A^. megalops. ) 



water is evident from these comparisons. 

 Nematoscelis gracilis old form is the dominant 

 Nematoscelis species occurring in the eastern 

 tropical Pacific. Along the coasts of Peru and Chile 

 this form is now known to be distributed as far 

 south as lat. 33°S (personal observation in a sam- 

 ple collected by Antezana). Only old forms were 

 found in the China Sea and in oceanic waters of 

 the Kuroshio system. However, the new and old 

 forms cooccurred in the Timor, Banda, Celebes, 

 Halmahera, and Molucca seas. The Indian Ocean 

 populations of both forms are therefore in con- 

 tinuity with those of the Pacific. In the Pacific the 

 eastern and western populations of the species as a 

 whole are linked along the equatorial zone be- 

 tween lat. 0° and 10°N (Brinton, 1962). Brinton 

 has pointed out that the lat. 20°N-20°S range of iV. 



gracilis in the east and the lat. 10°N-10°S range in 

 the west corresponds reasonably well to the range 

 of the equatorial water mass (Sverdrup, Johnson, 

 and Fleming, 1942). 



Geographical Distribution of 



N. megalops 



Indian Ocean 



Nematoscelis megalops was recorded during the 

 IIOE between lat. 30°S and 45°S. This is the area 

 of transition between subantarctic and Indian 

 Central water (Sverdrup et al., 1942). The number 

 of samples collected from this zone is too scanty to 

 permit a seasonal study. Larvae, juveniles, and 

 adults were caught during both seasons along the 



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