GOPALAKRISHNAN: ZOOGEOGRAPHY OF NEMATOSCELIS 



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20" so- W SO" so- TO* W 90* IOC no- 120" 130* ►40' too- 



Figure 4. — Locality records and daytime abundance of larvae and juveniles of Nematoscelis gracilis and A^. megalops in the Indian 

 Ocean: b - SW Monsoon {jeriod. (Solid lines represent approximate distribution boundaries of N. gracilis and wavy lines represent those 

 of N. megalops . ) 



was during August and December. (In both areas 

 metanauplii were clearly underestimated.) A 

 Student's t -test carried out on means of develop- 

 mental stages during February, August, and De- 

 cember indicated that the frequencies of larvae in 

 the Bay of Bengal were significantly different 

 (P<0.01) from those in the Arabian Sea during 

 the same months. Frequencies during other 

 months were not significantly different between 

 the two populations. Since most of the develop- 

 mental stages were caught each month, it appears 

 that spawning is continuous; only the rate of pro- 

 duction is subjected to seasonal changes. 



The distributional patterns of the two forms of 

 A^. gracilis so far discussed are based on adults 

 caught from the upper 200-m layer. As pointed out 

 before, the vertical distribution of this species ex- 



tends much greater than this depth. Figure 7a 

 shows the distributions of new and old forms based 

 on deeper samples. Evidently these are similar to 

 those based only on the upper layer samples (cf. 

 Figures 5, 7a). Both forms were caught from the 

 same station only near the Equator, and inter- 

 mediate forms were found only at the areas of 

 overlap near the Equator. 



Atlantic Ocean 



Nematoscelis gracilis has not been reported 

 from the tropical Atlantic Ocean, nor was it found 

 in any collections examined during the present 

 survey. The only record from the Atlantic Ocean 

 was from the southwest coast of Africa (Lusiad 

 VII-IKMT, station 63-539, lat. 33°47'S, long. 



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