BATHYPELAGIC SQUID BATHYTEUTHIS 187 



the same phenomenon exists in the Humboldt squid, Dosidicus gigas. 

 Finally, our observations on Architeuthis, as sparse as they are, indi- 

 cate that the males mature at a much smaller size than the females, 

 and apparently they do not attain the larger size of the females. All 

 of these species are oceanic forms that live mostly in the upper water 

 layers. Until now information on size differences between sexes in 

 deep-sea forms has been entirely lacking. 



A priori it would seem that once the males of the forms mentioned 

 have fully developed spermatophores packed in Needham's sac, no 

 biological necessity would exist for attaining a larger size, so long as 

 small size did not render the males incompatible with the larger 

 females. 



Another presently unempirical possibility is that large males of B. 

 abyss/cola are able to escape the net, while females, all fully ripe at the 

 larger size, are unable to avoid capture. B. abyssicola, however, is gen- 

 erally a poor swimmer; it is not equipped for rapid motion, and it is 

 difficult to imagine that even the "sleek"' males could be significantly 

 more agile than the females to avoid being captured. 



5. Comparison of Antarctic and Gulf of Guinea Tows 



A rough estimate of the relative abundance of Bathyteuthis in differ- 

 ent parts of its range can be made by comparing trawl-catches between 

 two different regions. Midwater trawl tows were made during the two 

 cruises of the R/V Pillxhury to the Gulf of Guinea ; this material gives 

 the only available information that can be used to compare with the 

 Eltanin tows. Unfortunately, no vessel has conducted a survey that 

 adequately compares with the program on the Eltanin. Therefore, 

 the data from the Pillshiiry are offered only as a preliminai*y indica- 

 tion of relative abundance. 



Table XVI is a summary of tows and catches made by the Pillsbwry 

 in the Gulf of Guinea and the Eltanin in the Antarctic. In brief, the 

 PilUhury tows that were set at depths (300 to 3000 m) where B. abyssi- 

 cola might be caught were 17% successful ; in the Antarctic 52% of the 

 tows in the same depth range was successful. This figure includes 28 

 tows in less than 500 m where B. abyssicola normally does not occur 

 in Antarctic waters. The captures in the Gulf of Guinea averaged 0.21 

 specimens per total tows, while those in the Antarctic averaged 2.3 

 specimens per total tows, (The difference is even greater if the 300-500 

 m column is omitted.) Again, the Pillsbwry data are meager in com- 

 parison with the Eltanin data, but they reflect relative numbers of 

 B. abyssicola in Antarctic and Guinean waters. Eltanin tows were 

 three times more successful than Pillsbu/'y tows and they captured 10 

 times the number of spex-imens. This may be a i-easonable estimate be- 

 cause, although no data from other vessels are available, a great amount 



321-534 O— 69 13 



