FISHERY BULLETIN: VOL. 76, NO. 3 



were captured either around 200 m or below 600 

 m. Apparently the size at which young begin their 

 descent to adult depths is rather variable. The 

 deep captures exhibit a clear pattern of ontogene- 

 tic descent. At 25 mm ML or larger all specimens 

 (excluding brooding females) were captured be- 

 tween depths of 975 and 1,425 m. Four females, 

 apparently brooding, were captured between 

 about 800 and 870 m. 



The pigmentation of the female changes as she 

 becomes gravid: the chromatophores over the 

 mantle and especially over the aboral surface of 

 the arms and web become more numerous, and the 

 oral surfaces of the arms and web develop an even 

 denser pigmentation. Nearly all iridophores are 

 lost. At the same time the arms and the web be- 

 come thicker. The web between the dorsal six arms 

 becomes more extensive, and the web between the 

 two ventral arms is reduced. These dark octopods 

 spawn and apparently brood their young (Young 

 1972b). Five specimens taken from horizontal 

 tows exhibited this increased pigmentation. In 

 four cases, the ovary was depleted, and in the fifth, 

 captured at 1,400 m, the eggs were not fully ma- 

 ture, but were considerably larger than in an im- 

 mature female of approximately the same size. In 

 two cases egg strings with developing embryos 

 were found in the same trawl with dark and pre- 

 sumably brooding females. 



No mature males were taken. However, judging 

 from the development of the hectocotylus, the 

 penis, and the spermatophore glands, two speci- 

 mens captured at 1,200 and 1,425 m were nearly 

 mature. Another slightly less mature specimen 

 was taken at 1,325 m. Three still less mature 

 specimens were taken between 1,175 and 1,200 m. 



while a large male taken at 1,025 m was the least 

 developed of all. 



Photosensitive Vesicles (Figure 44 A) 



The photosensitive vesicles consist of a single 

 pair of organs; each organ is a spherical vesicle 

 attached to the posterior margin of the stellate 

 ganglion. 



Japetella diaphana Hoyle 1885 



Vertical Distribution (Figure 45) 



Seventy-four specimens were captured. Diel 

 vertical migration does not occur. Specimens <20 

 mm ML were captured mostly in two regions, be- 

 tween 170 and 270 m and between 500 and 800 m. 



Oj 1 r— — I— — r- 



<^ • 



-1 1— I 1 1 r 





,t. 



Wo 



.w? 



% 



* o 



9 



II 



I . I 



® 



20 30 40 50 60 70 



MANTLE LENGTH, m • 



Figure 45. — Vertical distribution of Japetella diaphana. Cir- 

 cles with crosses represent brooding females. Double circles rep- 

 resent gravid females. Otherwise symbols as in Figure 1. 



*"^. 



\ 





STG 



STG 



Figure 44. — A. Section through the photosensi- 

 tive vesicle of adult Eledonella pygmaea. B. 

 Photosensitive vesicles ofAmphitretuspelagicus. 

 ST. G. — Stellate ganglion. Otherwise symbols as 

 in Figure 1. 



B 



606 



