YOUNG; VERTICAL DISTRIBUTION AND PHOTOSENSITIVE VESICLES 



Two species of the genus Abralia occurred off 

 Hawaii. A 6ra//a trigonura was a common vertical 

 migrator in the area sampled of the open ocean, 

 while A. astrosticta was never taken there. Ab- 

 ralia astrosticta seems to be a vertical migrator 

 that moves in close proximity to the ocean floor 

 (Roper and Young 1975). 



Two species of Mastigoteuthis were taken. Both 

 species shared the same day habitat at 700 to 800 

 m. At night, the population of M. inermis spread 

 upward in the water column 400 or 500 m. Al- 

 though the data were few, M. famelica appeared to 

 spread little or not at all. 



One of the clearest cases of habitat separation of 

 congeners occurred in Liocranchia . Liocranchia 

 valdiviae was taken in lower mesopelagic depths 

 during the day and it did not migrate. Liocranchia 

 reinhardti was taken in near-surface waters at 

 night and apparently occurred in upper 

 mesopelagic depths during the day. 



Although the octopods Japetella diaphana and 

 Eledonella pygmaea are placed in separate genera, 

 they are very closely related. Both were taken in 

 deep waters and did not migrate. The adults (ex- 

 cept brooding females) were taken at distinctly 

 different depths: E . pygmaea occupied depths from 

 975 to 1,425 m while J. diaphana occupied depths 

 primarily from 700 to 950 m. Young stages prior to 

 descent were found in near-surface waters. In this 

 habitat E. pygmaea was captured primarily at 200 

 m or just above while J. diaphana was captured 

 primarily below 200 m. Young stages of both 

 species in the process of descent occupied depths of 

 about 400 to 800 m or more. The data indicated, 

 however, that at any given size, except for those 

 just beginning descent, the young of £■. pygmaea 

 occupied greater depths than the young of J . 

 diaphana. 



In the geruis Abraliopsis three species were tak- 

 en: Abraliopsis sp. A and Abraliopsis sp. C form 

 the most closely related species pair. The available 

 data show no obvious habitat differences. Al- 

 though the more common Abraliopsis sp. A 

 reached a considerably larger size than species C 

 (43 mm ML vs. 33 mm ML), young individuals of 

 species A, however, apparently cooccurred with 

 species C of the same size. The day and night 

 habitats of Abraliopsis sp. B were not separable 

 from its two congeners. 



Three other groups of congeners were taken 

 (i.e., in Enoploteuthis , Histioteuthis, and 

 Chiroteuthis). No differences in habitats were 



found within these groups; however, the data were 

 extremely sparse. 



Reproduction 



Young ( 1972b) presented evidence for brooding 

 in Eledonella pygmaea (incorrectly reported as 

 Bolitaena microcolyla) and suggested that brood- 

 ing occurs in all pelagic octopods. Additional evi- 

 dence from the present study substantiated the 

 brooding habit for E. pygmaea. In addition, evi- 

 dence indicating brooding in the octopod Jape^e//a 

 diaphana was found. This species underwent 

 changes at maturity similar to E. pygmaea. 

 Further, newly hatched young have been found in 

 the same trawl with spent females, and in one case 

 the remnants of an egg string was found attached 

 to an arm sucker of such a female. 



In both species, gravid or near-gravid females 

 were taken only at the lower limits of the species' 

 vertical range. Although mature males were not 

 taken, those nearest maturity were also taken in 

 the lower parts of the depth range. Apparently, 

 mating takes place at the lower depth limits of the 

 population. Brooding females, on the other hand, 

 were found only at the upper limit of the adult 

 population in J. diaphana and only well above the 

 upper limit of the remaining adult population in 

 E. pygmaea. The brooding females of both species 

 occurred around 800 m. Presumably the females 

 migrate upward to around 800 m either just before 

 or just after spawning. The increased risk of pre- 

 dation above 800 m probably pi-events the female 

 from further upward movement: the numbers of 

 fishes increase greatly above 800 m (Amesbury 

 1975), and visual detection of the large silhouette 

 presented by a brooding female should be possible 

 above about 750 to 775 m (Young and Roper 1977 ). 

 The upward movement must be unrelated to feed- 

 ing since brooding females do not feed (Young 

 1972b). The upward migration may simply de- 

 crease the distance the young must travel after 

 hatching to their larval habitat near 200 m. 



A number of cephalopods may spawn at the 

 lower end of their depth range. Evidence for deep- 

 spawning was found in several vertically migrat- 

 ing species. A single spent female of Liocranchia 

 reinhardti was captured at 775 m at night, well 

 below its normal night habitat in the upper 200 m. 

 A single gravid, mated female of Brachioteuthis 

 sp. was captured at 1,125 m at night; its normal 

 night habitat is in the upper 200 m. Heteroteuthis 

 hawaiiensis migrated vertically and exhibited 



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