YOUNG: VERTICAL DISTRIBUTION AND PHOTOSENSITIVE VESICLES 



Table 2. — Trawling time in minutes. Since trawls of two different sizes were used, a correction 

 factor of 0.6 was applied to the trawling times of the Tucker trawl to compute the adjusted total 

 trawling time. This factor represents the approximate difference in effective mouth areas of the 

 two nets. Open tows = timeofeach tow was assigned to one depth. Opening-closing tows = time 

 of each tow was apportioned among depth zones traversed by the trawl. IKMT = Isaacs-Kidd 

 midwater trawl. 



text. Specimens captured during twilight periods, 

 with a few exceptions, have also been excluded 

 from the charts. 



Species examined are listed in Table 3. Larvae 

 or juveniles of several additional species were cap- 

 tured but are not included in this study. These are: 

 Tremoctopus violaceus, Argonauta sp., Cranchia 

 scabra, Thysanoteuthis rhombus, Onykia sp. One 

 pelagic species reported from Hawaii by Berry 

 (1914), Iridoteuthis iris, was not taken. This 

 species belongs in the genus Nectoteuthis and 

 probably lives in association with the ocean floor. ^ 



Photosensitive vesicles of most species were 

 sectioned. Material was fixed either in 

 glutaraldehyde-osmium tetroxide or Bouin's so- 

 lution and was embedded in Epon 812^ or paraffin. 

 All vesicles sectioned contained cells with photo- 

 sensitive processes and, therefore, appeared to be 

 functional. In only a few cases did the general 

 histology of the organs add to our understanding of 



^Roper, C, and R. Young. Review of the Heteroteuthinae. 

 Unpubl. manuscr. 



^Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



their function. As a result, histological details are 

 not included for most species. 



In order to quantify the size of vesicles, an at- 

 tempt was made to obtain dry weights. Many types 

 of vesicles proved difficult to remove and clean 

 completely. Vesicles from a series of similar-sized 

 Pyroteuthis addolux, which are easily removed, 

 were weighed and found to vary by a factor of 1.5. 

 Because of the large individual variations and in- 

 accuracies due to difficulties in isolating many 

 types of vesicles, this method of quantification was 

 abandoned. As a result, camera lucida drawings of 

 photosensitive vesicles provide the only measure 

 of organ size: their relative size can be approxi- 

 mately determined by comparison with the brain 

 size. 



RESULTS 



Pyroteuthis addolux Young 1972 

 Vertical Distribution 



During the day, 39 specimens captured by the 

 Tucker trawl indicate a vertical range for this 



585 



