File:Stauroteuthis syrtensis - Image from page 46 of "The Biological bulletin".jpg

English: Title: The Biological bulletin

Identifier: biologicalbullet197mari Year: (s) Authors: Marine Biological Laboratory (Woods Hole, Mass. ); Marine Biological Laboratory (Woods Hole, Mass. ). Annual report 1907/08-1952; Lillie, Frank Rattray, 1870-1947; Moore, Carl Richard, 1892-; Redfield, Alfred Clarence, 1890-1983 Subjects: Biology; Zoology; Biology; Marine Biology Publisher: Woods Hole, Mass. : Marine Biological Laboratory Contributing Library: MBLWHOI Library Digitizing Sponsor: MBLWHOI Library

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Text Appearing Before Image: BIOLUMINESCENCE IN A DEEP-SEA OCTOPOD 37

Text Appearing After Image: Figure 10. Digiti/ed frames of in situ video of Stauroteuthis syrtensis: (A) bell posture; (B) distended balloon posture; (C) pumpkin posture (distinguished from the balloon posture by the fact the web is not fully inflated); (D) inverted umbrella posture; (E) animal twisting and opening its arms after ballooning. The highlights on the mantle in A. C, and E are reflections from the submersible lights. those described from videos of two other specimens ob- served by Vecchione and Young (1997). When first ap- proached. S. syrtensis is generally found with its arms spread in an umbrella or bell posture, with the mouth oriented either upwards or downwards (Roper and Brund- age, 1972; Vecchione and Young, 1997; Villeneuva et a!.. 1997). Since the animal almost certainly detects the rela- tively large and well-lit submersible well before itself being captured on video, it is difficult to know whether this is the natural posture or a defensive reaction. Given the assump- tion that the animals are in an undisturbed, non-withdrawal state when first filmed, their posture and the location of their photophores are consistent with the use of bioluminescence as a lure. As mentioned above, the wavelength of peak emission approximates the wavelength of maximum light transmission. This suggests that the emission spectrum of the photophores has been selected for maximum visibility. Finally, because the intensity of upwelling light is only a small percentage of that of downwelling light (Demon, 1990), animals bioluminescing in the mouth-up posture would be highly visible to potential prey in shallower depths. Collectively, these observations give credence to the idea that 5. syrtensis uses photophores to attract prey. Existence and evolution of photophores in octopods Aside from the present study, the only other conclusive evidence of bioluminescence in octopods is restricted to the breeding females of the family Bolitaenidae (Herring. 1988). However, the existence of light organs within suck- ers (at the base of the peduncle) has been suggested in the cirrate octopod C. nuimivi (Chun. 1910, 1913). As in the photophores of 5. svrtensis, these organs have a bright white appearance due to reflection from a connective tissue layer and are found in suckers that have many reduced traits compared to typical octopod suckers (Aldred et ui, 1983). Unlike the photophores of S. syrtensis, the postulated light organs of C. mtirmyi are not found within the sucker itself. In addition, the connective tissue layer is situated such that the produced light would be reflected into the tissue of the arm. After a complex subsequent study (Aldred et ai, 1978, 1982, 1983), Aldred et nl. (1984) tentatively interpreted the organs as unusual nerve ganglia (see also Vecchione, 1987). Because photophores and photocytes have a bewildering variety of morphologies (Buck, 1978; Herring, 1988), con- clusive determination of the presence or absence of light organs (which often emit only dim light) requires observa- tion of a healthy specimen in near-total darkness by a thoroughly dark-adapted observer (i.e., in near-total dark- ness for a minimum of 10 min) (Widder et ai, 1983). Owing to the bright lights of submersibles and remotely operated vehicles, bioluminescence is seldom observed in situ. In addition, since most bioluminescent animals produce light when disturbed, deep-sea cephalopods collected in nets generally have exhausted their light production by the time they reach the surface. Finally, observations of spontaneous luminescence are rare; most bioluminescent animals must be physically stimulated (often for a considerable period of time) before light is observed (Widder et «/., 1983). The evolutionary history of photophores in any animal group is extremely difficult to determine because biolumi- nescence has no fossil record (Buck, 1978). The evolution of bioluminescence in the coleoid cephalopods is particu- larly intriguing because of the extraordinary diversity and complexity of photophores in deep-sea decapods and vampyromorphs and their apparent rarity and simplicity in deep-sea octopods (Herring, 1988). However, biolumines- cence in the deep-sea octopods may not be as rare as previously assumed. For the reasons given in the previous paragraph, bioluminescence may be under-reported in the deep-sea octopods. Cirrothuuimi innrniyi and Cirroteitthis

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