Tuatara: Volume 15, Issue 2, July 1967
Luminescence in A Squid Moroteuthis SP. (Probably Ingens Smith), and A Possible Feeding Mechanism in the Sperm Whale Physeter Catodon L
Luminescence in A Squid Moroteuthis SP. (Probably Ingens Smith), and A Possible Feeding Mechanism in the Sperm Whale Physeter Catodon L.
During 1963-64 a total of 133 sperm whale stomachs were examined by the author and his assistants at the Tory Channel whaling station. Results obtained showed that a squid of the genus Moroteuthis (probably ingens Smith) made up 74.8 per cent by weight of the fresh squid species in the stomachs (Gaskin and Cawthorn, in press).
Observations made on the Cook Strait whaling grounds in the same period showed sperm whales making feeding dives lasting fifty minutes (Gaskin, 1964). Whaling company records for a sample of 177 sperm whales seen in full daylight show that only 11 of this number were making deep dives and bringing up squid and fish when sighted (Gaskin and Cawthorn, ibid.). Matsushita (1955), considered that sperm whales fed mainly at night. Uda (1959), showed that squid frequently sink into deep water during daylight hours and rise into the surface layers at night.
Luminescence in the Squid Moroteuthis sp.
In October 1964, Mr M. W. Cawthorn, formerly of the Fisheries Laboratory, Wellington made an interesting observation on the squid species mentioned above. A number of fresh squid taken from the stomach of a sperm whale had been left lying on the flensing deck at Tory Channel whaling station. Crossing the deck in darkness Mr Cawthorn noticed that the animals were glowing a bluish white, and that the light was visible for many yards.
Examination of this phenomenon could only be carried out briefly by matchlight. Cawthorn was able to determine that the luminescence could not easily be washed from the mantles of the squid, but came away readily on the hands. It was not being produced from specific ‘light organs’ and was not confined to any particular part of the squid mantles. It was not possible to discover if the light was caused by some property of the mucus covering the squid or by unicellular organisms held in suspension.
Another pertinent observation was made by Mr T. Norton, formerly gunner on the whale chaser Orca in the 1963-64 whaling seasons. He informed the author that on several occasions he had observed sperm whales rising towards the bow of the chaser in dark clear water, and that the pale skin around the angle of the jaw showed distinct luminescence.
Luminescence not produced from special light organs has been recorded in several groups of deep sea animals, including siphonophores, echinoderms, jellyfish and fish (Günther and Deckert, 1956, p. 162). These authors consider that in the latter case, the light source is a mucus which becomes luminescent on emerging from glands that produce it and then spreads over the skin of the fish. Generalised luminescence of the kind recorded by the present author does not appear to have been recorded previously for squid in available literature.
The size of squid taken by sperm whales varies considerably, but most are relatively small animals, from two to three feet in length (Clarke, 1956; Gaskin and Cawthorn, in press).
Although sperm whales make deep dives lasting fifty minutes or more it seems unlikely that all their food is obtained in this way. Daytime diving may be an indication that food is scarce. Sperm whales examined by the author at the New Zealand whaling station and in the Southern Ocean usually had stomachs full of fresh squid if captured early in the morning.
No study of the energy relationships involved in the feeding of sperm whales has been made, but the author has always considered it unlikely that such a large animal as a full-grown male sperm page 88 whale, weighing perhaps 50 tons, could conceivably chase separately every squid eaten. Considerable energy must be expended swimming down to depths of perhaps 500 fathoms, without taking into account actually chasing squid, which are fast-moving animals. The long narrow shape of the lower jaw of the sperm whale does not seem compatible with the capture of fast-moving prey at speeds of several knots. The jaw has little lateral movement.
If active feeding is discounted, a plausible method of passive feeding must be suggested. The luminescent mucus described above could easily be transferred to the lining of the sperm whale's mouth and act as a lure to attract more squid. If the mucus collected on or between the mandibular teeth the regular spacings might at a distance give the appearance of a fish or other animal with light organs along its flanks. Predatory squid or fish could be attracted to the light, and the sperm whale could lie almost motionless in the water and swallow the animals as they came to its mouth. The whale might have to capture a few squid actively before enough mucus accumulated.
Since squid are known to rise into surface waters during the night it is not necessary to postulate deep feeding dives by sperm whales to account for all the food taken. The feeding mechanism suggested above would work just as well near the surface at night as in very deep water in the daytime. Feeding near the surface would probably involve much less expenditure of energy than deep diving.
Clarke R., 1956. Sperm Whales of the Azores. Discovery Rep., 28: 237-98.
Gaskin, D. E., 1964. Recent observations in New Zealand waters on some aspects of behaviour of the sperm whale. Tuatara, 12: 106-14.
Gaskin, D. E. and Cawthorn, M. W., in press. The diet and feeding habits of sperm whales in the Cook Strait region. N.Z. Jl. Mar. Freshwat. Sci. 1 (2).
Matsushita, T., 1955. Daily rhythmic activity of the sperm whales in the Antarctic Ocean. (In Japanese, with English abstract). Bull. Japan. Soc. Sci. Fish., 20: 770-3.
Uda, M., 1959. The Fisheries of Japan. Report (mimeographed) for the Fisheries Research Board of Canada, Nanaimo Biological Station. 96pp.
Günther, K., and Deckert, K., 1956. Creatures of the Deep Sea. George Allen and Unwin Ltd, London. English edition, translated by E. W. Dickes 222 pp. illus. 140 figs.