Annotated Bibliography

Here is just a selection of the papers out there on this fascinating family of squid.

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Santos, M.B., G.J. Pierce, A.F. González, F. Santos, M.A. Vázquez, M.A. Santos, and M.A. Collins. 2001. First records of Taningia danae (Cephalopoda: Octopoteuthidae) in Galician waters (north-west Spain) and in Scottish waters (UK). Journal of the Marine Biological Association of the United Kingdom 81:355-356.

Taningia danae is a large squid that inhabits the deep ocean worldwide, though mainly tropical to subtropical water. There is evidence that paralarvae and juveniles are present in the mid North Atlantic from captured specimens and sperm whale stomach contents. However, are any post-juvenile or reproductively active individuals present in these waters as well?

Santos et al. report on the first records of specimens of Taningia danae from Galician and Scottish waters. A mature or maturing female was caught at 400 m from Galician waters, while a juvenile was caught at 800 m from the waters around Scotland. Both specimens were caught independently in trawls. Statoliths from the female were ground and examined to estimate age, and the contents of her stomach were inspected.

Estimates placed the female at 542 days old, and with a mantle length of 1.6 m and a weight of 61.4 kg. The juvenile was a mere 32 mm mantle length. From examination of the stomach contents it appears that the female was feeding on blue whiting, Micromesistius poutassou.

The positive identification of a post-juvenile Taningia danae, the mature or maturing female, is a first for these waters. These deep-water squid are rarely seen, making every opportunity to examine them valuable and insightful.
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González, A.F., A. Guerra, and F. Rocha. 2003. New data on the life history and ecology of the deep-sea hooked squid Taningia danae. Sarsia 88:297–301.

As a deep-water squid, most of Taningia danae’s habits remain a mystery. What does it eat? How or even where does it reproduce? The capture of three individuals in northern Spanish waters shed much light on their species and themselves.

Specimens were caught on the Carrandi fishing grounds of Spain between depths of 400 and 600 m by the pair trawler Boer. Full morphometric measurements were taken, statoliths were ground for aging, and the stomach contents and reproductive systems were examined.

González et al. describe the heaviest recorded female and the first mature male of T. danae, with the third specimen being another female. As the heaviest individual, the first female weighed 124 kg and measured 132.0 cm mantle length, with an estimated fecundity of 5 x 10⁶ oocytes. Both females appeared to have eggs at various stages of development. Strikingly, the male’s penis extended 23 cm outside of its mantle cavity, giving it a total length of 73 cm, and contained mature spermatophores. Two of the three stomachs contained food items, and comprised blue whiting, Micromesistius poutassou, crustacean exoskeleton, and hooks and beaks from squid of the genus Gonatus.

The capture of these squid supports the idea that post-juvenile and adult individuals are present this far north. The variable egg maturation demonstrated in both females is indicative of multiple spawning, which is not typical of shallow cephalopod species but is increasingly believed true for deep-water species. Additionally, capture at depths of 400 to 600 m is not contrary to the hypothesis that this is a bottom spawning species. Due to the presence of a large penis in males, González et al. concluded that males implant spermatophores in the mantle and arms of females as demonstrated in other similarly equipped squid species.

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Kubodera, T., Y. Koyama, and K. Mori. 2007. Observations of wild hunting behaviour and bioluminescence of a large deep-sea, eight-armed squid, Taningia danae. Proceedings of the Royal Society B 274:1029–1034.

Taningia danae is a large mesopelagic squid that is believed to occur commonly throughout tropical and subtropical waters, yet a living adult specimen has never been observed. The species is characterized by the presence of two large photophores borne on the tips of two of its arms. Given its preference for deeper water, what would this large predatory squid look like in the wild and how does it use its large photophores?

Kubodera et al. investigated this by deploying a high definition underwater camera system. The camera was baited with a bag of shrimp chum and a fresh Japanese common squid, Todarodes pacificus, and bore lights for illumination. The system was deployed at depths ranging between 240 and 940 m.

The resulting video footage showed individuals demonstrating attacking and bioluminescent behaviours. Consistent with its predatory nature, T. danae was shown to be an active swimmer, capable of speed bursts and quick direction changes. Light from photophores appeared in two forms: short flashes associated with a final attack sequence on the bait, and disjointed long glows suggestive of courtship behaviour.

Kubodera et al. provided the first footage of live adult T. danae in the wild. The footage showed that T. danae is an active predator and employs its photophores in a number of different behaviours. Flapping the large lateral fins provided most of the propulsion necessary, and its flexible body accommodated sharp direction changes.
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