Tropical and subtropical waters of the Pacific and Indian Oceans, from southern Africa to the Galapagos Islands (NSW, VIC, TAS, SA).Features:
A soft-bodied squat squid of open ocean that reaches around 50 cm long. It has a conical body, small relative to the head and arms. It has rounded fins at the rear of the body, a large head and different sized eyes. The left eye of adults is considerably larger than the right. The shell is a thin transparent structure. This squid has eight large arms and two extendable feeding tentacles. The arms and tips of the feeding tentacles have suckers armed with horny, toothed rims. The common name comes from the regular scatter of small light organs over the body, head and arms, particularly under the body. The skin is generally pink to red with the light organs being blue and red. The skin is smooth.Ecology/Way of Life:
This deep-sea squid lives hanging midwater or near the seafloor, typically to depths of around 1000 metres. As for other members of this family, it is likely that this squid uses pockets of ammonia solution in its flesh to make it buoyant. The ammonia liquid is less dense than seawater and provides enough lift to make the animal float midwater. Many species of jewel squids show daily vertical migrations, rising to shallower waters at night to feed.
The most obvious feature of these squids is the regular light organs scattered over the body (see photo of species from Hawaii). These light sources are powered by chemical reactions that break down a chemical called luciferin. Jewel squids have evolved complex structures to house these light sources, complete with reflectors, lenses and colour filters. These squids use the light to hide their shadow from predators beneath them. The squids hang in the water at a 45 degree angle with the body up. At this angle all the light organs face downwards. The squid can adjust the light output to exactly match the weak light coming down from the surface above.
The uneven eye size in these squids relates to how they find their own food, mainly fish. The larger eye is used to look upwards for the silhouettes of other animals passing above them. The smaller eye keeps an eye out for predators by looking down at the same time. The large left eye of some species of jewel squid is telescopic like the Telescope Octopus.
Jewel Squids are important in the diets of sperm whales, dolphins, tuna and some pelagic sharks.
Little is known of the reproduction in these squids. Males have both upper arms modified for passing sperm packets to females.Interaction with Humans/Threats: There are no commercial harvests of this deep-sea squid. Its soft flesh and high ammonia content makes it unsuitable for human consumption. Further Reading:
Norman, M.D. 2000. Cephalopods: A world guide. ConchBooks, Hackenheim, Germany.
Text and map by Mark Norman, Museum Victoria; Photograph by Dick Young, Line drawing by K Hollis.Sponsorship welcomed:
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