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Euprymna tasmanica (Family Sepiolidae)

Southern Dumpling Squid

Distribution:

Southern Australia from Brisbane in the east to Shark Bay, Western Australia in the west. A very similar form also occurs across northern Australia (QLD, NSW, VIC, TAS, SA, WA).

Features:

A small round squid that reaches around 6 cm in length. The eyes are large and the pupil is a horizontal slit. A pair of large rounded fins are present on the rear third of the body. There are eight arms and two retractable feeding tentacles. The arms and the clubs of the feeding tentacles all bear numerous suckers, each armed with a toothed horny rim. There is no internal shell. Colour is generally iridescent green with large dark brown spots (chromatophores). The skin is smooth. The gill cavity (underneath the body) contains a large, butterfly-shaped light organ.

Ecology/Way of Life:

This squid lives in sand and mud in shallow coastal waters, often in association with seagrass meadows. It buries in the sand during the day, emerging at night to hunt for small shrimp and fish. It generally remains on the seafloor, only swimming for short hops. If flushed from the sand during the day, this squid has a unique means of camouflage and defense. The skin on the upper head and body is covered in mucous glands that can be used to glue a coat of sand over the whole animal. This allows the squid to swim around matching the sand background. If it is attacked it can quickly shed the sand coat using acid glands in the skin to dissolve the mucous. The squid jets away using the sinking sand coat as a decoy, leaving the attacker with a mouth full of sand. In effect, the squid has its own glue and anti-glue built into its skin.

At night, this squid uses a different way of remaining hidden. It has a light organ in its gill cavity. It contains special glowing bacteria that are fed sugars by the squid in return for making light. This is called a bacterial symbiosis. The squid uses this light to hide its silhouette as it swims around. The squid measures the amount of light coming from the night sky above and shows just enough light to make its underside invisible to the fish below. Each morning it spits out all the dead bacterial cells and grows up a new crop for the next night.

Adult males have a few very large suckers on their arms that may be used for fighting off other males or impressing females. Mating occurs by the male approaching the female from below and inserting a special upper arm into her gill cavity. He places sperm packets in a special pouch close to the opening of her single oviduct. If she has already mated, he uses strange biting suckers on his modified arm to destroy the previous male's sperm. Females lay round orange-cream eggs in clumps. The young hatch without a light organ and need to catch the correct bacteria from the seawater before they can grow one.

Interaction with Humans/Threats:

There is no recreational or commercial harvest of this small squid.

Further Reading:

Norman, M.D. and C.C. Lu. 1997. Redescription of the Southern Dumpling Squid Euprymna tasmanica Pfeffer, 1884 of southern Australian waters and revision of the Indo-West Pacific genus Euprymna (Cephalopoda: Sepiolidae). Journal of the Marine Biological Association, 77: 1109-1137.

Norman, M.D. and A. Reid. 2000. A guide to the squid, cuttlefishes and octopuses of Australasia. Gould League/CSIRO Publishing, Melbourne. 96 pp.

Norman, M.D. 2000. Cephalopods: A world guide. ConchBooks, Hackenheim, Germany.

Topics: Camouflage

Acknowledgments:

Text and photographs by Mark Norman, Museum Victoria.

Sponsorship welcomed:

Please Contact ABRS if you wish to discuss sponsoring this or other pages.


 

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