Southern Bobtail Squid

Members of this genus can glue sand grains to their upper body to aid camouflage with their environment.

Identification

Each arm possesses four rows of suckers, with mature males having enlarged suckers on the inner and outer rows or arms 2-4. A saddle-shaped bacterial light organ is present inside the mantle cavity.

Habitat

Euprymna tasmanica lives on sand and mud areas, often in association with seagrass beds. They are found up to depths of at least 80m.

Distribution

Southern Indo-Pacific: found in Australian waters from Brisbane south around to Shark Bay.

Feeding and diet

E. tasmanica emerges at night to forage for crustaceans and fish.

Other behaviours and adaptations

The light organ is used at night to cancel out their silhouette from predators on the seafloor. The organ is filled by luminescent bacteria that are trapped from the seawater by the organ.

Like other species in the genus Euprymna, E. tasmanica bury themselves in the seafloor during the day and use their second pair of arms to rake sand grains over its head and body. The entire upper surfaces of their skin contain two very special cell types. One acts like a glue, holding a coat of sand over the body- so that even if flushed out of the sand by a predator the sand will remain. The second are special acid cells that can be used to disconnect the entire sand coat at once- leaving it as a sinking decoy for a predator while the squid jets away.

Breeding behaviours

Spawning typically occurs in spring and summer months when females lay pale orange eggs in loose clumps, usually at the base of seaweeds or seagrass. Hatchlings will quickly settle to the seafloor and bury in the sand. Young hatch without the bacteria needed for their light organ and must obtain this from the water column.

References

• Jereb, P., & C.F.E Roper (eds) (2005) Cephalopods of the World: Chambered Nautiluses and Sepioids, Food & Agriculture Organization of the United Nations Catalogue for Fishery Purposes, Rome, No. 4, Vol. 1
• Norman, M., (2000) Cephalopods- A World Guide, ConchBooks, Germany (Hackenheim)
• Norman, M & A. Reid., (2000) A Guide to Squid, Cuttlefish and Octopuses of Australasia, CSIRO Publishing, Victoria (Collingwood)