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Berry's Bobtail Squid (Euprymna berryi) photo by Rokus Groeneveld

I have written before about the beautiful cuttlefish (marine mollusks of the order Sepiida). Cuttlefish are closely related to another order of mollusks, the Sepiolida, or bobtail squid, which are perhaps even more endearing.  With huge expressive eyes, tiny little tentacles, and opalescent skin, bobtail squids look like they were designed by a Sanrio artist having a strange day.  Sepiolida cephalopods appear to be all head (they are also known as dumpling squid or stubby squid because of this shape)–and their large rounded navigation fins, which stick out like Dumbo’s ears only add to the impression.   Members of the Sepiolida do not have cuttlebones but they are far more similar to cuttlefish than to other squid—perhaps their taxonomical classification will change as they are better understood.

Southern Dumpling Squid (Euprymna tasmanica) photo by David Mitchell

There are approximately 70 known species of bobtail squid living in the shallow coastal waters from the Mediterranean, to the Indian Ocean, to the Pacific.  To quote the Tree of Life Website, “Members of the Sepiolida are short (mostly 2-8 cm), broad cephalopods with a rounded posterior mantle.” The animals are gifted hunters which eat shrimp, arthropods, and other small animals which they chomp apart with a horny beak at the center of their arms. During the day, bobtail squid bury themselves in the sand with only their eyes protruding and then they hunt at night.  Certain species of bobtail squid are known to be poisonous, like the lovely Striped Pyjama Squid (Sepioloidea lineolata).  This poison is not well understood and may be contained in the slime produced by the creatures.

Striped Pyjama Squid (Sepioloidea lineolata) photo by Tony Brown

Bobtail squid are bioluminescent and they use this ability to disguise their profile when viewed from below–a helpful sort of camouflage which serves them as predators and prevents them from becoming prey.  Young bobtail squid are not born with the bioluminescent bacteria but must capture them from the water column in order to start the symbiotic colony within their own bodies.  The symbiotic relation between the bobtail squid and the bacterial colony has been much studied in the laboratory.

Bobtail Squid (photo by Adam Minu)

It was thanks to such studies that scientists first began to understand the method through which bacteria communicate with each other.  Called “quorum sensing”, such communication takes place within a group of bacteria by means of signaling molecules.  The chemical conversations allow bacteria to respond quickly and in aggregate to changes in their environment (to such a degree that a bobtail squid can tell the bacteria within its own tissues how much to fluoresce and can thereby determine its own luminosity by communicating with millions of living entities inside itself).  I have written before about how critical bacteria are to the planet and the Earth’s ecosystem.  Studying the bobtail squid provided the first understanding of the way that bacteria communicate with each other, but we are now beginning to suspect that such communication might take place on a vast—perhaps even a global—scale.

Juvenile Common Botail Squid (Sepietta oweniana)


Ye Olde Ferrebeekeeper Archives

September 2011