Bobtail squid are cephalopods belonging to the Monotypic taxon superfamily Sepioloidea of the order Sepiolida.
Sepiolids live in shallow coastal waters of the Pacific Ocean and some parts of the Indian Ocean and Atlantic Ocean as well as in shallow waters on the west coast of the Cape Peninsula off South Africa. Like cuttlefish, they can swim by either using the Cephalopod fin on their mantle or by jet propulsion. They are also known as "dumpling squid" (owing to their rounded mantle), "stubby squid", or "bottletail squid".
Light organ
Bobtail squid have a
symbiotic relationship with
bioluminescent bacteria (
Aliivibrio fischeri), which inhabit a special light organ in the squid's mantle. The luminescent properties of the bacteria regulate gene expression in the light organ.
The bacteria are fed a sugar and amino acid solution by the squid and in return hide the squid's
silhouette when viewed from below by matching the amount of light hitting the top of the mantle. This method of counter-illumination is an example of animal
camouflage.
The organ contains filters which may alter the wavelength of luminescence closer to that of downwelling moonlight and starlight; a lens with biochemical similarities to the squid's eye to diffuse the bacterial luminescence; and a mirror which directs the light .
Reproduction
Sepiolida are
iteroparous and a female might lay several clutches, each of 1–400 eggs (dependent on
species), over her estimated one-year-long lifetime.
The eggs are covered with sand and left without parental care.
[ Symbiosis with A. fischeri from the surrounding seawater is initiated immediately upon hatching, and the bacteria's colonisation of the juvenile light-organ induces morphological changes in the squid that lead to Sexual maturity.]
Classification
About seventy species are known. Sepiolid taxonomy within the Coleoidea cephalopods is currently controversial, thus their position is subject to future change.
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