8-424: Idiosepiidae Sepiolidae Bobtail squid (order Sepiolida) are a group of cephalopods closely related to cuttlefish . Bobtail squid tend to have a rounder mantle than cuttlefish and have no cuttlebone . They have eight suckered arms and two tentacles and are generally quite small (typical male mantle length being between 1 and 8 cm (0.39 and 3.15 in)). Sepiolids live in shallow coastal waters of
16-449: 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
24-603: Is elongate, obovate to cigar-shaped, with its posterior margin bluntly pointed at the distal tip. Their internal chitinous shell is vestigial, and the dorsal surface of the mantle has a unique oval adhesive organ, which secretes a sticky substance and is used to attach itself to seaweed or seagrass blades. The head is prominent while the arms are short. In males, both ventral arms are differentiated, but they are also different from each other. Females are generally larger and achieve sexual maturity later than males. Idiosepiidae have an Indo-west Pacific distribution, from South Africa in
32-660: 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 fins on their mantle or by jet propulsion. They are also known as "dumpling squid" (owing to their rounded mantle) or "stubby squid". Bobtail squid have a symbiotic relationship with bioluminescent bacteria ( Aliivibrio fischeri ), which inhabit
40-520: The pygmy squids , is a family of squids in the superorder Decapodiformes . They are the smallest known squids. It is the only family in the monotypic order Idiosepida and the monotypic superfamily Idiosepioidea . Phylogenomic analyses have shown that species in the family Idiosepiidae are sister to all other Decapodiformes . Idiosepiidae are the smallest known squids: males can grow to about 15 mm (0.6 in) and females to about 21 mm (0.8 in) in mantle length. The mantle
48-501: 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 reflector which directs the light ventrally . 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
56-416: 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 maturity . About seventy species are known. Sepiolid taxonomy within the coleoid cephalopods is currently controversial, thus their position is subject to future change. Idiosepiidae Idiosepiidae , also known as
64-606: The west to Japan and Russia in the east. They appear to be short-lived and have multiple generations per year. In temperate climates their population declines at the end of the warm season. They generally live in shallow water among seagrass and mangroves. They often adhere themselves to substrate, enabling camouflage and concealment during the day. They are solitary. Mating is promiscuous with multiple matings. Young individuals are planktonic. They appear to be sit-and-wait predators . They feed mainly on small crustaceans like Latreutes acicularis . The following genera are recognised in
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