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[Bobtail Squid Phylum: Mollusca] [Class: Cephalopoda] [Order: Sepiolida] [Superfamily: Sepioloidea]
Around 70 species of bobtail squid belong to the order Sepiolida. They are tiny marine animals (cephalopods) that display bilateral symmetry.
Check out these fascinating fun facts about bobtail squid, including where they live, what they eat, and how these stubby little bioluminescent creatures reproduce.
The family Sepiolidae contains some tiny bioluminescent cephalopods that are found in warm shallow coastal waters around the world, most notably:
The typical habitats for bobtails tend to be the neritic, intertidal zones down to depths approaching two hundred (200) metres, even though some species can tolerate deeper conditions over 1,000 metres below sea level.
Bobtail squids flourish best around sandy or muddy seabeds, coral reef formations, coastal lagoons, and seagrass beds.
This type of environment means they can bury themselves during the sunlight hours for effective camouflage and maximum protection.
Many of the fascinating characteristics of squid are reiterated in these small cephalopods. Even so, several unique traits, such as being shorter and rounder, help to set them apart from their close relatives, cuttlefish (Sepiida) and octopus (Octopoda).
Their body shape is small and they have a rounded mantle. But, unlike 'true squids', they lack any fin extensions and they do not have the familiar long tail.
Instead, they have a pair of small rounded fins on each side of the mantle, generally used for hovering and gentle swimming. They have eight (8) arms and two (2) retractable tentacles with suckers - used for capturing prey.
Here's the thing:
Having a combination of chromatophores, iridophores, and leucophores in the skin allows them to change colour in an instant, whether it's for camouflage or for signaling.
The most famous trait of the bobtail squid is the light-producing organ that contains symbiotic bacteria, more often 'Aliivibrio fischeri' which is a Gram-negative, rod-shaped bacterium.
It's used for counter-illumination camouflage, mainly by producing light on the underside to match the moonlight - and to hide their shadow from any predators that may be lurking below.
Idiosepius paradoxus (the pygmy squid) is considered as being the smallest of the bobtail species, with a mantle size of fifteen (15) millimetres (0.6 inches).
By comparison, the female Austrorossia australis is one the biggest of all bobtail squids, with a total mantle length of about 6.3 centimetres (2.5 inches).
Fun Fact: Some weird fish names come from a resemblance to other objects. The rounded mantle of the bobtail squid is the main reason why they're also called the 'bottletail squid', the 'dumpling squid', and the 'stubby squid'.
They have huge, well-developed eyes, which are ideal for hunting in low-light conditions. Despite their miniscule size, bobtail squids become efficient carnivorous predators at night, usually feeding on:
Interesting Fact: Stubby squid are mid-level predators that help to control excessive populations of fish larvae and small crustaceans. They are also an important food source in coastal food webs for other animals, such as marine mammals and seabirds.
The lifespan of the bobtail squid (Sepiolida) is short, typically less than twelve (12) months. As a consequence of that, and like most cephalopods, they tend to have rapid cycles of growth and reproduction.
Being dioecious animals means males and females are separate individuals with their own reproductive organs. So, the timing for the mating behavior usually occurs during the darkness, a time when bobtails are most active.
During the courtship ritual, males try to attract females by displaying major colour changes combined with specific body movements. It's also common for some species to signal their readiness by releasing pheromones.
Then...
The male uses a special arm (called a hectocotylus) to transfer packets of sperm (called spermatophores) into the mantle cavity or close to the mouth of the female.
Following a successful fertilisation, a female may lay hundreds of gelatinous or opaque white eggs in clusters, and attach them to discarded shells, rocks, sand grains, or underneath coral ledges.
It's a brief process that rarely lasts more than a few minutes. There is no parental care and the adults will die soon after mating and egg-laying - a phenomenon known as semelparity.
One of the surprising facts about squids is their high level of intelligence. Bobtail squids are clever also, and they are well-camouflaged. Still, they face a number of natural predators in their coastal habitats - and some human-related threats as well.
In the wild, their main predators are crabs, groupers, snappers, marine mammals (e.g., dolphins and whales), and sea birds (especially gulls and terns).
Some of the most significant threats to their long term survival are caused by human-related activities, such as:
Important: The International Union for Conservation of Nature (IUCN) does not see any specific risk for the population status of bobtail squids (superfamily Sepioloidea).
Note: The short video [2:31 minutes] presented by "Deep Marine Scenes" contains more bobtail squid facts and intriguing information about the googly-eyed stubby squid (scientific name Rossia pacifica).