Common Name: “bobtail squid”, “dumpling squid”, or “stubby squid”
Families: 1 - Sepiolidae
Anatomy: no internal shell; 8 small, suckered arms and 2 tentacles; rounded mantle; bioluminescent due to symbiotic bacteria
Diet: small crustaceans, mollusks, fish, and annelids
Habitat/Range: shallow coastal waters of the Pacific Ocean, some parts of the Indian Ocean and Atlantic Ocean, and on the west coast of the Cape Peninsula off South Africa
Evolved in: unknown
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Bobtail squid have a symbiotic relationship with bioluminescent bacteria (Aliivibrio fischeri), which live inside 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, camouflage the squid's silhouette when viewed from below by matching the amount of light hitting the top of the mantle. Symbiosis with A. fischeri from the surrounding seawater is initiated immediately upon the bobtail squid’s hatching, and the bacteria's colonisation of the juvenile’s light-organ induces morphological changes in the squid that lead to maturity.
Unlike most other cephalopods, Sepiolida are iteroparous and a female can lay several clutches, each consisting of 1–400 eggs (dependent on species), over her estimated one-year-long lifetime.
The Common Bobtail Squid (Sepietta oweniana) is known to have one of the shortest life spans among cephalopods. They can reach maturity in about 6–9 months.
Common Bobtails are estimated to begin declining due to climate change, as the waters during their reproductive seasons may be too warm for their eggs to develop.
Sepiolida. This order is made up of Bobtail squid, which has a round mantle. They have a light organ inhabited by bioluminisecent bacteria, which it uses to provide light below them to obscure its sillhouette.
Nautilida. This order is made up of nautilis, which have a unique planispiral shell, and move via jet propulsion. They're morphologically veyr similar to their ancient relatives, and are often called living fossils.
Closely related to cuttlefish, it’s no surprise that bobtail squid are masters of camouflage. These species have a special symbiotic relationship with a bioluminescent bacteria called Aliivibrio fischeri; the bacteria inhabit a special organ in the squid’s main body, and emit light to match the amount of light around it, thus hiding the squid’s silhouette. In return, bobtail squid provide their bacteria with a mixture of sugar and amino acids.
(Image: A hawaiian bobtail squid (Euprymna scolopes) by Doug Perrine)
The stubby squid (Rossia pacifica), is a species of bobtail squid native to the northern Pacific Ocean, living in symbiosis with biolumininscent bacteria.
The southern dumpling squid or southern bobtail squid (Euprymna tasmanica) is a bobtail squid that lives in the shallow (0.5 m to at least 80 m) temperate coastal waters of southern Australia's continental shelf. It lives for between 5 and 8 months and the adults can grow up to 6 or 7 cm long with a mantle length of 3 to 4 cm. They are found in seagrass beds or areas with soft silty or muddy bottoms from Brisbane on the east coast to Shark Bay on the west, as well as around Tasmania. Southern dumpling squid are nocturnal and hide during the day. Like other bobtail squid, southern dumpling squid have a light organ fueled by symbiotic bioluminescent bacteria. The light organ, which is butterfly-shaped, is situated in the mantle cavity and is used to cancel out the bobtail squid's silhouette.
You're Not Hallucinating. That's Just Squid Skin. | Deep Look
Octopuses and cuttlefish are masters of underwater camouflage, blending in seamlessly against a rock or coral. But squid have to hide in the open ocean, mimicking the subtle interplay of light, water, and waves. How do they do it? (And it is NOT OCTOPI)
Editing RNA may give cephalopods smarts, but there’s a trade-off.
Octopus, squid and cuttlefish don’t always follow the rules laid out in their DNA. Straying from prescribed genetic instructions may have increased the cephalopods’ thinking prowess, but comes at a cost, a new study suggests.
Once genes have been copied from DNA into RNA, these cephalopods heavily edit the genes’ protein-making directions, researchers report April 6 in Cell. The study involved a squid species, two octopus species and a cuttlefish species, all coleoids, or shell-less cephalopods. Each contained between 80,000 and 130,000 RNA sites that had been edited. This high level of editing contrasts with only 1,150 edited sites in RNA from a nautilus and 933 in a mollusk.
RNA editing changes one of the information-carrying subunits of RNA from the nucleotide adenosine to one called inosine. That substitution can change how a cell reads the genetic instructions to build proteins, exchanging one amino acid for another not specified by the DNA instructions. Generally, such tweaks to proteins have harmful effects, and evolution has gradually weeded out the changes. In the brains of humans and other mammals, fewer than 1 percent of RNA editing sites change protein-coding instructions.
But squid, octopus and cuttlefish edit about 11 to 13 percent of the protein-building RNAs in their brains, computational biologists Noa Liscovitch-Brauer and Eli Eisenberg of Tel Aviv University in Israel and colleagues discovered. Cephalopods edit RNA in other tissues, too, but not as much as in the brain.
Some genes contained multiple possible editable sites. Octopus and their brethren may edit all of the sites, or edit some but not others. Adding up all the edited and unedited combinations could produce hundreds to thousands of different versions of a protein within a cell. “It introduces immense complexity and diversity,” says Eisenberg.
All four coleoid cephalopod species share 1,146 editing sites in 443 proteins, the researchers discovered. Exactly why the species edit RNAs in the same place isn’t yet clear, but such sharing is a signal that editing at those sites was important in cephalopod evolution.
