#sepiolida

(Sources - 1, 2, 3, 4)

Order: Sepiolida

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

Propaganda under the cut:

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.

The stubby squid (Rossia pacifica), is a species of bobtail squid native to the northern Pacific Ocean, living in symbiosis with biolumininscent bacteria.

Photo by Clayton Moran | Info

You're Not Hallucinating. That's Just Squid Skin. | Deep Look

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.