Squilla Discors

''Squilla'' is a genus of mantis shrimp, whose first appearance in the fossil record came 145 million years ago. They are found in marine habitats in tropical and sub-tropical climates all over the world, though they exist in high concentrations around the Indian Ocean and Mediterranean sea. They are often caught unintentionally by fisheries in their climate, and they are not used for human food or fish meal, though valuable compounds such as chitin and chitosan can be extracted from their shells. This genus includes the following species:

*'' Squilla aculeata'' Bigelow, 1893
*'' Squilla biformis'' Bigelow, 1891
*'' Squilla bigelowi'' Schmitt, 1940
*'' Squilla brasiliensis'' Calman, 1917
*'' Squilla cadenati'' Manning, 1970
*'' Squilla caribaea'' Manning, 1969
*'' Squilla chydaea'' Manning, 1962
*'' Squilla deceptrix'' Manning, 1969
*'' Squilla discors'' Manning, 1962
*'' Squilla edentata'' (Lunz, 1937)
*'' Squilla empusa'' Say, 1818
*'' Squilla grenadensis'' Manning, 1969
*'' Squilla hancocki'' Schmitt, 1940
*'' Squilla intermedia'' Bigelow, 1893
*'' Squilla latreillei''
*'' Squilla lijdingi'' Holthuis, 1959
*'' Squilla mantis'' (Linnaeus, 1758)
*'' Squilla mantoidea'' Bigelow, 1893
*'' Squilla obtusa'' Holthuis, 1959
*'' Squilla panamensis'' Bigelow, 1891
*'' Squilla parva'' Bigelow, 1891
*'' Squilla rugosa'' Bigelow, 1893
*'' Squilla surinamica'' Holthuis, 1959
*'' Squilla tiburonensis'' Schmitt, 1940

Physiology

''Squilla'' are small marine organisms, with a size range of 40-70mm. The males and females tend to be the same size. All the different species possess a form that is typical of most other Stomatopods, consisting of extended eyestalks, a rostrum, carapace, and a raptorial claw used for hunting.

All ''Squilla'' possess a bilaterally symmetrical body Additionally, ''Squilla'' have developed a nauplius eye, which is an eye that is composed of three to four pigment ocelli. Likely, this eye only allows the organism to determine the location of a light source. This means species within the ''Squilla'' genus have poorer eyesight than their more famous counterparts of the '' Odontodactylus'' genus, which can see more colors than even humans.

Synapomorphies

Though the many species of the ''Squilla'' genus vary greatly in location, they are all defined by a few common shared traits. One of those notable ones is the number of teeth on their claw, which tends to be of a middling size. Because ''Squilla'' lack a calcified appendage like some of their fellow Stomatopods, they cannot break open hard shells, and thus catch largely soft bodies prey for food. The claw of the ''Squilla'' genus is known to have six teeth. Another defining trait is the lack of a raised ridge in the exoskeleton of ''Squilla''—or rather, the extension of the ridge over the entire exoskeleton, as such creating the appearance of the lack of a ridge. Often referred to as a "carina", this ridge can be used to differentiate ''Squilla'' from other similar Stomatopods.

Aside from these major features used to differentiate ''Squilla,'' other features include a tail plate with four to six spines, unlike the fused tail plates found in other Stomatopods, and shorter antennular peduncles, which are the structures at the base of the shrimp's antennae that attach them to their head.

Feeding strategy

''Squilla'' are predatory benthic burrowers. They dig holes in the sand, hide, and await soft bodied prey that they are able to snatch up with their relatively weak claw. This means that, unlike other genuses of Stomatopods, ''Squilla'' cannot typically consume prey with hard shells. However, their burrowing strategy makes them a bio-diffuser, as they engage in ecosystem engineering that scatters organic and inorganic particles about the ocean floor. They tend to prey on other benthic organisms such as worms, krill, small fish, and even other species of ''Squilla'' when they are able. Despite their small size, ''Squilla'' has found great success with their strategy, as they have been around for over one hundred million years and have diversified into over a dozen different species.

Life Cycle and Reproduction

''Squilla'' go through a five stage maturity cycle of immature, early maturation, maturation, ripe, and spent, with their life cycle ending shortly after they reproduce. Their life cycles are short, being only eighteen months at the longest, and their reproduction season begins in spring, with most females going from maturation to ripe in winter and ending their life cycle spent in summer. In the studies that determined this, the stage of a female's life cycle was determined by how much space her ovaries consumed in regards to her entire body mass. In spring and summer, females tend to hide in galleries and tend to their eggs, leading to fisheries to catch more males. But in autumn, the females will leave the galleries and become more vulnerable to being caught by humans.

Bioactive compounds extracted from ''Squilla''

Though ''Squilla'' offers little nutritional value due to its very small size, the compounds chitin and chitosan are able to be extracted from ''Squilla'' exoskeletons, as is the case with many crustacean species. Chitosan, in particular, has been found to reduce blood plasma levels of HDL in humans, as well as protect against the growth of some microorganisms, most notably ''Candida'', which is a genus of yeasts''.'' New research has also demonstrated that chitosan produced from ''Squilla'' shells may also be beneficial in fighting fungus infections and cancerous growths.

These chemicals are extracted by first collecting large amounts of various ''Squilla'' species, which is often done unintentionally by fisheries who catch ''Squilla'' in their net while fishing for other larger species. These catches are then shelled, and the shells are put through multiple chemical treatments, including demineralization, decolorization, deproteinization, and deacetylation, before they can become finished commercial grade chitosan.

References

{{Taxonbar, from=Q3859898

Stomatopoda