Squilla

The title of this article is ambiguous. For the ancient Roman functionary see Marcus Gavius ​​Squilla Gallicanus (Consul 150) .

Squilla
Squilla empusa
Systematics
Class : Higher crabs (Malacostraca) Order : Mantis Shrimp (Stomatopoda) Subordination : Unipeltata Superfamily : Squilloidea Family : Squillidae Genre : Squilla
Scientific name
Squilla
Fabricius , 1787

The genus Squilla belongs to the mantis shrimp . Until the second half of the 20th century, almost all mantis shrimp were assigned to this genus. Today it still has 22 species (as of 2018).

features

They are relatively large mantis shrimp, with a body length of up to around 200 millimeters, but mostly only 150 millimeters, with the typical body shape of the order. Typical of the Squillidae are longitudinal keels on the entire body, in particular also a central longitudinal keels on the telson , which is also markedly thorn on the rear edge . The stalked eyes are T-shaped. The arched cornea is divided into two halves by a central band of hexagonal ommatidia, which consists of only two rows. The genus belongs within the order to the "spears", which impale prey organisms with the second maxillipedes that have been converted into catch legs.

The genus can be distinguished from other Squillidae by the combination of the following features: The body surface is smooth or slightly dotted. The eyes are noticeably wider than the eye stalks. The carapace is somewhat narrowed towards the front, it is keeled, and the central keel is often forked forwards. Its rear edge is concave, at most with an inconspicuous, rounded median process. Its front corners are always thorny. The lateral extension of the fifth thoracic segment is always simple, almost always designed as a spine bent forward. The dactylus (the movable member of the chela ) usually has six teeth (rarely five or seven), its propodus is incised in a comb shape with three movable teeth at the base. The abdomen is relatively compact, the first five segments have eight keels, the sixth six of them. The telson bears a central keel and three pairs of teeth on the edge, their submedians with immobile tips.

In the Mediterranean, is Oratosquilla massavensis , the only kind of comparable size, easily accessible from the here often occurring together with her Squills mantis distinguishable Squills mantis is excellent among other things, on the central keel on the Telson wearing also almost always two prominent dark spots.

distribution

The genus is common in the western and eastern Atlantic and eastern Pacific, with one species, Squilla mantis , also in the Mediterranean. In addition to this species, only two other species, Squilla biformis and Squilla cadenati , occur in the Eastern Atlantic .

Squilla species live on the seabed (benthic), in the shelf sea near the coast, usually on soft substrates, both on sand and on muddy bottom.

Species list

The genus currently includes 22 species.

• Squilla aculeata Bigelow , 1893. In two subspecies, subsp. aculeata on the American Pacific coast, subsp. calmani in the Atlantic, both on the American and African coasts.
• Squilla biformis Bigelow, 1891. American Pacific coast, from the Gulf of California to Peru.
• Squilla bigelowi Schmitt, 1940. American Pacific Coast, Gulf of California
• Squilla brasiliensis Calman , 1917. Atlantic coast of Brazil and Uruguay.
• Squilla cadenati Manning , 1970. African Atlantic coast.
• Squilla caribaea Manning, 1969. Caribbean, Gulf of Mexico.
• Squilla chydaea Manning, 1962. American Atlantic coast from Louisiana to Mexico.
• Squilla deceptrix Manning, 1969. American Atlantic coast from North Carolina to Brazil.
• Squilla discors Manning, 1962. American Atlantic coast, Brazil, Venezuela, Nicaragua, Bahamas.
• Squilla edentata (Lunz, 1937). American Atlantic coast, South Carolina, Texas, Gulf of Mexico to Suriname.
• Squilla empusa Say , 1818. Atlantic coast of North and Central America, from Maine to Suriname.
• Squilla grenadensis Manning, 1969. American Atlantic coast, Grenada and Brazil.
• Squilla hancocki Schmitt, 1940. American Pacific coast, Gulf of California to Peru.
• Squilla intermedia Bigelow, 1893. Caribbean.
• Squilla lijdingi Holthuis , 1959. American Atlantic coast from the Guyanas to Brazil.
• Squilla mantis ( Linnaeus , 1758). Type species of the genus. European Atlantic coast from Great Britain to Portugal, African Atlantic coast from Morocco to Gabon, Canary Islands, Mediterranean Sea.
• Squilla mantoidea Bigelow, 1893. American Pacific coast from Mexico to Peru.
• Squilla obtusa Holthuis, 1959. American Atlantic coast from Puerto Rico to Brazil.
• Squilla panamensis Bigelow, 1891. American Pacific Coast, Gulf of California to Peru.
• Squilla rugosa Bigelow, 1893. American Atlantic coast from Alabama to Suriname.
• Squilla surinamica Holthuis, 1959. American Atlantic coast from Suriname to Brazil.
• Squilla tiburonensis Schmitt, 1940. American Pacific Coast, Gulf of California, and Mexican Pacific Coast.

In addition, eight fossil species are known (many, including Squilla cretacea from the German Cretaceous, are no longer considered to belong today). The genus has been documented since the Eocene . With Squilla hollandi Förster, 1982 an Eocene species also occurs in Germany. Other finds exist from France, Italy and Spain in Europe, Angola in Africa and California in North America.

Taxonomy

The genus was first described by Johann Christian Fabricius in his work Mantissa insectorum in 1787, the type species is Cancer mantis L. Until a revision by Raymond B. Manning , the genus was a poorly characterized taxon in which almost all species of mantis shrimp worldwide were classified. Manning completely reorganized these and described numerous new genera for species that had been described in the genus Squilla . In the following time a number of other species were removed from the genus. The monophyly of the genus in its current definition (status: 2018) is also considered not to be certain.

According to phylogenomic analyzes, the superfamily Squilloidea turned out to be monophyletic . The taxon coverage is so far too low for an analysis of the genus.

supporting documents

1. ^ Raymond B. Manning: Stomatopod Crustacea of ​​the Western Atlantic. Studies in tropical Oceanography no.8. University of Miami Press, 1969. 380 pages.
2. ↑ ^{a b} Charles HJM Fransen: Stomatopods. In Kent E. Carpenter & Nicoletta De Angelis (editors): The living marine resources of the eastern central Atlantic. Volume 1: Introduction, crustaceans, chitons and cephalopods. FAO species identification guide for fishery purposes. FAO, Rome 2014. ISBN 978-92-5-106477-1 .
3. ^ Ch. Lewinsohn and Raymond B. Manning: Stomatopod Crustacea from the Eastern Mediterranean. Smithsonian contributions to zoology no. 305, 1980. 22 pages.
4. ↑ Shane Ahyong : Squilla, Fabricius, 1787 ( en ) WoRMS. August 30, 2013. Accessed January 1, 2018.
5. ^ Hans-Georg Müller: World catalog and bibliography of the recent Stomatopoda. Wetzlar, 1994. ISBN 978-3-930311-11-8 .
6. ↑ Shane T. Ahyong, Sylvain Charbonnier, Alessandro Garassino (2013): Squilla taulinanus n. Sp. (Crustacea, Stomatopoda, Squillidae) from the Burdigalian (Miocene) of Taulignan, south-eastern France. Boletín de la Sociedad Geológica Mexicana 65 (2) online
7. ↑ JC Fabricius (1787): Mantissa insectorum sistens eorum species nuper detectas adiectis characteribus genericis, differentiis specificis, emendationibus, observationibus. Tom. I. Scan of the first description at biodiversitylibrary.org
8. ↑ C. Van Der Wal, ST Ahyong, S.YM. Ho, N. Lo (2017): The evolutionary history of Stomatopoda (Crustacea: Malacostraca) inferred from molecular data. PeerJ 5: e3844 doi: 10.7717 / peerj.3844