Afrololigo

Afrololigo
Scientific classification
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Cephalopoda
Order:	Myopsida
Family:	Loliginidae
Genus:	Afrololigo ; Brakoniecki, 1986
Species:	A. mercatoris
Binomial name
	Afrololigo mercatoris; (Adam, 1941) [1]
Synonyms [1]
	Lolliguncula mercatorisAdam, 1941

Last updated March 06, 2019

Afrololigo mercatoris, commonly known as the Guinean thumbstall squid, is a small species of squid in the family Loliginidae from the eastern central Atlantic Ocean. It is the only species in the monotypic genus Afrololigo.

Squid are cephalopods in the superorder Decapodiformes with elongated bodies, large eyes, eight arms and two tentacles. Like all other cephalopods, squid have a distinct head, bilateral symmetry, and a mantle. They are mainly soft-bodied, like octopuses, but have a small internal skeleton in the form of a rod-like gladius or pen, made of chitin.

Family is one of the eight major hierarcical taxonomic ranks in Linnaean taxonomy; it is classified between order and genus. A family may be divided into subfamilies, which are intermediate ranks between the ranks of family and genus. The official family names are Latin in origin; however, popular names are often used: for example, walnut trees and hickory trees belong to the family Juglandaceae, but that family is commonly referred to as being the "walnut family".

Loliginidae, commonly known as pencil squids, is an aquatic family of squid classified in the order Myopsida.

Description

Afrololigo mercatoris is a relatively small species of squid where the females reach a mantle length of 50mm and the males attain 35mm. Its mantle is wide, the width being equal to around 35% of the length of the mantle, and blunt at the posterior end. It has short, round fins, equalling 40-45% of the length of the mantle and between 55% and 65% of mantle length in width, with a convex margin at the rear. The head is short and the short and there are no buccal suckers on the buccal lappets. The tentacular club is small and narrow with suckers which are set out in 4 longitudinal series, 4 or 5 pairs of medial suckers on the central part of the club, the manus which are enlarged when compared to the lateral suckers. The club suckers have rings of 15 to 25 sharp teeth which become more pointed and increase in size towards the tip. Its dorsal arms are very short in comparison with its other arms and in males the left ventral arm is hectocotylized. The arm has 6 to 12 pairs of normal suckers at its base with the suckers replaced towards the tip by elongate papillae, these are more strongly developed in the dorsal row.^[2]

The manus is the zoological term for the distal portion of the fore limb of an animal. In tetrapods, it is the part of the pentadactyl limb that includes the metacarpals and digits (phalanges). During evolution, it has taken many forms and served a variety of functions. It can be represented by the hand of primates, the lower front limb of hoofed animals or the fore paw and is represented in the wing of birds, bats and prehistoric flying reptiles (pterosaurs), the flipper of marine mammals and the 'paddle' of extinct marine reptiles, such as plesiosaurs and ichthyosaurs.

Distribution and ecology

Afrololigo mercatoris occurs only off the west coast of Africa from Rio de Oro in Mauritania) to Lüderitz Bay in Namibia. This species is collected from depths of less than 50 m where there are mud and sandy-mud substrates. There is very little data available on its life cycle and biology. The eggs are small and the spermatophores have long bodies made of cement. This species is not a species of interest to fisheries.^[2]

Lüderitz Bay or Lüderitzbaai, also known as Angra Pequena, is a bay in the coast of Namibia, Africa. The city of Lüderitz is located at the edge of the bay.

A spermatophore or sperm ampulla is a capsule or mass containing spermatozoa created by males of various animal species, especially salamanders and arthropods, and transferred in entirety to the female's ovipore during reproduction. Spermatophores may additionally contain nourishment for the female, in which case it is called a nuptial gift, as in the instance of bush crickets. In the case of the toxic moth Utetheisa ornatrix, the spermatophore includes sperm, nutrients, and pyrrolizidine alkaloids which prevent predation because it is poisonous to most organisms. However, in some species such as the Edith's checkerspot butterfly, the "gift" provides little nutrient value. The spermatophore transferred at mating has little effect on female reproductive output. The alternative hypothesis of its usefulness is that the process of eating the spermatophore prevents the female from subsequent copulation, serving as a mating plug, thereby giving the male's sperm more time to fertilize. In some cephalopods, however, spermatophores from multiple males might be present inside the same female simultaneously.

Taxonomy

Afrololigo mercatoris shows some morphological similarity with the squids of the genus Lolliguncula , which is where William Adam originbally placed it when he described this species. However, based on morphology, genetic data and distribution Afrololigowas recognised as a distinct monotypic genus. The Red Sea species Uroteuthis abulati was also thought to be close to A. mercatoris.^[2]

Lolliguncula is a genus of squid from the family Loliginidae from the eastern Pacific and western Atlantic, known as brief squid. The genus is divided into two subgenera Lolliguncula and Loliolopsis. They are rather small squids with a maximum mantle length of 120mm, that inhabit shallow warm seas, although some species have been recorded in areas of low salinity. They are typified by having a short mantle, which is round at the posterior; and fins that are broader than long, but which have no posterior lobes. The males produce spermatophores with a long cement body and they lack a ventral crest on their hectocotylus. Their suckers have square teeth which ring the entire margin or are placed distally. The males do not have enlarged suckers on the left ventral arm. The tentacular club is expanded and contains suckers in four series. The two subgenera differ in the morphology of the hectocotylus.

William Adam was a Dutch / Belgian malacologist who specialised in cephalopods. Adam described a number of cuttlefish and bobtail squid species, including Euprymna hoylei, Sepia cottoni, Sepia dollfusi, Sepia dubia, Sepia reesi, Sepia sewelli, Sepia thurstoni, Sepia vercoi, and Sepiola knudseni.

A species description is a formal description of a newly discovered species, usually in the form of a scientific paper. Its purpose is to give a clear description of a new species of organism and explain how it differs from species which have been described previously or are related. The species description often contains photographs or other illustrations of the type material and states in which museums it has been deposited. The publication in which the species is described gives the new species a formal scientific name. Some 1.9 million species have been identified and described, out of some 8.7 million that may actually exist. Millions more have become extinct.

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References

1 2 Julian Finn (2016). "Afrololigo mercatoris (Adam, 1941)". World Register of Marine Species. Flanders Marine Institute. Retrieved 21 February 2018.
1 2 3 P. Jereb; C.F.E. Roper, eds. (2010). Cephalopods of the World an Annotated and Illustrated Catalogue of Cephalopod Species Known to Date Volume 2 Myopsid and Oegopsid Squids (PDF). Food and Agriculture Organization Rome. pp. 48–49. ISBN 978-92-5-106720-8.

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[WoRMS-1] 1 2 Julian Finn (2016). "Afrololigo mercatoris (Adam, 1941)". World Register of Marine Species. Flanders Marine Institute. Retrieved 21 February 2018.

[FAO-2] 1 2 3 P. Jereb; C.F.E. Roper, eds. (2010). Cephalopods of the World an Annotated and Illustrated Catalogue of Cephalopod Species Known to Date Volume 2 Myopsid and Oegopsid Squids (PDF). Food and Agriculture Organization Rome. pp. 48–49. ISBN 978-92-5-106720-8.