Wülker, 1920
Diagnosis
Fins posterior. Posterior part of mantle elongated tail-like structure. Eggs are small to medium sized, less than 4 mm. The dentition of the arm suckers is variable. The proximal suckers on the hectocotylus are unmodified. hectocotylus without ventral crest; the hectocotylisation consists of reduction in size of the sucker and elongation of sucker stalks to form papillae on either dorsal or both dorsal and ventral rows. Photophores absent. Spermatophore with short cement body. The tail-like elongation of the posterior mantle distinguishes Alloteuthis from Loligo, Lamarck, 1798.
Alloteuthis is present with two species in the area: Alloteuthis medius and Alloteuthis subulatus.
Remark
The name Alloteuthis was used for the first time by Wülker, 1920 for a subgenus of Loligo. Apparently, Alloteuthis became later a genus, holding the species media, subulata, and africana, as it is listed as such, in, for example, Nesis, 1987, Howson and Picton, 1997, Hansson, 1998c, and Costello and Emblow, 2000. In contrast, according to M.J. Sweeney (ITIS, 2000), Alloteuthis Wülker, 1920 is a junior synonym of Loligo Lamarck, 1798 and therefore invalid as genus name, but still valid (and in use) as subgenus.
Establishing subgenera within Loligo is subject of discussion because the characters other than the long "tail" — by which Alloteuthis is defined — are considered to be of small importance to separate subgenera (Vecchione et al., 1998). Nevertheless, Vecchione et al., 1998 retain Alloteuthis as a subgenus, and by consequence Loligo is the other subgenus — even though it is not certain that the species which are not accommodated by the subgenus Alloteuthis are monophyletic.
A recent phylogenetic study based on morphological, allozyme and DNA data of squids of the Family Loliginidae, shows that phylogenetic relationships within this group remain somewhat confused (Anderson, 2000). Strong support for any particular pattern of relationships among generic-level clades within the family is generally lacking. However, the species media, subulata and africana are considered to form together a monophyletic group and are ranked in the genus Alloteuthis (Anderson, 2000).
If subgenera are accepted within Loligo, the North Sea species should be noted as follows:
Loligo (Alloteuthis) media (Linnaeus, 1758); see Alloteuthis medius
Loligo (Alloteuthis) subulata Lamarck, 1798; see Alloteuthis subulatus
Loligo (Loligo) forbesii Steenstrup, 1856; see Loligo forbesii
Loligo (Loligo)vulgaris Lamarck, 1798; see Loligo vulgaris