Shape variable from short and stout to long and slender. Fins terminal or marginal, but always united posteriorly; funnel-locking apparatus a simple, straight groove. Eyes covered with transparent skin (corneal membrane); buccal connectives attached to ventral borders of fourth arms; 7 buccal lappets supplied with small suckers (except in Lolliguncula and Alloteuthis); 8 arms and 2 tentacles around mouth; 2 rows of suckers on arms and 4 rows on tentacular clubs, hooks never present. Usually the left arm of the IV (ventral) pair is hectocotylized in males (used to transfer sperm packets from the male to the female); the structure of the modified portion (hectocotylus) of the arm is useful in most species as a diagnostic character (often, the suckers on the hectocotylus are reduced in size or number, or modified into fleshy papillae or flaps (lamellae), or they disappear altogether. Colour: usually reddish-brown, darker dorsally, but quite variable depending on the behavioural situation.
The egg masses typically are groups of finger-like gelatinous masses containing a few to many eggs each often woven together and always attached to the ocean floor.
Figure. Left - Side view of an egg mass of a loliginid that has been pulled out of its anchor in the sand, found at low tide off San Felipe, Baja California. Note the root like anchors at the bottom of the picture. Photograph by Mike Lang. Right - Ventral views of a late embryo within the swollen egg chorion, and a recently hatched paralarva of Loligo pealeii. Photographed by Clyde Roper.
The systematics of the myopsid squid family Loliginidae have long been in disorder. In addition to many problems with differentiation of species, loliginid systematics have been hampered throughout the last several decades of the 20th Century by the presence of two systems of generic-level classification. The differences between these two systems primarily involved a question of the importance of gladius structure at the generic level. Both systems have been used widely in the scientific literature, although many authors consistently qualified their use by stating that the family was badly in need of revision based upon a worldwide review.
Three separate morphological revisions have been completed (Natsukari, 1984b; Brakoniecki, 1986; Alexeyev, 1991); all concluded that a correct generic-level classification of the family is radically different from either of the previous classifications. Unfortunately, these new classifications also differed substantially from each other, were presented in unpublished dissertations and not widely disseminated, and none has gained full acceptance.
Obviously, the existence of five contrasting systems of classification can cause hopeless confusion to researchers studing these squids, in addition to obfuscating real relationships among the species. Species groupings into subgenera and genera have been based only on similarity. In a workshop publication, Vecchione et al. (1998), recognized six genera. Four of the genera are divided into subgenera: Lolliguncula (Lolliguncula and Loliolopsis); Uroteuthis (Uroteuthis and Photololigo); Loliolus (Loliolus and Nipponololigo); Loligo (Loligo and Alloteuthis). The generic affinities of several species were unresolved.
A follow-up workshop consensus on generic and sub-generic taxonomy of the family was published by Vecchione et al. (2005), based primarily on the phylogenetic research of Anderson (1996; 2000a; 2000b) and Alexeyev (1989; 1991). Both of those authors built upon the previous workshop proceedings. The most noteworthy differences in Vecchione et al. (2005) from the classification of Vecchione et al. (1998) include the following: (1) removal of mercatoris from Lolliguncula based primarily on gladius characters, DNA sequence data and biogeography, and recognition of Afrololigo Brakoniecki as a valid genus for this species; (2) elevation of Alloteuthis Wülker from sub-generic to full generic status based on gladius structure and DNA sequence data; (3) removal of American species from the genus Loligo because DNA sequence analyses indicate that Loligo sensu Vecchione et al. (1998) is probably paraphyletic. The generic name with priority for the American species is Doryteuthis Naef. This genus further comprises two natural subgroups based on differences in gladius and hectocotylus structure; these subgroups are considered here to be the subgenera Doryteuthis Naef and Amerigo Brakoniecki. Doryteuthis sanpaulensis does not belong in either of these subgenera and is therefore considered to be the sole recognized species in an undescribed subgenus; (4) removal of bleekeri from Loligo and recognition of Heterololigo Natsukari as a valid genus based on DNA sequence analysis; (5) removal of noctiluca from subgenus Uroteuthis of genus Uroteuthis and recognition of Aestuariolus Alexeyev as a valid monotypic subgenus of Uroteuthis primarily because of differences in photophore structure from the rest of the genus.
Barcode of Life Data Systems (BOLD) Stats Specimen Records:880 Specimens with Sequences:857 Specimens with Barcodes:837 Species:64 Species With Barcodes:61 Public Records:590 Public Species:60 Public BINs:46
^Vecchione, M., E. Shea, S. Bussarawit, F. Anderson, D. Alexeyev, C.-C. Lu, T. Okutani, M. Roeleveld, C. Chotiyaputta, C. Roper, E. Jorgensen & N. Sukramongkol. (2005). Systematics of Indo-West Pacific loliginids. PDFPhuket Marine Biological Center Research Bulletin 66: 23–26.
The family Loliginidae includes many species that are important in trophic systems, fisheries, and biomedical studies. Brakoniecki (1996) merged the Pickfordiateuthidae with the Loliginidae.
Loliginids are mostly neritic squids (i.e., they occupy waters over the continental shelves). Most are very muscular, "squid-like" in appearance and range in size from about 3 to 100 cm ML. All members of the family have a cornea that covers the lens of each eye. Among decapods, this feature is shared with all members of the Sepioidea but is absent in all oegopsid squids. Loliginids differ from sepioids in having a gladius that extends the full length of the mantle and a gill that (except in Pickfordiateuthis) has a branchial canal.
A myposid ...
with straight funnel locking-apparatus.
with mantle locking-apparatus reaching mantle margin.
Lesueur (1821) erected a family that he called Loligoidea (afterwards emended to Loliginidae, see Vecchione et al., 1998) to fit the "Loligos" (Leachia, Loligo and Onykia) into Cuvier's "natural order". He stated (Lesueur, 1821:88)--
"It is of little consequence what characters we select for the distribution of these animals into families and genera, if our arrangement is the most convenient, and exhibits, as near as possible, a graded transition from one to the other."
A consequence of the age of this family, and its early inclusion of all squids, is that many taxa, both correctly and incorrectly described, have been considered loliginids at one time or another. A summary of this history is found here. Therefore, taxonomic nomenclature in the squid literature can be very confusing.
A thorough nomenclatural review of the family can be found in Sweeney and Vecchione (1998).
Our present classification of the Loliginidae comes from a consensus report by the world's experts on he systematics of this family that was published in the Phuket Marine Biological Center Research Bulletin, No. 66, 2005. A copy of this paper can be found here.
Fins usually joined posteriorly and, except Pickfordiateuthis, without posterior lobes.
Bacterial photophores on viscera present or absent. If present, form single, apparently unconnected, pair.
Egg masses, where known, with eggs organized in finger-like masses and attached to substrate.
Characters that Vecchione et al. (1998) agreed were of generic importance within the Loliginidae include:
Tail-like extension of the posterior mantle.
extends beyond fins.
fins along sides to posterior tip.
large (longest axis >5mm).
small (longest axis <4mm).
Arm-sucker rings, proximal margin.
Arm-sucker rings, distal margin.
Hectocotylus, ventral row of suckers.
reduction of suckers and elongation of sucker stalks along modified portion of arm to form papillae.
ventral crest formed by fusion of the protective membrane with ventral row of papillae such that original form of conical papillae is completely obscured.
Hectocotylus, proximal region.
suckers and/or stalks modified.
Photophores on ventral ink sac.
one pair present.
Spermatophore, cement body.
The morphology of the gladius, as used formerly to distinguish the genus Doryteuthis, is no longer considered to be of generic importance, although it is important at the specific level (see also Alexeyev, 1989). The gladius is quite variable, both within and among species, and could be highly adaptive in response to differences in swimming behavior. Other traditional characters that Vecchione et al. (1998) consider too variable to be of use in the generic systematics of the Loliginidae include spermatophore deposition site, presence of suckers on the buccal lappets, adult chromatophore patterns (e.g. lateral "flame stripes"), and presence of a longitudinal mid-ventral ridge on the mantle.
Although the preliminary generic classification of Vecchione et al. (1998) represented an important step toward consensus on the genera of this family, subsequent analyses of DNA sequences (Anderson 2000) have indicated that a holophyletic classification requires recognician of generic-level species groups defined primarily on distributional characteristics.