The bigfin reef squid or oval squid, Sepioteuthis lessoniana, is a common, small to medium-sized loliginid squid 3.8 - 33 cm (1.5 to 13.0 inches) long that is native to temperate and tropical Pacific and Indian Ocean waters. It has recently been documented as spreading to the Mediterranean through the Suez Canal. They live near the shore, in areas with rocks or coral reefs, and eat mostly crustaceans and small fish. Taxonomic studies in the 1990s indicate that S. lessoniana is probably a cryptic species complex made up of several very similar and closely related species. Of the three species in the genus Sepioteuthis, S. lessoniana is has the largest distribution (Wikipedia 2014 and references therein).
As do all species in genus Sepioteuthis, bigfin reef squids have a large ovoid fin circling almost all the way around their mantle. This distinguishes them from other squids, and gives them a cuttlefish-like appearance, reflected in the genus name Sepioteuthis (Sepio is Greek for cuttlefish, teuthis means squid). Bigfin reef squid show social behavior such as schooling and shoaling of multiage individuals and less cannibalism than most other squid species (Boal and Gonzalez 2010; Ikeda et al. 2008). When the juveniles hatch they are miniature adults able to change body color and pattern (metachrosis) as do full adults. Bigfin reef squids have the fastest recorded growth rates of any large marine invertebrate, reaching 600 g (1.3 lb) in four months. They are a short-lived species, with a maximum recorded lifespan of 315 days (Wikipedia 2014; Boal and Gonzalez 2010; Izeda et al. 2008).
Sepioteuthis lessoniana are one of the most economically important squid species, fished year round in vast quantities for human food especially in Asia. They are regarded as a promising species for mariculture, because of their rapid growth rate, short life span, and tolerance to handling and captivity (Wikipedia 2014 and references therein). These squid have axons hundreds of times larger than other animals, used for very fast muscle contractions to enable their escape mechanisms. These giant axons play a valuable role in medical research in neuroscience (Lee et al. 1994). Sepioteuthis lessoniana are also noted as potential indicators of warming water temperatures, as population sizes respond very rapidly to temperature increase (Wikipedia 2014).