Bigfin reef squid

Sepioteuthis lessoniana, commonly known as the bigfin reef squid or oval squid, is a commercially important species of  loliginid squid. It is one of the three currently recognized species belonging to the genus Sepioteuthis. Studies in 1993, however, have indicated that bigfin reef squids may comprise a cryptic species complex. The species is likely to include several very similar and closely related species.

Bigfin reef squids are characterised by a large oval fin that extends throughout the margins of its mantle, giving them a superficial similarity to cuttlefish. They are small to medium-sized squids, averaging 3.8 to 33 centimetres (1.5 to 13.0 in) in length. They exhibit elaborate mating displays and usually spawn in May, but it can vary by location. The paralarvae resemble miniature adults and are remarkable for already having the capability to change body colouration upon hatching. Bigfin reef squids have the fastest recorded growth rates of any large marine invertebrate, reaching 600 g (1.3 lb) in only four months. They are a short-lived species, with a maximum recorded lifespan of 315 days.

The diet of bigfin reef squids comprises mainly crustaceans and small fish. They are found in the temperate and tropical waters of the Pacific and Indian Oceans, and have recently been introduced into the Mediterranean as a Lessepsian migrant. They are commonly found near the shoreline, near rocks, and coral reefs. They are fished in vast quantities for human food in Asia. Because of their rapid growth rate, short life span, and tolerance to handling and captivity, bigfin reef squids are regarded as one of the most promising species for mariculture. They are also a valuable source of giant axons for medical research.