''Ancistrocheirus lesueurii'', the sharpear enope squid, is the only species in the genus ''Ancistrocheirus'' and family Ancistrocheiridae. With a mantle length of , this moderately sized

squid A squid (: squid) is a mollusc with an elongated soft body, large eyes, eight cephalopod limb, arms, and two tentacles in the orders Myopsida, Oegopsida, and Bathyteuthida (though many other molluscs within the broader Neocoleoidea are also ...

may be found throughout the

tropical The tropics are the regions of Earth surrounding the equator, where the sun may shine directly overhead. This contrasts with the temperate or polar regions of Earth, where the Sun can never be directly overhead. This is because of Earth's ax ...

and

subtropical The subtropical zones or subtropics are geographical zone, geographical and Köppen climate classification, climate zones immediately to the Northern Hemisphere, north and Southern Hemisphere, south of the tropics. Geographically part of the Ge ...

oceans. They tend to be found at

mesopelagic The mesopelagic zone (Greek language, Greek μέσον, middle), also known as the middle pelagic or twilight zone, is the part of the pelagic zone that lies between the photic epipelagic and the aphotic bathypelagic zones. It is defined by light ...

depths ( down). Although only one species is recognized, some have suggested more than one species may exist due to differences in the paralarval

morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines *Morphology (archaeology), study of the shapes or forms of artifacts *Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies, ...

. Paralarva is the first free-living stage for

cephalopod A cephalopod is any member of the molluscan Taxonomic rank, class Cephalopoda (Greek language, Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral symm ...

Characteristics

The buccal crown of the sharpear enope squid is heavily pigmented. The squid has no vesicles. There are hooks on all its

arm In human anatomy, the arm refers to the upper limb in common usage, although academically the term specifically means the upper arm between the glenohumeral joint (shoulder joint) and the elbow joint. The distal part of the upper limb between ...

s. The suckers are absent from its manus and the squid's dactylus is reduced.

Photophores

Photophore A photophore is a specialized anatomical structure found in a variety of organisms that emits light through the process of boluminescence. This light may be produced endogenously by the organism itself (symbiotic) or generated through a mut ...

s occur throughout its body. Large photophores are present on its head, funnel, base of arms, and tentacular stalk. Other photophores are present on the ventral surface of its mantle (usually 22), with numerous very small photophores on its head, funnel, base of arms II and tentacular stalk. Mature males have large photophores on tips of arms IV opposite the mouth. Mature females have photophores on tips of their

dorsal Dorsal (from Latin ''dorsum'' ‘back’) may refer to: * Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism * Dorsal, positioned on top of an aircraft's fuselage The fus ...

six arms. The number of large photopores on the squid's mantle increases as it matures.

Ecology

They are eaten by the

sperm whale The sperm whale or cachalot (''Physeter macrocephalus'') is the largest of the toothed whales and the largest toothed predator. It is the only living member of the Genus (biology), genus ''Physeter'' and one of three extant species in the s ...

Southeast Asia Southeast Asia is the geographical United Nations geoscheme for Asia#South-eastern Asia, southeastern region of Asia, consisting of the regions that are situated south of China, east of the Indian subcontinent, and northwest of the Mainland Au ...

and the Galapagos waters

References

Tree of Life web project: ''Ancistrocheirus lesueurii''ITIS entry
Enoploteuthoidea Monotypic cephalopod genera Bioluminescent molluscs Taxa named by John Edward Gray Taxobox binomials not recognized by IUCN {{Squid-stub