Description

Dorsal spines (total): 0; Anal spines: 0; Vertebrae: 81 - 89. The cookiecutter shark Isistius brasiliensis is distinctive for the prominent dark collar marking around its throat, large nearly symmetrical caudal fin with a long ventral lobe over 2/3 length of dorsal caudal margin, and moderately large lower teeth in 25-32 rows. Eyes set anterior of head but sufficiently far back to lack an extensive anterior binocular field. Pectoral fins subquadrate; pelvic fins larger than dorsal fins (Ref.247). Tooth count: 30-37/25-31. Vertebral count: 81-89. Spiral valve count: 8-10 (Ref. 48844). Dark brown dorsally, paler ventrally except for blackish band across throat; tips of caudal lobe blackish (Ref. 6577). As with the other member of the genus Isistius , it has a characteristic small cigar-shaped body with two small close-set spineless dorsal fins far posterior on back, no anal fin, huge, triangular-cusped teeth without blades, short, bulbous snout and a unique suctorial lips (Ref. 247).

Common Names

No common names available.

Taxonomic Hierarchy

Kingdom: Animalia

Phylum: Chordata

Class: Elasmobranchii

Order: Squaliformes

Family: Dalatiidae

Genus: Isistius

Species: Isistius brasiliensis (Quoy & Gaimard, 1824)

Climate Zone

Location

Biology

Oceanic species (Ref. 247). Epi- to bathypelagic at 1-3500 m (Ref. 58302). Makes diurnal vertical migrations from below 1,000 m in the day to or near the surface at night (Ref. 6871, 58302). Travels long vertical distances in excess of 2,000 to 3,000 m on a diel cycle (Ref. 247). Feeds free-living deepwater prey such as large squid, gonostomatids, crustaceans but is also a facultative ectoparasite on larger pelagic animals such as wahoo, tuna, billfishes, and cetaceans (Ref. 247). Ovoviviparous (Ref. 205), with 6-12 young per litter (Ref. 48844). The cookiecutter shark has specialized suctorial lips and a strongly modified pharynx that allow it to attach to the sides of it prey (Ref. 247). It then drives its saw-like lower dentition into the skin and flesh of its victim, twists about to cut out a conical plug of flesh, then pull free with the plug cradled by its scoop-like lower jaw and held by the hook-like upper teeth (Ref. 247). Teeth are shed as a complete unit; the lower teeth are swallowed, perhaps to maintain sufficient calcium levels in its body (Ref. 247). Interconnection at the bases of individual tooth allows a whole row of teeth to move if one tooth is touched. This shark is reported to radiate light for as long as three hours after its death. Not dangerous to people because of its small size and habitat preferences (Ref. 247).

Habitat

bathypelagic