Cookiecutter Shark

Up to 20 inches. Max length : 42.0 cm TL male/unsexed; 56.0 cm TL

Family	Dalatiidae
Description	Sleeper sharks
Environment	Marine
Etymology	Greek, dalos, -ou = torch
Genus	7
No. of Species	9
Order	Squaliformes
Class	Elasmobranchii
Reproductive Guild	Bearers
Distribution	Antarctic to Arctic, Northern and Southern Hemisperes, coastal and oceanic. Includes four subfamilies (Etmopterinae, Somniosinae, Oxynotinae, and Dalatiinae). Except in Etmopterinae , most members without spines in dorsal fin; luminous organs present (except in Somniosus pacificus), appearing as black dots mainly on ventral surface. Etmopterinae has grooved spines in both dorsal fins, caudal fin with subterminal notch. Oxynotinae has very high, and compressed body, triangular in cross section; dorsal fins very high, each with a spine. The subfamilies are sometimes separated as independent families by various authors: Oxynotidae; Somniosidae (dorsal fins without spines, first dorsal fin originating in front of pelvic fins but much closer to pectoral fins) and Etmopteridae (dorsal fin with spines, teeth with prominent central cusp flanked by one or two smaller cusplets) . Dalatiidae has dorsal fins without spines, first dorsal fin originating in front of pelvic fins but much closer to pelvic fins

Cookiecutter

Caught at night, sometimes at surface or at depths up to 11,500 feet. Oceanic species. Epi- to bathypelagic at 1-3500 m. Makes diurnal vertical migrations from below 1,000 m in the day to or near the surface at night. Travels long vertical distances in excess of 2,000 to 3,000 m on a diel cycle. 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 . Ovoviviparous, with 6-12 young per litter. The cookiecutter shark has specialized suctorial lips and a strongly modified pharynx that allow it to attach to the sides of it prey. 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. Teeth are shed as a complete unit; the lower teeth are swallowed, perhaps to maintain sufficient calcium levels in its body. 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

Brownish black with a dark collar around the gill region and bright green eyes; sometimes referred to as the "cigar" shark; small dorsal fins are at the rear of its body. Likes to eat squid, small fish, crustaceans; also bites off flesh from larger fishes, cetaceans and sharks. Dorsal spines (total): 0; Dorsal soft rays (total): 0; Anal spines: 0; Anal soft rays: 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. Tooth count: 30-37/25-31. Vertebral count: 81-89. Spiral valve count: 8-10. Dark brown dorsally, paler ventrally except for blackish band across throat; tips of caudal lobe blackish. 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

Presumably ovoviviparous; 6 or 7 large eggs have been found in ovaries. Distinct pairing with embrace. Viviparous, without a yolk sac placenta, 6-12 young per litter. Males mature at about 36 cm, with a maximum length of 42 cm; females mature at 39 cm, with a maximum length of 56 cm. Size at birth is unknown.

Summary of Distribution: Western Atlantic: Bahamas and southern Brazil. Eastern Atlantic: Cape Verde, Guinea to Sierra Leone, southern Angola and South Africa, including Ascension Island. Indo-Pacific: Mauritius to New Guinea, Lord Howe Island, and New Zealand, north to Japan and east to the Hawaiian Islands. Eastern Pacific: Easter Island and the Galapagos.
Note: Distribution range colors indicate degree of suitability of habitat which can be interpreted as probabilities of occurrence (fishbase.org)