Steve Backshall learns about sharks.

Shark Bites - Netflix

Type: Documentary

Languages: English

Status: In Development

Runtime: 5 minutes

Premier: 2017-09-04

Shark Bites - Cookiecutter shark - Netflix

The cookiecutter shark (Isistius brasiliensis), also called the cigar shark, is a species of small dogfish shark in the family Dalatiidae. This shark occurs in warm, oceanic waters worldwide, particularly near islands, and has been recorded as deep as 3.7 km (2.3 mi). It migrates vertically up to 3 km (1.9 mi) every day, approaching the surface at dusk and descending with the dawn. Reaching only 42–56 cm (16.5–22 in) in length, the cookiecutter shark has a long, cylindrical body with a short, blunt snout, large eyes, two tiny spineless dorsal fins, and a large caudal fin. It is dark brown, with light-emitting photophores covering its underside except for a dark “collar” around its throat and gill slits. The name “cookiecutter shark” refers to its feeding habit of gouging round plugs, as if cut out with a cookie cutter, out of larger animals. Marks made by cookiecutter sharks have been found on a wide variety of marine mammals and fishes, as well as on submarines, undersea cables, and even human bodies. It also consumes whole smaller prey such as squid. Cookiecutter sharks have adaptations for hovering in the water column and likely rely on stealth and subterfuge to capture more active prey. Its dark collar seems to mimic the silhouette of a small fish, while the rest of its body blends into the downwelling light via its ventral photophores. When a would-be predator approaches the lure, the shark attaches itself using its suctorial lips and specialized pharynx and neatly excises a chunk of flesh using its bandsaw-like set of lower teeth. This species has been known to travel in schools. Though rarely encountered because of its oceanic habitat, a handful of documented attacks on humans were apparently caused by cookiecutter sharks. Nevertheless, this diminutive shark is not regarded as highly dangerous. The International Union for Conservation of Nature has listed the cookiecutter shark under least concern, as it is widely distributed, has no commercial value, and is not particularly susceptible to fisheries.

Shark Bites - Life history - Netflix

Like other dogfish sharks, the cookiecutter shark is aplacental viviparous, with the developing embryos being sustained by yolk until birth. Females have two functional uteri and give birth to litters of six to 12 pups. A case has been recorded of a female carrying 9 embryos 12.4–13.7 cm (4.9–5.4 in) long; though they were close to the birth size, they still had well-developed yolk sacs, suggesting a slow rate of yolk absorption and a long gestation period. The embryos had developed brown pigmentation, but not the dark collar or differentiated dentition. Newborn cookiecutter sharks measure 14–15 cm (5.5–5.9 in) long. Males attain sexual maturity at a length of 36 cm (14 in), and females at a length of 39 cm (15 in).

Shark Bites - References - Netflix