Smalltooth Cookiecutter Shark, Isistius brasiliensis Click to enlarge image
Teeth of a Smalltooth Cookiecutter Shark caught in an Isaacs-Kidd midwater trawl, east of Fiji, March 2013. The small pointed teeth in the upper jaw and large triangular teeth in the lower jaw allow the fish to 'carve' out pieces of muscle from its prey. Image: Michael Miller
© Michael Miller

Fast Facts

  • Classification
    Species
    brasiliensis
    Genus
    Isistius
    Family
    Dalatiidae
    Order
    Squaliformes
    Class
    Chondrichthyes
    Subphylum
    Vertebrata
    Phylum
    Chordata
    Kingdom
    Animalia
  • Size Range
    It grows to about 50 cm in length

Introduction

The Smalltooth Cookiecutter Shark is named after the cookie-shaped wounds that it leaves on the bodies of larger animals. It attaches itself to its prey with its suctorial lips, and then spins to cut out a cookie-shaped plug of flesh from the larger animal.



Identification

The species has a small cigar-shaped body, a conical snout and two low, spineless dorsal fins positioned posteriorly on the body. It is dark brown dorsally, lighter below, and has a distinct dark collar around the gill region. The entire ventral surface, with the exception of the dark collar, is covered in a dense network of tiny photophores, which in life produce an even greenish glow. The genus name Isistius is derived from Isis, the Egyptian goddess of light.

This species has small, erect teeth in the upper jaw and large triangular teeth in the lower jaw. The appropriately named Largetooth Cookiecutter Shark, is the second species in the genus Isistius. The two specie can be separated by tooth numbers, colouration and fin positions.



Habitat

They vertically migrate, being found in deep water, probably below 1000 m during the day, and migrating into surface waters at night.

Distribution

Cookiecutter Sharks are recorded from scattered localities around the world. In Australia they have been recorded from Queensland, New South Wales, Tasmania and Western Australia.

The map below shows the Australian distribution of the species based on public sightings and specimens in Australian Museums. Click on the map for detailed information. Source: Atlas of Living Australia.



Feeding and diet

The Smalltooth Cookiecutter Shark attaches itself to its prey with its suctorial lips, and then spins to cut out a cookie-shaped plug of flesh. Many species show evidence of attacks , including White Sharks.



Widder (1998) suggested that the feeding behaviour of the Smalltooth Cookiecutter Shark may be even stranger than originally thought. The fish is counterilluminated - the ventral light organs making the fish appear darker above and lighter below.

The dark-pigmented collar is not illuminated, so would appear silhouetted against the light from above. The theory suggests that this dark area would look like a small fish from below, and the Smalltooth Cookiecutter Shark would wait for a larger predator to attack the "small fish". As the predator is about to attack, the Smalltooth Cookiecutter Shark would turn and attack the attacker. The forward motion of the larger animal may even assist the Smalltooth Cookiecutter Shark in removing a plug of flesh.

In addition to plugs of flesh from larger animals, the Smalltooth Cookiecutter Shark is also known to eat squid. There are even reports of this species leaving crater-marks on the sonar domes of submarines.


Cookiecutter bite on sonar dome
The image shows damage to the sonar dome of a submarine. The cookie-shaped divot is probably the result of a bite from a Cookie-cutter Shark. The grooves left by the teeth are clearly visible. Image: -
© Australian Museum


Danger to humans

In their 2011 paper (see references, below), Honebrink and colleagues describe the first documented attack on a live human by a Cookiecutter Shark.

References

  • Compagno, L.J.V. 1984. FAO species catalogue. Vol. 4, Sharks of the World. An annotated and illustrated catalogue of shark species known to date. Part 1 - Hexanchiformes to Lamniformes: viii, 1-250.
  • Gadig, O.B.F. & U.L. Gomes. 2002. First report on embryos of Isistius brasiliensis. Journal of Fish Biology. 60: 1322-1325.
  • Honebrink, R., Buch, R., Galpin, P., & G. Burgess. 2011. First Documented Attack on a Live Human by a Cookiecutter Shark (Squaliformes, Dalatiidae: Isistius sp.). Pacific Science. 65(3): 365-374.
  • Last, P.R. & J.D. Stevens. 1994. Sharks and Rays of Australia. CSIRO. Pp. 513, Pl. 1-84.
  • McGrouther, M.A. 1994. Cookie Cutter Capers. Muse. Australian Museum News and Events. Dec - Jan: 4,11.
  • Papastamatiou Y.P., Wetherbee, B.M., O’Sullivan, J., Goodmanlowe, G.D. & C.G. Lowe. 2010. Foraging ecology of Cookiecutter Sharks (Isistius brasiliensis) on pelagic fishes in Hawaii, inferred from prey bite wounds. Environmental Biology of Fishes. 88: 361-368.
  • Widder, E.A. 1998. A predatory use of counterillumination by the squaloid shark, Isistius brasiliensis. Environmental Biology of Fishes. 53: 267-273.