Overview

Comprehensive Description

Biology

A very rare species known only from few localities in epipelagic waters. Apparently feeds on small epibenthic and epipelagic invertebrates and fish. Its powerful jaws, big mouth and enormous lower teeth enable it to bite off large portion of its prey in one sweeping motion. A facultative ectoparasite evidenced by its suctorial lips and feeding apparatus. It has extremely short snout and anteriorly positioned eyes which allows for binocular vision (Ref. 247). Caught by mid-water trawl (Ref. 55584). Ovoviviparous (Ref. 205). Has large oily liver which helps it to become neutrally buoyant (`hepatic float').
  • 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. FAO Fish. Synop. 125(4/1):1-249. Rome: FAO. (Ref. 247)
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Distribution

Range Description

Possibly circumglobal, but at present known from scattered locations in the Pacific and Atlantic (Zidowitz et al. 2004, Compagno in prep. a.).
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Atlantic: off Alabama, USA and the Gulf of Mexico; including Brazil and West Sahara and off Azores. Northwest Pacific: off Okinawa, Japan and Australia (NSW). A very rare species (Ref. 52580).
  • Zidowitz, H., H.O. Fock, C. Pusch and H. von Westernhagen 2004 A first record of Isistius plutodus in the north-eastern Atlantic. J. Fish Biol. 64:1430-1434. (Ref. 52580)
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Western Atlantic and western Pacific.
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Physical Description

Morphology

Dorsal spines (total): 0; Dorsal soft rays (total): 0
  • 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. FAO Fish. Synop. 125(4/1):1-249. Rome: FAO. (Ref. 247)
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Size

Maximum size: 420 mm TL
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Max. size

42.0 cm TL (male/unsexed; (Ref. 247))
  • 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. FAO Fish. Synop. 125(4/1):1-249. Rome: FAO. (Ref. 247)
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Diagnostic Description

The largetooth cookiecutter shark Isistius plutodus has no collar marking around throat, a small asymmetrical caudal fin with a short ventral lobe less than half the length of dorsal caudal margin, bigger mouth and gigantic lower teeth (proportionately the largest in any living shark) in 19 rows (upper teeth = 29 rows). Eyes set well forward on head, with extensive anterior binocular field. Pectoral fins rounded, pelvic fins smaller than dorsal fins. 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).
  • 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. FAO Fish. Synop. 125(4/1):1-249. Rome: FAO. (Ref. 247)
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Type Information

Holotype for Isistius plutodus Garrick & Springer
Catalog Number: USNM 188386
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Fishes
Year Collected: 1960
Locality: Mississippi River Delta, Louisiana, United States, Gulf of Mexico, Atlantic
Depth (m): 814 to 997
Vessel: Oregon
  • Holotype: Garrick, J. A. & Springer, S. 1964. Copeia. 1964 (4): 679, figs. 1a, 2a, 2c; table 1.
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Ecology

Habitat

Habitat and Ecology

Habitat and Ecology
Little information available on the species' biology as it is presently known only from 10 specimens. Epibenthic (~100 m depth over the continental shelf) and epipelagic (depths of 60 to 120 m over continental slopes with bottom depths of 815-2,060m; and, 200m over the Riu-Kyu Trench with bottom depth of 6,440 m) with all known specimens collected close to land (Zidowitz et al. 2004, Compagno in prep. a).

Suggested to be a weaker, less active swimmer than I. brasiliensis (Compagno in prep. a). This species is a facultative ectoparasite, like I. brasiliensis, but with a probable different biting/cutting action (Compagno in prep. a).

Life history parameters
Age at maturity (years): Unknown.
Size at maturity (total length cm): Unknown.
Longevity (years): Unknown.
Maximum size (total length): At least 42 cm TL (Garrick and Springer 1964, Zidowitz et al. 2004, Compagno in prep. a.)..
Size at birth (cm): Unknown.
Average reproductive age (years): Unknown.
Gestation time (months): Unknown.
Reproductive periodicity: Unknown.
Average annual fecundity or litter size: Unknown.
Annual rate of population increase: Unknown.
Natural mortality: Unknown.

Systems
  • Marine
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Environment

pelagic-neritic; marine; depth range 60 - 200 m (Ref. 52580)
  • Zidowitz, H., H.O. Fock, C. Pusch and H. von Westernhagen 2004 A first record of Isistius plutodus in the north-eastern Atlantic. J. Fish Biol. 64:1430-1434. (Ref. 52580)
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Depth range based on 3 specimens in 1 taxon.
Water temperature and chemistry ranges based on 3 samples.

Environmental ranges
  Depth range (m): 200 - 2035
  Temperature range (°C): 3.738 - 19.222
  Nitrate (umol/L): 2.884 - 27.201
  Salinity (PPS): 34.842 - 35.036
  Oxygen (ml/l): 3.722 - 4.933
  Phosphate (umol/l): 0.267 - 1.731
  Silicate (umol/l): 3.022 - 27.750

Graphical representation

Depth range (m): 200 - 2035

Temperature range (°C): 3.738 - 19.222

Nitrate (umol/L): 2.884 - 27.201

Salinity (PPS): 34.842 - 35.036

Oxygen (ml/l): 3.722 - 4.933

Phosphate (umol/l): 0.267 - 1.731

Silicate (umol/l): 3.022 - 27.750
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

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Trophic Strategy

Found on the continental shelf (Ref. 75154).
  • Hoese, D.F., D.J. Bray, J.R. Paxton and G.R. Allen 2006 Fishes. In Beasley, O.L. and A. Wells (eds.) Zoological Catalogue of Australia. Volume 35.2 Australia: ABRS & CSIRO Publishing, 1472 p. (Ref. 75154)
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Life History and Behavior

Life Cycle

Distinct pairing with embrace (Ref. 205).
  • Breder, C.M. and D.E. Rosen 1966 Modes of reproduction in fishes. T.F.H. Publications, Neptune City, New Jersey. 941 p. (Ref. 205)
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Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
LC
Least Concern

Red List Criteria

Version
3.1

Year Assessed
2006

Assessor/s
Kyne, P.M., Gerber, L. & Sherrill-Mix, S.A.

Reviewer/s
Heupel, M.R., Simpfendorfer, C.A. & Cavanagh, R.D. (Shark Red List Authority)

Contributor/s

Justification
A rare epibenthic and epipelagic cookiecutter shark known from 10 specimens. Possibly circumglobal but at present recorded from scattered locations in the Pacific and Atlantic with all specimens collected close to land (in contrast to its congener Isistius brasiliensis). Largest recorded specimen just over 42 cm total length, but very little known of the biology of this facultative ectoparasite. Probably an irregular bycatch of trawl (benthic and pelagic) and longline fisheries (taken by hook or attached to its captured prey). Although little is known about this species it is probably widely distributed with no significant threats apparent and is thus assessed as Least Concern.
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Population

Population
This species is rarely encountered compared to Isistius brasiliensis (the cookiecutter shark). Compagno (in prep. a.) suggests that this may be due to more localized or limited distribution of I. plutodus, its occurrence in deeper water or its lower abundance.

Population Trend
Unknown
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Threats

Major Threats
Rarely caught in trawl (pelagic and benthic) and longline fisheries. The Australian specimen was probably taken by otter trawl targeting prawns (not known if taken on/near the bottom or in midwater) (McGrouther 2001). The Azores specimen was taken by pelagic trawl (Zidowitz et al. 2004) and the Brazilian specimens were collected from longline fisheries operating out of Santos in the south of the country. One specimen was retrieved attached to a hooked blue shark Prionace glauca (Sadowsky et al. 1988, Amorin et al. 1998).
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Least Concern (LC)
  • IUCN 2006 2006 IUCN red list of threatened species. www.iucnredlist.org. Downloaded July 2006.
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Management

Conservation Actions

Conservation Actions
Further specimens are required to better define distribution and obtain information on biology.
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Relevance to Humans and Ecosystems

Benefits

Importance

fisheries: of no interest
  • Coppola, S.R., W. Fischer, L. Garibaldi, N. Scialabba and K.E. Carpenter 1994 SPECIESDAB: Global species database for fishery purposes. User's manual. FAO Computerized Information Series (Fisheries). No. 9. Rome, FAO. 103 p. (Ref. 171)
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Wikipedia

Largetooth cookiecutter shark

The largetooth cookiecutter shark (Isistius plutodus) is a rare species of dogfish shark in the family Dalatiidae, reported from depths of 60–200 m (200–660 ft) at scattered locations in the Atlantic and Pacific Oceans. As its common name suggests, it is similar in appearance to the cookiecutter shark (I. brasiliensis) but has much larger lower teeth. Most individuals also lack the dark "collar" of I. brasiliensis. This species reaches a maximum known length of 42 cm (17 in). The largetooth cookiecutter shark feeds by gouging out chunks of flesh from larger animals, including bony fishes, sharks, and marine mammals, and is able to take larger bites than I. brasiliensis. Little is known of its life history; it is thought to be a weaker swimmer than I. brasiliensis, and is presumably aplacental viviparous like the rest of its family. This shark is an infrequent bycatch of commercial trawl and longline fisheries, but is not thought to be much threatened by these activities.

Taxonomy[edit]

The largetooth cookiecutter shark was originally described by Jack Garrick and Stewart Springer, in a 1964 issue of the scientific journal Copeia. Their description was based on a 42 cm (17 in) long adult female caught in a midwater trawl in the Gulf of Mexico, some 160 km (100 mi) south of Dauphin Island, Alabama. The specific epithet plutodus is derived from the Greek ploutos ("wealth" or "abundance") and odous ("tooth").[2] This species may also be referred to as the bigtooth or longtooth cookiecutter shark, or the Gulf dogfish.[1]

Distribution and habitat[edit]

Much rarer than I. brasiliensis, only ten specimens of largetooth cookiecutter shark are known, caught from a handful of widely scattered localities: off Alabama in the United States, Bahia in Brazil, the Azores, and Western Sahara in the Atlantic Ocean, and off Okinawa and New South Wales in the Pacific. Those captures were made in the epipelagic zone 60–200 m (200–660 ft) down, close to land over continental shelves, continental slopes, or oceanic trenches that may descend as far as 6.44 km (4.00 mi).[1] The shark's rarity may be due to a restricted distribution or, more likely, it normally preferring deeper waters.[3]

Description[edit]

The largetooth cookiecutter shark has a long, cigar-shaped body with an extremely short, blunt head and snout. The large, oval eyes are positioned to allow binocular vision, and are followed by wide, angled spiracles. The nostrils are small, each with a low, pointed skin lobe in front. The mouth is transverse, with a deep fold enclosing its corners and fleshy suctorial lips.[2] The jaws are larger and more powerful than those of I. brasiliensis,[3] and contain fewer tooth rows, numbering around 29 in the upper jaw and 19 in the lower jaw. The upper teeth are small, narrow, and smooth-edged, upright at the center of the jaw and becoming more angled towards the corners.[2] The lower teeth are massive, the largest teeth relative to body size of any living shark.[4] They are triangular in shape, with minutely serrated edges and interlocking rectangular bases. The five pairs of gill slits are minute.[2]

The small dorsal fins have rounded apices and are placed far back, on the last third of the body. The first dorsal fin originates slightly ahead of the pelvic fins, while the second dorsal originates closely behind and measures almost a third again the height of the first. The pectoral fins are small and rounded, and positioned relatively high on the body behind the fifth gill slit. The pelvic fins are tiny, and there is no anal fin. The caudal fin is very short, with the upper lobe twice as long as the lower and bearing a prominent ventral notch near the tip. The coloration is a plain dark brown, with translucent margins on the fins and sparsely scattered light-emitting photophores on the belly.[2] Most specimens have lacked the dark "collar" found on the throat of I. brasiliensis. However, a specimen caught in 2004 off the Azores did possess the collar.[5] The maximum recorded length is 42 cm (17 in).[6]

Biology and ecology[edit]

Based on its smaller dorsal and caudal fins, the largetooth cookiecutter shark is believed to be less active than I. brasiliensis and an overall weak swimmer. Much of its body cavity is occupied by an enormous oil-filled liver, which allows it to maintain neutral buoyancy in the water column with little effort. Unlike I. brasiliensis, this shark possesses binocular vision, which may allow it to target its prey with greater precision.[3] Virtually nothing is known of its biology; it is presumed to be aplacental viviparous.[6]

Like I. brasiliensis, the largetooth cookiecutter shark is an ectoparasite that feeds by excising plugs of flesh from larger animals. While I. brasiliensis is theorized to latch onto the surface of its prey and bite with a twisting motion, producing a circular wound containing spiral grooves inside from its lower teeth, the largetooth cookiecutter shark seems to employ a "sweeping" bite that produces a larger, more elongate (twice as long as the width of the mouth), oval wound containing parallel tooth grooves.[7] This shark has been known to bite bony fishes, sharks, and marine mammals.[1][3][8] One study has found that the largetooth cookiecutter shark is responsible for 80% of the cookiecutter wounds found on cetaceans off Bahia, Brazil. The flank was the most often-attacked area, followed by the head and abdomen. In at least three cases, bites to dolphins appeared to have resulted in their subsequent deaths by stranding.[8] Another prey species in the area is the subantarctic fur seal (Arctocephalus tropicalis); at least two cases of juveniles fatally stranding after being bitten have also been recorded.[9]

Human interactions[edit]

Other than possibly damaging billfishes or other valued species, the largetooth cookiecutter shark is of no import to commercial fisheries.[3] All but one of the known specimens have been caught as bycatch in commercial trawls or longlines. However, given the infrequency of these catches and this species' probable wide distribution, the International Union for Conservation of Nature (IUCN) has assessed it as of Least Concern.[1]

References[edit]

  1. ^ a b c d e f Kyne, P.M.; Gerber, L.; Sherrill-Mix, S.A. (2006). "Isistius plutodus". IUCN Red List of Threatened Species. Version 2010.4. International Union for Conservation of Nature. Retrieved {{{downloaded}}}. 
  2. ^ a b c d e Garrick, J.A.F.; Springer, S. (December 31, 1964). "Isistius plutodus, a New Squaloid Shark from the Gulf of Mexico". Copeia 1964 (4): 678–682. doi:10.2307/1441443. 
  3. ^ a b c d e Compagno, L.J.V. (1984). Sharks of the World: An Annotated and Illustrated Catalogue of Shark Species Known to Date. Rome: Food and Agricultural Organization. p. 95–96. ISBN 92-5-101384-5. 
  4. ^ McGrouther, M. (June 19, 2009). Largetooth Cookiecutter Shark, Isistius plutodus Garrick & Springer, 1964. Australian Museum. Retrieved on September 24, 2009.
  5. ^ Zidowitz, H.; Fock, O.; Pusch C.; von Westernhagen, H. (2004). "A first record of Isistius plutodus in the north-eastern Atlantic". Journal of Fish Biology 64 (5): 1430–1434. doi:10.1111/j.0022-1112.2004.00382.x. 
  6. ^ a b Froese, Rainer and Pauly, Daniel, eds. (2009). "Isistius plutodus" in FishBase. September 2009 version.
  7. ^ Pérez-Zayas, J.J.; Mignucci-Giannoni, A.A.; Toyos-González, G.M.; Rosario-Delestre, R.J.; Williams, E.H., Jr. (2002). "Incidental predation by a largetooth cookiecutter shark on a Cuvier’s beaked whale in Puerto Rico". Aquatic Mammals 28 (3): 308–311. 
  8. ^ a b Souto, L.R.A.; Abrão-Oliveira, J.G.; Nunes, J.A.C.C.; Maia-Nogueira, R.; Sampaio, C.L.S. (March 2007). "Analysis of cookiecutter shark Isistius spp. (Squaliformes; Dalatiidae) bites in cetaceans (Mammalia; Cetacea) on the Bahia coast, northeastern Brazil". Biotemas 20 (1): 19–25. 
  9. ^ Souto, L.R.A.; Abrão-Oliveira, J.G.; Maia-Nogueira, R.; Dórea-Reis, L.W. (2008). "Interactions between subantarctic fur seal (Arctocephalus tropicalis) and cookiecutter shark (Isistius plutodus) in the coast of Bahia, north-east of Brazil". JMBA2 - Biodiversity Records (published online). 
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