Diagnostic Description
provided by Fishbase
This slender-bodied shark is readily distinguished from its larger congener (H. griseus) by having a narrower head, relatively larger eyes, 5 large lower comb-shaped anterolateral teeth, a long slender dorsal-caudal space, with distance from the dorsal origin to the upper caudal origin being at least twice the length of the dorsal fin base; with the upper and lower caudal postventral margins forming a strong arch. In life, Color of dorsum a uniform pale brown without a light line extending along the lateral body trunk, the trailing fin edges are white in some specimens and the ventral surface is lighter (Ref. 94780).
- Recorder
- Estelita Emily Capuli
Life Cycle
provided by Fishbase
Ovoviviparous, with number of young 13 in one litter. Length at birth about 43 cm (Ref. 247). Distinct pairing with embrace (Ref. 205).
Morphology
provided by Fishbase
Vertebrae: 155
- Recorder
- Estelita Emily Capuli
Trophic Strategy
provided by Fishbase
Found on the continental shelf and slope (Ref. 75154).
Biology
provided by Fishbase
Found on continental and insular shelves and upper slopes, from 90 to 600 m depth, usually on or near bottom, may move to the surface at night (Ref. 247, 5578). Probably feeds on bony fish and crustaceans (Ref. 13573). Ovoviviparous (Ref. 205), with 13 young in a litter (Ref. 247). Size at birth measures to about 40-43 cm TL (Ref. 94780). Not dangerous to people as far as is known (Ref. 247). Utilized for its fins, meat and liver oil but of little value due to its relatively small size (Ref.58048).
- Recorder
- Kent E. Carpenter
Importance
provided by Fishbase
fisheries: subsistence fisheries
- Recorder
- Kent E. Carpenter
分布
provided by The Fish Database of Taiwan
廣泛分布於世界各溫帶及熱帶之部分海域。臺灣東北部海域曾發現。
利用
provided by The Fish Database of Taiwan
偶由延繩釣、流刺網或底拖網捕獲，非重要之食用魚，一般以加工食之。
描述
provided by The Fish Database of Taiwan
體頗延長，前部較粗大。頭寬扁；尾基上下方無凹窪。吻短而鈍。眼大，卵圓形，無瞬膜。鼻孔小，近於吻端。口裂寬，弧形；上下唇褶不甚發達。兩頜齒異形；上頜無正中齒，每側16個，前面2齒簡單而細尖，齒頭外斜，中間7齒，外側具1-3小齒頭，最後7齒低小圓形，幾無齒頭；下頜正中具一齒，中央齒頭尖長，側齒頭3，每側12齒，前面5齒寬扁長方形，具8-11小齒頭，後面6齒細小。噴水孔細小，位於眼後緣上方。鰓孔6個。背鰭一個，小而後位，起點與腹鰭後端上方，後緣凹入，上角鈍圓，下角延長尖突；胸鰭寬大，鐮刀狀，後緣凹入，外角鈍尖，內角鈍圓；尾鰭狹長，尾椎軸稍翹，上葉見於尾端，下葉前部具顯著三角形突出，中、後部間具缺刻。體背側暗褐色；吻腹側及腹部淡色。
棲地
provided by The Fish Database of Taiwan
棲息於大陸棚或島嶼棚斜坡的近、外海底棲大型鯊類，一般棲息深度在90-600公尺附近，具日夜垂直分布，白天棲於底層，晚上至上層覓食。主要以小型硬骨魚類、甲殼類及烏賊等為食。卵胎生，一胎可產下約13尾幼鯊，剛出生之幼鯊體長可達43公分。
Bigeyed sixgill shark
provided by wikipedia EN
The bigeyed sixgill shark (Hexanchus nakamurai) is a cow shark of the family Hexanchidae. Its dorsal surface has a brownish-gray color, and is sharply separated from the light coloring of its ventral surface. The eyes are a fluorescent green while the shark is alive. The body of this shark is small, slim, and fusiform in shape. As the name suggests, this shark has six gill slits, unusual among most shark species. The head is narrow and somewhat flattened, and the mouth contains 5 rows of large, comb-shaped teeth. This shark's single dorsal fin is pushed back towards the caudal fin, and is behind the pelvic fins. The upper caudal fin is much longer than the lower, with a deep notch near the tip. All fins have thin white margins on the edge. In juveniles, the upper caudal fin has a black tip.
Measurements
Length at birth for this species is 34–45 cm; adults average 1.2 m for both genders, with a maximum of 1.8 m. Mature adults weigh around 20 kg.
Range and habitat
Bigeyed sixgills are found in the Indian Ocean and the western Pacific Ocean. Populations in the western Atlantic Ocean formerly grouped within this species are now considered their own species, the Atlantic sixgill shark (Hexanchus vitulus). These sharks live near the sea floor between 90 and 600 m deep, but may move closer to the surface at night to take advantage of prey there. They make their home on continental shelves, insular shelves, and upper slopes. These sharks do not inhabit abyssal environments.[2]
Parasites
As with other sharks, bigeyed sixgill sharks harbour a number of parasite species. Monogeneans of the genus Protocotyle (family Hexabothriidae) have been found only on the gills of species of Hexanchus.[3] The species Protocotyle euzetmaillardi Justine, 2011 was recently described from the gills of Hexanchus nakamurai off New Caledonia, South Pacific Ocean.[4]
Behavior
Little is known about the feeding habits of the bigeyed sixgill. Based on the few stomach examinations of these sharks, they are thought to feed mainly on small to moderately sized bony fish and bottom dwelling crustaceans. Like all sharks of the order Hexanchiformes found so far, this shark is ovoviviparous, meaning the eggs are retained inside the female's body until hatching. The bigeyed sixgill, after an unknown gestation period, gives birth to litters of up to 13 pups.[5]
Conservation
The bigeyed sixgill is listed as near threatened by the IUCN Red List. Based on what little is known of the species, these sharks are not suffering major declines to their population, but pressure is growing from deepwater fisheries. According to the International Shark Attack File, the bigeyed sixgill is harmless, as its natural environment is far from people, and no attacks on humans by the species have been reported.[6]
H. nakamurai, upper teeth
H. nakamurai, six gill openings
See also
References
-
^ Finucci, B., Barnett, A., Cheok, J., Cotton, C.F., Kulka, D.W., Neat, F.C., Rigby, C.L., Tanaka, S. & Walker, T.I. 2020. Hexanchus nakamurai. The IUCN Red List of Threatened Species
-
^ Bigeyed Sixgill Sharks, Hexanchus nakamurai Archived 18 August 2013 at the Wayback Machine. marinebio.org
-
^ Euzet, L. & Maillard, C. (1974) Les Monogènes Hexabothriidae Price, 1942. Historique, systématique, phylogenèse. Bulletin du Muséum National d'Histoire Naturelle, 3° série, 206, Zoologie 136, 113-141.
-
^ Justine, J.-L. (2011). "Protocotyle euzetmaillardi n. sp. (Monogenea, Hexabothriidae) from the bigeye sixgill shark Hexanchus nakamurai Teng (Elasmobranchii, Hexanchidae) off New Caledonia". Systematic Parasitology. 78 (1): 41–55. doi:10.1007/s11230-010-9275-6. PMID 21161490.
-
^ Hexanchus nakamurai Teng, 1962. Fishbase
-
^ Compagno, Leonardo, Dando, Marc and Fowler, Sarah (2005). Sharks of the World. Princeton University Press. pp. 67–68. ISBN 9780691120720
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- Wikipedia authors and editors
Bigeyed sixgill shark: Brief Summary
provided by wikipedia EN
The bigeyed sixgill shark (Hexanchus nakamurai) is a cow shark of the family Hexanchidae. Its dorsal surface has a brownish-gray color, and is sharply separated from the light coloring of its ventral surface. The eyes are a fluorescent green while the shark is alive. The body of this shark is small, slim, and fusiform in shape. As the name suggests, this shark has six gill slits, unusual among most shark species. The head is narrow and somewhat flattened, and the mouth contains 5 rows of large, comb-shaped teeth. This shark's single dorsal fin is pushed back towards the caudal fin, and is behind the pelvic fins. The upper caudal fin is much longer than the lower, with a deep notch near the tip. All fins have thin white margins on the edge. In juveniles, the upper caudal fin has a black tip.
- license
- cc-by-sa-3.0
- copyright
- Wikipedia authors and editors
Description
provided by World Register of Marine Species
Found on the continental and insular shelves and slopes, usually on or near bottom, but occasionally at the surface in the tropics. Ovoviviparous with 13 young in a litter. Feeds on small to medium-sized fishes, and probably bottom invertebrates. Length at birth about 43 cm TL. Not dangerous to people as far as is known.
Froese, R. & D. Pauly (Editors). (2023). FishBase. World Wide Web electronic publication. version (02/2023).
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- copyright
- WoRMS Editorial Board
