Thursday, January 25, 2007
Rare Video of Prehistoric Frilled Shark (January 2007)
Officials from the Awashima Marine Park in Shizuoka, Tokyo caught a 'living fossil' earlier this week after a fisherman from a nearby port informed them of the existence of a strange eel-like creature.
More info on Chlamydoselachus anguineus, a primitive species of shark with 6 gills instead of 5, available from Biology of Sharks and Rays:
"...body elongated and eel-like; snout blunt, jaws long and narrower at tip than at corners..."
Another video from the National Oceanic and Atmospheric Administration (NOAA): "Ocean Explorer - A frilled shark" [Prehistoric]
Information on the Frilled Shark from the International Union for Conservation of Nature and Natural Resources Red List of Threatened Species*:
Justification: A generally rare to uncommon deepwater species, with a few localities where it is taken more commonly as bycatch in several fisheries. Not an important target species, but a regular though small bycatch in many bottom trawl, midwater trawl, deep-set longline, and deep-set gillnet fisheries. As bycatch, this species is variously either used for meat, fishmeal, or discarded. Occasionally kept in aquaria (Japan). There is some concern that expansion of deepwater fisheries effort (geographically and in depth range) will increase the levels of bycatch. Although little is known of its life history, this deepwater species is likely to have very little resilience to depletion as a result of even non-targeted exploitation. It is classified as Near Threatened due to concern that it may meet the Vulnerable A2d+A3d+4d criteria.
Range: Generally rare, only a few localities where it is more common. Range almost worldwide.
Population: No information on population size anywhere.
Habitat and Ecology: Marine, demersal or benthopelagic, reported as occasionally pelagic on the upper and middle continental slope, 100–1,500 m, usually 500–1,000 m. An active predator on deepwater squid and a variety of fish (including other sharks). Large mouth with sharp inwards-pointing teeth can take large prey, but this shark is not considered dangerous to man. Born 40-60 cm total length (TL). Mature 97-117 cm TL (males), 135-150 cm TL (females). Maximum approximately 196 cm TL (females). Ovoviviparous with 6-12 pups per litter, possibly a long gestation period but life cycle basically unknown.
Threats: Not a targeted fisheries species, but taken as bycatch in bottom and midwater trawls, deep-set longlines, and in deep-set gill nets. No population baseline or trends available. Some concern that increased deepwater fisheries effort (geographically and in depth range) may increase levels of bycatch. The bycatch is sometimes utilized for fishmeal and for meat. Occasionally kept in aquaria (Japan).
Conservation Measures: None known for this species. A very few states are developing or have developed shark management plans within the context of the FAO IPOA-Sharks, but few if any of these include measures for the management of deepwater fisheries bycatch.
*Citation:Paul, L. & Fowler, S. 2003. Chlamydoselachus anguineus. In: IUCN 2006. 2006 IUCN Red List of Threatened Species.
Tanaka, S., Shiobara, Y., Hioki, S., Abe, H., Nishi, G., Yano, K. and Suzuki, K. 1990. The reproductive biology of the frilled shark, Chlamydoselachus anguineus, from Suruga Bay, Japan. Japanese Journal of Ichthyology. 37(3): 273–291.
An analysis of the reproductive biology of the frilled shark , Chlamydoselachus anguineus, was made on the basis of a collection of 264 specimens from Suruga Bay, Japan. This species is caught mainly from December to July. Almost all specimens were mature. The frilled shark appears to segregate by size and reproductive stage. Males mature below 1,100 mm total length (TL), while females reach sexual maturity between 1,400 and 1,500 mm TL. Males have active testes throughout the year. Females do not have a defined reproductive season. Ova emerge through each ovulation pore on the ovarian epithelium at a size of 230-250 g, and only enter the right oviduct. Ovarian eggs do not continue to develop during gestation. Egg capsules are shed when embryos reach between 60 and 80 mm TL.
Young are born at a size of about 550 mm TL and 380 g body weight. Litter size ranges from 2 to 10, with a mean of 6. Late stage embryos may receive nutrients from the mother. The intervals of ovulation seem to be about two weeks. The ovulation season in each female extends over a few months. The gestation period to last at least three and a half years. The encapsulated embryos maintained in artificial conditions grow at a rate of between 10 and 17 mm per month for a period up to 134 days.
A paper presented at the 7th Indo-Pacific Fish Conference (IPFC) at Taipei, Taiwan (16-21 May 2005):
Histological Observation of Organogenesis, Especially gonadogenesis, in Frilled Shark Embryos
(School of Marine Science and Technology, Tokai University)
The frilled shark, Chlamydoselachus anguineus, is known as one of ancient type sharks. The organogenesis in the frilled shark embryos was examined histologically. A total of 38 embryos from 15 mm to 356 mm in total length were collected from 13 pregnant sharks. The epithelium of stomach and intestines were developed abruptly in 20-30 mm TL and specialized in 100 mm TL. Rathke’s pouch was observed in 15 mm TL embryo. The ventral lobe of pituitary gland was specialized in 100 mm TL. Thyroid gland was formed in 15 mm TL embryo.
Several sizes of follicles were observed in 127 mm TL. Follicles of 219 mm TL embryo possessed a secretion in the inside. Pronephros was observed in 15 mmTL embryo and renal tubule was in 40 mm TL. Rectal gland was recognized in 30 mm TL embryo. The excretory tubules were specialized in 128 mm TL. Primordial germ cells were observed in the dorsal epithelium of abdominal cavity of 15 mm TL embryo. The germinal ridge was formed in 30-40 mm TL. The cortex of germinal ridge was developed in 56 mmTL embryo and the embryo was supposed to be female. Embryo in 108 mm TL possessed a pair of claspers and follicle-like cells in the medulla of germinal ridge.
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