Bravo C2NICO, J'étais certain qu'il ya avait des intellectuels et des scientifiques sur ce forum On arrive toujours à trouver une réponse à sa question Je trouvais cette plaie circulaire sur un thon jaune tout à fait surprenante
Sur internet on trouve plein de photographies sur la dentition et les poissons avec cette plaie circulaire Ci- joint une explication envoyée par Yann Colas COOKIECUTTER SHARK Order - Squaliformes Family - Dalatiidae Genus - Isistius Species - brasiliensis
Taxonomy
This small shark was originally described by Quoy & Gaimard in 1824 as Tristius brasiliensis. This name was later changed to Scymnus brasiliensis, followed by the currently valid Isistius brasiliensis (Quoy & Gaimard, 1824). The genus name Isistius is derived from Isis, the Egyptian goddess of light; the species name brasiliensis refers to its presence in the waters off the coast of Brazil. Synonyms in past scientific literature include Scymnus brasiliensis torquatus Müller & Henle 1839, Scymnus unicolor Müller & Henle 1839, Scymnus brasiliensis unicolor Müller & Henle 1839, Scymnus torquatus Müller & Henle 1839, Squalus fulgens Bennett 1840, and Leius ferox Kner 1864.
Common Names
The cookiecutter shark is named after the cookie-shaped wounds that it leaves on the bodies of its prey items. English language common names include cookiecutter shark, cigar shark, cookie-cutter shark, and luminous shark. Other common names include almindelig cookiecutterhaj (Danish), brasilianvalohai (Finnish), cação luminoso (Portuguese), darumazame (Japanese), kleiner leuchthai (German), koekjessnijder (Dutch), squalelet féroce (French), tiburón cigarro (Spanish), tiburón puro (Spanish), and tollo cigarro (Spanish).
Geographical Distribution
This small shark is found in the western Atlantic Ocean from the Bahamas south to the coast of southern Brazil. In the eastern Atlantic Ocean, it is found from Cape Verde, Guinea to Sierra Leone, southern Angola and South Africa including Ascension Island. The cookiecutter shark also lives in the waters of the Indo-Pacific from Mauritius to New Guinea, Lord Howe Island, and New Zealand north to Japan and east to the Hawaiian Islands. It is found off Easter Island and the Galapagos in the eastern Pacific Ocean. Records of cookiecutter sharks off Australia include the waters off Queensland, New South Wales, Tasmania, and Western Australia.
World distribution map for the cookiecutter shark
Habitat
Found in deep water at depths below 3,281 feet (1000 m) during the day, cookiecutter sharks migrate vertically to surface waters at night to feed.
Biology Cookiecutter shark, A. Side view, B. frontal view of the head, C. dorsal view of the head, D. ventral view of the head source: FAO
· Distinctive Features The cookiecutter shark has a small cigar-shaped body with a short conical snout and unique suctorial lips. The eyes are located toward the front of the head, but far enough back that the shark lacks much of a binocular field of vision. There are two close-set spineless dorsal fins of equal size positioned toward the rear of the body. The pelvic fins are larger in size than the dorsal fins; the pectoral fins are subquadrate in shape. The caudal fin is large with a long ventral lobe. The anal fin is absent on this species.
Isistius plutodus is a similar species to the cookiecutter shark, however I. plutodus has fewer and larger teeth and lacks the dark colored collar as well as the dark tips on the caudal fin. Also, the base of the second dorsal fin is over twice as long as the base of the first dorsal fin of I. plutodus.
· Coloration The dorsal portion of the cookiecutter shark is dark brown with a lighter ventral surface. There is a distinct dark brown collar around the gill region. The entire ventral surface of the cookiecutter shark with the exception of the dark collar, contains a network of tiny light producing organs called photophores. Photophores produce an even greenish colored glow on the underside of this shark. These photophores reportedly produce light for up to three hours after the death of the shark. The fins have pale margins with the exception of the caudal fin which has dark tips.
· Dentition Cookiecutter sharks have 30-37 small, erect teeth in the upper jaw and 25-31 larger triangular teeth in the lower jaw with larger specimens having the larger numbers. The teeth are interconnected at the bases, allowing the entire row of teeth to move if one tooth is touched. The teeth are lost as a complete unit rather than individual teeth common to most sharks. As the lower teeth are shed, they are ingested by the shark. This is thought to aid in maintaining the calcium levels in the body.
· Dermal Denticles The denticles are roughly square-shaped with a depression in the middle and raised points at the corners.
Enregistré le: Dim Nov 02, 2008, 11:49 Messages: 2938 Localisation: trop loin de la mer
Superbe séjour et quels coups de lignes , le banc HAWKINS est la hauteur de sa réputation et Yann est un super skipper. Mais le problème de rodrigue c'est la houle, la mer est rarement calme.
Je craignais Rodrigues pour ses conditions météo, mais j'ai été surpris même avec 20 noeuds et 3 m de creux de vent on peut pêcher avec le bateau de Yann et pour le mal de mer que je crains un peu, quasiment pas eu de pb avec le scopoderm. le pb c'est plutôt le déplacement du bateau contre le vent et les vagues là cela tape un peu mais une fois sur le banc pas de pb idem avec le vent et les vagues dans le dos pas de pb Sur 10 jours soit 6 jours de pêche en mer on a eu au moins 3 jours de mer très calme Si vous voulez faire un record sur TDC ou tout simplement prendre de gros doggy allez à Rodrigues n'ayez pas peur de la mer Rodriguaise, mais dépechez vous il yaura bientôt des longliners sur ce banc
Enregistré le: Ven Oct 08, 2010, 19:53 Messages: 1490 Localisation: Le Cannet, les Issambres
Et dire que quelques fois je passe des heures en mer à sonder n'importe où pour un ....serran ! moi ce genre de report ça me tue !! J'en rève la nuit !!
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