Regalecus russelii
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Regalecus russelii |
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| ( Cuvier , 1816) |
Regalecus russelii ( Syn .: Gymnetrus russelii , Cuvier, 1816 ) is a species from the belt fish family(Regalecidae). Behind its sister species Regalecus glesne it is the second longest bonefish in the world.
features
Regalecus russelii is elongated and flattened laterally. It can reach a length of 5.5 to a maximum of 8 meters. The number of vertebrae is 113 to 122, of which 34 to 37 are trunk vertebrae (127 to 163 or 45 to 56, in Regalecus glesne ). The fish is silvery, only the ridges on the head formed from up to one meter high fin rays are reddish. The first ridge is formed by 3 to 6 fin rays connected to each other by a fin membrane (6 to 8 in Regalecus glesne ), the second by a single, patterned fin ray (5 to 11 in Regalecus glesne ). This is not connected to the anterior ridge or the dorsal fin by a fin membrane. The dorsal fin begins above the back of the head, extends to the tail and thus extends over the entire length of the fish's body. It is supported by 333 to 371 soft rays (414 to 449 in Regalecus glesne ). Of these soft rays, fewer than 82 are located above the abdomen (90 to 120 in the case of Regalecus glesne ). With its undulating movements, the dorsal fin is the main organ for the fish to move. An anal fin is missing, the caudal fin, which is only present in juvenile fish, is small and has four, more rarely three, long fin rays. The long, chest-like ventral fins consist of a single fin ray with more than three appendages formed by the fin membrane. The pectoral fins are supported by 11 to 14 fin rays and have a base oriented horizontally to the body axis, so that when placed on the body, they are directed vertically upwards. Large, fully grown fish have 47 to 60 long, bristly gill rakes on the first gill arch (33 to 47 in Regalecus glesne ).
The mouth is toothless and can be pushed forward far (protractile). At the end of the stomach there is a long appendix that extends to the end of the body. The muscle segments of the trunk muscles are, in addition to the horizontal, vertical and transverse intermuscular septa of most of the remaining teleostei , divided by up to three further dorsal , horizontal and three further ventral , horizontal septa.
Regalecus russelii is capable of self-amputation ( autotomy ). A rear part of the body, e.g. B. the caudal fin, alone or with one or two posterior vertebrae, shed. With increasing age, more and more body sections are shed in the course of a serial autotomy and all specimens that are longer than 1.5 meters have a blunt body end that has been shortened by autotomy. The autotomy does not damage any vital organs and it can only be performed just before the anus . The body parts that are thrown off are never regenerated. There may be a connection between the self-amputation and a lack of food.
Way of life
Regalecus russelii is rare and lives in the open ocean in the tropical and subtropical Pacific and Indian Oceans . Dead specimens were u. a. Washed up on the coasts of Japan, Taiwan, California and Baja California . Underwater photos showed the species with an elongated, stiff body, vertical, with the head up and slowly swimming with the undulating dorsal fin. The fish may adopt the vertical posture in order to be able to better see the silhouette of their prey, consisting mainly of light shrimp , other crustaceans and small fish, in front of the bright water surface as a background. Regalecus russelii often occurs in two or three specimens, but never in a swarm. When meeting conspecifics, the head crests formed by the anterior dorsal fin rays are often held vertically upwards and the long ventral fins are stretched horizontally away from the body. The fish likely spawn between July and December, in the North Pacific west of the Mariana Islands and possibly off the coast of southeastern South Africa. Larvae are found near the sea surface.
Systematics
The first scientific description of Regalecus russelii was provided by the French zoologist and paleontologist Georges Cuvier in 1816 under the name Gymnetrus russelii . Together with Regalecus glesne , Regalecus russelii forms the genus Regalecus and, together with Agrostichthys parkeri , the two species form the belt fish family (Regalecidae), which are the largest representatives of the lampriformes .
Synonyms of Regalecus russelii are: Regalecus caudatus Zugmayer, 1914 , Regalecus glesne pacificus Wood-Jones, 1929 , Regalecus kinoi Castro-Aguirre, Arvizu-Martinez & Alarcón-Gonzalez, 1991 and Regalecus woodjonesi Whitley, 1933 .
literature
- Tyson R. Roberts (2012): Systematics, Biology, and Distribution of the Species of the Oceanic Oarfish Genus Regalecus (Teleostei, Lampridiformes, Regalecidae). Mémoires du Muséum national d'histoire naturelle Paris, ISBN 978-2-85653-677-3 .
Web links
- Regalecus russelii on Fishbase.org (English)