Presence of protocercal tail in some highly developed fishes is possibly due to its secondary modification. Other fins are mainly used as steering devices and rudders.
Chimaera jordani S. Tanaka (I), 1905 (Jordan's chimaera) Chimaera lignaria Didier, 2002 (carpenter's chimaera) Chimaera macrospina Didier, Last & W. T. White, 2008 (longspine chimaera) Chimaera monstrosa Linnaeus, 1758 (rabbit fish) Chimaera notafricana Kemper, Ebert, Compagno & Didier, 2010 Cape chimaera Cloaca is absent. The upward terminal portion of vertebral column is withdrawn.
They have internal ears which help the fish keep its balance. The caudal fin is mostly heterocercal -asymmetrical (Gr.heteros- different). It is the intermediate type in which vertebral column bends upwards and reaches up to the tip of the more prominent dorsal lobe, thus, making the caudal fin strongly asymmetrical (Gr., heteros = different, other). These include pectoral fins anteriorly Both the unpaired median and paired fins are supported by skeletal rods called radials and dermal fin rays. The median or unpaired fins in fishes are believed to have originated from a continuous fold of tissue.
Latimeria and extinct coelacanths have unique symmetrical three-lobed tail with a marked median lobe. The homocercal (Gr., homos = common, alike) caudal fin is the characteristic of the higher bony fishes (teleosts).
Oil is extracted from its liver. According to this theory, recent workers claim that the so-called “several pairs of fins” in acanthodians indicate nothing but a special kind of multiplication of the defensive spines, which may often support membranous structures.
Fish are very different in appearance, size and shape. According to this theory, the paired fins have originated from a paired lateral continuous fin-folds running down each side of the body behind the gill-openings up to the end of the tail.
Fish swim mainly by lateral movement of tail and tail fin. This website includes study notes, research papers, essays, articles and other allied information submitted by visitors like YOU. In India, Scoliodon dumerili is common in the Bay of Bengal, here are present some pores, the ampullary pores on the upper and lower surface of the head: each pore leads into an ampulla(pl. Torpedo can generate electric current. This theory was accepted by most of the workers in this field of research. Aug 3, 2016 - In Greek myth, a chimera ia a combination of various animals. Rhinobatus (guitar fish) Pnstis, Zygaena, Carcharodon (Great White Shark). Male has a frontal or cephalic clasper on the dorsal surface of the head, its function is unknown. Torpedo) and some possess poison sting (e.g.Trygon). In bottom dwelling rays, the caudal fin tends to become reduced and in the sting rays the caudal fin is lacking. Chimaeras are cool-water, marine fishes that live at shallow to moderate depths between 80 and 2600 m, where they usually swim just above the bottom. Three main types of caudal fins are found in fishes. The position of the pelvic fins can be explained on the assumption that some of the posterior gill-arches have been shifted posteriorly.
This makes for some interesting beings, including humans. Surprisingly little is known about their general biology and natural history. Urea is chief nitrogenous waste.
The skin is tough, containing minute placoid scales, which are dermal in origin. Heart is two chambered (one auricle and one ventricle).
Subsequently all spines and webs may have been lost except one anterior and one posterior pair which later evolved into pectoral and pelvic fins.
This is called abbreviated homocercal caudal fin. 15. There is no apparent dorsal lobe but the ventral lobe is greatly enlarged and divided into two equal superficial lobes. The dorsal half is called epichordal lobe and the ventral half is known as hypochordal lobe. Other ostracoderms had ventro-lateral rows of dermal spines similar to extra fins of acanthodians.
It is a voracious surface feeder and fast swimmer. Most of these spines were lost while some were retained in the pectoral and pelvic regions, thus, accounting for the origin of paired fins (and limbs) from ostracoderm ancestors. In some deep sea fishes, the terminal part of vertebral column is straight and greatly elongated to form isocercal caudal fin or tail. The protocercal or diphycercal type of caudal fin is considered as the most primitive type, the heterocercal as the intermediate stage and the homocercal condition represents the advanced stage. 16. Our mission is to provide an online platform to help students to share notes in Biology. It uses the denticles for offence and defence.Its body is intermediate between the sharks and the rays. According to Graham Kerr, paired fins and their skeleton are derived from external gills which occur temporarily in some larval forms. The body is somewhat kite-shaped. It is an interesting fish that represents the characters of a shark and a bony fish.
(i) Basic skeletal structures of paired and unpaired fins are similar indicating a common mode of origin, (ii) In the embryos of certain elasmobranchs, early stages show continuous series of muscle bands which disappear, except those forming the isolated paired and unpaired fins. 8. Scoliodon is also eaten as food by some persons. 6. The vertebral column extends up to the tip of the tail and divides the caudal fin into two equal halves. The Elephant Fish is caught commercially during the inshore migration, either in trawls or set nets. Chimaera: ADVERTISEMENTS: It is commonly called rabbit fish, rat fish, ghost fish or king of her rings. Furthermore, no true primitive fossil fish with completely continuous fins is still known. The strokes of larger dorsal lobe in swimming serve to direct fish towards bottom. What are the functions of HCl of the gastric juice? There is well developed renal portal systems RBCs are oval and nucleated.