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Guitarfish have a body form intermediate between those of sharks and rays. The tail has a typical shark-like form, but in many species, the head has a triangular, or guitar-like shape, rather than the disc-shape formed by fusion with the pectoral fins found in other rays.
The pectoral fins have fused to the branchial region of the head, the body begins to gain pigment, and the eyes have developed. When stage four is reached, the embryos still have an external yolk sac, but entirely resemble adults. The dorsal surface is brown and spots on the snout have developed. Claspers in males at this stage also become visible.
The thresher sharks have an extreme example of this tail in which the upper lobe has evolved into a weapon for stunning prey. Bottom-dwelling sharks such as catsharks and carpet sharks have tails with long upper lobes and virtually no lower lobe. The upper lobe is held at a very low angle, which sacrifices speed for maneuverability.
The eastern shovelnose ray is an elasmobranch, a subclass of cartilaginous fish including sharks, rays, skates and sawfish — the modern descendants of the first jawed vertebrates. [11] This subclass are generally apex predators and therefore occupy the highest trophic level in their ecosystems, meaning they are at the top of the food-chain.
Rhina ancylostoma, also known as the bowmouth guitarfish, shark ray or mud skate, is a species of ray and a member of the family Rhinidae.Its evolutionary affinities are not fully resolved, though it may be related to true guitarfishes and skates.
With his hand close to razor sharp teeth, shark expert Neil Harvey attempts tonic immobility in a large reef shark. Tonic can be induced by turning a shark upside down, but that's not the only way.
"We have to think about it in terms of the food web that's out in the ocean: Ultimately, at the very top of that cycle of life are the sharks and if we removed the sharks, smaller fish species ...
Many sharks can contract and dilate their pupils, like humans, something no teleost fish can do. Sharks have eyelids, but they do not blink because the surrounding water cleans their eyes. To protect their eyes some species have nictitating membranes. This membrane covers the eyes while hunting and when the shark is being attacked.