Evolutionary theories regarding why countershading evolved include the benefits of self-shadow concealment which results in improved background matching when viewed from below. When light falls on an object it makes it appear solid, acting as a visual cue which makes the object easier to detect. Natural selection favored this form of camouflage as it reduces the ease of detection by predators and prey by counterbalancing the effects of self-shadowing. All sea turtles' undersides are lightly colored, and the dorsal surface is dark grey and/or black. CountershadingĬountershading, also known as Thayer’s Law, is a pattern of animal coloration that aids in camouflage. The "Green" common name comes from the greenish color of turtles’ fat found in layer between their inner organs and their shell. The Green sea turtle carapace has various color patterns that change over time. Sheath of upper jaw possesses a denticulated edge, lower jaw has stronger, serrated and defined denticulation. Front appendages have only a single claw, hawksbill has two claws on each flipper. Its closest relative is hawksbill turtle, but green turtle’s snout is shorter and beak is unhooked. The Green sea turtle is the only species in genus Chelonia, is native to tropical and subtropical seas around the world. Even though Hawksbill is spongivorous, scientists believe they evolved from carnivorous ancestors. Evolutionary adaptation against predators. Hawksbill sea turtle flesh can become toxic due to its consumption of venomous cnidarians. They have a shell that changes color depending on the water temperature. The common name "Hawksbill" comes from their sharp, curving beak. comparatively, Green and Leatherback sea turtles crawl symmetrically. Hawksbill sand tracks are asymmetrical because they crawl on land with an alternating gait. They possess a flattened body shape, protective carapace, and flipper-like arms adapted for swimming in the open ocean. There exists an Atlantic and Pacific subspecies. The Hawksbill is the only extant species in the genus Eretmochelys. Leatherbacks are the largest sea turtle, with their shells reaching as long as 7 feet and weighing over 1,000 pounds at maturity. They are unique developmentally among reptiles in that their scales lack beta keratin. Instead of scutes, this turtle has thick leathery skin with embedded miniscule osteoderms. The Leatherback bears a mosaic of bony plates beneath its leathery skin, and does not have a bony carapace. It is the only living species in the genus Dermochelys. The Leatherback is the only sea turtle that does not have a hard shell. Each species is individually distinguishable by the presence or absence of prefrontal scales on the head, the number and shape of scutes (keratin-based segment of the shell) on the carapace, and the type of inframarginal scutes on the plastron. All species except the Leatherback belongs to the Cheloniidae family. All species of turtles belong to the Testudines order. After analyzing genomes of green sea turtle, results indicated the close relationship of the turtles to the bird-crocodilian lineage from which they plit 267-248 million years ago (Upper Permian to Triassic Period). Sea turtles became distinct from all other turtles at least 110 million years ago.
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