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This process involves cells migrating inward to form a structure similar to a blastopore. During this stage, cells undergo significant morphological alterations, wherein the main body of each cell is propelled into the interior of the embryo. Despite this inward movement, cells remain connected to the embryo's exterior via a slender extension ...
The majority of amphibians use cutaneous respiration, or the process of breathing through the skin. Due to the importance of the skin, amphibians are very sensitive to what goes through their permeable skin, the stratum corneum is the main skin barrier which is much thinner than other classes such as mammals or birds.
The skin colour of amphibians is produced by three layers of pigment cells called chromatophores. These three cell layers consist of the melanophores (occupying the deepest layer), the guanophores (forming an intermediate layer and containing many granules, producing a blue-green colour) and the lipophores (yellow, the most superficial layer).
The structure of the feet and legs varies greatly among frog species, depending in part on whether they live primarily on the ground, in water, in trees, or in burrows. Adult anurans have four fingers on the hands and five toes on the feet, [51] but the smallest species often have hands and feet where some of the digits are vestigial. [52]
In frogs and toads, the tympanum is a large external oval shape membrane made up of nonglandular skin. [2] It is located just behind the eye. It does not process sound waves; it simply transmits them to the inner parts of the amphibian's ear, which is protected from the entry of water and other foreign objects.
The main bodies of the cells lie outside of the pigment cup, while the cilia extend into the pigment cup before turning and exiting. The cells bear the opsin c-opsin 1, except for a few which carry c-opsin 3. [60] [62] The Row 2 cells are serotonergic neurons in direct contact with Row 1 cells. Row 3 and 4 cells are also neurons.
These are reduced in adulthood, their function taken over by the gills proper in fishes and by lungs in most amphibians. Some amphibians retain the external larval gills in adulthood, the complex internal gill system as seen in fish apparently being irrevocably lost very early in the evolution of tetrapods. [12]
The largest part of it is a special structure called the valvula, which has an unusually regular architecture and receives much of its input from the electrosensory system. [ 66 ] Most species of fish and amphibians possess a lateral line system that senses pressure waves in water.