Amphibian+Anatomy

Mucous and poison glands are most common on amphibians and are found all over the body. Mucous glands are the most abundant and continuously secrete a clear mucouse that maintains a moist, thin layer over the skin. Poison, or granular, glands are mostly found on the head and shoulders of amphibians. Although amphibians do not have scales they do have some structures made of keratin. Some examples of these are; the spiny or rough skin of somes salamanders and frogs, the spades of the pelobatid frogs, and the claw like tips at the toes of pipid frogs(p. 47) While the structures previously mentioned occur year round, there are some keratinouse strucures that appear only seasonally, like for mating season.

** Skin  ** Mucous and poison glands are most common on amphibians and are found all over the body. Mucous glands are the most abundant and continuously secrete a clear mucous that maintains a moist, thin layer over the skin. Poison, or granular, glands are mostly found on the head and shoulders of amphibians. Although amphibians do not have epidermal scales they do have some structures made of keratin. Some examples of these are; the spiny or rough skin of some salamanders and frogs, the spades of the pelobatid frogs, and the claw like tips at the toes of pipid frogs (p. 47). While the structures previously mentioned occur year round, there are some keratinous structures that appear only seasonally, and are usually for mating. For example, some male salamanders and frogs will have nuptial pads on their thumbs during mating season (p. 47). Such structures are generally shed at the end of the season. Of all amphibians, only caecilians have dermal scales, and not all caecilians have them. These dermal scales are bony plates that are buried in the annular grooves. As adults, amphibians will shed their skin in cycles that range from a few days to a few weeks. This shedding is called ecdysis. The stages of ecdysis are controlled by hormones. First, new cells that are made by the stratum germinativum move out and up as other new cells are made beneath them. After the new cells and the basement cells lose contact division stops and they lose their sub cellular organelles as they mature (p. 48). The skin splits mid-dorsally over the head then down the back. (p.48) Amphibian color is affected by the pigment cells, chromatophores. There are three classes of chromatophores: melanophores; which are black, brown, or red in pigment, Iridophores; which are reflective or white, and xanthophores; which have yellow, orange, or red pigment. ** Skeleton and Muscles  ** As amphibians evolved from fish major reorganizations of the muscles and skeletal structure was necessary. As aquatic life switched to terrestrial life, buoyancy support disappeared. The more intense pull of gravity required a strengthening of the spinal column. Because of the shift from undulatory to limbed movement a more tightly linked vertebral column was needed, along with elaborate limbs and girdles, and modified cranium for the better capture of food. (p.49-50) The skull is made up of three parts. The chondrocranium, the splanchnocranium, and the dermocranium. The chondrocranium is the part of the skull surrounds the brain and sense organs. The splanchnocranium is the visceral arch. This is the upper and lower jaws, the gill arches, and the hyobranchium. The dermocranium is the roofing elements. (p. 50) The vertebral column is rigid and strong so that it can support the girdles and head, while being flexible enough that lateral movement is possible.  Each individual vertebra has a Centrum (central cylinder) and a dorsal neural arch. The anterior end of each Centrum connects to the posterior end of the preceding Centrum. Ribs are shorter in amphibians than in other tetrapods. (p.55)

Order Caudata

Order Gymnophiona

Order Anura