Study Of Morphological Development In The Giant Salamander Embryo Of The Respiratory Organs

Chinese giant salamander(Andrias davidiamus) referred to as giant salamander. commonly known as giant salamander, belong to Amphibia. Caudata inplicit gill giant salamander families. Chinese giant salamander is the biggest and rarest amphibian in actual existened in the world, State Class II of evolutionary history in the study of vertebrates from aquatic to terrestrial.In order to accumulate and provide basic date for the giant salamander embryo development, artificial breeding and resource protection,the histological structure changes of respiratory organs of giant salamander in post-embryonic development were examined in this pape, by means of normal paraffin section method, microcopy system and digital camera. The main result and conclusions as follows:1. The structure and post-embryonic development of external gill.Giant salamander has three pair external branchia. external branchia begins atrophy at 300 day after hatching, external branchia still exists at 450 day after hatching but gill filament attenuat and shorten, at 470 day after hatching disappears. Filum branchiale consists of respiratory epithelial cell and connective tissue, epithelial cells most are cuboidal. connective tissue distributes parenchima, chromatophore and capillary. With the development of giant salamande chromatophore and capillary become more and more, at 60 day after hatching the capillary quantities increase evidently, and reach the most at 300 day after hatching, and then become decrease gradually. From the characteristic of post-embryonic development of giant salamander, we can see that external branchia is the primary respiratory organs of larva.2. The structural characteristic and post-embryonic development of skin. There is many diversity in the thickness in different part of giant salamander, the skin of head and back is the thickest, and then the tail, the abdomen is thinest. At 1 day after hatching the thickness of epidermis is about 20μm.1-2 layer, circular or elliptic, loose; With the development of post-embryonic, the number of epidermis plies is increasing and differentiate, the number of cell plies is 6-8 layer, and the thickness is 100μm. at 200-250 day after hatching become divided into germinative layer and pinacocyte pinacocyte layer, the local of epidermis occur slight keratinization; besides at 100 day after hatching the head epidermic cells become divided into superficial neuromast. and then develop to the nines at 150 day after hatching. The dermis is made of tectorium and tight layers, tight layers distribute 3 glandular integumentaria; At 40 day after hatching, the back becomes conscious of mucous gland and granular gland; At 60 day after hatching, the tail appears mucous gland and granular gland, and the abdomen becomes conscious of granular gland:At 200 day after hatching, the head appears granular gland; At 250 day after hatching, the back and abdomen appear mucous gland; At 450 day after hatching, the head and abdomen appear mixed gland; With the development of giant salamander, the quantity and thickness of the skin and gland in each part become more and more. There is capillary in the epidermis and dermis. the back is the most, and then the head and tail, the abdomen is the fewest; There is capillary in the dermis at 1 day after hatching, at 200 day after hatching, the germinative layer of back appears capillary, at 350 day after hatching, the head, abdomen and tail also appear capillary; With the development of post-embryonic, the capillary in the epidermis and dermis is increasing. So we can see that the skin plays an important part during the respiratory.3. The post-embryonic development of lung. The lung of giant salamander is coupled, hollow, conical, thin-walled capsule. At the 40 day after hatching king appears, lung pouch wall consist of 2-5 layer cell, those cells are analogous basically, and have not happened differentiation; At the 60 day after hatching, lung pouch wall divided epithelia, which is orderly and is cuboidal or compressed; At the 300 day after hatching, some of the intineof lung forms hollow; At the 350 day after hatching, the hollow deepen; At the 450 day after hatching, the terminal of hollow near to the outside surface. With the development of giant salamander, the quantity of capillary in lung become more and more, so we can see that the respiratory function of lung is becoming perfect.4. The larva of giant salamander uses external gill to breathe, the skin play a part of accessorial breath. With the development of giant salamander, lung appears, but external gill shrinks gradually, during the period of shrinking of external gill, lung have not developed perfectly, so during this period cutaneous respiration seems more important. In short, giant salamander breath under the mating of external gill, skin and lung, wich can help giant salamander acquire more oxygen.