Research And Development Of The Skeletal System Tadpole Rana (Rana Quadrana)

The amphibians are the first transition species from aquatic to terrestrial life, whose structure and developmetal process of skeletal system were characteristic. In our study, the development of the Rana quadrana of skeleton from larva to metamorphosis was investigated and studied using double-stained methods. Moreover, we describe the weight and the total lengths of the tadpoles determine the correlation between Gosner development stage and the development of skeleton and external morphology. Theses rusults will provide experimental basis and reference for the skeletal system research of amphibians. The main developmental patterns and conclusions as follows:Skull Skull is composed of cranium, feeling capsule and its internal bone. In the G28stage, tadpoles’skeletal ossification began from the parasphenoid, along the spine from head to tail. In the skull of tadpoles Rana quadranus, ossification of parasphenoid was from stage G26until about stage G28and exoccipital was from stage G28to G30, frontoparietal was from stage G26to G29; prootic was from stage G28to G31, otic capsule was from stage G40to G41and cartilago meckeli and palatoquadrate both began to degenerate in stage G41, after stage G44were degraded completely.Hyobranchial skeleton Brabchial skeleton began to degenerate from stage G42, which may be related to the formation of tadpoles’forelimbs to adapt to terrestrial life. The ceratohyalia are the most robust cartilages in the hyobranchial apparatus, and they gradually got close to the branchial basket with tadpole growth, finally degenerates. Hyoid bone, pars reuniens and hypobranchial plate in early developmental stages are transparent sheet. With the tadpoles development growth, chondrification of hyoid was from two sides to the middle, after which hypobranchial plate gradually hyalinize as ceratohyal began to degenerate, Branchial basket first extended to the ceratohyal and reached a maximum around stage G38, then they began to shrink and eventually disappear from the outside, namely ceratobranchial I. Gill rakers began to grow and develop in stage G26and gill spicules disappeared after stage G41.Vertebral column Vertebral column is composed of eight pre-sacral vertebrae, the sacral vertebra, and the urostyle. It began to develop with the posterior part of the body at stage G26and ossify at stage G28. The ossification began with the junction betwen atlas-sacral lamina of vertebral arch and transverse processes extending from lateral to t center of the vertebral arch. The growth and ossification center of vertebral column begins in a cephalo-caudal sequence (stage G36-G48). Before forelimb appearing, vertebral column has been well (stage G41) and completely (stage G44) ossified. Caudal vertebrae and ventral hypochord completely are fused and formed urostyle. Before stage G38, there are good short transverse processes in vertebral column Ⅲ and Ⅳ clearly. After stage G41, Transverse processes of each vertebral column almost are very clear, especially the sacral process, but the transverse process of vertebrae Ⅲ are always longest. Later metamorphosis, sacroiliac cartilage are formed, hypochord and spinal cord cavity of urostyle are fused together to form urostyle with the tail disappearance.Appendicular skeleton pectoral girdle and sternum The ossification of appendicular skeleton is from proximal to distal. Hindlimb began to develop at G26stage and its phalangeal formula is2-2-3-4-3. The first ossifications of the hindlimb form at the femur, tibia, fibula, and fibulare at stage G34. Their relative sequence of appearance could not be established. The tibia ossified in stage G36and fibula in stage G35, the both bone fused in about stage G40. First formation of metatarsal III and IV occurred in stage G35. Metatarsal ossified at the same time or later rather than femur, tibia, fibula, and fibulare.The forelimb began to develop at stage G33and its phalangeal formula is2-2-3-3. Cartilaginous primordia of the scapula, coracoid, humerus, radius, ulna, radiale, and ulnare are present at stage G34. The radius and ulna ossified independently, merged at stage G38. Pectoral girdle began to ossify at stage G40, the ossification of are later about one Gosner stage than suprascapula and coracoid, at the same time than clavicle. The ossification of phalanges started with digits III and IV (stage G38).