Changes In Bone Morphology During Metamorphosis Of Chinese Forest Frog

The development of the skeletal system is an extremely important part of the field of developmental biology.At the present,studies on bones have focused on a single period of adult or larvae of a species,and studies on the morphological changes of bones during growth and development have rarely been reported.In this paper,the Gonser stage method was used to select the 21 stages of Rana chensinensis G26-G46 which are widely distributed in northern China and have strong adaptability to terrestrial life.Firstly,the basic data such as body length,body weight,and total length were measured for the selected experimental samples.Then the modified bone morphological double staining method of Toyal et al.was used to perform bone staining on Rana chensinensis G26-G46.After staining,the cartilage of the Rana chensinensis sylvatica is blue and its bone is red.With stereomicroscope,the morphological changes of bone in the growth and development of Rana chensinensis were compared and observed,and the images were collected and analyzed under the same parameters.The study reveals intuitively the appearance sequence,morphological changes and ossification order of whole-body bones of Rana chensinensis at different developmental stages in order to provide morphological basis for the evolution of vertebrates from aquatic to terrestrial.The main results and conclusions are as follows:1.Obtained image data of whole-body bone of Rana chensinensis sylvatica G26-G46.2.Acomprehensive observation and description of the appearance order,morphological changes and ossification order of whole body bones of Rana chensinensis sylvatica during metamorphosis development.3.The occurrence and ossification of the axial ridge of Rana chensinensis sylvatica was earlier than that of the appendicular bone.The order of appendicular bone appeared from the proximal to the distal and the ossification of the single joint from the center to both ends.4.The cranial cartilage of Rana chensinensis sylvatica consists of the maxilla,mandible,trabecular bone,cartilage of sacral side,cranial cavity,cap bone,and auditory sac.Before the G38 stage,the cartilage cranial parts grew at the same rate,and the G42 stage cartilage skull began to undergo more severe deformation;the ossification of the cartilage skull began from the G34 stage until the ossification of the G44 stage was basically completed.5.The hyobranchial skeleton of Rana chensinensis sylvatica are composed of four parts:the tympanic bone,the associated bone,the infrapatellar plate,and the orbital basket structure.Before the G40 stage,the tongue and tarsal bones grew at equal rates.In the G42 stage,the spasmodic structure of the tongue and cheekbones was rapidly degraded and turned into a part of the hyoid bone in the G46 stage.6.The spine of Rana chensinensis sylvatica consists of eight sections of the sacral anterior vertebrae(including one sacral vertebrae),one sacral vertebrae,and one caudal vertebrae.At the time of G26,it had already had a spine shape,and the G30 stage had started to ossification,and by the time of G42 ossification was basically completed.The front end of the spine of the Rana chensinensis sylvatica has already had a sacral spine,which makes the head have a certain ability to move.However,since only one sacral vertebra is differentiated,the range of motion of the head is still small.7.The appendicular bone of Rana chensinensis is composed of forelimb bone and hindlimb bone.The appendicular bone contains bone and free limb bone.The forelimbs and hind limbs were visible in the G36 stage,and the fingers/toes were completely present by the G40 stage.The appendicular bone begins to ossification in the G38 stage,and G42 ossification has been substantially completed.The appearance and ossification of appendicular bones have enabled Rana chensinensis sylvatica to have appendages of the five-finger/toe type and have acquired basic conditions for adapting to terrestrial conditions.