Research On The Growth And Development Of Tadpole Of Leptobrachium Boringii,under Natural Conditions

The life history of most amphibians has two different stages,namely the aquatic tadpole period and the terrestrial or amphibious adult period.Most amphibians development by metamorphosis in their life history.With the change of ecological environment,the morphological characteristics from larvae to adults have also changed greatly.There are many characteristics of adults that have been inherited from larvae,that is,many traits of the adult are determined at the larval stage.Therefore,the growth and development of larvae cannot be ignored in many amphibian studies.The tadpole of Leptobrachium boringii is metamorphosis development.And It has a very long tadpole period.How will such a long development period affect adults and the entire species?What is the mechanism?These are all interesting questions,but first we need a more comprehensive understanding of tadpole development.Therefore,this study took the tadpoles of L.boringii as the research object,and they live in the creek of Qinglong Bay in Badagongshan Nature Reserve of Hunan Province.We combined with field observation and morphological anatomy,tissue section and other experiments to comprehensively understand the growth and development of tadpoles of L.boringii.Subsequent research on L.boringii lay the foundation.We conducted continuous field observations of the tadpoles of L.boringii for more than four months.The natural growth and development of tadpoles of L.boringii are illustrated by analyzing the clutch size,the time of development in key developmental stages,the body size of each stage,diet and activity rhythm.We counted a total of 79 egg clusters,and the average number of eggs was 265.There was no significant difference in the number of eggs between each egg mass(P=0.486).We found that the development time of each stage is unequal.The development time of G1-G25 is about 75 days,the development time of G42 is about 30 days,and the development time of G42-G46 is around 65 days.Based on measuring and analyzing of the morphology of 1181 tadpoles of L.boringii,we found that there were extremely significant differences in body weight,body length,tail length,body width,and tail width in different periods(P<0.001).The body weight of G25-G40 stages increase with the growth period and reaches the maximum at stage G40.Whereas,the body weight of G40-G46 stages decrease with time.The tail length at G41 stage reaches the maximum,and the tail begins to shorten at the G42 stages.The head width increases gradually during the G25-G38 stages,and reaches the peak at G38,and then decreases gradually after G38.In addition,we found that tadpoles of L.boringii do not like strong light,and its activity habit is nocturnal.We used the methods of indoor dissection and tissue sectioning to study the developmental changes of internal organs of tadpole L.boringii.We found that the large intestine and small intestine have differentiated at the G25 stage.The shape of the large intestine and small intestine in the G25-G40 stage are not changed,but the volume increases with body size.There is no obvious change in the digestive tract of tadpoles of L.boringii in G25-G40,which may be related to the consistency of eating habits.Fat bodies have differentiated significantly since the beginning of the G25 stage,at this time they are elongated and bright yellow stripes.From G25 to G40 stages,the volume of fat body increase with time.At stage G27,the fat body starts to develop into finger shape,and the finger branch is few and short.With the growth of the period,the finger body branch becomes more and longer,and the volume becomes larger.We also conducted gonad section experiments at stages G25-G40(n=72).We found that the gonads of tadpole of L.boringii in the G25 stage have clearly differentiated into testes and ovaries.We totally identified 35 ovaries and 33 testes,and the sex ratio of female to male close to 1.Because we found testes and ovaries in each period,we speculated that the differentiation pattern of normal gonads tends to be directly differentiated.Overall,although the tadpole development of L.boringii took three years,some organs developed relatively quickly.The digestive tract of tadpoles has been developed in G25 stage,the gonads have been differentiated before G25 stage,the fat bodies have developed into thin bands in G25 stage,and the fingers have developed in G27 stage.These results lay a foundation for the future research on L.boringii.