Study On The Age Structure And Correlation Of Three Frog Populations In Tibet

In order to deeply understand the population characteristics of amphibians and age structure in Tibet,explore the current living conditions of amphibians,three samples of frogs obtained from our scientific expedition in Tibet were selected for skeletochronology study,the aim is to accumulate more relevant biological information and to provide a theoretical basis for the conservation of the species in the region.In this study,the age structure,body length,morphology of gonads and age of sexual maturity of three populations of three species of Tibetan,Bufo tibetanus(?29,?34)in Nyingchi City,Nanorana chayuensis(?49,?37)in Xiachayu Shama Village and Nanorana parkeri(?18,?30)in Nyingchi town were studied by using skeletochronology and supplemented by observation of gonad morphology and histological structure.Age was estimated by observing the number of lines of arrested growth on finger or phalangeal tissue sections,and established the age structure of population.Mann-Whitney U was used to test whether there was significant age difference between males and females at different ages.ANOVA analysis was used to examine the differences of lines of arrested growth distance among the three species.Spearman correlation was used to analyze the correlation between male and female body length and age of different species.Von Bertalanffy model SVL_t=SVL_max(1-e^-kt+b)was used to establish the growth curves of three populations to estimate the growth patterns of species.After staining with hematoxylin and eosin the tissue sections of finger or phalange were observed under microscope,the lines of arrested growth could be observed on the sections of all three species,indicating that the skeletochronology is suitable for the study of species in Tibet.This study observed population of Bufo tibetanus,which longevity of females(9 years)was longer than that of males(8 years),and the sexual maturity age of both sexes was 4 years.In the Nanorana chayuensis population,the maximum life span of females is 7 years and that of males is 6 years.The age of sexual maturity of both sexes is the same,which is 4 years.The maximum life span of females and males in the population of Nanorana parkeri is 7 years,the age of female sexual maturity is 4 years,and the age of male sexual maturity is 3 years.The results showed that the age structure of Bufo tibetanus,Nanorana chayuensis and Nanorana parkeri showed growth type and stable type during the time of collection,with healthy development potential.There was a significant correlation between body length and age of the three species(P<0.01).No significant difference in the average age of male and female of among the three species(P>0.05).There was no significant difference in body length between male and female in different age groups of Bufo tibetanus(P>0.05).The body length between males and females of Nanorana chayuensis only at the 2nd,5th and 6th were different(P<0.05).Except for the2nd age group,there was no significant difference in body length between male and female in all age groups of Nanorana parkeri(P>0.05).