A Skeletochronological Of Age In A Population And Proximate Mechanisms Responsible For Random Mating By Size In The Duttaphrynus Himalayanus

Duttaphrynus himalayanus belongs to the genus Duttaphrynus in the Bufonidae of Anura,class Amphibia.The Duttaphrynus himalayanus is widely distributed in southeastern Xizang,China,with an altitude range of 1680-2800m.In addition to the study of the mitochondrial sequence of the Himalayan toad,other parameters related to life history characteristics such as age of sexual maturity,life span,reproduction time,reproduction mode,etc.are poorly understood.This study mainly explored the age structure data of the Himalayan toad population;the matching pattern of body size between hug individuals;and the proximate mechanism that caused the formation of this body size matching pattern.The specific results are as follows:1.Understanding the age structure of the population can better predict the future development of the population and provide a basic scientific basis for species protection.In this study,skeletal age identification was carried out on the phalanx sample of No.136 Himalayan toad using the method of skeletal age.The results showed that the average age of males in Himalayan toad was 4.54±1.04 years(n=80),and the average age of females was 5.43±1.11 years(n=56).There was a very significant difference between the ages of females and males(t=-4.777,df=134,P<0.001).Among them,the age range of male individuals is 2 to 7 years old,and the age range of female individuals is 3 to 8 years old.It can be seen that the age of sexual maturity of males is 2 years,while the age of sexual maturity of females is 3 years.In males,most individuals are mainly concentrated in the age group of 4 to 5 years old,accounting for 70%of the total number of individuals;in females,most individuals are mainly concentrated in the age group of 5 to 6 years old,accounting for 66%of the total number of individuals.In addition,the average body length of males of Himalayan toad is 78.04±5.78 mm(n=80),and the average body length of females is 95.71±4.29 mm(n=56).There was no significant difference between female body length and male body length(t=9.387,df=134,P<0.001).Correlation analysis showed that female age and body length were significantly positively correlated(r=0.338,n=56,P<0.01),and male age and body length were not correlated(r=0.179,n=80,P>0.01).This research not only increases our understanding of the age structure of the Himalayan toad population,but also provides a research foundation for the breeding ecology and life history of the population.2.The D.himalayanus size-assortative mating the body size of the individuals:It is of great significance for understanding sexual selection to explore whether the evolutionary mechanisms that affect the occurrence of size matching in the animal kingdom.The theory predicts that when there is no correlation between female body size and fertility,an unskewed availability ratio and a short breeding period will result in random pairings of anura body size.We tested this prediction with toads that live in the eastern Himalayas.The study found that female body size did not correlate with fertility,and there was no significant bias in sex ratio during breeding.In addition,the toad's short breeding season,which lasts from late April to early May,is typical of explosive breeding.Our results revealed no apparent size-assortative pairing in the study population of the Himalayan toad.This study has increased people's understanding of the evolutionary mechanisms of whether size matching occurs in lifelong amphibians pairs.3.Proximate mechanism of size matching in D.himalayanusThe theory predicts that when there is no correlation between female body size and fertility,non-skewed effectiveness ratio and shorter breeding period will lead to random pairing of body size of anuras.Our field research found that the body size of the female toad has nothing to do with the number of eggs,egg diameter(egg size)and the size of the nest(Number of eggs:r₃₅=0.12,P=0.489;Egg diameter:r₃₅=-0.01,P=0.389);Litter volume:r₃₅=-0.01,P=0.974).In addition,there is no obvious male or female skew in the ratio of the number of males to females during the breeding period(Male:Female=1.3:1,?~2=3.47,P=0.062).Finally,the Himalayan toad has a short breeding period,which lasts from late April to early May,and is a typical explosive breeder.This study can increase people's understanding of the proximate mechanism of whether size matching between males and females occurs when amphibians hold pairs.