| The Bombina maxima was belonged to Bombina,Discoglossidae,Anura,which was main distributed in yunnan,guizhou and sichuan provinces.At present,studies on this species are mainly focused on the extraction and separation of antimicrobial peptides from skin secretions,drug development and molecular biology,but no sexual dimorphism and reproductive ecology had been reported.In this study,with B.maxima as the research object,field observations and laboratory experiments were carried out during the two-year breeding period in 2018 and 2019.The sexual dimorphism,reproductive habit,mating pattern,female reproductive ability and reproductive output and the influence of density on the growth development and survival of B.maxima tadpoles of this species have been studied.This study was beneficial to enrich the biological data of B.maxima and has important theoretical significance for the learning and understanding of this species.The primary research results and conclusions are as follows:1.The results of sexual dimorphism studing showed that the average body length of B.maxima males was(53.54±1.14)mm and females was(52.74±1.45)mm.The average body length ratio of males and females was 1.015 and the heterosexual index was 0.015.The B.maxima was belongs to the amphibians of male was larger than the female and the degree of sexual dimorphism was smaller.There were no significant differences in body length and body mass between male and female(P>0.05),but there were significant differences in head length,snout length,diameter of lower arm,leg length,tibia length,tibia width and length of foot and tarsus(P<0.05).In addition,the growth rate of these 7 local morphological characteristics with body length was greater in males than in females.The sexual dimorphism of B.maxima between female and male adults were mainly manifested in these 7 local morphological characteristics,which related to the success rate of males competing for mating rights.The success rate in the competition for mating rights promoted the male to develop towards larger size,which was consistent with the hypothesis of sexual selection.2.B.maxima select the small puddle of temporary water as the impermanent breeding sites.The average size of the puddle was 2.7 m~2and the average water depth was 7.89 cm.The spawning was not affected by the plant species and with or without plants in the puddle.The selection of breeding sites was mainly reflected in the water area,water depth and water temperature.The breeding time of each year was related to the rainy season,mainly in June and July,and the ratio of female to male was different in every year.The reproduction behavior includes three processes of mating calls,bonding and spawning,all of which are completed in water.The spawning occurs mostly at night and early in the morning and it belongs to the batch multiple spawning type.The average distance from the egg mass to the puddle was(19.61±1.50)cm;The average depth of the egg mass in the puddle was(1.69±0.38)cm;The average spawning amount was(267.58±31.04)grain;The average incubation time was(5.40±0.24)d;The average hatchability was(87.64±1.94)%;The average follicle diameter was(6.89±0.73)mm;The average egg diameter was(3.33±0.20)mm.There are two main reasons why B.maxima choose temporary puddles as the impermanent breeding sites:(1)Because the skin secretions on the body surface of the B.maxima are highly toxic,the skin is rough and the brightly coloured bodies are a warning colour,so predators are afraid to hunt.That's why they're daring to breed in these exposed areas,compared with the amphibians with non-toxic,this species has more advantages.(2)The temporary puddles are strongly affected by rainfall and it was poor breeding habitats for most other amphibians,so other species cannot reproduce normally in such habitats or have was low reproductive success rate.However,B.maxima have been fully adapted to complete the whole reproductive process in this special habitat through the regulation of long-term reproductive strategies and reproductive behavior mechanism,which is the result of the long-term adaptive evolution of this species.3.The results of independent sample t test showed that the body length between the males with successful mating and the males without successful mating of B.maxima was not significantly different(P>0.05).Therefore,the mating pattern of B.maxima was not the body advantage mating pattern.The head length,head width,length of lower arm and hand,leg length and tibia length of the female have a significant positive correlation with the head length,head width,length of lower arm and hand,leg length and tibia length of the male(P<0.05).It showed that the mating pattern of the B.maxima was assortative mating was based on these 5 local morphological characteristics.4.The results showed that the average brood amount of females B.maxima was(384.85±23.34)grain.There was significant positive correlation between the brood amount and body length,body mass,snout length,width of upper eyelid,diameter of eye,tibia length and tibia width(P<0.05),but no correlation between the brood amount and other morphological characteristics such as head length,head width and length of lower arm and hand.The partial correlation analysis of female body length as the control variable showed that the brood amount was only significant correlated with body mass and tibia width,but not with width of upper eyelid,diameter of and tibia width(P<0.05).It showed that the females with larger body length,tibia width and body mass are more reproductive capacity.The females can increase their reproductive output by increasing the size of their own body to increase the size of their abdominal cavity.5.In this study,three groups with densities of A(30/L),B(60/L)and C(90/L)were set to conduct comparative experiments on the growth and development of B.maxima tadpoles.The results of correlation and linear regression analysis showed that the density was significantly negatively correlated with the total length,tail length and body width(P<0.05).The r value of correlation coefficient was:group A<group B<group C.Taking the density of each group as the independent variable and the total length,tail length and body width of B.maxima tadpoles as the dependent variables,the linear regression slope relationships were group A<group B<group C.The results of correlation and regression analysis showed that the growth rate of the B.maxima tadpoles decreased along with the increasing of density,that is,the higher of density the smaller of growth rate.Moreover,there was a extremely significant correlation between density and survival rate(r=0.877,P<0.01).The survival rate of each group was higher in the early stage but gradually decreased in the middle and late stages,and the survival rate under high-density feeding condition was always lower than that under low-density.These findings indicated that B.maxima tadpoles feeding in the higher of density,the lower of survival rate,the slower of growth and development,and enter abnormal phase earlier.In addition,the total length,tail length and body width of the tadpoles during metamorphosis stage were smaller. |
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