Reproductive Biology Of Mastacembelus Armatus

1.Differential significance analysis,principal component analysis,R-cluster analysis and discriminant analysis were used to measure and analyze 3 quantitative characters and 25 standardized characters traits of 248 individuals in the Pearl River basin.In the characters where the variances are homogeneous（P>0.05）difference significance analysis results show that there were 2 characters of Upper jaw length/Head length and L_1-3/Body length reaching a significant level,12 characters reaching a very significant level.In the principal component analysis,7 principal components were extracted,and the cumulative contribution rate reached 77.040%.Combined with the results of principal component analysis and R-cluster analysis,it is shown that the differences in the individuals of the M.armatus are mainly concentrated in the head,fish morphology and tail.Sixteen characters were screened out from 25 standardized morphological characters of 248 M.armatus by stepwise discriminant analysis.The sex discriminant equation was established,and the comprehensive discriminant accuracy rate for male and female population was 69.2%.Females have longer heads and trunks,wider eye spacing,and higher body height than males;males have longer upper and lower jaws,longer tails,and longer body lengths than females.The above research results can provide a method and theoretical basis for the identification of the sex of M.armatus.2.In this study,we studied the gonadal development and serum sex steroid hormone changes of 247 individuals of M.armatus by morphological measurement,histology and enzyme-linked immunosorbent assay.During the reproductive season,the female fish had a lighter body color,pale yellow,the abdomen was enlarged,soft to touch and the figure was short and thick.The male fish had a darker body color and furvous,with no obvious abdominal enlargement and the figure was slender.The reproductive period of M.armatus is mainly from March to July.It belongs to the type of multiple spawning and batch asynchronism.The testis of M.armatus belongs to the foliate type.The absolute fecundity was 455-7064 eggs and the relative fecundity was 9.10-61.81 eggs/g.Pearson correlation test showed that there was no significant correlation between GSI and HSI（P>0.05）,but there was a significant positive correlation between fullness and GSI（P<0.05）,and a significant negative correlation between fullness and HSI（P<0.05）.The changes of serum sex steroid hormone levels were similar to those of GSI,reaching peak values at reproductive stage of gonadal maturation.Pearson correlation test showed that estradiol and testosterone in female fish were positively correlated with GSI（P<0.05）,while estradiol in male fish was positively correlated with GSI（P<0.05）,while testosterone was positively correlated with GSI coefficient and fullness（P<0.05）.3.We cloned the Foxl2 gene and analyzed its expression in the reproductive cycle of M.armatus.Foxl2 gene was 1872 bp in length with a 918 bp open reading frame encoding 305 amino acids.The C-terminal region and the forkhead domain of Foxl2 in M.armatus were highly conserved,but the N-terminal region was quite different from that of other teleost fish,birds,amphibians,and mammals.Quantitative real-time polymerase chain reaction showed that Foxl2 was highly expressed in the ovary.During the embryonic and early larval development,Foxl2 expression showed two peaks,one at the gastrula stage and another at 25 d after hatching.During the gonadal development,Foxl2 expression in the gonad was higher at later stages（peaking at stage V）of ovary maturation,while it was higher at earlier stages（peaking at stage III）of testis development.In the brain of female and male fish,high expression of Foxl2 was observed during the later stages IV and V of gonadal maturation.In situ hybridization experiments showed that Foxl2 gene of Mastacembelus armatus was mainly expressed in the follicle cells of the ovary and in the interstitial cells of the testis.These results suggest that the Foxl2 gene is involved in the regulation of early development and gonad development in M.armatus.