Estimation of repeatability and phenotypic correlation of reproductive traits in zebrafish Danio rerio

This study was conducted to estimate the repeatability and phenotypic correlation of reproductive traits of zebrafish Danio rerio, in captive condition. Breeding trials were conducted on 10 breeding pairs (2 male:1 female). The data on fecundity, fertility, hatchability and survival rate were recorded. The repeatability values were computed as a measure of consistency using the intra-class correlation coefficient. The repeatability estimates for fecundity, fertility, hatchability of total eggs, hatchability of fertilised eggs, survival rate of total eggs and survival rate of larvae were 0.701, 0.406, 0.336, 0.049, 0.295 and 0.314, respectively. Most of the reproductive traits analysed had moderate repeatability values barring the hatchability of fertilised eggs. The phenotypic correlation was calculated using the Pearson correlation method. The phenotypic correlations of fertility with hatchability of fertilised eggs; hatchability of total eggs; survival rate of total eggs and survival rate of larvae were highly significant (p≤0.01). This study provided valuable information on the consistency of reproductive parameters which would serve as model for conducting research in other fish species

Study of the transient nature of classical Be stars using multi-epoch optical spectroscopy

Variability is a commonly observed property of classical Be stars (CBe) stars. In extreme cases, complete disappearance of the H{\alpha} emission line occurs, indicating a disc-less state in CBe stars. The disc-loss and reappearing phases can be identified by studying the H{\alpha} line profiles of CBe stars on a regular basis. In this paper, we present the study of a set of selected 9 bright CBe stars, in the wavelength range of 6200 - 6700 {\AA}, to better understand their disc transient nature through continuous monitoring of their H{\alpha} line profile variations for 5 consecutive years (2015 -- 2019). Based on our observations, we suggest that 4 of the program stars (HD 4180, HD 142926, HD 164447 and HD 171780) are possibly undergoing disc-loss episodes, whereas one other star (HD 23302) might be passing through disc formation phase. The remaining 4 stars (HD 237056, HD 33357, HD 38708 and HD 60855) have shown signs of hosting a stable disc in recent epochs. Through visual inspection of the overall variation observed in the H{\alpha} EW for these stars, we classified them into groups of growing, stable and dissipating discs, respectively. Moreover, our comparative analysis using the BeSS database points out that the star HD 60855 has passed through a disc-less episode in 2008, with its disc formation happening probably over a timescale of only 2 months, between January and March 2008.Comment: 19 pages, 7 figures, 2 tables, accepted in JAp