Effect of Incubation Temperature on Embryonic Development, Hatching and Sex Ratio inLabeo rajasthanicus
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Date
2016
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MPUAT, Udaipur
Abstract
Recently, Labeo rajasthanicus is identified as a new species. It has good local demand and being considered as an endemic species in the West and South-West part of Rajasthan, India. Development of captive breeding protocol and effect of temperature on embryonic development and sex ratio of this species is necessary for production of seed at commercial scale as well as to conserve gene pool of this species. The experiments were conducted to find out the optimum dose of Gonopro-FH and suitable temperature for breeding, incubation and rearing of spawn.
To determine the optimum dose of Gonopro-FH for Labeo rajasthanicus, breeding trials were conducted during breeding season of 2014 and 2015. For this purpose, four hormone treatments (i.e., 0.2, 0.3, 0.4 and 0.5 ml/kg body weight) were tried in captive conditions. The result obtained from this study indicated that relative fecundity was highest with hormonal dose of 0.4 ml/kg of Gonopro-FH. However, it was not significantly different from other treatments. Fertilization and hatching rate were highest with 0.2 ml/kg dose of Gonopro-FH.
The effect of temperature on breeding, fertilization, hatching and hatchling survival was studied under controlled conditions. The fish, Labeo rajasthanicus was induced bread using 0.2ml/kg dose of Gonopro-FH (selected through preliminary experiments) under different temperature treatments (22, 26, 30, 34 and 380C). The optimal temperature for breeding and egg incubation of L. rajasthanicus ranged from 22 to 300C.Higher fertilization, hatching rate and hatchling survival was recorded at a temperature range of 26-290C. Further, the highest and lowest survival rate were observed in 26 and 340C treatments respectively. Average survival rates at different temperatures were generally decreased with increasing temperature.
To assess the impact of temperature on growth and survival of L. rajasthanicus spawn, the experiment was conducted under laboratory conditions using FRP tanks (1m3). Four temperature treatments (22, 26, 30 and 340C) were used in triplicate. Total five thousand spawn were stocked in each tank and their growth and survival was monitored for a period of 21 days. The weight gain had positive relationship with temperature treatments and growth gain increased with increasing temperature (22 to 300C). However, the further increase in rearing temperatures (30 to340C) resulted a reduced growth rate. SGR was significantly higher at 300C (5.19 ± 0.11) as compared to other treatments except 260C. Whereas, lowest SGR (4.04 ± 0.06) was found in lowest (220C) temperature treatment. In general the spawn reared at 300C and lower temperature performed better than that reared at higher (340C) temperature
To assess the embryonic development of Labeo rajasthanicus, eggs were incubated at five different temperatures (22, 26, 30, 34 and 380C). Developmental stages were monitored by sampling embryos in five different temperatures at particular intervals. The eggs incubated at 38°C did not developed beyond two cell stage. Maximum duration for hatching and times to reach different life stages was observed at 22°C followed by 26°C.Hatching of eggs was observed after 20.27±0.29, 17.48±0.16, and 15.03±0.13 and 17.13±0.20 hours of fertilization in 22, 26, 30 and 340C respectively. The hatching time and time to attain different ontogenic stage were decreased with increased temperatures. This study demonstrated that incubation temperature significantly (p<0.05) influenced hatching duration, and ontogenic development in L. rajasthanicus.
The percentage of males and females in Labeo rajasthanicus population reared initially for 28 days at different temperatures (22, 26, 30 & 34 ⁰C) and subsequently at normal temperature for six months was significantly different between lower (22-260C) and higher (30-340C) temperature ranges. A two-way analysis of variance showed that the increase of water temperature in favour of males over females among offspring of L rajasthanicus. The temperature at which all offspring would be females was found to be 16.020C. Whereas the average temperature at which all offspring would be all males was found to be 25.88°C.
Description
Effect of Incubation Temperature on Embryonic Development, Hatching and Sex Ratio inLabeo rajasthanicus
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Citation
Paliwal and Saini, 2016