| The breeding and ripening of parent shrimp directly affect its reproductive performance,which is very important in the large-scale artificial breeding of Exopalaemon carinicauda.At present,the source of parent shrimp of E.carinicauda mainly depends on offshore or shrimp pond capture.Its gonad development is uncontrollable and easy to carry pathogens.Subsequent parent shrimp transfer and transportation will inevitably cause varying degrees of mechanical damage.These factors will bring certain losses and difficulties to the large-scale artificial breeding of E.carinicauda and restrict the development of industrialized breeding of E.carinicauda.Therefore,this paper uses the single factor control variable method to study the effects of main environmental factors and male female ratio on the growth,gonad development and biochemical indexes of E.carinicauda under the condition of industrialized culture,so as to explore the suitable conditions for promoting the maturation of E.carinicauda,so as to provide theoretical reference for the standardized artificial breeding and industrialized culture of E.carinicauda.1.Effects of different photoperiods on growth and gonadal development of E.carinicaudaIn order to explore the effects of different photoperiods on the growth and gonadal development of E.carinicauda,the growth,gonadal development and hemolymph biochemical components of E.carinicauda under five photoperiods(light L,16L:8D,12L:12D,8L:16D,darkness D,L represents the length of light and D represents the length of darkness)were measured.The survival rate of group 16D:8L was the highest in the whole group;In terms of specific growth rate,the specific growth rate of 8L:16d group was(2.49 ± 0.20)%/d,which was significantly higher than that of darkness group(P<0.05);In terms of molting rate,the molting rate of 8L:16D group was the highest,which was(6.96 ± 0.50)times/(tail·d);The gonadal index increased gradually with the shortening of light time,and reached the highest value of(2.37 ±0.04)% when the light time was 8L,which was significantly higher than that in other groups(P<0.05);The ovarian maturation rate in 8L:16D group was(42.93 ± 4.57)%,which was significantly higher than that in darkness group(P<0.05);The relative length of ovary in 8L:16D group was significantly higher than that in other groups on the 30 th day of the experiment(P<0.05).The concentrations of hemolymph protein and cholesterol in 8L:16D group were significantly higher than those in light group,16L:8D group and darkness group(P<0.05);The glucose concentration in 8L:16d group was significantly higher than that in light group and darkness group(P<0.05);The concentration of triglyceride in 8L:16D group was significantly higher than that in other groups(P<0.05).When the photoperiods was 8L:16D,the relative expression of gonadal inhibitory hormone gene(GIH)in the eyestalk of E.carinicauda was significantly lower than that in other groups(P<0.05).The above results show that12L:12D～8L:16D is a more suitable photoperiods for parent shrimp ripening and industrialized culture.2.Effects of different salinity on growth and gonadal development of E.carinicaudaIn order to explore the effects of different salinity on the growth and gonadal development of E.carinicauda,E.carinicauda were raised in five salinity gradients(16,20,24,28 and 32)to detect the effects of different salinity on the growth,ovarian development,ovarian nutrient concentration,vitellogenin and sex hormone level.The results showed that the survival rate of E.carinicauda in salinity 24 test group was the highest;The final body weight and specific growth rate of E.carinicauda increased first and then decreased with the increase of salinity(P<0.05).It grew fastest under the condition of salinity 24,and then slowed down with the increase of salinity;The gonadal index first increased and then decreased with the increase of salinity(P<0.05).The gonadal index of salinity 24 group was the highest;When the salinity was 28,the ovarian maturation rate was the highest;The concentrations of total protein,total cholesterol and triglycerides in ovaries increased first and then decreased with the increase of salinity(P<0.05),and reached the highest value under the condition of salinity of 24;The concentration of vitellogenin in hepatopancreas increased first and then decreased with the increase of salinity(P<0.05).The concentration was the highest under the condition of salinity 24,and the concentration of estradiol in the ovary of ridge tail white shrimp in salinity 24 and 28 groups was at a high level.The above results show that 24～28 is a more suitable salinity for promoting the maturation of parent shrimps and industrialized culture.3.Effects of different temperatures on growth and gonadal development of E.carinicaudaIn order to explore the effects of different temperatures on the related indexes of growth and gonadal development of E.carinicauda,five temperature gradients(16,20,24,28 and 32)were set up to culture E.carinicauda,the indexes such as growth,digestive enzyme activity,ovarian development,ovarian nutrient concentration,vitellogenin and sex hormone level were measured.The results showed that the survival rate of E.carinicauda decreased gradually with the increase of temperature between 20℃ and 32℃;The final body weight and specific growth rate increased first and then decreased with the increase of temperature(P<0.05);Lipase activity first increased and then decreased with the increase of temperature(P<0.05),reached the highest value(1.22 ±0.09)(U/gprot)at 28℃,trypsin activity increased with the increase of temperature,and reached the highest value(1695.45 ± 163.42)(U/mgprot)at 32℃;Gonadal index and ovarian maturation rate increased with the increase of temperature;The concentrations of total protein,total cholesterol and triglyceride in ovaries increased with the increase of temperature;The vitellogenin in hepatopancreas increased first,then decreased and then increased with the increase of temperature(P<0.05).At 24℃ and 28℃,the concentration of gonadotropin releasing hormone in lymph was relatively high and close,which were(81.82 ± 4.03)ng/L and(82.67 ±3.22)ng/L respectively.The highest concentration of estradiol in ovary was(26.62 ± 1.49)ng/L at 28℃.The above results show that 24～28 is a more suitable temperature for parent shrimp ripening and industrialized culture.4.Effects of different male female ratio on growth and gonadal development of E.carinicaudaThis study evaluated the effects of male E.carinicauda on the growth and gonadal development of female E.carinicauda,as well as the potential role of contact,chemical,visual and chemical and visual coexistence signals in this physiological process,and explored the optimal male female ratio in artificial culture of E.carinicauda.Under the conditions of temperature 28℃,salinity 24 and photoperiod 8L:16D,the female shrimps(4.75 ± 0.26 cm)were raised in glass aquarium with the same number of heterosexuals or homosexuals respectively for 5 weeks,and the related indexes of growth and gonadal development were measured.The results showed that the presence of male shrimp slowed the growth of female shrimp,but significantly increased the ovarian development rate of female shrimp;The growth rate of female shrimp raised with the same sex was significantly accelerated,but the ovarian development rate was relatively slow;Further,the communication modes of female and male shrimp are set as free contact,chemical signal,visual signal and the coexistence of chemical and visual signal.The results showed that only allowing free contact between female and male shrimp individuals can promote the development of female shrimp ovary,which is reflected in the shortening of female shrimp ovary development cycle,the accumulation of more nutrients in the ovary,the increase of the content of sex hormone and vitellogenin in the body,the decrease of the relative expression of GIH gene,and the testosterone released by male shrimp may play a role in the above phenomenon;And set the E.carinicauda as male and female(♀: ♂=1:1)、(♀:♂=1:2)、(♀: ♂=1:3)kept in Plastic Aquarium(75×50×50 cm),and the related indexes of growth and ovarian development were detected.The results showed that the proportion of male and female had no significant effect on the growth of E.carinicauda,but the proportion of male and female ♀: ♂=1:2 significantly increased the development speed of female shrimp ovary. |
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