A Preliminary Study Of Discus Fish (Symphysodon Haraldi) Epidermal Milk In The Breeding Period

The discus fish(Symphysodon haraldi)is an important ornamental fish,its economic value and ornamental value was high.The discus fish had an unique breeding habits,after the larva hatching the discus had a lactation period.In the breeding period,the discus would secrete more mucus for the larva biting,the mucus was the milk,the milk secreting status directly impacted the growing condition.Although the discus fish breeding technology had been taken,the unstable mucus secreting restricted the discus fish largescale breeding;the egg laying amount was not abundant,if we could rise the quality of the milk,the larva's growing speed and rate of survival could rise,we can short the breeding cycle and rise the yield of discus larva.To guide the discus fish large-scale breeding,there is a necessity to study the component of the milk.Knowing the component of the milk could help us to understand the difference of variety,gender and period and selected the discus which had a better lactation ability to rise the breeding speed and quality.To explored the component of the discus fish's epidermal milk,the study was divided into three parts to analyze the component of epidermal milk in different breeding period.The experiment 1,collected parent fish's epidermal milk from two kinds discus fish the pigeon blood and the solid red which is in different breeding period(intervalbreeding period,egg-spawn period,hatched period,free-swimming period,freeswimming 1 week,free-swimming 2 week).To measure five components of the epidermal milk,they were cortisol,IgM,total protein,lactic acid and glucose.The experiment 2,selected five parent fish in the breeding cycle,collected parent fish's epidermal milk from interval-breeding period and free-swimming 1 week and make an metabonomic analyze for them.The experiment 3,collected parent fish's epidermal milk from interval-breeding period and breeding period,hydrolyzed them and tested the free amino acid and tested the water content.The experiment result showed as fellow.The content of cortisol,IgM,total protein,lactic acid and glucose in the epidermal milk would change significantly(P<0.05)with the sampling period.Cortisol,IgM and total protein didn't have significant difference between different variety.The content of cortisol didn't have significant difference before the free-swimming 2 weeks except a few sampling periods,the content of cortisol had a significantly descend.The rule of IgM and total protein's changing had a descending-ascending-descending process except a few sampling periods.Lactic acid and glucose had significant(P<0.05)difference between different variety.The pigeon blood's content of lactic acid and glucose both have a descending tendency except a few sampling periods.However,the solid red's content of lactic acid and glucose both have an ascending tendency.Except in a few cases,each component didn't have significant difference between female and male,had a tendency of alternately rise.The cortisol had an inhibiting effect for IgM,total protein,lactic acid and glucose.The change of IgM and total protein had a correlation.The change of lactic acid and glucose had a correlation.The content of cortisol,IgM,total protein,lactic acid and glucose would change significantly when went into the ‘milking' period.The solid red could support more nutrient substance for the larva.To analyze the result of metabonomic.We can find that the difference between the female and male in the interval-breeding period was little,only 10 components had a change in the relative transcript level which could prove that the components difference between female and male in the interval-breeding period.When the female and male discus fish went into the breeding period,the female had 118 components change in the relative transcript level,the male had 78 components change in the relative transcript level,when went into the breeding period,the female 111 components in the epidermal milk would descend in the relative transcript level and 7 components in the epidermal milk would ascend in the relative transcript level,the male 78 components in the epidermal milk would descend in the relative transcript level and 20 components in the epidermal milk would ascend in the relative transcript level.The male had more substance ascending than the female.However,in the breeding period most of the relative transcript level of the components in the epidermal milk male were higher than female.Therefore,we could consider that the male discus fish played a prior role in the lactation period,male could provide more components for the larva,such as the amino acid and the amino acid analogue,purine,pyrimidine,nucleoside,hormone,organic acid and so on.The change of the 17 free amino acid of the epidermal milk had a significant regulation in the breeding period and interval-breeding period,the content of each amino acid female was significantly(P<0.05)lower than the female whenever in the intervalbreeding period or breeding period.The content of each amino acid of male would rise significantly(P<0.05)when go into the breeding period.However,the female didn't have significant change.Most of the hydrolytic amino acid were Glu,Asp,Leu and Lys.In conclusion,in the condition of this experiment the solid red discus fish can provide more nutrient substance for the larva than the pigeon blood discus.The male discus fish can provide more nutrient substance for the larva than the female discus.