| Poyang Lake loach is a small economic fish.Because of its typical black spot characteristics,it is divided into big blackspot,small blackspot,and non-blackspot loach.In this thesis,the pigment cell composition,pigment content,tyrosinase activity and content of the three kinds of loach were determined,and the preliminary function of the MaMCH gene,a gene related to the regulation of the pigment of the loach,was discussed.Educational goals provide theoretical basis.The main findings are as follows:(1)There are 3 kinds of pigment cells in loach: melanocytes,yellow pigment cells and iridescent pigment cells.There are two types of melanocytes in the back skin of the big blackspot loach: dendritic and round melanocytes.There are only dendritic melanocytes in the blackspot and non-blackspot loach.There is no significant difference in the morphology of yellow pigment cells and iridescent pigment cells in the skin of the three kinds of loach.The number of melanocytes in the back skin of the loach is more than that of the abdominal skin.The melanocytes of the back skin of the big and small blackspot loach are mainly distributed in the epidermis and the loose layer.There are more melanocytes in the blackspot loach mainly in the muscle layer and dermis layer.The melanocytes of the big blackspot loach are bigger and distributed independently.The melanocytes of the small blackspot and non-blackspot loach form pigment bands.There are differences in the maturity and quantity of melanosomes in the melanocytes of the three kinds of blackspot loach.In the back skin: the third and fourth stages of the big blackspot loach have the most number and higher maturity;the small blackspot loach has one to four stages of melanosomes;There are one to three stages of melanocytes in the non-blackspot loach.In the abdominal skin: there are two to four stages of melanosomes in the big blackspot loach;there are one to three stages of melanosomes in the small blackspot and non-blackspot loach.(2)In order to further explore whether the phenotypic difference of the back mottling of the three species of loach is related to the pigment content,the pigment content,tyrosinase content and activity of the three species of loach were tested.The experimental results showed that:There were no significant differences in the melanin content of the abdominal skin,the lutein content of the back and abdomen skin,and the carotenoid content of the back and abdomen skin of the three kinds of blackspot loach(P >0.05).The melanin content of the back skin and abdominal skin of the big blackspot loach was extremely significant(P<0.01),and the melanin content of the back skin was 1.17±1.11 times that of the abdominal skin.There was no significant difference in tyrosinase activity in the serum of the three kinds of loach(P>0.05).The content and activity of tyrosinase in the back skin of the large blackspot loach is the highest,and the content and activity of tyrosinase in the back skin of the non-blackspot loach are significantly lower than that of the large and small blackspot loach(P<0.01),the large blackspot loach The tyrosinase content of the back skin is1.104±95.97 times of that of the blackspot loach,and the tyrosinase content of the back skin of the small blackspot loach is 1.098±90.47 times of that of the blackspot loach.(3)Since the three kinds of loach are mainly caused by the differences in melanocytes and melanin content,the preliminary function of the MaMCH gene in the melanin signaling pathway was studied,and the loach was carried out under continuous light for 8 days and continuous darkness for 8 days,respectively.q PCR was used to detect the m RNA expression of MaMCH gene in brain,back skin,abdominal skin,muscle,liver,heart and intestine on 2 d,4 d,6 d and 8 d.The results show that the MaMCH gene is highly expressed in the brain,back skin and abdominal skin regardless of whether it is under continuous light or continuous darkness.Under dark conditions,the m RNA expression trends of the MaMCH gene in the back skin of the three blackspot loaches were the same,all increased first and then decreased,and the peak appeared on the 4th day;under light conditions,the MaMCH gene of the back skin of the large blackspot loach and the small blackspot loach had the same effect.The m RNA expression first increased and then decreased,and its peak appeared on the 6th day(P<0.01).The peak m RNA expression of the MaMCH gene in the back skin of the blackspot loach appeared on the 2nd day,and then began to decrease gradually.On the 6th day,the m RNA expression level of MaMCH gene in the back skin of the three blackspot loach under continuous light was higher than that under dark conditions(P<0.01).The m RNA expression level of MaMCH gene under the three blackspot loach under light conditions was respectively 474.46 ± 166.69 times,8.07±5.81 times,5.35±1.85 times under dark conditions.In the continuous light group,the expression of MaMCH in the back skin of big blackspot loach was higher than that of small blackspot loach and non-blackspot loach(P<0.01).The m RNA expression of the MaMCH gene of the large blackspot loach under light conditions was the small flower respectively 25.2±160.41 times and 73.3±164.76 times of spot loach and non-spotted loach.(4)In order to further explore whether the MCH gene regulates the ingestion of the three blackspot loach to cause the difference in the growth performance of the three blackspot loach,this paper sets up the starvation group and the normal feeding group,and the experiment time is 20 d,q PCR was used to detect the m RNA expression of MaMCH gene in the brain,back skin,abdominal skin,muscle,liver,heart,and intestine at 5d,10 d,15d and 20 d.The results show that the MaMCH gene is highly expressed in the brain,back skin and abdominal skin regardless of whether it is under continuous fasting or continuous normal feeding.under normal feeding conditions,the m RNA expression trends of the three MaMCH genes in the brain tissue of the three species of loach were the same,all of which first decreased,then increased and then decreased,and the lowest value appeared on the 5th day(P<0.01);Under fasting conditions,the m RNA expression levels of MaMCH in the brain tissues of the three blackspot loaches were higher than those in the normal feeding group(P<0.01).Under fasting conditions,the m RNA expression levels of the MaMCH genes of the three blackspot loaches were the normal feeding group.241.14±0.89 times,433.75±0.42 times,and 163.83±0.46 times.The highest m RNA expression levels of the three kinds of blackspot loach MaMCH in brain tissue appeared on the5 th day(P<0.01).Under fasting conditions,the m RNA expression levels of MaMCH of the three blackspot loaches were those of the small blackspot loach and the non-blackspot loach 2.12±0.47 times,1.96±0.44 times;while the change range of10-20 d time period is not large.In summary,the variegation differences of the three blackspot loaches may be closely related to the morphology and distribution of melanocytes and the maturity of melanosomes,and are related to the melanin content,tyrosinase content and activity.Among them,MaMCH is involved in the loach pigment.Regulating process,the results of this study provide a theoretical basis for further research on the differences of the variegation of the three blackspot loach and the regulation mechanism of the body color of the three blackspot loach. |
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