EMBRYONIC DEVELOPMENT AND SALINITY TOLERANCE OF MUDSKIPPER (PERIOPHTHALMUS MAGNUSPINNATUS)

Abstract

Periophthalmus magnuspinnatus inhabit in China which was previously mistaken as Periophthalmus modestus and recently reported from the coasts of Bohai Sea,Yellow Sea,East China Sea,and South China Sea.For the taxonomically new P.magnuspinnatus,there is only one study on the skin structure and investigating the life history Lifestyle of Korean mudskipper.This paper was studied the fecundity and effects of salinity on embryonic development of the P.magnuspinnatus in Qiantang River estuary.The fertilized eggs were observed through a semi-dry artificial fertilization method,which were cultured and analysed in constant temperature of sea water with weak aeration in different salinities.The embryonic development of mudskipper was characterized by continual viviperception.The results indicated that the individual absolute fecundity(F) ranged from 2249 to 3472 eggs,the average was 2746 eggs,and the standard error of mean was 230.The individual relative fecundity(FL) ranged from 32 to 44 eggs per millimeter,the average was 35 eggs,and the standard error of mean was 2.The individual relative fecundity(FW) ranged from 643 to 1320 eggs per gram,the average was 698 eggs,and the standard error of mean was 71.From the injection of 0.2 μg of LHRH-A3(luteinizing hormone releasing hormone-analogue) then after 24 hours injection of 20 IU of HCG(Human Chorionic Gonadotropin) into female fish and 20 IU of HCG into male fish,each male fish received one injection at the same time as female fish received the second injection.Most of experimental fish was able to develop to mature.With the water temperature of 27 ℃,salinity of 10‰,and pH of 7.8±0.3,the embryonic development required 158 hours and 46 minutes,while the accumulated temperature was up to 4286.70 h.℃.The development time from heart beating to hatch larva was relatively longer which need 127 hours and 52 minutes under 27 ℃ and 10‰ salinity condition,accounting for 80.5% of the total embryonic development time.The development time from air bladder formation(the last development stage) to hatch larva was 88 hours and 52 minutes,accounting for 56.0% of the total embryonic development time.Before the eggs were hatched,the organs had differentiated normally in shape already,such as distinct gut,visible anus,air bladder elliptical,and melanophore of eyes per minute.The time series of embryonic development was slightly different from other Gobioidei species which experienced intestinal canal formation,blood circulation and pectoral fin appearance successively.The heart rate in heart beating stage of P.magnuspinnatus was ranged from 52 to 78 times per minute,and then sped up which could reach to 283 times per minute until hatch larva stage.The optimum salinity for embryo development was 5‰-15‰.The hatchability under 5‰,10‰ and 15‰ salinity was 38.5%,47.3% and 42.8% respectively.Experimental observation results indicated that salinity showed no influence on embryonic development of P.magnuspinnatus,but the development time and development accumulative temperature shortened as the decrease of salinity.Under high salinity concentrations of 35‰,30‰,25‰,and 20‰,the fish larvaes were not hatched from the fertilized eggs.