| Sea perch (Lateolabrax japonicas), one of the most important economical aquaticproducts in China, is widespread across the coastal waters of China. In this thesis,morphological and histological observations of sea perch larvae were conducted. Inaddition, a new method of cryopreservation of sperm from sea perch was discussed.In sum, this thesis is aimed at promoting and supporting the germplasm conservation,distant hybridization breeding and large-scale production of sea perch.1. Morphological observation on the development of sea perch larvaeDuring the period of artificial breeding, some discussions were given. Firstly,within proper temperature range, the growth rate of sea perch larvae was promotedremarkably by the higher temperature. Then, desalting2to3degrees each day startedin post stage of larva. Finally, exogenous feeding started at9dhp, and the larvaeneeded to be fed at9.0am and2.0pm when ingestion reached peak. By utilizing theanatomical lens, morphological observation was performed. The average length ofnewly hatched larva was3.71mm, and the yolk-sac occupied almost half of the body.Digestive tract was a straight-shaped blind tube. The yolk-sac was absorbedsignificantly at1dph, and the terminal of digestive tract was slightly downward.2dph,digestive tract wriggled but not yet connected. Meanwhile, the rudiment ofhepatopancreas appeared.5dph, the mouth opened making the oral fissure obvious,and the digestive organs began to differentiate.9dph, the yolk-sac was almost fullyabsorbed, and digestive tract connected, which enabled the larvae to prey on rotifers.12dph, the swim bladder and the operculum appeared.17dph, all the melanin on eyeswere appeared.20dph, the swim bladder inflated, and the amount of melanin spots onthe back of digestive tract and abdomen increased.25dph, the head occupied about1/4of the overall length of larva, and operculum began to be opaque.2. Histological observation on early development of sea perch organsBy utilizing the histological method, the early development of sea perch organswas observed.1-3dph, the digestive tract which was long and lathy adjoined the backof the yolk-sac.4dph, the rudiment of stomach appeared.7dph, the stomach began toexpand, and wrinkles appeared on the gastric mucosa of which the epithelium was simple columnar epithelium.8dph, the cardia, basilaris part and pyloric caecum ofstomach were differentiated.20dph, stomach wall thickened, and the epithelium wassimple cuboidal epithelium. Meanwhile, goblet cells appeared on the cardia ofstomach.3dph, the intestinal tract was slightly swollen.5dph, wrinkles appeared onposterior segment of intestinal tract of which the epithelium was columnar epithelium.8dph, when the larvae began to prey, the intestinal epithelium was ciliated columnarepithelium among which there were several goblet cells.13dph, the amount of gobletcells on posterior segment of intestinal tract increased dramatically.24dph, striatedborder on the mucous epithelium were obvious, and the amount of longitudinalwrinkles increased. The hepatopancreas appeared at3dph, and began to be vacuolar at10dph. Then it was fully developed in17dph. The retina, of which the visual cellswere cone cells, was differentiated at7dph.13dph, the gill was basically developed,forming4branchial clefts.3. Cryopreservation of sperm from sea perch4℃short-term store and cryopreservation of sea perch sperm were conducted inthis part. In4℃short-term store experiment, the MOT, VCL and VSL of sperm alldecreased with prolongation of storage period in each group. Within24h, the vitalityof sperm stored in MPRS was the highest; however, after24h, the vitality of spermstored in150mM NaCl was the highest, and the MOT remained90.9%after72h.Taking MPRS as extender, the MOT of sperm, of which the sperm/extender ratio was1:3, was still over50%after120h storage, whereas that of1:1and1:10ratio weredecreased significantly (under40%).In cryopreservation experiment, the preservation effect of150mM NaCl wasexcellent. When the concentration of DMSO was10%, the MOTs of sperm in150mMNaCl and MPRS were both over50%(P>0.05). When the concentration of DMSOwas20%or30%, the MOT of sperm in150mM NaCl was obviously higher than thatof MPRS (P<0.05), whereas the preservation effect of ELS3was not good. TakingDMSO as cryoprotectant, the preservation effect was better. Especially, when the theconcentration of DMSO was20%, the MOT was the highest. However, the mycosewas not suitable for cryopreservation of sea perch sperm, and it could weaken thepreservation effect of DMSO. |
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