The Occurrence And Development Of The Testis And The Sperm Characteristics Of Silurus Asotus

Silurus asotus belongs to Siluridae and Siurus,and was an important kind of economic fish.The article invovled the occurrence and differentiation of catfish testis,the structure of testis,the development period of testis,variation of mature testis,the ultrastructural of sperm,sperm motility and et al.The flowing results were obtained:1.Studies of testis occurrence and differentiation in Silurus asotusThe development of gonad started on day 3 after the emergence of Silurus asotus,which of sign was the appearance of the genital ridge.Sex differentiation in male happened on day 18~40: The sign for ovaries differentiation was the emergence of the ovarian cavity on day 22,and that of the testis differentiation was the appearance of spermatogenium on day 30.The ovarian differentiation was completed on day 24,and there were a large number of primary oocytes appeared in the ovary.The primary spermatocytes came into being on day 30,and the testis differentiation end.2.Studies of testis development in Silurus asotusFrom sex differentiation to maturation,the testis development was divided into Ⅰ~Ⅵ stages,according to the morphological character of testis and spermatogenesis: During the stageⅠ,the testis was transparent or light yellow in the shape of thread,lengthed 1 um to 2 um,weighed less than 0.03 g.During the stage Ⅱ,the testis was transparent or lightly white in the shape of "V" on both sides,and its surface was smooth with a little of capillary vessels,lengthed less than 35 mm,weighed 0.02 g to 0.12 g.During the stage Ⅲ,the volume of testis was increased and the shape of it was irregular with jagged edges and a few wrinkles.The testis was light pink and had a few but clear capillary vessels,and lengthed 40 mm to 62 mm,weighed 1.0 g to 3.73 g.During the stage Ⅳ,the testis was white or pale red arborization with no obvious branch,lengthed 81 mm to 109 mm,weighed 1.8 g to 4.8 g,and its surface was full of folds and a great quantity of vessels.During the stage Ⅴ,the testis was mature and the shape of it came clearer,which was highly branched arborization with branched on branched.It was white or pale red,and lengthed 89 mm to 117 mm,weighed 2.34 g to 5.0 g.When on the stage Ⅵ,testis was also arborizat but its size was greatly reduced and sharp was not plump.The testis was pale red with masses of shrink vessels.3.The variation of mature testis of Silurus asotus in annualIn spring,the mature testis in stage Ⅲ~Ⅳ,was pale pink owing to a small of vessels.In summer,the testis was white which filled of with signif icant vessels,and GSI was 1.24% to 1.83% in stage Ⅳ~Ⅴ.In autumn,the testis in stage Ⅲ~Ⅳ and Ⅵ changed into pale yellow which was obviously atrophic.The mature spermatozoa of the testis had been release fully at that time.In winter testis had been get through dormant period.4.Mature testis structureTestis consists of tunica albugine and parenehyma.The parenehyma included interstitial substance,seminiferous lobule,ductus deferens and spermatheca.The interstitial substance included capillary vessels,interstitial celsl and fibroblast cells.The seminiferous lobule was irregular tubular.The spermatogenetic cyst was birthland of spermatogenic cells in testis.A amount of sperm was stored in the spermatheca.5.The ultrastructural of spermThe spermatozoon of Silurus asotus mainly consisted of the head and the flagellum,and the neck was not obvious.The spermatozoon had a round head with the length 1.85 μm to 2.51 μm in diameter.The spermatozoon head had no acrosome or acrosomal vesicle with highly condensed chromatin in it.The fossa located in the end of the head contains proximal centrioles and distal centriole.The sleeve lied between uncleus and the plasma membrane was rich of cytoplasm,mitochondria,vesical and so on.The flagellum lengthed 44.3 μm to 50.7 μm,and the cross section of it was a round ball which was 0.269 μm to 0.308 μm in diameter.The flagellum was consisted of axoneme and accessory fibers.The axoneme was a typical structure of the "9+2" model.6.The study of sperm motilityThe effect of water pH on spermatozoon motility showed that the suitable pH for spermatozoon is 7.0-8.5.When water pH was 8.0,spermatozoon motility was the strongest.The effect of water temperature on spermatozoon motility showed that the suitable temperature for spermatozoon was 25-29 ℃.When water temperature was 28 ℃,spermatozoon motility was the strongest.