The histology, evolution of the structure, composition and morphology of oogonia and primary oocytes in different phases during the ovary development of snakehead, Channa scopoli, were studied. The traditional method ...The histology, evolution of the structure, composition and morphology of oogonia and primary oocytes in different phases during the ovary development of snakehead, Channa scopoli, were studied. The traditional method of wax section was employed to perform the hematoxylineosin staining. The ovary of snakehead is overlaid by the 2layer membrane featured with abundant veins. The primordial germ cell of ovary extends into the ovary together with the inner connective tissue membrane to develop into many ovarial lamellae that arrange radiately around the ovarium cavity. With regard to the developing snakehead, the pattern and structure of its oogonia and early primary oocyte are of fundamental homology with most of the osteichthyes, while the nutrimental composition, accumulation, distribution and the composition of ova membrane for the primary oocyte in phase Ⅲ and Ⅳ are of preferable difference with them. The nutriment of its oocyte is primarily composed of glucoprotein which is included in the vesicle. But the amount of yolk which is primarily composed of protein is comparatively small, even the same for the oocyte developing into the phase Ⅳ which is featured with the deviation of nucleus. So the amount of nucleoli in the primary oocyte of the snakehead is significantly limited than most of the osteichthyes. The primary oocyte in phase Ⅲ and Ⅳ of the snakehead only have 1 layer of ova plasmalemma which is covered by another 2 layers follicular membrane developed from the follicle cell, but there is not any radiated belt of jelly membrane between the membrane and the follicular membrane which is developed from the primary ova membrane and the secondary one in most of the osteichthyes cases.展开更多
Background: The banning of fisheries discards by imposing an obligation to land unwanted catch constitutes a key point of the Common Fishery Policy reform proposed by the European Commission. The effect of such a ban ...Background: The banning of fisheries discards by imposing an obligation to land unwanted catch constitutes a key point of the Common Fishery Policy reform proposed by the European Commission. The effect of such a ban on discards on top marine predators such as seabirds is largely unknown, especially in oligotrophic systems of the Medi?terranean. The current study investigates the presence of scavenging seabirds around fishing trawlers as well as the exploitation of discards produced by bottom trawlers in the eastern Ionian Sea.Methods: On?board observations were randomly conducted in May and December 2014, in order to record the presence and use of fishery discards by two common seabird species, namely, Scopoli's Shearwater(Calonectris diomedea) and the Yellow?legged Gull(Larus michahellis).Results: A total of 3400 seabirds were counted during May of which 2190 individuals were Scopoli's Shearwaters and 1210 were Yellow?legged Gulls. The latter species was the only scavenger observed during winter and in total, 768 individuals were counted. Differences in species abundance in the study area are related to breeding phenology and migratory movements. The number of seabirds attending bottom trawler operations during morning and afternoon hours showed no significant differences for both seabird species. Both scavenging seabirds extensively exploited fishery discards, which were mainly demersal fish, and consumed 70–80% of the total fishery discards biomass; how?ever, they appeared to avoid poisonous species and/or large?sized fish. Yellow?legged Gulls displayed kleptoparasitic behaviour on Scopoli's Shearwater during feeding experiments. The number of such incidents depended on the number of gulls around the fishing vessel, with more than 90% success rates.Conclusions: Considering the average annual biomass of discards estimations and the consumption rate found in this work, 106.1–117.9 t may be offered as a food subsidy to scavenging seabirds in the study area and should support a substantial part of local populations. Our results constitute baseline information on the annual amount of fishery discards and their exploitation rate by seabirds in the Ionian Sea, and suggest further work for a complete understand?ing of the potential impacts of the discards reform bill on seabirds.展开更多
文摘The histology, evolution of the structure, composition and morphology of oogonia and primary oocytes in different phases during the ovary development of snakehead, Channa scopoli, were studied. The traditional method of wax section was employed to perform the hematoxylineosin staining. The ovary of snakehead is overlaid by the 2layer membrane featured with abundant veins. The primordial germ cell of ovary extends into the ovary together with the inner connective tissue membrane to develop into many ovarial lamellae that arrange radiately around the ovarium cavity. With regard to the developing snakehead, the pattern and structure of its oogonia and early primary oocyte are of fundamental homology with most of the osteichthyes, while the nutrimental composition, accumulation, distribution and the composition of ova membrane for the primary oocyte in phase Ⅲ and Ⅳ are of preferable difference with them. The nutriment of its oocyte is primarily composed of glucoprotein which is included in the vesicle. But the amount of yolk which is primarily composed of protein is comparatively small, even the same for the oocyte developing into the phase Ⅳ which is featured with the deviation of nucleus. So the amount of nucleoli in the primary oocyte of the snakehead is significantly limited than most of the osteichthyes. The primary oocyte in phase Ⅲ and Ⅳ of the snakehead only have 1 layer of ova plasmalemma which is covered by another 2 layers follicular membrane developed from the follicle cell, but there is not any radiated belt of jelly membrane between the membrane and the follicular membrane which is developed from the primary ova membrane and the secondary one in most of the osteichthyes cases.
基金performed within the framework of the ECODISC project,entitled“ECOsystem effect of fisheries DISCards”,partially funded by the NSRF 2007-2013 Operational Programme“Education and Lifelong Learning”,which is cofinanced by Greece and the European UnionFisheries data were collected within the framework of the 2014 Greek National Fisheries Data Collection Programme(EPSAD)funded by the Greek Government and the European Union under Regulation 199/2008/EU
文摘Background: The banning of fisheries discards by imposing an obligation to land unwanted catch constitutes a key point of the Common Fishery Policy reform proposed by the European Commission. The effect of such a ban on discards on top marine predators such as seabirds is largely unknown, especially in oligotrophic systems of the Medi?terranean. The current study investigates the presence of scavenging seabirds around fishing trawlers as well as the exploitation of discards produced by bottom trawlers in the eastern Ionian Sea.Methods: On?board observations were randomly conducted in May and December 2014, in order to record the presence and use of fishery discards by two common seabird species, namely, Scopoli's Shearwater(Calonectris diomedea) and the Yellow?legged Gull(Larus michahellis).Results: A total of 3400 seabirds were counted during May of which 2190 individuals were Scopoli's Shearwaters and 1210 were Yellow?legged Gulls. The latter species was the only scavenger observed during winter and in total, 768 individuals were counted. Differences in species abundance in the study area are related to breeding phenology and migratory movements. The number of seabirds attending bottom trawler operations during morning and afternoon hours showed no significant differences for both seabird species. Both scavenging seabirds extensively exploited fishery discards, which were mainly demersal fish, and consumed 70–80% of the total fishery discards biomass; how?ever, they appeared to avoid poisonous species and/or large?sized fish. Yellow?legged Gulls displayed kleptoparasitic behaviour on Scopoli's Shearwater during feeding experiments. The number of such incidents depended on the number of gulls around the fishing vessel, with more than 90% success rates.Conclusions: Considering the average annual biomass of discards estimations and the consumption rate found in this work, 106.1–117.9 t may be offered as a food subsidy to scavenging seabirds in the study area and should support a substantial part of local populations. Our results constitute baseline information on the annual amount of fishery discards and their exploitation rate by seabirds in the Ionian Sea, and suggest further work for a complete understand?ing of the potential impacts of the discards reform bill on seabirds.
