摄食水平对食蚊鱼生长、卵巢发育和能量收支的影响

在室内（27.5±0.5）℃水温下设高、中和低3个摄食水平,研究雌性食蚊鱼(Gambusia affinis)幼鱼至初次性成熟期间的生长发育和能量收支,为探讨食蚊鱼的环境适应性和生态入侵机制提供基础数据.结果显示:初次性成熟雌性食蚊鱼的体长、体质量、丰满度、特定生长率、肝指数、性腺系数、成熟卵子数量和鱼体能量密度均随摄食水平增加显著增加；低水平摄食组雌性食蚊鱼初次性成熟的个体最小,体长为(17.98±0.98) mm,体质量为（104.41±3.31）mg,但成熟卵子干重和卵径均不受摄食水平显著影响.实验期间,干、湿物质饵料转换效率均随摄食水平增加呈下降趋势,低水平摄食组饵料转换效率著高于高水平摄食组.随摄食水平减,食蚊鱼摄食能量分配在生长和卵巢发育的比例显著增加,在低水平摄食组其分配比例分别达到56.22％和10.42％.以上结果表明:在食物不足的条件下,食蚊鱼初次性成熟个体呈小型化,但卵子大小稳定,饵料转换率较高,摄食能量分配在生长和繁殖上的比例增大,这些特点有利于其适应不同入侵生境.

Effects of food ration on growth and development of ovary and energy budgets of Gambusia affinis

Thisstudyinvestigatedtheeffectsoffoodrationongrowthanddevelopmentofovaryandenergybudgetsoffemaletofirstsexualmaturity.The25-dayoldwithoocyteswiththeslowestgrowthstageswereselectedrandomly,andplacedinaquariumcagesinthelaboratoryatandgiventhreefoodrationlevels(low,mediumandhighrepletion]).EfoodsupplydatawereanalyzedtoidentifyinvasivemechanismsofResultsshowedthatattheonsetofsexualmaturity,bodylength,wetmass,fullness,specificgrowthrate,hepatosomaticindex,gonadosomaticindex,numbersofmatureeggsandcalorificvaluesignificantlyincreasedwithincreasingrationlevels.Therewerenosignificantdifferencesindrymassanddiameterofmatureeggsunderdifferentrationconditions.Fishbodysizeattheonsetofsexualmaturitywasminimalwithlowfoodration(averagelengthofmgweightsdecreasedwithincreasingrationlevelsweresignificantlyhigherthanthoseatrepletionrations.Theproportionoffoodenergyallocatedtogrowthandovariesincreasedwithdecreasingrationlevels.Themaximumproportionoffoodenergyallocatedtogrowthwas56.22%,andthatallocatedtoovarieswas10.42%whenlowfoodrationswereprovided.Thus,whenwereexperiencingfoodshortages,thebodysizesoftheindividualsatfirstsexualmaturitydecreased.Inaddition,feedconversionefficienciesincreased,andtheproportionoffoodenergyallocatedtogrowthandreproductionincreased.Thisphysicaladaptationmaybebeneficialfor