Some environmental factors affecting the reproduction of Aphanius dispar (Rüppell, 1828)

摘要: In order to determine the suitability of thecyprinodont fish Aphanius dispar as a biologicalcontrol agent for mosquito larvae, effects oftemperature, salinity, feeding rate and photoperiod onits reproductive condition were studied. The factorsexamined gonado-somatic index (GSI) fourdistinct stages cell maturation in ovaries(oogonia, primary oocytes, secondary oocytes andmature ova). found be tolerant awide range examined factors. GSI's notaffected by ambient temperatures over of18 °C 37 °C. However, oocyte maturationstages increased rose from 18 °Cto 27 °C, with mature ova first being at thelatter temperature. No significant differences amongmaturation between27 °C–37 At salinities ranging of0 ppt 56 ppt, no betweenmean GSI's, except two extremes testrange. ovaries kept distilled watercontained primordial germ cells only. feedingexperiments, onlybetween (GSI's maturationstages) deprived food those fed at≥ 1% body weight per day. Regarding photoperiod,a decrease day length 14L:10D (the longest dayof year) 10L:14D shortest) caused adecrease stages. Fish theintermediate level (12L:12D) still had ovariessuitable spawning, whereas didnot. results this study show that limitinglevels adequate foundfor some factors investigated, however, rangesof above these levels relativelylarge. That dispar's reproductivecondition may controlled an artificialenvironment is essential it mass produced,and prerequisite its use larvae.