Sperm viability in wild-caught males of Macrobrachium tenellum (Smith, 1871) (Decapoda: Caridea: Palaemonidae) fed with different diets

Abstract The relationship of body weight and length with sperm load and spermatophore weight was evaluated in wild males of Macrobrachium tenellum (Smith, 1871). In addition, the influence of a commercial and natural feed on the load and viability of sperm was determined in wild males. In 28 wild males spermatophore extraction was performed by electrostimulation 24 h after capture to analyze the relationship between body length/weight and sperm load and viability, respectively. Spermatophore weight (SW), total number (TS), dead (DS) and abnormal sperm cells (AS) were used as indicators of sperm viability. The results obtained show that there is a positive correlation between TS per spermatophore compared to body length and weight of the male. To study the effect of different diets on sperm load, three diets were employed: Diet A, commercial shrimp feed; Diet B, natural feed (mixture of squid, sardine and clam); and Diet C, combination of natural and commercial diet. To assess the initial reproductive status of the males at the beginning of the experiment, sperm viability was determined in a subsample of specimens after capture. Broodstock were fed ad libitum once a day during 70 days. TS, DS, AS and SW were evaluated. The results of the bioassay did not show differences between treatments in the parameters analyzed, except DS, which was higher in the initial group. In conclusion, the present work suggests that it is feasible to substitute fresh feed for an artificial diet for the maintenance in captivity of male M. tenellum broodstock shrimp.

摘要 本研究评估了野生细螯沼虾（Macrobrachium tenellum, Smith, 1871）雄性个体的体重、体长与精子负载量及精荚重量之间的关系。此外，本研究还探究了商用饲料与天然饲料对野生雄性个体精子负载量与精子活力的影响。研究共纳入28尾野生雄性个体，于捕获后24小时采用电刺激法提取精荚，分别分析体长/体重与精子负载量、精子活力之间的相关性。以精荚重量（spermatophore weight, SW）、总精子数（total number of sperm, TS）、死亡精子数（dead sperm cells, DS）及异常精子数（abnormal sperm cells, AS）作为精子活力的评价指标。所得结果表明，单个精荚的总精子数与雄性个体的体长、体重呈正相关。为探究不同日粮对精子负载量的影响，本研究设置了三种日粮处理组：A组为商用虾饲料，B组为天然饲料（由鱿鱼、沙丁鱼及蛤蜊混合制成），C组为天然饲料与商用饲料的混合日粮。为评估实验开始时雄性个体的初始繁殖状态，研究人员于捕获后对部分亚样本个体的精子活力进行了检测。试验期间，每日对亲虾进行饱足投喂，连续饲养70天，期间对总精子数（TS）、死亡精子数（DS）、异常精子数（AS）及精荚重量（SW）进行了检测。生物学试验结果显示，除死亡精子数（DS）外，各处理组的各项检测指标均无显著差异，且初始取样组的DS值更高。综上，本研究表明，在人工饲养条件下维持细螯沼虾雄性亲虾种群时，可使用人工饲料替代天然新鲜饲料，该方案具备可行性。