实验室条件下唐鱼两性异形及其与游泳能力关系

Sexual dimorphism and its relationship with swimming performance in Tanichthys albonubes under laboratory conditions

为了解唐鱼两性异形及其与游泳能力关系,检测了性成熟阶段唐鱼躯干部和鱼鳍形态特征以及爆发游泳速度（U_（burst））和临界游泳速度（U_（crit））在雌雄之间的差异,旨在从形态适应角度探究长期进化中雌雄唐鱼各自面对选择压力所产生的游泳能力差异及其机制,从而为野生唐鱼保护提供基础数据.结果表明：雌性唐鱼的体长、头高、头宽、尾鳍面积以及吻端至枕骨后末端、腹鳍起点至背鳍末端等长度均与雄性无显著差异.而体高、体宽、腹鳍起点至背鳍起点等反映腹腔大小的形态参数以及吻端至背鳍起点、吻端至臀鳍起点、枕骨后末端至背鳍起点等反映躯干部大小的形态参数均显示为雌性显著大于雄性,但头长以及胸鳍面积、腹鳍面积、背鳍面积和臀鳍面积均显示为雄性显著大于雌性.对所有数据进行主成分分析,结果显示第1主成分贡献率为74.2%,负载量较大的是体长、头长、头高、体高、头宽、体宽以及各鳍之间距离等主要反映唐鱼躯干整体特征的参数;第2主成分贡献率为15.7%,负载量较大的是胸鳍面积、腹鳍面积、背鳍面积和臀鳍面积等主要反映鱼鳍特征的参数.唐鱼性别在第1主成分上无法区分,但在第2主成分却可以明显区分.根据体宽、胸鳍面积、腹鳍面积、背鳍面积和臀鳍面积等建立的性别判别方程对雌雄判断准确率达到91.8%～92.5%.唐鱼游泳能力测定结果显示,雌性U_（burst）与雄性无显著差异,但U_（crit）显著小于雄性.以上结果表明,雌雄唐鱼两性异形主要集中在与游泳能力相关的鱼鳍特征上.相比雄性,雌性唐鱼虽然胸鳍等鱼鳍面积较小导致其U_（crit）小于雄性,却具有更长的躯干部以保证其同样具有较高的爆发游泳能力,从而有利于在流速波动很大的溪流中躲避捕食和进行其他应急活动;相比雌性,雄性唐鱼则具有较大的鱼鳍面积保证其U_（crit）高于雌性,以利于日常活动及在繁殖过程中追逐雌性等相对持久性游泳运动.

To explore the sexual dimorphism of Tanichthys albonubes and its relationship with swimming performances, the morphological characteristics of fins and trunks of male and female T. albo- nubes were measured and analyzed by using multivariate statistical analysis methods, aiming to explore the difference and its mechanism of swimming performance between male and female under different selected pressure in long-term evolution period and then, providing meaningful information for the protection of T. albonubes. The results showed that body lengths, head depths and breadths, caudal fin areas, distances of snout tip to occipital bone terminus and ventral fin origin to dorsal fin terminus had no significant difference between male and female T. albonubes. The females had sig-nificantly higher values in head depths, body breadths, distances of ventral fin origin to dorsal fin origin, snout tip to dorsal fin and to anal fin origin, occipital bone terminus to dorsal fin origin than those in the males. However, head lengths, pectoral fin, dorsal fin, ventral fin and anal fin areas were significantly lower in the females. The results of principal component analysis showed that the contribution rate of the first principal component （PC1） was 74.2%. Obviously loading factors were body lengths, depths and breadths, head lengths, breadths and depths and the distances of each fin mainly reflecting body overall characteristic parameters of T. albonubes. For the second principal component （PC2）, the contribution rate was 15.7% and the obviously loading factors were pectoral fin, dorsal fin, ventral fin and anal fin areas which mainly reflected the characteristic parameters of fins. The gender identification of T. albonubes was indistinguishable on PC1, but could be obviously distinguished from PC2. Accuracy rates of sexual discriminant equation which was established by pectoral fin, dorsal fin, ventral fin and anal fin areas and body breadths were 91.8%-92.5%. The results of swimming performance showed that burst swimming speeds （Uburst ） had no significant difference between male and female T. albonubes. However, the critical swimming speeds （ Ucrit ） were significantly decreased in the females than in the males. The findings indicated that the sexual dimorphism of T. albonubes was mainly concentrated on fin characteristics associating with swimming performance. Also having lower Ucirt due to its lower pectoral fins areas than the male, the female T. albonubes had longer hindquarters cadres to ensure high Uburat which facilitated them to avoid predators and other emergency events in volatile streams. Larger fin areas than in the female caused higher Ucirt in the male contributing to chasing female in breeding period and other persistent exercises