东太平洋茎柔鱼耳石形态差异性分析

Morphological variation of statolith of the jumbo flying squid(Dosidicus gigas)in the eastern Pacific Ocean

茎柔鱼是大洋性重要经济头足类,其耳石包含着重要的生态信息。根据2008年5月—2009年10月智利、哥斯达黎加、秘鲁外海采集的茎柔鱼耳石样本,分析三海区间耳石外部形态特征及生长模式差异。研究认为,不同海区间耳石形态特征差异显著(P<0.05),耳石长度指标均出现显著性差异,角度指标中仅背侧区夹角出现显著性差异。主成份分析认为,耳石总长(TSL)是表征耳石形态特征的最显著指标,吻区夹角是表征智利、秘鲁外海耳石的显著性角度指标,吻侧区夹角是表征哥斯达黎加外海耳石的显著性角度指标。在整个生长过程中三海区耳石各部分均异速生长,其形态变化趋势为整体变得狭长、背区逐渐宽大,耳石重心不断向背区转移,符合中上层头足类耳石特征。TSL为1 600μm时,三个海域耳石的长度指标RDL均出现显著变化。哥斯达黎加外海、秘鲁外海茎柔鱼耳石的TSL分别为2 000和1 800μm时,其角度指标吻区夹角出现显著变化,智利外海茎柔鱼耳石的吻区夹角则没有显著差异。由于角度变化迟于耳石形态长度变化,因此TSL为1 600μm时可作为茎柔鱼栖息水层变化的重要标志。

The jumbo flying squid（Dosidicus gigas）is one of important economic cephalopods with statolith providing important ecological information.According to the statolith morphology of the squid caught in waters off Chile,Peru and Costa Rica from May,2008 to Oct,2009,the differences of statolith morphology and growth patterns were analyzed.It was found that the statolith morphological characteristics in different areas had statistically significant differences（P0.05）.The length index and only the ventral dorsal dome angle（DDA）angle index had significant differences.The result of the principal component analysis was that total statolith length（TSL）was the most significant indicator of statolith morphology.The significant indicator of statolith angle was rostrum angle（RA）in waters off Chile and Peru,and rostrum lateral dome angle（RDA）in waters off Costa Rica.The growth of various parts was synchronized and allometric during the growth process,and the changing tendency of morphology was narrow body,long and narrow rostrum and large dorsal tallied with the characteristics of pelagic cephalopods statolith.Statolith growth consisted of two phases.According to the data of rostrum lateral dome length（RDL）,there were marked differences in morphology between TSL smaller and larger than 1 600 μm.Based on the data of the angle,there were marked differences in RA between TSL smaller and larger than 2 000 μm in waters off Costa Rica,and 1 800 μm in waters off Peru,and there were marked differences in RA in waters off Chile.The angle increased later than the length of statolith,so TSL of 1 600 μm might be regarded as an valid indicator of changes in water layer.