南海西沙群岛海域鸢乌贼(Sthenoteuthis oualaniensis)角质颚微结构及生长特性研究

角质颚是鸢乌贼重要的摄食器官,信息储存能力强,被广泛用于重建头足类生活史等研究。根据2017年5—8月中国灯光罩网渔船在南海西沙群岛海域采集的860尾鸢乌贼样本,结合经研磨后角质颚微结构中的日龄轮纹,对角质颚微结构及其外形生长特性展开了研究。结果表明,鸢乌贼角质颚上颚微结构分为头盖部和脊突部,两部均由明暗交替的日龄生长纹组成,头盖部的日龄生长纹较为清晰且易于读取。选取上头盖长(UHL)、上脊突长(UCL)、上侧壁长(ULWL)、上翼长(UWL)、下头盖长(LHL)、下脊突长(LCL)、下侧壁长(LLWL)和下翼长(LWL)作为描述西沙群岛海域鸢乌贼角质颚生长的外形特征参数。协方差分析表明,角质颚外形特征参数不存在性别间显著性差异。AIC分析表明, UCL和LCL与日龄的生长关系最适用线性生长模型表示, ULWL和LLWL与日龄的生长关系最适用对数生长模型表示, UHL、UWL、LHL和LWL与日龄的生长关系则均最适用于逻辑斯蒂生长模型表示。随着日龄的增加,鸢乌贼角质颚外形特征参数与胴长的比值基本稳定。日龄范围为211—240 d时,鸢乌贼角质颚UHL、UCL、UWL、LHL、LCL、LLWL和LWL的绝对生长率(AGR)较低。鸢乌贼角质颚在日龄介于121—210 d时生长迅速,在日龄介于211—240 d时生长速率下降,日龄211—240 d可能是鸢乌贼角质颚外部形态生长的拐点。研究结果为后续利用角质颚研究南海鸢乌贼的渔业生物学、生态学和关键生活史提供了科学依据。

BEAK MICROSTRUCTURE AND GROWTH CHARACTERISTICS OF STHENOTEUTHIS OUALANIENSIS IN THE XISHA ISLANDS WATERS OF THE SOUTH CHINA SEA

Beak is an important feeding organ of Sthenoteuthis oualaniensis with abundant information, and could be widely used reconstruct the cephalopods life history. The daily age, microstructures, and morphological characteristics growth of the beak were analyzed for 860 specimens of purple-back flying squids S. oualaniensis collected on Chinese lighting falling-net vessels in the Xisha Island waters of the South China Sea during May to August in 2017. The microstructure of the upper beak could be divided into hood region and crest region. The two regions composed of clear dark-bright alternated daily growth increments that are more readable in the hood region. The upper hood length (UHL), upper crest length (UCL), upper lateral wall length (ULWL), upper wing length (UWL), lower hood length (LHL), lower crest length (LCL), lower lateral wall length (LLWL), and lower wing length (LWL) were selected as the morphological characteristic parameters to describe the growth characteristics of S. oualaniensis beaks. Results show that there was no significant difference in the relationships between age and the morphological characteristic parameters in different genders as indicated by the analysis of covariance. Moreover, revealed by the Akaike information criterion (AIC) analysis, relationship of age to UCL or LCL was linear in growth model, and that to ULWL or LLWL was logarithmic, while that to UHL, UWL, LHL, or LWL was logistic in growth model. The ratios of morphological characteristic parameters of beak to the mantle length were largely constant with the increasing age. The absolute growth rates (AGR) of UHL, UCL, UWL, LHL, LCL, LLWL, and LWL were lower in age of 211-240 d. A turning point of the beak growth in age of 211-240 d was recognized, before which (121-210 d) the beak growth was fast and after which (211-240 d) it slowed down. This study provided a scientific basis for understanding the fishery biology, ecology, and key growth stages of S. oualaniensis in the South China Sea by studying microstructure of beak.