Macromedusae of Southern Brazil: temporal variation, population structure and biochemical composition

Abstract The objectives of this study were to record the macromedusae species on the north coast of Santa Catarina, and to estimate their population dynamics and variations in their biochemical composition, based on the specimens obtained in the by-catch of artisanal shrimp fishing between January 2012 and October 2014. Cohort analysis was performed to evaluate the population dynamic of the most frequent species. Biochemical analyses of the umbrellas were conducted on their water, carbohydrate, protein, lipid, ash and metals contents. Six species of macromedusae were found: Chiropsalmus quadrumanus and Tamoya haplonema (Cubozoa); Olindias sambaquiensis and Rhacostoma atlanticum (Hydrozoa), and Chrysaora lactea and Lychnorhiza lucerna (Scyphozoa). The species with the highest occurrence, and typical of the region, were Olindias sambaquiensis and Rhacostoma atlanticum. These species showed high inter-year variability, the highest densities being observed between autumn and winter 2014, associated with a less severe winter and coastal water with higher salinity. The distribution of size classes of O. sambaquiensis suggests two well-defined cohorts in spring/summer and in autumn/winter. R. atlanticum showed continuous reproduction and inter-year variation but a high value for protein content related to the reproductive peak in autumn. However, the Cubozoa species showed higher organic matter and metal content than the other classes.

摘要 本研究旨在记录圣卡塔琳娜州北海岸的大型水母（macromedusae）物种，并基于2012年1月至2014年10月间手工虾类捕捞副渔获物中采集的标本，评估其种群动态及生化组成的变化。研究采用队列分析（cohort analysis）对出现频率最高的物种的种群动态进行评估。针对水母伞状体开展生化检测，分析其水分、碳水化合物、蛋白质、脂质、灰分及金属元素的含量。本次调查共发现6种大型水母：四手箱形水母（Chiropsalmus quadrumanus）与哈氏箱形水母（Tamoya haplonema，立方水母纲Cubozoa）；桑巴基奥笛水母（Olindias sambaquiensis）、大西洋笠形水母（Rhacostoma atlanticum，水螅虫纲Hydrozoa）；以及乳状海刺水母（Chrysaora lactea）、卢氏杖腕水母（Lychnorhiza lucerna，钵水母纲Scyphozoa）。其中出现频率最高、为该区域典型物种的是桑巴基奥笛水母与大西洋笠形水母。这两个物种呈现出显著的年际波动：2014年秋冬季的种群密度最高，这与当年冬季气候较为温和以及近岸海水盐度更高密切相关。桑巴基奥笛水母的体长分级分布显示其存在两个特征明确的种群队列，分别对应春/夏季与秋/冬季。大西洋笠形水母则表现出持续繁殖及年际变化特征，其蛋白质含量峰值与秋季的繁殖高峰期相契合。而立方水母纲物种的有机质与金属元素含量均高于其他类群的水母。