Cnidom variation through distinct developmental stages in the sea anemone Aulactinia marplatensis (Zamponi, 1977) (Cnidaria: Actiniaria)

The cnidae are the exclusive diagnostic structures of phylum Cnidaria. The inventory of all cnidae types of a particular species is called the cnidom. The study of cnidae has been widely addressed in all classes of cnidarians. Particularly in the order Actiniaria (sea anemones), the study of the composition, size and distribution of cnidae is essential to the identification and description of species. In the present study, we examine the cnidom of the sea anemone Aulactinia marplatensis in three different stages of development throughout its life cycle. We found that the composition and abundance patterns are very similar between the adult and juvenile stages, although significant differences in the size capsules were found between both stages and in all cnidae types observed, being bigger those from the adult forms. The planula larvae stage presents a less diverse cnidom in comparison to the juvenile and adult stages; however, it presents an exclusive cnidae type (the mesobasic p-mastigophore) which is the biggest in size of all the cnidae types observed in the species. These results highlight the importance of considering the stage of development when cnidae is used as a diagnostic character, and the particular relevance of the study of the cnidom in larval stages.

刺胞（cnidae）是刺胞动物门（Cnidaria）特有的诊断性结构。某一物种的全部刺胞类型的汇总被称为刺胞组（cnidom）。针对刺胞的研究已在刺胞动物的所有纲中得到广泛开展。尤其在海葵目（Actiniaria，海葵）中，对刺胞的组成、大小与分布的研究是物种鉴定与形态描述的必要依据。本研究针对马尔普拉塔海葵（Aulactinia marplatensis）生命周期内的三个不同发育阶段的刺胞组展开系统分析。研究结果显示，成体与幼体阶段的刺胞组成与丰度模式极为相似，但二者在所有观测到的刺胞类型的囊体大小上均存在显著差异，成体的刺胞囊体显著更大。浮浪幼虫（planula larvae）阶段的刺胞组多样性显著低于幼体与成体阶段，但该阶段存在一种专属刺胞类型——细颈型p-刺丝囊（mesobasic p-mastigophore），其为该物种所有观测刺胞类型中体积最大的一类。上述研究结果凸显了在将刺胞作为物种鉴定特征时考虑发育阶段的重要性，同时也彰显了刺胞组研究在幼虫阶段的特殊科研价值。