Morphology and ichthyotoxicity as defensive strategies in soft corals from the Great Barrier Reef

Three collections of common soft corals were made for an ichthyotoxicity study. Morphological features relating to structural defence against fish predation were also assessed. The first set of samples, comprised of 68 specimens derived from 16 genera and 57 species was collected from Britomart Reef, Davies Reef, Slashers Reef and Orpheus Island between August and October, 1980. The second set of 36 specimens derived from 9 genera and 34 species, was collected from Britomart Reef, Rib Reef and Myrmidon Reef between August and October 1982. A final set of samples was collected at Lizard Island and was comprised of 67 specimens derived from 16 genera and 55 species.Initially, 16 attributes (each with between 2 and 4 levels) presumed to be of adaptive significance in morphological defence against fish were recorded for 68 alcyonacean corals from a wide range of species. These characters fell into the more general categories of: gross colony form (encrusting or erect); colony texture (including sharpness or spikiness, hardness, flexibility, and penetrability); presence of mucus; color; polyp retractility; sclerite morphology and distribution (including density of sclerite packing, length, sharpness, placement, and orientation within the colony - assessed microscopically). The soft coral species used in this study were then categorised from most toxic to least toxic (1-9) based on previous ichthyotoxicity studies of behaviour and mortality levels in test fish. A second set of observations concentrated on 28 specimens of the genus Sinularia and 28 specimens from the family Nephtheidae, which vary widely in both their morphological and ichthyotoxic characteristics. A more restricted and clearly defined set of morphological characters were considered: consistency of exposed colony parts; superficial armament of the polypary; mineralization of coenenchymal mass; anthocodial armament; and polyp retractility. In this study, soft coral species were classified as toxic or non-toxic based on relative mortality levels of test fish after 12 hours. This research was initiated to investigate the relationship between morphological features and ichthyotoxicity in defence against fish predation in soft corals.

为开展鱼类毒性研究，本研究采集了三组常见软珊瑚样本，同时针对与抵御鱼类捕食的结构防御相关的形态学特征进行了评估。第一组样本共包含68份标本，隶属于16个属、57个物种，于1980年8月至10月间采自布里托马特礁（Britomart Reef）、戴维斯礁（Davies Reef）、斯拉舍礁（Slashers Reef）以及奥费斯岛（Orpheus Island）。第二组样本共36份标本，隶属于9个属、34个物种，于1982年8月至10月间采自布里托马特礁、里布礁（Rib Reef）与米尔迈顿礁（Myrmidon Reef）。第三组样本采自蜥蜴岛（Lizard Island），共包含67份标本，隶属于16个属、55个物种。最初，研究人员针对涵盖多个物种类群的68份八放珊瑚（Alcyonacea）标本，记录了16项（每项包含2至4个等级）被认为在抵御鱼类捕食的形态防御中具有适应意义的特征。这些特征可归纳为以下几大类：群落整体形态（包括壳状或直立型）；群落质地（包括尖锐度或棘刺性、硬度、柔韧性以及穿透性）；黏液存在情况；体色；珊瑚虫（polyp）收缩性；骨针（sclerite）形态与分布（包括骨针排列密度、长度、尖锐度、在群落中的位置与朝向，该部分通过显微镜评估）。随后，基于此前针对实验鱼行为与死亡率开展的鱼类毒性研究结果，本研究涉及的软珊瑚物种按毒性从高到低被划分为1至9个等级。第二组观测聚焦于28份肉芝软珊瑚属（Sinularia）标本以及28份穗珊瑚科（Nephtheidae）标本，这两类类群的形态学特征与鱼类毒性特征均存在显著差异。本次观测选取了一组范围更窄、定义更明确的形态学特征：裸露群落部分的质地；珊瑚体表面防御结构；共肉团矿化程度；珊瑚虫（anthocodium）防御结构；以及珊瑚虫（polyp）收缩性。本研究中，研究人员根据实验鱼暴露12小时后的相对死亡率水平，将软珊瑚物种划分为有毒与无毒两类。本研究旨在探究软珊瑚抵御鱼类捕食的形态学特征与其鱼类毒性之间的关联。