Crustaceans are associated with a wide diversity of hosts, using both chemical and visual cues to recognize them. The pea crab Dissodactylus primitivus is an ectoparasite of two species of irregular echinoids living in the Caribbean Sea. Previous studies showed that the crab chemically discriminates its hosts from non-host species. The possibility that the parasite also visually localizes its host was investigated here through behavioral and morphological approaches. The responses of the parasite to visual cues were investigated in aquaria and show a limited visual ability, leading to sheltering rather than to host localization. This suggests that visual cues are not required to maintain the specificity of the parasitism. Microscopical investigations corroborate this conclusion by revealing a pair of small compound eyes mainly localized under the cephalothorax. The ommatidia (facets) were only found on the covered surface (below the cuticle). Interestingly, a lot of setae were observed around or even directly on the eye and might participate in the overall chemical detection.

中文翻译：

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看到或闻到：视觉在外寄生蟹对宿主的识别中的作用

甲壳类动物与多种宿主相关联，它们使用化学和视觉线索来识别它们。豌豆蟹Dissodactylus primitivus是生活在加勒比海的两种不规则类棘突类动物的外寄生物。先前的研究表明，螃蟹在化学上将其宿主与非宿主物种区分开。通过行为和形态学方法研究了寄生虫还可以在视觉上定位其宿主的可能性。在水族馆中研究了寄生虫对视觉线索的反应，显示出有限的视觉能力，导致了庇护而不是宿主的定位。这表明不需要视觉提示来维持寄生虫的特异性。显微镜检查揭示了一对主要位于头胸部下方的小复眼，从而证实了这一结论。眼泪（小平面）仅在覆盖的表面（角质层下方）发现。有趣的是