Zalota Anna K, Savchenko Alexandra S, Miroliubov Aleksei A, Waiho Khor, Fazhan Hanafiah, Chan Benny K K, Kolbasov Gregory A
Shirshov Institute of Oceanology, Russian Academy of Sciences, Moscow 117997, Russia.
Invertebrate Zoology Department, Biological Faculty, Moscow State University, Moscow 119991, Russia.
Zoology (Jena). 2025 Jan;168:126234. doi: 10.1016/j.zool.2024.126234. Epub 2024 Nov 29.
Coral reefs house a great variety of symbiotic associations, including parasitism. One of the crucial issues in the host-symbiont interactions is the parasites' feeding mode. Does the parasite/symbiont use the host's tissues for nutrition, steal food from the host's digestive system, or take food directly from the environment? However, most of the parasitism in corals is endosymbiotic (endoparasitic). Their trophic interactions are difficult to identify since they only occur in intact associations. This work uses stable isotope analysis (SIA) of carbon and nitrogen and morphological analysis to study the trophic relationship between the crustacean endoparasites, the Ascothoracida (genera Baccalaureus, Sessilogoga, and Zibrowia) and their various coral hosts ranging from Zoantharia (Palythoa) to Antipatharia (Antipathes), and Scleractinia (Dendrophyllia). The hosts belong to different coral taxa and obtain food from different sources, reflected in their stable isotope values. The SIA, supported by the morphological analysis, suggests that the Zibrowia parasite feeds directly on its Dendrophyllia host. Sessilogoga retains vagility within and around the black coral colony. It has typical generalized piercing mouth parts with numerous teeth and denticles. Sessilogoga may use antipatharian tissues for food directly as well as sucks food fluids from the host's gastrovascular system. There is no clear trophic shift trend between Palythoa and its parasite Baccalaureus. Such differences exclude the possibility of the parasite feeding predominantly on its host's tissues and suggest a broad spectrum of food sources. Thus, SIA reveals that endosymbiotic ascothoracidans may not always be true parasitic but also opportunistic feeders, which steal food directly from the host gastric cavity.
珊瑚礁中存在着各种各样的共生关系，包括寄生关系。宿主与共生体相互作用的关键问题之一是寄生虫的进食方式。寄生虫/共生体是利用宿主组织获取营养，从宿主消化系统窃取食物，还是直接从环境中获取食物？然而，珊瑚中的大多数寄生现象是内共生的（体内寄生）。由于它们只发生在完整的共生关系中，其营养相互作用很难确定。这项研究利用碳和氮的稳定同位素分析（SIA）以及形态学分析，来研究甲壳类体内寄生虫——软甲亚纲（Baccalaureus属、Sessilogoga属和Zibrowia属）与它们的各种珊瑚宿主之间的营养关系，这些宿主包括六放珊瑚亚纲（葵珊瑚属）到角珊瑚亚纲（角珊瑚属），以及石珊瑚目（树珊瑚属）。这些宿主属于不同的珊瑚分类群，从其稳定同位素值可以看出它们从不同来源获取食物。形态学分析辅助下的SIA表明，Zibrowia寄生虫直接以其树珊瑚宿主为食。Sessilogoga在黑珊瑚群体内部及周围具有移动性。它有典型的、带有许多齿和小齿的通用穿刺口器。Sessilogoga可能既直接利用角珊瑚组织作为食物，也从宿主的消化循环系统吸食食物液。葵珊瑚与其寄生虫Baccalaureus之间没有明显的营养转移趋势。这些差异排除了寄生虫主要以宿主组织为食的可能性，并表明其食物来源广泛。因此，SIA揭示出内共生软甲亚纲动物可能并不总是真正的寄生者，也可能是机会主义觅食者，它们直接从宿主胃腔窃取食物。
