Symbioses

Abstract

Cleaner shrimps are ecologically important members of coral reef communities, but for many species, cleaner status (i.e. dedicated, facultative and mimic), clientele and ecological role remain unverified or described. On Caribbean coral reefs, the spotted ‘cleaner’ shrimp Periclimenes yucatanicus forms symbioses with sea anemones that may serve as cleaning stations for reef fishes. The status of this species as a cleaner is ambiguous: only a single in situ cleaning interaction has been reported, and in the only test of its efficacy as a cleaner, it did not effectively reduce parasite loads from surgeonfish. It has subsequently been hypothesized by other authors to be a cleaner mimic. We conduct a comparative investigation of cleaning behaviour between P. yucatanicus and the ecologically similar, closely related, dedicated cleaner shrimp Ancylomenes pedersoni in Curacao, Netherlands Antilles. We provide the first detailed field observations on cleaning behaviour for P. yucatanicus and test multiple behavioural expectations surrounding mimicry in cleaning symbioses. We found that P. yucatanicusregularly signals its availability to clean, client fishes visit regularly and the shrimp does engage in true symbiotic cleaning interactions, but these are brief and our video reflects a species that appears hesitant to engage posing clients. In comparison to A. pedersoni, P. yucatanicus stations had significantly fewer total visits and cleans, and 50% of all cleaning interactions at P. yucatanicus stations were shorter than 10 s in total duration. Our behavioural observations confirm that P. yucatanicus is a true cleaner shrimp; we reject the hypothesis of mimicry. However, investigation is needed to confirm whether this species is a dedicated or facultative cleaner. We hypothesize that P. yucatanicus has a specialized ecological role as a cleaner species, compared to A. pedersoni.

Coral reefs harbour an immense diversity of species, many of which live in association with one or more host organisms. Stony corals (Scleractinia) have been documented to host nearly 900 organisms, of which > 310 are decapod crustaceans. This associated fauna is also involuntary host to a diverse parasite fauna. Coral-dwelling gall crabs (Cryptochiridae) are obligate symbionts of scleractinian corals; however, records of their parasites are scarce, with only two named epicaridean isopod species known. Fieldwork focused on cryptochirids in the Indo-West Pacific and Caribbean yielded diverse new collections of both hosts and parasites. This new material was compared with material deposited in museum collections. Both previously described species were encountered in the newly collected material, as well as a new genus and species of bopyrid, a new genus and species of cryptoniscoid, four new species of Danalia, and the first record of a rhizocephalan parasitizing a gall crab, which is also described as a new species. Parasitism of gall crabs is more widespread than what could be assumed based on literature records, and all parasite species appear to be specific to hosts in this crab family. This is the first review of hypersymbioses between stony corals, gall crabs and the crabs' parasites and hyperparasites

https://www.sciencedirect.com/science/article/abs/pii/S1055790323000325

Abstract

Symbioses play important roles in forming the structural and distributional patterns of marine diversity. Understanding how interspecies interactions through symbioses contribute to biodiversity is an essential topic. Host switching has been considered as one of the main drivers of diversification in symbiotic systems. However, its process and patterns remain poorly investigated in the marine realm. Hexacoral species of the order Zoantharia (=zoantharians) are often epizoic on other marine invertebrates and generally use specific taxa as hosts. The present study investigates the patterns of host switching and the diversification history of zoantharians based on the most comprehensive molecular phylogenetic analyses to date, using sequences from three mitochondrial and three nuclear markers from representatives of 27 of 29 genera. Our results indicate that symbiotic zoantharians, in particular those within suborder Macrocnemina, diversified through repeated host switching. In addition, colonization of new host taxa appears to have driven morphological and ecological specialization in zoantharians. These findings have important implications for understanding the role of symbioses in the morphological and ecological evolution of marine invertebrates.