A scaleworm (Polychaeta: Polynoidae) living with corals
T. A. Britayev, T. I. Antokhina & I. N. Marin
Marine Biodiversity ISSN 1867-1616 Mar Biodiv DOI 10.1007/s12526-014-0305-5
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Author's personal copy Mar Biodiv DOI 10.1007/s12526-014-0305-5
OCEANARIUM
A scaleworm (Polychaeta: Polynoidae) living with corals T. A. Britayev & T. I. Antokhina & I. N. Marin
Received: 31 July 2014 / Revised: 5 December 2014 / Accepted: 8 December 2014 # Senckenberg Gesellschaft für Naturforschung and Springer-Verlag Berlin Heidelberg 2014
Scleractinian corals provide a set of complex habitats for a diversity of associated animals that often form close interactions with their hosts. Studies of specialized coral associates have focused on the biology of decapod crustaceans (Patton 1994), while only Spirobranchus spp. (Serpulidae) have been considered among polychaetes (Stella et al. 2011). Species of another polychaeta family, Polynoidae (scaleworms), are common symbionts of octocorals, although they were also reported as accidental associates on scleractinians. Their relationship with corals remains virtually unknown (Martin & Britayev 1998). Here, we consider an association and diet of an undescribed species of scaleworm Hololepidella sp. with the coral Galaxea astreata (Oculinidae). Specimens of Hololepidella were found in washings from G. astreata colonies in the Bay of Nhatrang, Vietnam. Scaleworms were semitransparent and hardly distinguishable on their hosts (Fig. 1a, b). They reach 35 mm in length and live under the canopy of coral tentacles. Seventy-four of 101 inspected colonies harboured Hololepidella. Infested colonies could have up to five worms per colony, while 91 % of these colonies had only one or two scaleworms per colony. Out of 30 scaleworms that we have dissected, five had no food remains. Others contained mucus with unicellular algae and cnidocysts (23 specimens, Fig. 1c, d), and fragments of copepods (seven specimens). Copepods resemble Hetairosyna wedensis (Fig. 1e), which is an obligatory symbiont of Galaxea species (Humes 1996). The algae were similar in size, shape and color to the zooxanthellae of Galaxea, which indicates that the scaleworms are feeding on other coral symbionts as well as
T. A. Britayev (*) : T. I. Antokhina : I. N. Marin A.N. Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences, Leninsky pr. 33 119071 Moscow, Russia e-mail:
[email protected]
Fig. 1 a. Galaxea astreata colony in situ, b. Hololepidella sp. on the host colony, c. Fragment of a Hololepidella sp. gut, d. Detail of zooxanthellae from the gut, e. Remnants of copepod Hetairosyna sp. from the gut
Author's personal copy Mar Biodiv
on host tissues. These observations suggest intimate parasitic interactions between Hololepidella and their host. The relationships of other scleractinian symbionts (e.g., crabs and shrimps) with corals are known to be mutually beneficial (cleaning or defensive symbioses, Stewart et al. 2006). However, like Hololepidella, they also feed on coral mucus and tissues, thus more field and experimental studies are needed to discriminate the position of Hololepidella - Galaxea relationship on the symbiotic continuum. Acknowledgments This work was supported by the Russian Scientific Foundation, project No 14-14-01179.
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