Diet relationships between parasitic gastropods Echineulima mittrei (Gastropoda: Eulimidae) and sea urchin Diadema setos
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SHORT NOTE
Diet relationships between parasitic gastropods Echineulima mittrei (Gastropoda: Eulimidae) and sea urchin Diadema setosum (Echinoidea: Diadematidae) hosts Polina Yu. Dgebuadze1 · Elena S. Mekhova1 · Nguyen T. N. Thanh2 · Anna K. Zalota3 Received: 16 April 2020 / Accepted: 28 August 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Gastropods from the family Eulimidae are known as parasites of all living classes of echinoderms. Here we determine the trophic relationships between ectoparasitic eulimids Echineulima mittrei and their hosts, sea urchins Diadema setosum in Vietnam. Stable isotope analysis showed the differences in δ13C and δ15N saturation in echinoderms tissues. The eulimids’ muscle and gonad tissues have the same carbon isotopic composition as the gonads of the hosts; however, they are more saturated with heavy nitrogen isotopes. The isotopic signatures indicate that ectoparasites feed on the fatty tissues of their hosts, especially gonads. Moreover, we suggest selective feeding in eulimids and possible migration of parasites’ proboscis among different host gonads and probably changes in the metabolism of parasites.
Introduction Gastropods from the genus Echineulima are widely distributed in tropical ecosystems and can only be found in associations with sea urchins. In total, this genus includes eleven valid species (WoRMS). It is known that these molluscs attach to their hosts’ oral side among the spines bordering on the peristomal membrane and penetrate deep into the hosts’ test using the proboscis (Warén 1983). The salivary glands and radula are absent. The alimentary tract is divided into the well-developed short length buccal cavity, small buccal muscular pump, elongate oesophagus, small stomach, digestive glands, and rectum (Lützen and Nielsen 1975). The representatives of the genus Echineulima feed on hosts’ internal Responsible Editor: S. Uthicke. Reviewed by J. C. Hernández and an undisclosed expert. * Polina Yu. Dgebuadze [email protected] 1
A.N. Severtsov Institute of Ecology and Evolution, RAS, Leninsky prospekt, 33, Moscow, Russia 119071
2
Coastal Branch, Russian-Vietnamese Tropical Research and Technology Center, Nguyễn Thiện Thuật, 30, Nha Trang 57154, Vietnam
3
Shirshov Institute of Oceanology, RAS, Nakhimovsky prospekt, 36, Moscow, Russia 117218
organs and tissues using their acrembolic proboscis, which reaches the perivisceral cavity. Moreover, it has been suggested, that these eulimids attach to their hosts permanently, however in some cases they are able to leave and, probably, search for another host (Lützen and Nielsen 1975). Judging by the measurements of gastropods from the genus Echineulima, some authors considered that the proboscis can reach most organs in the sea urchins’ perivisceral cavity. There is one exception where the proboscis was introduced into the intestine and pierced its wall. In all cases the proboscis was not attached to any of the hosts’ organs. Moreover, in different parts of the gastropods’ aliment
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