Host selection and distribution of Hypermastus placentae (Eulimidae), and ectoparasitic gastropod on the sand dollar Arachnoides placenta (Echinoidea)

Abstract

The intertidal sand dollar Arachnoides placenta is parasitized by the eulimid Hypermastus placentae at Pallarenda Beach, Townsville, Queensland. A. placenta is the only echinoderm species in the region with which H. placentae associates. Sand dollars are distributed in an aggregated pattern within the littoral zone at Pallarenda Beach, and the distribution of parasites within the adult sand dollar population conforms closely to Poisson expectations. A. placenta adults in all size classes are equally susceptible to parasitization by H. placentae, whereas juveniles are not parasitized; host selection may be determined by a requirement for host gonadal tissue in the diet of the parasite. Infestation rate and number of parasites per host decrease as host density increases. Parasite body size is not related to host body size.

The Ecology of Biotic Interactions in Echinoids

“…Predators and parasites of echinoids include gastropods (Moore 1956;Chesher, 1969;Hughes and Hughes, 1971;Hendler, 1977;Gladfelter 1978;Serafy, 1979;Warén, 1980a;Warén, 1980b;Hughes, 1981;Kier, 1981;Warén et al 1983;Fujioka, 1985;Alekseev and Endelman, 1989;Levitan and Genovese, 1989;Warén and Moolenbeek, 1989;Warén and Mifsud, 1990;Warén and Crossland, 1991;Crossland et al, 1991Crossland et al, , 1993McClintock and Marion, 1993;Oliverio et al, 1994;Rinaldi and Malacologico, 1994;Warén et al, 1994;McClanahan, 1999;Nebelsick and Kowalewski, 1999;Ceranka and Złotnik, 2003;Vaïtilingon et al, 2004;Złotnik and Ceranka, 2005a, b;Neumann and Wisshak 2009;Meadows et al, 2015), polychaetes (Wisshak and Neumann, 2006), crustaceans (Tegner and Levin, 1983;Smith, 1984;Wirtz et al, 2009) including barnacles (Madsen and Wolff, 1965;Cross and Rose, 1994;Donovan et al, 2016) and copepods (Margara, 1946;Roman, 1954), echinoderms (Merril and Hobson, 1970;…”

Eulimids (Gastropoda, Eulimidae) on the Sea Cucumber Holothuria mexicana (Ludwig, 1875) (Holothuroidea, Holothuriidae) in Belize

“…Eulimids are parasites of all extant classes of echinoderms with which they associate (Warén 1983). Most eulimids are ectoparasitic that feed on the body fluids of echinoderm hosts by using their long proboscis and radula (when present) to pierce the skin and reach internal organs (Crossland et al 1993, Warén 1980, 1983, or the coelomic fluid, with no serious consequences to the host (Purcell et al 2016). The eulimids Melanella acicula (Gould, 1849) and Peasistilifer nitidula (Pease, 1860), for instance, insert their proboscis into the lacunae of the host's body wall, not fully penetrating the body wall, and feed upon the coelomocytes (Warén 1980(Warén , 1983.…”

“…The last one, an undescribed species of the genus Melanella, is known to live as an ecto or endoparasite of holothuroids in the orders Holothuriida (formerly Aspidochirotida) and Dendrochirotida (Warén 1983). Some eulimids are known to be host specific, while others are generalists (Crossland et al 1993).…”