Echinoderms, Cnidarians, & The Gastropods That Parasitize Them

The recent Invertebrate Wars reminded me of spectacular, but often ignored, group of gastropods. The parasites! This is a group that I have totally geeked out on in the past. In my previous work I have focused on the Ptenoglossa likely a paraphyletic or polyphyletic group, established originally of unspecified rank by Gray (1853). It is generally agreed upon that the group is above the level of family and generally is defined as a suborder (Bouchet & Rocroi 2005). The group includes usually includes the families Cerithiopsidae, Triphoridae, Janthinidae, Epitoniidae, Aclidae, and the Eulimida. Most ptenoglosates possess radulae distinctive to the group (Ponder & Lindberg 1997).

Most eulimids are highly specialized and exclusively ectoparasitic (external parasites) on echinoderms. Most are permanently attached to a single host, although some species may transfer between hosts repeatedly during their lifespan. However a few species have undergone numerous morphological adaptations, including anatomical reductions, to exploit hosts as endoparasites particularly on the sea cucumbers! Shell morphology can be extremely variable, reflecting specialization for parasitism, with males typically smaller than females. Epitoniids are generally considered to be ectoparasites, although some authors have defined this group by various degrees of commensalism and predation (Smith 1998). In contrast to eulimids, epitoniids are exclusively ectoparasitic on cnidarians, primarily anemones and corals, and reside in the sediment near their hosts. A modified radula and jaw are used to bite pieces of their hosts. The host specificity of aclids is less clear is not known. Cerithiopsidae and Triphoridae feed on sponges possibly in a manner that could be construed as parasitic. The Janthinidae, or violet snails, are parasites on the various pelagic Cnidarians like Portuguese Man-'O-War, Porpita, and Velella.

So its obvious once again that Mollusks, specifically Gastropods, are better than cnidarians and echinoderms (capitalization, or lack thereof, is intended)

See below for pictures.

Janthina globosa feeding on Porpita
Eulimid on crinoid

Examples of Epitoniids (Wentletraps)

Eulimid snail on Ophiothrix sp

Parasitic Eulimid Shell on a Fire Urchin

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So, the ability to evolve parasitic lifeforms is a hallmark of superiority? Please, these molls are so pathetically frightened of the 'real' world that they have to mooch off others to survive. Sad, how sad.

By Dr. Whore (not verified) on 24 Mar 2008 #permalink

I have small bivalve gastropod shells from Santa Monica beach. I would like to identify the species.
I can easily supply a picture. They were obtained from the beach. they are of a very similar shape but they're all different colors. Some have stripes radiating from the central region, some have horizontal stripes. And they all have a vast array of colors, ranging from white to pale orange, to dark brown to almost black, and various striping patterns throughout. Are they of the same species? What does the coloration indicate? I've noticed the white ones are more worn on the edge and surface whereas the darker ones have a more defined ridge pattern on their surface and well-defined edge. I'm wondering if the white ones live closer to the surface and are subjected to higher surf action.

By Greg Parr (not verified) on 10 Jun 2010 #permalink