Thermarces cerberus (Rosenbatt and Cohen 1986)
Feeding Strategy: Predation
Thermarces cerberus mainly feeds on gastropod mollusks, with particular preference to Lepetodrilus elevatus, as well as amphipod crustaceans, such as Ventiella sulfuris and Halice hesmonectes (Sancho et al., 2005; Pond et al.¸ 2008). L. elevatus is the most common prey, likely as it can be found at numerous zones within the hydrothermal vent site, especially amongst the Riftia, and in high abundance (Fig. 1) (Desbruyéres et al., 2006). Likewise, both amphipod crustacean species are found in high abundance in the vestimentiferan zone and near vent openings, respectively (van Dover et al., 1992; Desbruyéres et al., 2006); this high abundance is expected to be the reason for T. cerbreus to target them as prey species. Occasionally, if preferred prey is unattainable, this fish species will feed on polychaete worms or crustaceans (Sancho et al., 2005). However, T. cerberus is generally unable to eat species that possess symbiotic bacteria, as the bacteria acts as a deterrent to the fish (Kicklighter et al., 2004).
Considering the main prey of T. cerberus is a grazing gastropod, T. cerberus could be classed as a keystone species – whereby a keystone species is a species that largely influence the community structure of the ecosystem (Oxford Dictionary of Biology, 2006). This is because the predation of L. elevates reduces grazing, thus promoting successful settlement and recruitment of juvenile vestimentiferans and other sessile invertebrates, in this harsh environment (Micheli et al., 2002; Sancho et al., 2005). Consequently, if this fish species was removed from the vent site, there would likely be a trophic cascade, in which an increase in grazing gastropods causes a decline to the overall ecosystem by increased grazing pressure (Micheli et al., 2002). It is for this reason that T. cerberus are important to vent site ecosystems as well as dominating them.
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