Prey selection of corallivorous muricids at Koh Tao (Gulf of Thailand) four years after a major coral bleaching event

Abstract

Corallivorous Drupella (Muricidae) snails at Koh Tao are reported to have extended their range of prey species following a major coral bleaching event in 2010. Populations of their preferred Acropora prey had locally diminished in both size and abundance, and the snails had introduced free-living mushroom corals in their diet. Although the coral community largely recovered, the Drupella population grew and reached outbreak proportions. For this study, corallivorous muricids at Koh Tao were studied more intensively to examine their identities, distribution and prey choice four years after the bleaching event. Drupella rugosa was identified as the major outbreak species and occurred at densities > 3 m -2 in depth ranges of 2-5 and 5-8 m. The density of D. rugosa was related to the live coral cover, Acropora colony density, and depth. Resource selection ratios revealed that species of Acropora, Psammocora and Pavona corals were attacked more frequently than would be expected based on their availability. Strikingly, fungiid corals were now avoided as prey in the recovered coral community, despite them being part of the preferred diet directly after the bleaching. Although D. rugosa showed a clear prey preference, it appears to be plastic by changing with prey availability. The muricids Drupella margariticola and Morula spinosa occurred in much lower densities and were less often associated with corals. Snails of the opportunistic corallivore D. margariticola usually co-occurred in D. rugosa aggregations, although they also formed feeding aggregations by themselves. Whether M. spinosa generally associates with corals as a corallivore or a scavenger has yet to be determined. Molecular analyses did not reveal cryptic speciation among snails sampled from different coral hosts and also no geographic variation. The present study also showed that corallivory is more common among D. margariticola and M. spinosa than previously known.

Host-dependent variation in density of corallivorous snails (Coralliophila spp.) at Curaçao, southern Caribbean

“…The distribution of snails was not random over the available hosts colonies for either of the studied host species. The number of snails per host was positively related to host coral size, which is consistent with research on corallivorous Drupella snails in the Indo-Pacific (Cumming 2009;Schoepf et al 2010;Moerland et al 2016). Intuitively, larger host colonies (with increasing age) have more likely become colonized by snails over time than smaller and younger host colonies, and also offer more available space for larger snail aggregations.…”

“…For a better Communicated by R. Vonk * Bert W. Hoeksema bert.hoeksema@naturalis.nl understanding of the damage inflicted by corallivorous snails, information on their choice of prey is needed, which can be inferred from the host corals on which they have been found. Many known studies have investigated the diet of Drupella snails associated with Indo-Pacific scleractinians (Boucher 1986;Turner 1994;Cumming 1999;Morton et al 2002;Shafir et al 2008;Schoepf et al 2010;Al-Horani et al 2011;Hoeksema et al 2013;Moerland et al 2016) and Cyphoma snails (Ovulidae: Simniinae) associated with Caribbean octocorals Chiappone et al 2003;Burkepile and Hay 2007;Reijnen et al 2010;Schärer and Nemeth 2010;Lucas et al 2014). Snails of those genera appear to be generalists regarding their choice of host, which is in part dependent on variable host availability Moerland et al 2016).…”

Relationships between a common Caribbean corallivorous snail and protected area status, coral cover, and predator abundance

“…Our surveys showed that a common corallivore, the short coral snail Coralliophia abbreviata, is abundant on reefs throughout Florida as it in on many reefs in the Caribbean 9 . The results of our study suggest that while local abundances of C. abbreviata are related to the amount of living coral food resources, their abundances also appear to be regulated within protected areas, potentially reducing chronic stress on corals that leads to mortality 16,28,30 , disease 26,27,29 , and reduced growth 28 , fecundity 40 , and hampered coral resilience [9][10][11] . This relationship may be due to the presence or increased abundances of key C. abbreviata predators within protected sites.…”

Genetic and morphological variation in corallivorous snails (Coralliophila spp.) living on different host corals at Curaçao, southern Caribbean

“…Aggregations of C. caribaea were generally smaller. Large aggregations of snails of the genus Drupella Thiele, 1925 (Muricidae: Ergalataxinae) can have a damaging effect on Indo-Pacific reef corals (Hoeksema et al, 2013;Moerland et al, 2016;Scott et al, 2017; references herein), suggesting that large C. galea aggregations are harmful as well, confirming earlier findings (Bruckner et al, 1997;Knowlton et al, 1988Knowlton et al, , 1990Hayes, 1990a;Baums et al (2003aBaums et al ( , 2003b. Predation on Alcyonacea by C. caribaea is also relevant, as gorgonians represent a large part of Caribbean and Brazilian reef communities (e.g.…”

“…Migration between host species with age could induce host-associated size structuring. In the Indo-Pacific corallivorous snail Drupella cornus (Röding, 1798), prey preference seems to change as snails age (Black and Johnson, 1994;McClanahan, 1997;Schoepf et al, 2010;Moerland et al, 2016). Age-dependent host preference would result in a clear host-associated size structuring as seen within Coralliophila spp.…”