Population dynamics, infestation and host selection of Vexilla vexillum, an ectoparasitic muricid of echinoids, in Madagascar

Abstract

The symbiotic interaction, population and infestation dynamics of the muricid Vexilla vexillum (Gmelin, 1791) on 2 echinoid species, Tripneustes gratilla (Linnaeus, 1785) and Echinometra mathaei (Blainville, 1825), was investigated on the barrier reef off Toliara (Madagascar). V. vexillum is an ectoparasitic muricid which was exclusively found in association with sea urchins, on which it moves freely and browses over the integument. Host recovery from damage caused by muricid grazing was dependent on lesion size. Small lesions regenerated while larger ones were subjected to secondary infections, which led to host death. A 27 mo survey (2000 to 2003) of the muricid's population dynamics revealed annual recruitment episodes during the mid-summer season (December to January). Patterns of recruitment peaks were apparently linked to its reproductive cycle. Demographic parameters including growth and mortality rates of the muricid were estimated from analysis of sizefrequency distributions. Growth was described by the von Bertalanffy function. The model predicts that V. vexillum is a fast-growing species in which asymptotic shell length (L ∞ = 1.024 cm) is reached 6 to 7 mo after recruitment. The growth rate constant K, and shell length at settlement L 0 , were estimated from the model. Estimated mortality rate was 55% yr -1 ; V. vexillum has a short lifespan. The observed high growth rate together with the high mortality rate suggest that V. vexillum is a semelparous species. A field survey of the infestation dynamics of V. vexillum was performed during 3 consecutive years, with seasonal variation in parasite prevalence on both echinoid host species. Although both T. gratilla and E. mathaei were infested, a preference towards T. gratilla was noted. This was attributed to T. gratilla's test morphology (which allows better accessibility for grazing), to the muricid's higher recognition capacity of T. gratilla (as determined by olfactory experiments) and to the high recruitment predictability of that particular host. This study provides novel information on the biology of V. vexillum, an echinoid epidermal grazer, and its relationship with 2 ecologically and economically important echinoid species.

Microbiological study of the body wall lesions of the echinoid Tripneustes gratilla

“…Infections then progress through the test, often causing fatal perforations (Vaïtilingon et al 2004). The present study examines this infection that leads to the death of T. gratilla.…”

“…A recent survey on the southwest coast of Madagascar (off Toliara) revealed the presence of the parasitic gastropod Vexilla vexillum on 2 echinoid species, Tripneustes gratilla and Echinometra mathaei (Vaïtilingon et al 2004). The gastropod is always found associated with these echinoids and is never observed free-living.…”

“…In both species, the gastropod grazes the body surface, which progressively turns black as the infection by microorganisms develops. Infections then progress through the test, often causing fatal perforations (Vaïtilingon et al 2004). The present study examines this infection that leads to the death of T. gratilla.…”

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“…These organisms are primarily carnivores (Abe, 1980(Abe, , 1983Carriker, 1981;Hughes, 1986;Harper and Morton, 1994;Navarette, 1996), however several species have evolved other modes of feeding such as omnivory, scavenging (Keable, 1995;Tsuchiya, 2000), detritivory (Vermeij and Carlson, 2000), parasitism (Vaïtilingon et al, 2004), corallivory (Taylor, 1983;Boucher, 1986;Turner, 1994), and even herbivory (Vermeij and Carlson, 2000;Kantor, 2002). Most species are seasonal spawners (Yamamoto, 1997) and deposit large aggregates of egg masses to avoid predation.…”

Echinoderm Adhesive Secretions: From Experimental Characterization to Biotechnological Applications

“…Although they suggested that tissue adhesion is a fourth type of adhesion, we rather propose that this is a sub-category of either permanent, transitory or temporary adhesion, that should be opposed to adhesion to abiotic substrata. Indeed, examples of tissue adhesion include permanent attachment of parasitic barnacles on whale skin (Ridgway et al 1997), transitory attachment of parasitic gastropods on echinoderm epidermis (Vaitilingon et al 2004), or temporary attachment of parasitic monogeneans on the gills or skin of fishes (Whittington and Cribb 2001). There are, however, invertebrate adhesive systems that do not fit into the three types of adhesion described above.…”