Vicious circle in the intertidal: Facilitation between barnacle epibionts, a shell boring polychaete and trematode parasites in the periwinkle Littorina littorea

Abstract

We studied interactions between three organisms associated with a common gastropod of northern Atlantic shores, the periwinkle Littorina littorea: barnacle epibionts Balanus crenatus, a shell boring polychaete Polydora ciliata, and tissue invading trematodes which use the periwinkles as first intermediate host. Snails collected shortly after barnacle settlement with N 50% cover of barnacles had significantly higher infestation of shell boring worms compared to unfouled snails, while trematode infestation was similar. The result was the same at two sites, and we conclude that the worm P. ciliata facilitates barnacle fouling on snails. The reverse was also the case. In an experiment with 14 weeks of exposure, snail treatments with barnacle epibionts had a significantly higher P. ciliata load than unfouled and cleaned snails. Again, trematode infestations were similar. The reciprocal positive interactions between barnacle epibionts and shell boring worms on snail houses is regarded as a case of facultative mutualism. On the other hand, for the snail basibiont, both barnacles and shell boring worms exert strongly negative effects by reducing fecundity, growth, and survival, resulting in a vicious circle for the snails. The combined effects of these associated organisms may rival in importance any competitive or predacious effects on the host L. littorea.

Habitat-specific size structure variations in periwinkle populations (Littorina littorea) caused by biotic factors

“…Since both, P. ciliata and trematodes occur exclusively in periwinkles ¸12 mm shell height (Lauckner 1984;Buschbaum et al 2007;Thieltges and Buschbaum 2007), only individuals of this size range were sampled.…”

“…Similarly, the prevalence of shell boring polychaetes P. ciliata is also higher in large-sized L. littorea and may be about 70% in snails above 18 mm shell height on soft bottoms in the northern Wadden Sea Thieltges and Buschbaum 2007). Whether an infestation with P. ciliata leads directly to an increased mortality in L. littorea is unknown.…”

“…Other factors may be likewise important for determining the size structure of marine gastropod populations, e.g. food availability and intraspeciWc competition (Kemp and Bertness 1984;Fenske 1997), predation pressure (Palmer 1990;Yamada et al 1998;Trussel 1996;Trussel and Nicklin 2002;Buschbaum et al 2007), parasitism (Lauckner 1984;Huxham et al 1993) and overgrowth by epibionts (Wahl 1996;Buschbaum and Reise 1999;Thieltges and Buschbaum 2007).…”

Associated fauna and effects of epibiotic barnacles on the relative growth and reproductive indices of <em>Stramonita haemastoma</em> (Gastropoda: Muricidae)

“…Abundant colonization could have serious and deleterious consequences on the basibiont. Indeed, Thieltges and Buschbaum (2007) and Buschbaum et al (2007) showed that the presence of the worm Polydora ciliata on the shell of Littorina littorea facilitates barnacle fixation, leads to a gradual destruction of the shell, reduces the resistance against predators and reduces the fecundity and the growth of the gastropods. According to Lleonart et al (2003), an infestation of 30% in the gastropod Haliotis spp.…”

Chemical antifouling defences of sea stars: effects of the natural products hexadecanoic acid, cholesterol, lathosterol and sitosterol

“…For example, biofouling may reduce the photosynthesis and growth of marine algae (Dixon et al 1981, Drake et al 2003, affect the shell condition, growth rate and survival of bivalves (Lodeiros & Himmelman 1996, Taylor et al 1997, Kaehler & McQuaid 1999, Thieltges & Buschbaum 2007 and affect the condition and function of the appendages of crabs (Botton 1981, Cadee 1991. Many marine plants and animals have evolved behavioural, mechanical, physical and/or chemical defences to reduce these disadvantages and ecological costs (reviewed by Wahl 1989).…”