The predominantly facultative nature of epibiosis: experimental and observational evidence

Abstract

Epibiosis is a spatially close association between 2 or more organisms belonging to the same or different species. Through direct and indirect interactions, this association has major effects on the species involved and on community dynamics. When the effects are predominantly beneficial for epibiont and basibiont, coevolution can be expected to lead to associational specificity. Circumstantial evidence, however, suggests that many epibionts are non-specific substratum-generalists. In this article, we investigate the commonness of specificity in epibiotic associations. In a first approach, we investigated the in situ recruitment preferences of potential epibionts when choosing between artificial and living substrata. After exposure for 3 wk in early summer, an early successional community had established, comprising cyanobacteria, diatoms, sesslle colonial ciliates and red algae. All species recruited on almost all substrata available. However, artificial substrata were usually preferred over living surfaces. Consequently, the species studied are class~fied as facultative epibionts. An analysis of a list of over 2000 epibiotic associations corroborated these results, the majority of described 'epibionts' are not basibiont-specific and generally occur on non-living substrata as well. Also, basibiont species usually bear more than 1 epibiont species. Relative to each other, epibionts and basibionts are characterised by a typical set of life history traits. We conclude that specific and obligate epibionts are rare. Their scarcity is discussed in view of multilevel antifouling defences and presumptive evolutionary transitions from epibiosis towards endoparasitism or endosymbiosis.

Cirripedia Balanomorpha del estuario del Río Paripe (Isla de Itamaracá, Pernambuco, Brasil)

“…En cuanto a la competición por el espacio en el estuario estudiado, se observó un alto grado de epibiosis de las especies incrustantes y sesiles, que, según Garduño (1980), llega a se convertir en un factor limitante; esto fenómeno fue defi nido por Wahl & Mark (1999) como una relación de dos o más especies que, por medio de interacciones directas o indirectas, ejercen mayor efecto en las especies asociadas y en la dinámica de las comunidades. Silva-Brum & Martins (1996) observaron que las especies Amphibalanus amphitrite, A. improvisus, Chthamalus bisinuatus y C. proteus además de otras tres especies marinas, son comúnmente encontradas sobre conchas de moluscos.…”

A novel symbiosis between chemoautotrophic bacteria and a freshwater cave amphipod

“…However, the presence of a unique phylotype of Thiothrix, to the exclusion of filamentous e-proteobacteria and closely related Thiothrix phylotypes many times more numerous in the environment, is indeed remarkable. The phylogenetic specificity demonstrated by the N. ictus-Thiothrix association is extremely unusual for epibiotic associations (Wahl and Mark, 1999) and is an important hallmark of symbioses. The Thiothrix clade contains strains that are capable of both autotrophic and heterotrophic growth.…”

“…Epibiotic associations have been proposed as the initial step toward more integrated, intracellular symbioses (Smith, 1979;Cavanaugh, 1994;Wahl and Mark, 1999), leading eventually to the development of obligate endosymbioses and organelles. In the marine environment, symbioses between animals and chemoautotrophic bacteria are an ancient phenomenon, often involving obligate, intracellular microbial partners.…”

Polysiphonia spp as epibiont of Caligus rogercresseyi (Crustacea: Copepoda) in Salmo salar farming centers

“…As previously mentioned, algae are able to grow over a number of species including crustacean (Wahl and Mark 1999) that can serve as a substrate for spore germination, growth of thallus and subsequent development of filaments, acting as epibiont.…”

“…The colonization of animals by benthic sessile marine organisms is a survival strategy (epibiosis) which provides the epibiont with this valuable resource (AbeIló et al 1990). Consequently a number of bacteria, diatoms, sessile colonial ciliates and macroalgae have been described as epibionts (Wahl and Mark 1999).…”