An experimental investigation of interactions in snail-macrophyte-epiphyte systems

Abstract

An experimental investigation under field conditions of enclosures containing freshwater pulmonate snails, the macrophyteCeratophyllum demersum and epiphytes, produced evidence of beneficial interactions.Ceratophyllum growth, measured in terms of stem length, numbers of leaf-nodes and growing tips and leaf survival was significantly enhanced in the presence of snails. This effect was attributed to the increased availability of plant nutrients of snail origin, such as phosphates and ammonia, as well as to the snails' action as "cleaning symbionts" in reducing the density of bacterial and algal epiphyton potentially deleterious to macrophytes. Principal component analysis revealed both seasonal and treatment effects of snail grazing on algal epiphyton. Small adnate algal species (e.g.Cocconeis placentula) survived grazing and benefited from the removal of larger, competitor, species. Snail densities increased in all treatments, despite high (86%) juvenile mortality. It is concluded that freshwater pulmonate snails are strong interactors in lentic habitats, enhancing the growth ofCeratophyllum and producing characterisic epiphyte communities. This benefits not only the snails, but also the plants and epiphytes that are associated with them. Thus the interactions between these component parts of the community can be considered as mutualistic.

The habitat type and trophic state determine benthic macroinvertebrate communities in lowland shallow lakes of China

“…The macrophyte-dominated regions were mainly characterized by gastropods (Pan et al, 2012) and very few individuals were collected in the other habitats. Our findings are in accordance with the snail-macrophyte-epiphyte mutualistic hypothesis, which proposes that gastropods, macrophytes and periphytons could form a structure of mutualistic (Thomas, 1990;Underwood et al, 1992). In contrast, there is no such space structure in the algae-dominated regions, which could not provide the diversity of food conditions and restrict the species diversity, but some adaptive macroinvertebrates could increase to large numbers.…”

Changes in macrozoobenthic assemblages in a shallow subtropical lake (Lake Taihu, China): 1987–1988 vs. 2007

“…In this study, we found high species richness of gastropods in the East Bay in both sampling periods. This result can be explained by the macrophyteÀherbivore mutualistic relationship (Underwood et al 1992), where macrophytes provide refuge from predators, physically stable habitats, better food conditions, and higher DO levels. Furthermore, the more diversified substrates provided by macrophytes contain more ecological niches than homogeneous systems, allowing more species to coexist.…”

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“…Kufel & Ozimek (1994) y Scheffer (1998) enfatizaron el importante papel que tienen en establecer y mantener un estado estable dominado por macrófitos acuáticos, restringiendo la abundancia de fitoplancton. Además, los carófitos, debido a que su presencia se mantiene durante la mayor parte del año, sobre todo en los ecosistemas de aguas permanentes, tienen efectos positivos sobre las comunidades de peces (Scheffer, 1998;Wetzel, 2001), aves (Pereyra-Ramos, 1981;Hargeby & al., 1994), y determinados invertebrados (Hanson, 1990;Underwood & al., 1992;Hargeby & al., 1994), aunque desde antiguo se conozca su efecto perjudicial para las larvas de dípteros (Caballero, 1922) y el ya mencionado sobre el fitoplancton (Wium-Andersen & al., 1982).…”