Biomass and productivity of trematode parasites in pond ecosystems

Abstract

Summary1. Ecologists often measure the biomass and productivity of organisms to understand the importance of populations and communities in the flow of energy through ecosystems. Despite the central role of such studies in the advancement of freshwater ecology, there has been little effort to incorporate parasites into studies of freshwater energy flow. This omission is particularly important considering the roles that parasites sometimes play in shaping community structure and ecosystem processes. 2. Using quantitative surveys and dissections of over 1600 aquatic invertebrate and amphibian hosts, we calculated the ecosystem-level biomass and productivity of trematode parasites alongside the biomass of free-living aquatic organisms in three freshwater ponds in California, USA. 3. Snails and amphibian larvae, which are both important intermediate trematode hosts, dominated the dry biomass of free-living organisms across ponds (snails = 3Á2 g m À2 ;amphibians = 3Á1 g m À2 ). An average of 33Á5% of mature snails were infected with one of six trematode taxa, amounting to a density of 13 infected snails m À2 of pond substrate.Between 18% and 33% of the combined host and parasite biomass within each infected snail consisted of larval trematode tissue, which collectively accounted for 87% of the total trematode biomass within the three ponds. Mid-summer trematode dry biomass averaged 0Á10 g m À2 , which was equal to or greater than that of the most abundant insect orders (coleoptera = 0Á10 g m À2 , odonata = 0Á08 g m À2 , hemiptera = 0Á07 g m À2 and ephemeroptera = 0Á03 g m À2 ). 4.On average, each trematode taxon produced between 14 and 1660 free-swimming larvae (cercariae) infected snail À1 24 h À1 in mid-summer. Given that infected snails release cercariae for 3-4 months a year, the pond trematode communities produced an average of 153 mg m À2 yr À1 of dry cercarial biomass (range = 70-220 mg m À2 yr À1 ). 5.Our results suggest that a significant amount of energy moves through trematode parasites in freshwater pond ecosystems, and that their contributions to ecosystem energetics may exceed those of many free-living taxa known to play key roles in structuring aquatic communities.

Patterns of parasite transmission in polar seas: Daily rhythms of cercarial emergence from intertidal snails

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It’s a predator–eat–parasite world: how characteristics of predator, parasite and environment affect consumption

“…Communities with a high diversity and abundance of both vertebrate and invertebrate taxa have the potential to regulate transmission of the widest breadth of parasite species. Furthermore, predation risk may change seasonally based on the presence of small, early ontogenetic stages of predators, which may prefer parasite prey as well as correspond with peaks in availability of cercariae in the environment (Kaplan et al 2009;Preston et al 2013). Our results also highlight the role of visibility in determining predation risk to parasites.…”

“…We tested the capacity of two common aquatic predator groups, fish and larval insects, to consume free-living infective stages of four trematode species, which are an important group of parasites in aquatic ecosystems (Lafferty et al 2008;Preston et al 2013). We investigated the following questions:…”

Behavioural influences on disease risk: implications for conservation and management

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