Temporal Community Structure in Two Gregarines (Rotundula gammariandHeliospora longissima) Co-Infecting the AmphipodGammarus fasciatus

Abstract

This study surveyed gregarine parasites that infect the amphipod, Gammarus fasciatus , to investigate temporal dynamics in infracommunity structure. We sampled a population of hosts for 2 yr from the north branch of the Raritan River in New Jersey. These hosts were infected with 2 direct life cycle gregarine parasites, Rotundula gammari and Heliospora longissima. Infections were separated temporally, with the prevalence of R. gammari peaking within the amphipod population in the fall (prevalence = 78% year 1 and 97% year 2) and H. longissima peaking in early spring (prevalence = 41% year 1 and 52% year 2). Increases in host population density did not significantly correlate with the abundance of these 2 parasites. However, H. longissima abundance was positively correlated with host body weight while R. gammari showed no significant relationship. The mean body mass of amphipods infected with H. longissima was 20.7 ± 1. 2 mg, and with R. gammari 8.1 ± 0.2 mg, which suggests a sized-based infection pattern. Mixed species infections were infrequent with an overall prevalence of 4.6%. When both gregarine species co-infected the same host, the R. gammari but not the H. longissima infrapopulation size was significantly lower when compared to single-species infections, suggesting asymmetric interactions. We conclude that the observed temporal patterns of infection by the 2 parasites are driven by a seasonal change in host demographics and size-dependent infections. We argue that specificity for host developmental stages may have arisen as a mechanism to avoid overlap between these gregarine species.

Droplet digital PCR as a tool for investigating dynamics of cryptic symbionts

“…In addition, the infection load was lower when host density was high, although the estimate was not significant. A similar non-significant negative effect of host density on prevalence was detected in apicomplexans infecting amphipods (Grunberg & Sukhdeo, 2017).…”

High parasite diversity in the amphipodGammarus lacustrisin a subarctic lake

“…Finally, the gregarine Rotundula sp. can co-occur with other gregarines in amphipods, (as reported byGrunberg & Sukhdeo, 2017). Altogether, these studies indicate that our results likely underestimate the number of parasite species in G. lacustris in Takvatn.…”

“…ranged from 2% to 28% among sites and years (Supplementary Table S2), which is lower than the 40%–90% found in other studies of Gammarus spp. (Bojko et al., 2017; Grunberg & Sukhdeo, 2017; Sorcetti & Di Giovanni, 1984). Even though intensities of gregarines can be high (>50), as seen in Takvatn, the pathology of these infections may be limited (Bojko et al., 2017; Grunberg & Sukhdeo, 2017).…”

“…(Bojko et al., 2017; Grunberg & Sukhdeo, 2017; Sorcetti & Di Giovanni, 1984). Even though intensities of gregarines can be high (>50), as seen in Takvatn, the pathology of these infections may be limited (Bojko et al., 2017; Grunberg & Sukhdeo, 2017). Our total lengths for Rotundula sp.…”

Parasites shape community structure and dynamics in freshwater crustaceans

“…Direct and indirect consequences of parasite mediation will vary in time, possibly leading to large fluctuations in host populations. Temporal variations in parasite communities have been shown to impact host demographics in other systems (Grunberg and Sukhdeo, 2017). It is thus likely that they will affect top-down and bottom-up trophic interactions within this community (Hunter and Price, 1992).…”