Seasonal dynamics in an intertidal mudflat: the case of a complex trematode life cycle

Abstract

Seasonal fluctuations of host densities and environmental factors are common in many ecosystems and have consequences for biotic interactions, such as the transmission of parasites and pathogens. Here, we investigated seasonal patterns in all host stages associated with the complex life cycle of the intertidal trematode Maritrema novaezealandensis on a mudflat where this parasite's prevalence is known to be high (Lower Portobello Bay, Otago Harbour, New Zealand). The first intermediate snail host Zeacumantus subcarinatus, a key second intermediate crustacean host, the amphipod Paracalliope novizealandiae, and definitive bird hosts were included in the study. The density (snails, amphipods), abundance (birds), prevalence, i.e. percentage of infected individuals, and infection intensity (snails, amphipods) of the studied organisms were assessed. Furthermore, temperature was recorded in tide pools, where transmission mainly occurs, over a 1 yr period. Overall, the trematode prevalence in snail hosts was 64.5%, with 88.4% of infected snails harbouring M. novaezealandensis. There was a strong seasonal signal in prevalence and infection intensity in second intermediate amphipod hosts, with peaks for both parameters in summer (over 90% infected; infection intensity: 1 to 202 parasites per amphipod). This peak coincided with the highest abundance of definitive bird hosts and of small and still uninfected snails present on the mudflat. Our observations indicate that all of the transmission events necessary to complete the complex life cycle of this parasite primarily occur during warmer months. KEY WORDS: Seasonality · Parasite transmission · Host -parasite interactions · Temperature · Maritrema novaezealandensis · Paracalliope novizealandiae · Zeacumantus subcarinatus Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 455: [79][80][81][82][83][84][85][86][87][88][89][90][91][92][93] 2012 1995, Wilson et al. 2002). In intertidal ecosystems, the extent of environmental fluctuations is inherently pronounced. Trematode parasites are very common and highly influential components of these ecosystems and usually have complex life cycles involving several members of an intertidal community. Trematodes have been shown to play crucial roles in host population dynamics as well as community and food web structures (e.g. Lauckner 1984, Sousa 1991, Mouritsen & Poulin 2002b, Thompson et al. 2005, Wood et al. 2007, Mouritsen & Poulin 2010, and they constitute a considerable and highly underestimated amount of biomass in natural systems (Kuris et al. 2008).Infection levels of trematodes in intertidal host populations substantially differ not only spatially (e.g. Smith 2001, Kube et al. 2002a, Latham & Poulin 2003, Hechinger & Lafferty 2005, Byers et al. 2008) but also temporally (e.g. Hughes & Answer 1982, Lauck ner 1987, Meißner & Bick 1997, Al-Kandari et al. 2000, Kube et al. 2002b, Jen sen et al. 2004, Al-Kandari et al. 2007). Many aspects of the transmission of trematodes ar...

Coastal ecosystems on a tipping point: Global warming and parasitism combine to alter community structure and function

“…In the extreme‐scenario experiment, six of the eight mud snails were infected in the parasite‐treatments creating an infection prevalence of 75%. This high level of parasitism corresponds roughly to values recorded in the highly parasitized Lower Portobello Bay (Fredensborg et al., ; Studer & Poulin, ; unpublished data).…”

“…In the subsequent extreme‐scenario experiment, these figures equalled 19.4°C (range: 16.8–26.5°C) and 25.1°C (range: 22.7–29.0°C), respectively (Student's t test, t 154 = 24.50, p < 0.0005). Note that these experimental temperature ranges are all within values measured in situ (Studer & Poulin, ). For simplicity, these four temperature treatments will be denoted 17, 21, 19, and 25°C, respectively.…”

“…Regarding levels of parasitism in the standard‐warming experiment, three of the eight added mud snails (37.5%) were infected by M. novaezealandensis in the parasite treatments, whereas no snail was infected in no‐parasite treatments. The 37.5% prevalence of infection corresponds roughly to the grand mean across Otago Harbour bays in the immediate vicinity of our study sites (see Fredensborg, Mouritsen, & Poulin, ; Studer & Poulin, ). In the extreme‐scenario experiment, six of the eight mud snails were infected in the parasite‐treatments creating an infection prevalence of 75%.…”

Estimating trematode prevalence in snail hosts using a single-step duplex PCR: how badly does cercarial shedding underestimate infection rates?

“…The illumination times differed because one species of cercariae shed from G. adansonii emerges more during dark periods [32], whereas larval trematodes infecting Z. subcarinatus emerge within 2-6 h of constant illumination [9,27,33]. …”

Life on the beach for a sand crab (Emerita rathbunae) (Decapoda, Hippidae): parasite-induced mortality of females in populations of the Pacific sand crab caused by Microphallus nicolli (Microphallidae)

“…Temporal and spatial variations in levels of infection in intermediate hosts are commonly observed patterns in studies of parasite ecology (Latham and Poulin 2002b;Oliva et al 2008;Smith 2007;Studer and Poulin 2012). Spatial variation in the level of infection such as that observed here has been attributed by other authors to differences in abundances It is possible that variation in the abundance of M. nicolli between the four locations is the result of a factor or process related to the size of the crabs that might influence this infection parameter (Poulin 1999).…”