Patterns of gregarine parasitism in dragonflies: host, habitat, and seasonality

Abstract

Gregarines are ubiquitous protozoan parasites that infect arthropods worldwide. More than 1,600 gregarine species have been described, but only a small percentage of invertebrates have been surveyed for these apicomplexan parasites. Adult dragonfly populations were surveyed for gregarines at two reservoirs in Texas, USA for 2 years. Gregarine prevalence and intensity were compared intraspecifically between host genders and reservoirs, among wing loads, and through time. Of the 29 dragonfly species collected, 41% hosted gregarines. Nine of these dragonfly species were previously undocumented as hosts. Among the commonly collected hosts, prevalence ranged from 18 to 52%. Parasites were aggregated among hosts and had a median intensity of five parasites per host. Gregarines were found only in hosts exceeding a minimum wing load, indicating that gregarines are likely not transferred from the naiad to adult during emergence. Prevalence and intensity increased during both years, suggesting that gregarine oocyst viability parallels increasing host population densities and may be short-lived. Prevalence and intensity also differed between dragonfly populations at two reservoirs. Regression analyses revealed that host species, host gender, month, and year were significant explanatory variables related to gregarine prevalence and intensity. Abundant information on odonate distributions, diversity, and mating activities makes dragonfly-gregarine systems excellent avenues for ecological, evolutionary, and parasitological research. Our results emphasize the importance of considering season, hosts, and habitat when studying gregarine-dragonfly ecology.

Higher gregarine parasitism often in sibling species of host damselflies with smaller geographical distributions

“…Within populations, variation between individuals appears to be the result of phenology, with changes in gregarine parasitism throughout the year. This can take the form of an increase during the season (Locklin & Vodopich, 2010) or a unimodal relationship with a peak in the middle of the season (Forbes et al, 2012), which matches a pattern seen for ectoparasitic mites in a natural insect population (Hassall et al, 2010). However, some species show no variation in gregarine parasitism over the season (Locklin & Vodopich, 2010).…”

“…This can take the form of an increase during the season (Locklin & Vodopich, 2010) or a unimodal relationship with a peak in the middle of the season (Forbes et al, 2012), which matches a pattern seen for ectoparasitic mites in a natural insect population (Hassall et al, 2010). However, some species show no variation in gregarine parasitism over the season (Locklin & Vodopich, 2010). Other work suggests that the nature of the habitat may influence gregarine parasitism, with populations inhabiting artificial wetlands exhibiting lower levels of infection than populations in natural wetlands (Mlynarek et al, 2011).…”

“…Our study controlled for locality and time of collection, thereby controlling for potential seasonal variability and latitudinal and longitudinal gradients in parasitism, which do appear to exist (e.g., Locklin & Vodopich, 2010).…”

Host diversity and seasonality of Hyalospora hemerobii (Apicomplexa: Eugregarinorida: Hirmocystidae) infections in lacewings

“…In damselflies density of gregarines is in a high positive correlation with density of hosts (Forbes et al 2012). Locklin & Vodopich (2010) provide possible explanation for strong seasonality of gregarine parasitism in dragonflies. The possible reason for low parasite levels at the beginning of the season and high levels towards the end are oocyst viability and/or oocyst accessibility to hosts (Locklin & Vodopich 2010).…”

“…Seasonally determined occurrence of gregarines is well documented in Blattaria, Odonata, Coeloptera, Siphonaptera and Diptera (Ghose & Haldar 1989;Zervos 1989;Vezzari & Wisnivesky 2006;Avelar & Linardi 2008;Albicócco & Vezzari 2009;Locklin & Vodopich 2010;Forbes et al 2012;Alarcón et al 2013;Bunker et al 2013).…”