Environmental Correlates of Prevalence of an Intraerythrocytic Apicomplexan Infecting Caribbean Damselfish

Akacia K Halliday-Isaac,Jennilee B Robinson,Edwin Cruz-Rivera,Andrew G Campbell,Paul C Sikkel

doi:10.3390/parasitologia1020009

Abstract

Parasites are an integral part of coral reef ecosystems due to their influences on population dynamics, biodiversity, community structure, and food web connectivity. The Phylum Apicomplexa contains ubiquitous animal associates including the causative agents of globally important human diseases such as malaria and cryptosporidiosis. Despite their ubiquity, little is known about the biology, ecology, or distribution of these microorganisms in natural animal populations. In the US Virgin Islands, the dusky damselfish (Stegastes adustus) had a high but variable incidence of a Haemohormidium-like blood apicomplexan among 30 sites sampled. Microscopic analyses of blood smears allowed us to group these fish as infected, having low intensity infections, or uninfected. Regression analyses detected no significant differences in the condition indices (expressed as length–mass ratio). However, infection was clearly associated with potentially extremely high leukocyte counts among infected S. adustus that were not seen in uninfected fish. These results suggested the potential for some impact on the host. Linear mixed effects models indicated that S. adustus population density and meridional flow velocity were the main predictors of apicomplexan prevalence, with presence of other Stegastes species, population distance from watershed, zonal flow velocity, the complexity of the surrounding habitat, and season not showing any significant relationship with fish infection.

Highlights

Parasites are diverse and abundant, reaching high biomass in natural communities [1]and comprising up to 80% of organisms in tropical coral reefs [2]
Among a total of 387 Stegastes adustus sampled, we found apicomplexans, identical to those reported in our previous studies, inside the erythrocytes (A1) of 90
The prevalence of a Haemohormidium-like blood apicomplexan in the Caribbean damselfish S. adustus differed among sites and was correlated with S. adustus population density and the average meridional flow velocity of the area where the population was located

Summary

Introduction

Parasites are diverse and abundant, reaching high biomass in natural communities [1]and comprising up to 80% of organisms in tropical coral reefs [2]. Parasites are diverse and abundant, reaching high biomass in natural communities [1]. Parasites derive nutrients from their hosts and, by extension, have a potentially negative impact on infected organisms, influencing population dynamics, biodiversity, community structure, and food web connectivity (e.g., [3,4,5]). Generalist parasites can reduce biodiversity in habitats by mediating apparent competition [6,7], while specialist parasites can increase biodiversity by limiting the abundance of dominant species [6,7,8,9]. Parasites mediate trophic cascades; increase food web connectivity through their interactions with their host, its predators, its prey, and other parasites; and contribute substantially to ecosystem energy budgets [10,11,12,13].

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Results

Conclusion