Acanthocephalan parasites in sea otters: Why we need to look beyond associated mortality…

Abstract

The acanthocephalan parasite, Corynosoma enhydri, uses sea otters (Enhydra lutris) as definitive host. Despite high prevalence and abundance in southern sea otters (E. l. nereis), sublethal impacts of infection on otter health are unknown. Parasites are an integral part of ecosystem structure and functioning. Many affect host behavior, reproduction, predation, or prey preference. Parasites can suppress host immune response, facilitate secondary bacterial, viral, or parasitic infections, and influence concurrent microbial infection. Acanthocephalan infections can have significant effects on host metabolism, digestion, nutrient absorption, and energetics. Because high metabolic expenditures and resource limitations are known to affect southern sea otter populations, even subtle effects of infection could negatively impact individual health and population recovery. In this review we summarize reports of host–parasite‐environmental interactions for helminth infections and discuss how these same attributes could manifest in southern sea otters and coastal food web dynamics. Based on these data, investigation of potential sublethal impacts of C. enhydri is warranted. We recommend expanding understanding of the significance of parasites in marine ecosystems beyond associated mortality. Future investigation into the ecological implications of sublethal effects are essential to fully grasp parasite impacts on host populations, and predict potential additive effects with climate change in ecosystem functioning.

The energetic costs of sub‐lethal helminth parasites in mammals: a meta‐analysis

“…The effect size was, as predicted, weakest for opportunistic sampling. This may be because mammals found deceased in the wild are more likely to be in poor condition already due to disease processes or physical harm (Shanebeck & Lagrue, 2020). Cross‐sectional studies often cannot quantify infection period, limiting them to snapshot comparisons between infected and uninfected hosts.…”

Habitat selection and populations ofCorynosoma(Acanthocephala) in the intestines of sea otters (Enhydra lutris) and seals

“…Knowledge about C. enhydri ecology, infection patterns and pathogenicity is limited, and only a few publications are available (Rausch, 1953; Hennessey, 1972; Hennessey & Morejohn, 1977; Margolis et al ., 1997; Mayer et al ., 2003; Shanebeck & Lagrue, 2019; Shanebeck et al ., 2020). Previous prevalence (90%, Hennessey & Morejohn, 1977; 94.4%, Mayer et al ., 2003), compared with the 100% observed in this study, shows consistent infections in southern sea otters that suggest a stable Corynosoma population.…”

“…Members of the genus Corynosoma are obligate marine parasites, infecting the intestines of marine mammals and birds worldwide, most commonly in pinnipeds (Aznar et al ., 2006). Knowledge about the ecological relevance and sub-lethal effects of these parasites for marine mammals is limited (Shanebeck & Lagrue, 2019). Corynosoma enhydri infections in otters are reported to not cause peritonitis and to induce limited localized tissue reactions (Rausch, 1953; Kreuder et al ., 2003; Mayer et al ., 2003).…”

“…rely on marine food webs to transmit to their final host, and as soft-bodied absorptive feeders, can be particularly helpful in the monitoring of abiotic changes in marine ecosystems (Kennedy, 2006). Yet, though sea otters are such charismatic and vulnerable species, little knowledge exists about the only parasite that uses sea otters as its preferred definitive host (Mayer et al, 2003;Shanebeck & Lagrue, 2019). This study investigated the demographics of C. enhydri in sea otters and established a baseline of their population structure, to better understand their ecology and microhabitat preferences.…”

“…This study investigated the demographics of C. enhydri in sea otters and established a baseline of their population structure, to better understand their ecology and microhabitat preferences. Acanthocephalans are ubiquitous wildlife parasites and may be useful bioindicators for health and ecosystem-wide effects in vulnerable mammals (Kennedy, 2006;Shanebeck & Lagrue, 2019).…”