Building on 150 Years of Knowledge: The Freshwater Isopod Asellus aquaticus as an Integrative Eco-Evolutionary Model System

Abstract

Interactions between organisms and their environments are central to how biological diversity arises and how natural populations and ecosystems respond to environmental change. These interactions involve processes by which phenotypes are affected by or respond to external conditions (e.g., via phenotypic plasticity or natural selection) as well as processes by which organisms reciprocally interact with the environment (e.g., via eco-evolutionary feedbacks). Organism-environment interactions can be highly dynamic and operate on different hierarchical levels, from genes and phenotypes to populations, communities, and ecosystems. Therefore, the study of organism-environment interactions requires integrative approaches and model systems that are suitable for studies across different hierarchical levels. Here, we introduce the freshwater isopod Asellus aquaticus, a keystone species and an emerging invertebrate model system, as a prime candidate to address fundamental questions in ecology and evolution, and the interfaces therein. We review relevant fields of research that have used A. aquaticus and draft a set of specific scientific questions that can be answered using this species. Specifically, we propose that studies on A. aquaticus can help understanding (i) the influence of host-microbiome interactions on organismal and ecosystem function, (ii) the relevance of biotic interactions in ecosystem processes, and (iii) how ecological conditions and evolutionary forces facilitate phenotypic diversification.

Individual level microbial communities in the digestive system of the freshwater isopod Asellus aquaticus: Complex, robust and prospective

“…Questions regarding the role of the microbiome in facilitating the spread of the isopod populations, enabling the high polymer degradation activity, and helping the host to cope with different stressors remain to be answered. The complexity and variation of the A. aquaticus microbiome on the individual level uncovered in this study further emphasizes freshwater isopods as excellent model organism for studying the ecology and evolution of host-microbiome interactions (Lafuente et al, 2021;O'Callaghan et al, 2019).…”

Effects of anthropogenic stress on hosts and their microbiomes: Treated wastewater alters performance and gut microbiome of a key detritivore (Asellus aquaticus)

“…at point‐source discharges from wastewater treatment plants). Such effects of anthropogenic changes in general, and wastewater in particular, can be particularly striking when they affect keystone species, such as the detritivorous A. aquaticus (discussed in Lafuente et al, 2021 ), as they have the potential to cascade through influences on multiple trophic levels (e.g. on their mesopredators and/or parasites), as well as through nutrient cycling and decomposition (Feckler et al, 2016 ; Salo et al, 2017 ; Stamm et al, 2016 ).…”

“…We studied the impact of treated wastewater on a sexually dimorphic detritivore host (the freshwater isopod Asellus aquaticus ) and its gut microbiome and explored to what extent responses differ between males and females. Asellus aquaticus is a particularly well‐suited and ecologically relevant species for such integrative studies (Lafuente et al, 2021 ), as it is a keystone species with a broad environmental tolerance (including resilience to high levels of pollution; Maltby, 1991 , 1995 ) that feeds both on microbes and decaying plant matter (Graça et al, 1993 ; Kemp et al, 2020 ; Lafuente et al, 2021 ). Importantly, A. aquaticus (as many other isopod species) has a highly diverse gut microbiota in its hepatopancreas (i.e.…”

Responses to desiccation vary among populations of an endemic freshwater isopod, Paramphisopus palustris

“…This study shows the importance of studying the responses of endemic species to environmental change, as their responses are not always easily predicted from knowledge of more widespread and commonly studied species (e.g. A. aquaticus; Lafuente et al, 2021).…”