Phenotypic divergence in an intertidal mud snail induced by environmental stress and parasitic castrators

NICOLÁS BONEL; PILAR ALDA

Bahía Blanca

Congreso; 3 Congreso Argentino de Malacología; 2019

Inbiosur - Universidad Nacional del Sur

Phenotypic plasticity is a common feature in nature across many taxa and is the ability of an organism (or a single genotype) to express different phenotypes in dissimilar biotic or abiotic environments. Many studies indicate a role for plasticity in shaping phenotypic responses as an effective mechanism for the long-term persistence of populations facing new stressful environmental conditions brought about by climate change. Intertidal organisms are more likely to exhibit increased phenotypic plasticity in response to the harshness of the physical environment (e.g. desiccation, extremes in temperature and salinity) along the vertical zonation of the intertidal area. Phenotypic variation is particularly widespread in aquatic gastropods and their shells offer an easily measured and permanent record of how the organism responded to local abiotic (e.g. water chemistry temperature) and biotic (e.g. predation) inducing agents. Likewise, parasites can cause important shifts in the expression of host phenotypic traits, creating pronounced phenotypic differences between infected and uninfected hosts. In this study, we investigated whether environmental stress conditions and parasitic castrators induced phenotypic responses in the intertidal mud snail Heleobia australis (Cochliopidae). We collected and dissected individuals over four seasons from three distinct habitats from the intertidal area of the Bahía Blanca estuary, Argentina. We found that the subpopulations showed a strong phenotypic divergence for the variables and traits measured (snail density, prevalence, shell and aperture size and shape, shell and body weight) between habitats with high vs. low environmental stress conditions and between unparasitized vs. parasitized snails. Shell traits of juveniles varied across habitats conditions mirroring the pattern observed for adults, suggesting that phenotypic divergence occurred early in life. These differences may confer selective advantages to the snails in response to dissimilar environmental stress conditions. The next step will focus on determining whether the responses observed are genetically based rather than purely plastic.