Chronic exposure to soil salinity in terrestrial species: Does plasticity and underlying physiology differ among specialized ground-dwelling spiders?

Abstract

In salt marshes, the alternation of low and high tides entails rapid shifts of submersion and aerial exposure for terrestrial communities. In these intertidal environments, terrestrial species have to deal with an osmotic loss in body water content and an increase in sodium chloride concentration when salt load increases. In salt marshes, spiders represent an abundant arthropod group, whose physiological ecology in response to variations of soil salinity must be further investigated. In this study, we compared the effect of salinity on the survival and physiology of three species of Lycosidae; two salt marsh species (Arctosa fulvolineata and Pardosa purbeckensis) and one forest species (P. saltans). Spiders were individually exposed at three salinity conditions (0‰, 35‰ and 70‰) and survival, changes in body water content, hemolymph ions (Na(+), Ca(2+), Mg(2+), K(+); ICP-MS technique) and metabolites (mainly amino acids, polyols, sugars; LC and GC techniques) were assessed. The survival of the forest species P. saltans was very quickly hampered at moderate and high salinities. In this spider, variations of hemolymph ions and metabolites revealed a quick loss of physiological homeostasis and a rapid salt-induced dehydration of the specimens. Conversely, high survival durations were measured in the two salt-marsh spiders, and more particularly in A. fulvolineata. In both P. purbeckensis and A. fulvolineata, the proportion of Na(+), Ca(2+), Mg(2+), K(+) remained constant at the three experimental conditions. Accumulation of hemolymph Na(+) and amino acids (mainly glutamine and proline) demonstrated stronger osmoregulatory capacities in these salt-marsh resident spiders. To conclude, even if phylogenetically close (belonging to the same, monophyletic, family), we found different physiological capacities to cope with salt load among the three tested spider species. Nevertheless, physiological responses to salinity were highly consistent with the realized ecological niches of the spiders.

Broad-scale rather than fine-scale environmental variation drives body size in a wandering predator (Araneae, Lycosidae)

“…Larger females have an increased fecundity and they often produce a larger number of eggs (e.g., Simpson 1995;Prenter, Elwood, and Montgomery 1999;Fox and Czesak 2000;Puzin et al 2011). Spiders are suitable model organisms when focusing on individual-environment interactions (e.g., Wise 1993;Renault et al 2016), because prosoma width is fixed at each life stage and not, or only slightly, influenced by starvation (Miyashita 1968). Lycosid spiders are especially suitable for such a study for several reasons: (1) lycosid spiders are highly abundant in many ecosystems; (2) they can be easily sampled with pitfall traps; (3) they are known to show a strong relationship to micro-climate and vegetation structure.…”

Habitat filtering differentially modulates phylogenetic and functional diversity relationships between predatory arthropods

“…This unexpected result could be explained by the fact that spiders are more plastic to saline stress than carabids [27,40], and thus, more diverse non-specialized spiders could live in salt-marsh habitats. Laboratory experiments have revealed repeatedly that halophilic spiders, although strictly restricted to salt marshes, do perform better (in terms of both survival and fitness) without saline stress than under saline to hyper-saline stress [84,85]. Salinity probably had a strong influence on carabids because of their greater sensitivity to this stress (see above and [40,82]).…”