Morphological and behavioral differences in the gastropod Trophon geversianus associated to distinct environmental conditions, as revealed by a multidisciplinary approach.

MARQUEZ F.; NIETO VILELA R.A.; LOZADA M.; BIGATTI, G.

Journal of Sea Research

Royal Netherlands Institute for Sea Research

Año: 2015 vol. 95 p. 239 - 247

The gastropod Trophon geversianus exhibits shell polymorphisms along its distribution in subtidal and intertidalhabitats. Our hypothesis is thatmorphological and behavioral patterns of T. geversianus represent habitat-specificconstrains; subsequentlywe expect an association between shell morphology, attachment behavior, and habitat.In order to test this hypothesis we compared individuals from intertidal and subtidal habitats, at three sites inGolfo Nuevo (Argentina). We analyzed shell morphology using classic morphometric variables, 3D geometricmorphometrics and computing tomography scan. The results were complemented with field observations ofattachment to substrate and turning time behavior, as well as of the number of shell scars produced by crabpredation. Our results showed differences in shell size and shape between intertidal and subtidal-collectedindividuals. Centroid size, total weight and shell weight, as well as shell density and thickness were significantlylower in intertidal individuals than in subtidal ones. Gastropods from intertidal habitats presented a low-spiredshell and an expanded aperture which might allow better attachment to the bottom substrate, while subtidalindividuals presented a slender and narrower shell shape. The number of crab scars was significantly higher inshells from subtidal individuals. Observations of the behavior of gastropods placed at the intertidal splash zoneshowed 100% of attachment to the bottom in the intertidal individuals, while subtidal specimens only attachedin average in 32% of the cases. These latter took 12 times longer to re-attach to the bottom when faced up.Phylogenetic analysis of COI gene fragments showed no consistent differences among individuals sampled inboth habitats. All these results suggest that T. geversianus has developed two ecomorphs with distinct morphologicaland behavioral responses to physically stressful conditions registered in north Patagonian intertidals, asopposed to lower physical stress but higher predation pressure in the subtidal habitats. The findings of thiswork constitute a starting point in the study of ecological adaptation processes in gastropods from Patagoniancoastal environments.