Shell biomineralization and the role of nutritional quality on physiological traits of the marine turban snail Tegula atra

Abstract Herbivorous molluscs represent one of the greatest grazing impacts on abundance and diversity of primary producers in benthic ecosystems. However, shell biomineralization and the effects of nutritional content of kelp species on the physiological rate of herbivorous snails inhabiting intertidal-subtidal environments have scarcely been evaluated. Here, we investigated the mineralogy and organic composition of the shell on the marine turban snail Tegula atra. In addition, we conducted manipulative experiments to compare the nutritional quality of two kelp species, Lessonia spicata and Macrocystis pyrifera, and their influence on the feeding behavior and physiological rates of this snail species. Our results showed that the shell of T. atra consists of an outer calcitic and an inner aragonitic layer. Proteins were the main organic compounds at the inner surface of the shell, which showed an inverse pattern respect to carbonate signal. Experimental results demonstrated that L. spicata had the highest nutritional value (i.e., high organic matter and protein content), and was the preferred alga, compared with M. pyrifera in a choice experiment. However, no significant differences on consumption rate were found when the snails were maintained on a single algal species. Absorption efficiency and oxygen uptake were significatively higher for snails reared with L. spicata than M. pyrifera, but growth rate was similar. These results suggest that high metabolic activity was compensated by the high absorption efficiency of T. atra when it consumed the preferred L. spicata, which could explain the lack of relationship between preference and growth rate.