The Effect of Aquatic Plant Abundance on Shell Crushing Resistance in a Freshwater Snail

Abstract

Most of the shell material in snails is composed of calcium carbonate but the organic shell matrix determines the properties of calcium carbonate crystals. It has been shown that the deposition of calcium carbonate is affected by the ingestion of organic compounds. We hypothesize that organic compounds not synthesized by the snails are important for shell strength and must be obtained from the diet. We tested this idea indirectly by evaluating whether the abundance of the organic matter that snails eat is related to the strength of their shells. We measured shell crushing resistance in the snail Mexipyrgus churinceanus and the abundance of the most common aquatic macrophyte, the water lily Nymphaea ampla, in ten bodies of water in the valley of Cuatro Ciénegas, Mexico. We used stable isotopes to test the assumption that these snails feed on water lily organic matter. We also measured other factors that can affect crushing resistance, such as the density of crushing predators, snail density, water pH, and the concentration of calcium and phosphorus in the water. The isotope analysis suggested that snails assimilate water lily organic matter that is metabolized by sediment bacteria. The variable that best explained the variation in crushing resistance found among sites was the local abundance of water lilies. We propose that the local amount of water lily organic matter provides organic compounds important in shell biomineralization, thus determining crushing resistance. Hence, we propose that a third trophic level could be important in the coevolution of snail defensive traits and predatory structures.

Correlates of snail shell variation along a unidirectional freshwater gradient in Lithasia geniculata (Haldeman, 1840) (Caenogastropoda: Pleuroceridae) from the Duck River, Tennessee, USA

“…However, there is no direct evidence suggesting alternate forms would perform worse at the same locations along the river, nor that any fitness differences would exist. Data on whether selection is acting on genotypes for plasticity versus some other developmental or behavioural trait is also lacking, and correlations of fitness and heritability to form and function may vary (CHaves-CaMpos et al 2012). Future research focused on testing fitness of the various forms of L. geniculata in different environments can directly address the evolution, plasticity, and adaptive nature of shell variation in Lithasia.…”

Potential Indicator Value of Subfossil Gastropods in Assessing the Ecological Health of the Middle and Lower Reaches of the Yangtze River Floodplain System (China)

“…Studies suggest that hard water lakes provide a favourable environment for gastropod populations as these lakes contain a rich source of minerals and calcium needed for shell development [40,65]. Shells are formed during ecological processes, where water biogeochemistry plays a central role in physiological processes of snails [44,45].…”

“…The chemical components of gastropod shells, as well as the structure and shape of the shells, can provide indications of past conditions in lakes, including water quality and predator-prey interactions. For example, the available calcium and other inorganic and organic compounds in water are revealed by shell biogeochemistry [43][44][45]. Gastropods use carbon and mineral ions during metabolism, and the signature of carbon and ions are also preserved in their shells.…”

Substratum‐Associated Microbiota

“…Organic compounds not synthesized by snails were important for shell strength. To obtain strong shells, snails assimilated water lily organic matter that was metabolized by sediment bacteria (Chaves-Campos et al, 2012). In Lake Erken (Sweden) changes in periphyton composition (from algae dominated to bacteria dominated with increasing depth) were reflected in the dominant nematode feeding type: algae-feeding species in the shallow littoral zone and bacteria-feeding species in the deep littoral zone .…”

“…examined the effects of low and high toxic stress on an entire sediment assemblage, with cadmium (Cd) as the eucalypt stand. Runoff samples produced significant inhibitory effects on the bacteria Vibrio fischeri, the algae Pseudokirchneriella subcapitata and the macrophyte Lemna minor(Campos et al, 2012).…”