Resource partitioning in endemic species of Baikal gastropods indicated by gut contents, stable isotopes and radular morphology

Abstract

We used multiple analytical methods to demonstrate resource partitioning in five species of coexisting endemic gastropods in the family Baicaliidae and the genus Megalovalvata (Valvatidae) in rocky walls of the underwater canyons in Lake Baikal. We tested whether filter-feeding baicaliids and valvatids consume and assimilate different food using data from gut contents, stable d 13 C and d 15 N isotopes and radular morphology, with subsequent combined analyses. Our results showed that the four baicaliid species assimilate microalgae, diatoms and bacteria, whereas the single Megalovalvata species mostly assimilates plant detritus. The d 15 N variations in the baicaliids reflect differences in their digestion of seston components, whereas the d 13 C similarity illustrates consumption of food particles derived from similar primary producers. Gut contents in the baicaliids were dominated by a single species of planktonic diatom, although more than 30 species of microalgae were recorded in all seasons. However, the composition and quantity of additional food particles varied by species. Our results showed that baicaliids have significant fine scale differences in radular tooth morphology, which may allow partitioning of food resources.

Patterns of diatom treatment in two coexisting species of filter-feeding freshwater gastropods

“…Investigations into gastropod stomach contents showed that most diatom cells were broken and empty, but some diatoms remained intact with preserved plastids (Dillon and Davis, 1991;Kawamura et al, 1995Kawamura et al, , 2005). Similar results were described for Baikal gastropods (Sitnikova et al, 2012). The aim of the present study was to determine whether gastropod species employ different mechanisms for breaking frustules for large and small diatom cells.…”

“…Both of the snails are able to attach and hang continuously from vertical surfaces and overhanging rock using byssus threads ( Figure 1A) (Roepstorf et al, 2003;Sitnikova et al, 2012). Filtering seston, the gastropods passively ingest food particles from the littoral phytoplankton.…”

“…For example, 10 of the 40 known species of the family Baicaliidae occur together on the rocky littoral of the lake (Sitnikova et al, 2010;our data). It is known that one of the mechanisms of gastropod speciation in the world's ancient lakes is divergent adaptation to different trophic resources among sympatric species (e.g., Michel, 1994Michel, , 2000von Rientelen et al, 2004;2012;Glaubrecht and von Rientelen, 2008;Sitnikova et al, 2012). Sitnikova and colleagues demonstrated that five sympatric species of Baikal gastropods inhabiting the rocky littoral obtain sufficient amounts of food, mostly from seston, and they exhibit significant differences in diets, the stable isotopes δ 13 C and δ 15 N, and radular tooth morphology, which is evidence for food resource partitioning (Sitnikova et al, 2012).…”

“…It is known that one of the mechanisms of gastropod speciation in the world's ancient lakes is divergent adaptation to different trophic resources among sympatric species (e.g., Michel, 1994Michel, , 2000von Rientelen et al, 2004;2012;Glaubrecht and von Rientelen, 2008;Sitnikova et al, 2012). Sitnikova and colleagues demonstrated that five sympatric species of Baikal gastropods inhabiting the rocky littoral obtain sufficient amounts of food, mostly from seston, and they exhibit significant differences in diets, the stable isotopes δ 13 C and δ 15 N, and radular tooth morphology, which is evidence for food resource partitioning (Sitnikova et al, 2012). Diatoms are the main dietary component of Baikal gastropods regardless of feeding mechanisms -scrapping and/or filtering 4 (Roepstorf et al, 2003;Shirokaya, 2003;Sitnikova et al, 2012).…”

“…Sitnikova and colleagues demonstrated that five sympatric species of Baikal gastropods inhabiting the rocky littoral obtain sufficient amounts of food, mostly from seston, and they exhibit significant differences in diets, the stable isotopes δ 13 C and δ 15 N, and radular tooth morphology, which is evidence for food resource partitioning (Sitnikova et al, 2012). Diatoms are the main dietary component of Baikal gastropods regardless of feeding mechanisms -scrapping and/or filtering 4 (Roepstorf et al, 2003;Shirokaya, 2003;Sitnikova et al, 2012). Diatoms are a necessary and preferred food for many grazing marine and freshwater gastropods (Tsikhon-Lukanina, 1987;Dillon, 2000;Hernández & Siqueiros-Beltrones, 2010;Riera, 2010;Zhang et al, 2010;etc.).…”