Selective grazing by the mud snail Ilyanassa obsoleta.

Area of Science:

• Marine Biology
• Ecology
• Benthic Ecology

Background:

• Mud snails (Ilyanassa obsoleta) are important deposit feeders in coastal ecosystems.
• Understanding their feeding selectivity is crucial for comprehending nutrient cycling in sediments.

Purpose of the Study:

• To investigate the feeding selectivity of mud snails on sediment organic matter and diatoms.
• To determine if selective ingestion meets the energy requirements of Ilyanassa obsoleta.

Main Methods:

• Laboratory microcosms with starved mud snails fed on sediment cores.
• Analysis of sediment and snail gut contents for carbon, nitrogen, pigments, and diatom species composition.
• Comparison of nutrient and diatom concentrations at different sediment depths and in snail guts/feces.

Main Results:

• Surface sediments (0-2 mm) were 2-10 times richer in carbon, nitrogen, and pigments than deeper layers (7-10 mm).
• Snail guts showed 20-40 times higher concentrations of these materials compared to surface sediments.
• Migratory diatoms, abundant in surface sediments, were disproportionately represented in snail guts, indicating selective feeding.

Conclusions:

• Mud snails exhibit strong selective feeding, targeting nutrient-rich surface sediments and specific diatom communities.
• This selective ingestion strategy is sufficient to meet the daily energy demands of Ilyanassa obsoleta.
• Selective feeding by mud snails plays a significant role in benthic nutrient and energy transfer.