Suspension feeding in ciliated protozoa: Functional response and particle size selection

Area of Science:

• Protistology
• Microbial Ecology
• Aquatic Biology

Background:

• Ciliates are crucial microorganisms in aquatic ecosystems, playing significant roles in nutrient cycling and food webs.
• Understanding their feeding ecology, particularly particle size selection, is vital for comprehending their ecological niche and interactions with coexisting species.

Purpose of the Study:

• To quantitatively assess the ingestion rates of latex beads and live cells across various sizes by 14 ciliate species.
• To investigate the relationship between particle size, ciliate mouth morphology, and feeding functional responses.
• To explore the role of particle size selection in niche differentiation among coexisting ciliate populations.

Main Methods:

• Experimental feeding trials using latex beads and live cells of controlled sizes.
• Quantitative analysis of uptake rates at different food particle concentrations.
• Microscopic examination of ciliate mouth apparatus morphology.

Main Results:

• Ciliate uptake rates followed a hyperbolic functional response, correlating with mouth apparatus capabilities.
• Each ciliate species exhibited a specific particle size spectrum for retention and ingestion, linked to mouth morphology.
• Bacterivorous holotrich ciliates efficiently ingested particles from 0.3 to 1μm, with some retaining particles down to 0.1μm.
• Spirotrich ciliates demonstrated a minimum retention size of 1-2μm.

Conclusions:

• Ciliate particle size selection is strongly determined by their oral structures.
• Distinct particle size preferences contribute to niche partitioning, enabling coexistence of different ciliate species.
• The study provides quantitative data on ciliate feeding spectra, valuable for ecological modeling and understanding microbial food webs.