Novel Foraging Mechanisms in Atypical Excavate Flagellates.

Area of Science:

• Protistology
• Cellular Biology
• Fluid Dynamics

Background:

• Most excavates (flagellates) use a vaned flagellum to create feeding currents via a ventral groove.
• Some excavates exhibit atypical morphologies, lacking this crucial vane.

Purpose of the Study:

• To describe the foraging mechanisms of heteroloboseid flagellates (Discoba) that possess a ventral groove but lack a vaned flagellum.
• To investigate how these flagellates generate feeding currents without a typical vane.

Main Methods:

• Observational analysis of flagellar undulation and water flow in Percolomonads (AE-1, P. doradorae) and Pharyngomonas kirbyi.
• Fluid dynamics modeling (point sink, point force/stokeslet) to interpret flow patterns.
• Measurement of volumetric flow rate through the ventral groove.

Main Results:

• Percolomonads use four flagella with asymmetric undulation to create an erratic flow, acting as a point sink.
• Pharyngomonas kirbyi uses two posterior flagella for continuous flow, acting as a point force (stokeslet).
• Percolomonads have a higher volumetric flow rate, comparable to other phagotrophic flagellates; Ph. kirbyi has a lower rate, possibly due to its hypersaline environment.

Conclusions:

• Heteroloboseid flagellates exhibit diverse, atypical flagellar mechanisms for feeding current generation.
• These findings expand our understanding of flagellar function and foraging strategies in excavates.
• The distinct fluid dynamics generated by different flagellar arrangements highlight adaptive evolution in response to environmental conditions.