QUALITATIVE AND QUANTITATIVE STUDIES OF THE SWIMMING BEHAVIOR OF HINCKSIA IRREGULARIS SPORES (PHAEOPHYCEAE)

Abstract

The swimming behavior of spores of the brown alga Hincksia irregularis was analyzed using computer‐assisted motion analysis. We distinguished five main swimming patterns: straight paths, search circles, orientation, gyration, and wobbling. We suggest different functional values for the individual swimming patterns. Straight paths, search circles, and orientation are different but all may be important in small‐scale movements in the benthic boundary layer. As such, they could enable a spore to find a suitable microenvironment for germination and growth. Gyration occurs during the initial reversible phase of adhesion that can lead to settlement. Wobbling is typical for irritated or mechanically damaged spores and does not seem to be a typical pattern associated to settlement. The dominant swimming patterns changed with spore age (10 ± 5 to 60 ± 5 min of spore age), with young spores mainly swimming in straight paths and search circles and older spores in orientation and gyration. This change in swimming patterns can be quantified by speed (decrease over time) and rate of change of direction (increase over time). Based on these results, we suggest that computer‐assisted motion analysis of the swimming behavior of H. irregularis spores can be used to develop bioassays with both ecological and technological relevance.