CLONAL VARIATION IN PHOTOTAXIS AND SETTLEMENT BEHAVIORS OF HINCKSIA IRREGULARIS (PHAEOPHYCEAE) SPORES1

Abstract

Hincksia irregularis (Kützing) Amsler isolates from North Carolina were used to assess clonal variations in spore swimming behavior and settlement responses within a population. These behaviors were also compared with those previously reported from a Florida panhandle clone to assess differences between geographically distinct populations. Minor variation between morphologies, reproductive responses, and settlement intervals were observed between all clones. Spores from all North Carolina clones exhibited positive phototaxis, but there was significant variation in the lower threshold irradiances that could elicit the behavior. In contrast, spores from the previously studied Florida panhandle clone exhibited negative phototaxis. Hincksia irregularis spore settlement responses to hydrophobic and hydrophilic surfaces were consistent for all clones currently and previously tested. Interactive effects of light and charge on settlement were evident in spores from North Carolina isolates, but these effects differed from the Florida panhandle isolate. Settlement preference and swimming behavior differences may have a considerable effect on an individual's ecological fitness and placement within the marine environment. However, the perceived relevance of these differences needs to be validated further in light of previously reported genetic, physiological, and behavioral variations observed in other algal clones that have called into question traditional assessments of individuality.