Chemotaxis in the anisogamous brown alga Mutimo cylindricus (Cutleriaceae, Tilopteridales)

Abstract:

Locomotion of female and male gametes of Mutimo cylindricus was analysed using a high-speed recording system. Female and male gametes morphologically differed in terms of their cell size and flagellar length. Male gametes swam significantly faster than female gametes; although, the flagellar waveforms were almost the same. Thus, the different swimming velocities of male and female gametes may have been due to differences in their cell size. Chemotactic male gametes treated with the sex pheromone from settled female gametes behaved in a similar manner to the male gametes of the isogamous Ectocarpus siliculosus. The results of the study revealed the following: (1) free-swimming male gametes exhibited thigmotaxis, (2) the beat frequency of the anterior flagellum and the swimming velocity decreased, (3) the deflection angle of the anterior flagellum increased, (4) the unilateral beat of the posterior flagellum was affected by the sex pheromone gradient, and (5) the tracking radius of male gametes around female gametes decreased.

Key Words::

• Anisogamy
• Brown alga
• Chemotaxis
• Flagellar locomotion
• Mutimo cylindricus
• Sex pheromone
• Thigmotaxis

ACKNOWLEDGEMENTS

We sincerely thank Dr Toyoki Iwao, Fisheries Science Center of Toba, and Dr Akira Kurashima, Mie University, for collecting M. cylindricus.

SUPPLEMENTARY DATA

Supplementary data associated with this article can be found online at http://dx.doi.org/10.2216/15-150.1.s1.