. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 166 I. MAIER AND D. G. MULLER. FIGURE 11. Quantitative bio-assay with spermatozoids of Cutleria miiltifida. Experimental droplets (b, c, d) contain X 10~5 molar multifidene in FC-78. Blank droplet (a) is pure solvent FC-78. Scale bar 1 mm. From Mtiller (1976). a microliter syringe. Male gametes are added and dispersed uniformly. When working with phototactic gametes, the preparation is protected from unilateral light and the microscope illumination is switched off. After a fixed time, normally 4 minutes, the distribution
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 166 I. MAIER AND D. G. MULLER. FIGURE 11. Quantitative bio-assay with spermatozoids of Cutleria miiltifida. Experimental droplets (b, c, d) contain X 10~5 molar multifidene in FC-78. Blank droplet (a) is pure solvent FC-78. Scale bar 1 mm. From Mtiller (1976). a microliter syringe. Male gametes are added and dispersed uniformly. When working with phototactic gametes, the preparation is protected from unilateral light and the microscope illumination is switched off. After a fixed time, normally 4 minutes, the distribution of the gametes in the preparation is documented by a flashlight micro- photograph. The assay is based on counting cell numbers within a standard area on pheromone- containing droplets (Fig. 11) and comparison with the cell density on the control droplet in repetitive experiments, followed by statistical treatment of the data. The concentration of pheromones refers to the aqueous phase immediately adjacent to the surface of the droplets and is determined by using the partition coefficient characteristic for the system (Boland et al., 1981). The threshold concentration is defined as the pheromone concentration, that results in the lowest statistically significant attraction coefficient "Q-value" for the experimental droplets. Variability due to biological and technical parameters is determined in blank experiments with four solvent droplets. In brown algae, thresholds for chemotaxis towards the species-specific pheromones are usually in the concentration range of 10"" to 10~9 M (Miiller, 1976; Miiller and Seferiadis, 1977; Boland et al., 1981; Muller et al., 1982b, 1984, 1985b;). The lowest threshold concentration ever measured was X 10~13 M for chemotaxis in Scylo- siphon lomentaria (Muller et al., 1985). The sensitivity of the recognition systems is remarkably high. The authors concluded that even perception of single pheromone molecules can cause a gam
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