![]() Although a model has been developed that considers the distance over which individuals can recognize the opposite sex ( Baird & Jumper, 1995 Coates & Hovel, 2014), the cues used by animals for recognition remains unclear. ![]() For example, when individuals visually recognize others the encounter rate is low at low population densities whereas if individuals recognize each other through olfaction they can search for the opposite sex from a distant location ( Jumper & Baird, 1991). The cues used by individuals to recognize the opposite sex will affect the distance over which they can respond. However, the mechanism underlying aggregation has not been widely studied across multiple species or through theoretical models. ![]() Theoretical models including aggregation behavior demonstrate higher rates of fertilization compared to those without at the same population density ( Claereboudt, 1999 Lundquist & Botsford, 2004 Zhang, 2008). Although the distance between individuals of opposite sex decreases naturally with increasing population density, distance can also decrease because of aggregation behavior. Previous studies indicated that water flow ( Babcock & Keesing, 1999), spawning synchrony ( Calabrese & Fagan, 2004), and the distance between opposite sexes ( Babcock & Keesing, 1999 Levitan, Sewell & Chia, 2016) affect egg fertilization. Studies of the Allee effect in externally fertilized species are important for population management because a decreasing density of adults decreases the fertilization rate, potentially to the point of population collapse ( Berec, Angulo & Courchamp, 2007). Simple population genetic models indicated that the aggregating effect of MTF between the opposite sex members could be an evolutionary driving force.ConclusionsThese results suggest that observed MTF behavior might have evolved as a mechanism to increase the fertilization rates although other factors could also be involved. In the IBM the distance between opposite sexes was significantly reduced by MTF behavior however, the difference in distances between opposite sex compared to same sex individuals was only several centimeters. To examine whether MTF behavior evolved to reduce distances between members of the opposite sex, we constructed simple population genetic models of a diploid population with nonoverlapping, discrete generations.ResultsHaliotis discus hannai chose the y-maze arm with the mucus trail more frequently than the one without, regardless of the sex of the abalone that secreted the mucus or the reproductive season. Distances between members of the opposite sex of MTF individuals were compared to non-MTF individuals using an individual-based model (IBM) consistent with the behavior of H. discus hannai follows the mucus trails of other individuals. We also examined whether the fertilization rate increase with mucus-trail-following is an evolutionary driving force in mucus following behavior.MethodsWe used a y-maze to test whether H. ![]() We used the Ezo abalone Haliotis discus hannai as a model animal species to evaluate whether mucus trail following (MTF) facilitates aggregation by reducing the distance between members of opposite sexes. However, the process of aggregation has not been studied in detail, using either theoretical models or real world observations. BackgroundAggregation affects the fertilization rate of species that utilize external fertilization. ![]()
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