Biology Faculty (Bruce Smith) & Students Present in Canada

05/16/2005

Contributed by Nancy Pierce

Bruce Smith and two of his research students presented at the Ontario Ecology and Ethology Colloquium at Carleton University, Ottawa, Canada. May 2005.

Jennifer Kimball (’06) and Bruce Smith, “Bright coloration in mites – a warning to newts?”

Many species of water mites are bright red or orange; previous research has implied that these are aposematic (warning) colorations, alerting fish that mites are unpalatable. However, brightly colored water mites are most prevalent in ponds and temporary waters that lack fish predation. The red spotted newt, Notophthalmus viridescens, is a keystone predator of microcrustacea in ponds and temporary waters that lack fish predation. Mites are similar to microcrustacea in size and habitat, so in the experiments, red spotted newts were tested as potential predators of water mites. Water mites and Daphnia magna were offered sequentially to newts and the behaviours "mouth and reject", "eaten", and "did not attack" were recorded. In this study, we demonstrated that all water mites tested, regardless of color, were unpalatable to newts. Conspicuous water mites (Hydrodroma despiciens, a population of red Arrenurus manubriator, Limnochares americana, and Lebertia sp.) were mouthed and rejected more often than cryptic water mites (black and white Piona sp., and a population of blue Arrenurus manubriator). Only two mites out of 600 offerings were eaten, while 600 Daphnia magna of 600 offerings were ingested. We conclude that bright coloration does not serve as a warning to newts, and probably is either or both a 1. plesiotypic trait, retained in many earlyderivative species of water mite, 2. pigment used to block harmful components of sunlight.


Lindsey Massengale (’06) and Bruce Smith, “Intrasexual competition for mates: is there active interference among male Arrenurus manubriator mites?”

Male reproductive success in many species relies on the number of sexual partners he has; due to the scarcity of the female gametes compared to male gametes, females often become the subject of competition. We investigated malemale competition for mates in Arrenurus manubriator water mites. A previous study by Heather Proctor suggested that the unmated A. manubriator male in a triad often "harassed" the mating pair, and that in one case, the unmated male was able to take over mating. In this study, we performed triad tests using two virgin A. manubriator males and one A. manubriator virgin female. Behaviors (swimming, walking, arrestant behavior, leg fanning, leg crooking) and intermale distance were recorded every minute for five minutes prior to introducing the female into the container, every minute for five minutes after the female was added, and then continuing every five minutes for an hour after female introduction. Males were closer to each other when there was a female present compared to when there was no female, however we did not observe physical interference as had been noted in Proctor's study. We also tested pairs of males in one of 3 treatments: 1) control water, 2) water containing female sex attractant pheromone, 3) water with a female present. Behaviors were recorded when males were introduced into the container and every subsequent minute for five minutes. There was no statistical significance in the distance relationships among males in pheromone treated water compared to fresh water and in the presence of a female. While casual observations have indicated that male A. manubriator water mites physically interact while competing for matings, our evidence suggests that this is coincidental because both males are attracted towards the female, rather than the males being attracted to each other and actively interfering with each other.

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