Distance communication of sexual status in the crayfish Orconectes quinebaugensis: female sexual history mediates male and female behavior.

Chemical communication plays an important role in mediating social interactions of many taxa, particularly arthropods. Many individuals communicate information about their reproductive status to potential mates through distance and/or contact pheromones, an ability that may be advantageous to both signalers and receivers. In this paper, we describe tests of two hypotheses on the role of distance communication in the reproductive behaviors of crayfish (Orconectes quinebaugensis). First, we hypothesized that male crayfish would show stronger attraction towards virgin females (females with no viable sperm) than towards non-virgin females because of the fitness costs (to males) associated with sperm competition. Second, we hypothesized that female crayfish should show differential responses to mature male signals depending on their own sexual history: virgin females should be more strongly attracted to male signals than should non-virgin females because they must mate at least once to be able to fertilize eggs in the spring. Data from two Y-maze experiments yielded support for both hypotheses: males were attracted to signals from virgin females, but not to signals from non-virgins. Likewise, virgin females were attracted to signals from males, but non-virgin females were not. We discuss our data in the context of the potential costs and benefits of mate searching and suggest that distance chemical communication of sexual status may be particularly advantageous when the costs of mate searching are high.

CCL28 effects on periodontal pathogens.

BACKGROUND: Chemokines are small proteins that signal to and attract cells of the immune system; they are vital components in the modulation of immunity and wound healing. A newly described chemokine was reported to have antibacterial and antifungal activity. This chemokine, chemokine (C-C motif) ligand 28 (CCL28; also called mucosae-associated epithelial chemokine), is secreted by mucosal epithelial cells and is found in saliva and in breast milk. The objective of this study was to test whether CCL28 has antibacterial activity against two anaerobic periodontal pathogens: Porphyromonas gingivalis and Actinobacillus actinomycetemcomitans. METHODS: We used a bacterial viability test, in which two fluorescent dyes are bound differentially to living and killed bacteria. We tested the bacteria at concentrations of 2 x 10(7)/ml, exposing them to CCL28 at concentrations from 0.04 to 10 microM. RESULTS: CCL28 was effective at killing both organisms. After 1 hour of exposure to the chemokine under appropriate oxygen conditions, the percentage of living organisms was reduced significantly for each species. We estimated the 50% effective concentration to be approximately 0.7 microM for P. gingivalis and approximately 2.0 microM for A. actinomycetemcomitans (N = five experiments each). We confirmed these observations using standard bacterial plating methods. CONCLUSION: Because this chemokine is secreted into the saliva, a reduction in salivary flow (as in xerostomia) may diminish the oral self-defense mechanisms by also reducing the exposure of bacteria to the antibacterial action of CCL28.