Trichinella spiralis infection in voles alters female odor preference but not partner preference

Females may choose mates based on secondary sex traits that reflect disease resistance. Accordingly, females should be able to distinguish between unparasitized and parasitized males, and should prefer to mate with unparasitized individuals. Mate and odor preferences for uninfected males or males infected with the nematode, Trichinella spiralis, were examined among prairie voles (Microtus ochrogaster) and meadow voles (M. pennsylvanicus). In a 15-min odor preference test, only female meadow voles distinguished between bedding from parasitized and unparasitized conspecific males, and preferred to spend time with bedding from unparasitized males. Although T. spiralis infection influenced odor preference in female meadow voles, there was no effect of infection status on mate preference among either species. Testosterone and corticosterone concentrations were not different between parasitized and unparasitized males. However, among prairie voles, males that spent an increased amount of time with females during the mate preference test had elevated testosterone concentrations. Taken together, these data suggest that (1) female meadow voles can discriminate between unparasitized and parasitized males, (2) the effects of infection on steroid hormone concentrations may be masked by the effects of social interactions, and (3) parasites may represent a selective constraint on partner preference in voles; however, the life cycle of parasites may influence female preference and should be considered in studies of female preference. Received: 23 April 1998 / Accepted after revision: 25 October 1998     

Effect of low dissolved oxygen concentrations on the ventilation rhythm of three tubicolous crustaceans,with special reference to the phenomenon of intermittent ventilation

The pleopod ventilatory activity of the tube-dwelling amphipods Corophium volutator (Pallas) and C. arenarium Crawford is intermittent. Unlike the free-living amphipod Marinogammarus obtusatus (Dahl), which increases its rate of pleopod beating, the pleopod beat rate of both Corophium species is unaffected by low oxygen concentrations. However, the nature of the intermittent ventilation rhythm is altered so that, at low oxygen concentrations, the pleopods of Corophium beat almost continuously. It is suggested that the intermittent ventilation of Corophium can be interpreted as an adaptation to a tubicolous existence. The peracaridean Tanais chevreuxi Dollfus has 2 independent ventilatory systems, the maxilliped epipodites and the pleopods. The former, which respond to low oxygen concentrations, are thought to be the principal respiratory organs of T. chevreuxi, while the pleopods, which show no response to low oxygen tensions, are believed to be primarily concerned in filter feeding.     

Propanil in a Manitoba soil: an interactive spreadsheet model based on conventional chemical kinetics

An interactive spreadsheet model has been created for quantitative predictions of propanil sorption and reaction in a slurried Manitoba clay soil. Based on experimental values for the numbers of empty and filled sorption sites as reactants and products, the reaction mechanism has been described with conventional chemical kinetics. The on line HPLC μ extraction method revealed labile sorption, intraparticle diffusion, and a chemical reaction. Laidler's integral rate law for second order kinetics describes the labile sorption. Desorption, intraparticle diffusion, and the chemical reaction are all described by first order kinetics. The time dependent effects of initial concentration and amount of slurried soil can be predicted for sorption, intraparticle diffusion, and the amount of reaction product. Suggested applications include storm runoff and inputs for fate and transport hydrology models.     

NITROGEN MOVEMENT IN A SHALLOW AQUIFER SYSTEM OF THE NORTH CAROLINA COASTAL PLAIN1

ABSTRACT: Concentrations of ammonium- and nitrate-nitrogen of about 10,000 ppm moved from an untreated surface storage pond into the ground water in the sandy beds of the surficial sediments in northeastern North Carolina. This high concentration of nitrogen moved through the permeable sandy beds with the ground water above the Yorktown Formation aquiclude to the Chowan River with only minor dispersion normal to the hydraulic gradient. There was essentially no nitrogen movement into the Yorktown aquiclude even though solutions of 2,000 ppm (sol basis) had been in the overlying sediments for 2 to 3 years The possibility of the nitrogen moving into the deeper quifers used for community water supplies is very small. Only the shallow ground water above the Yorktown Formation in the immediate area will be contaminated with nitrogen because there is little lateral dispersion away from the flow of ground water toward the Chowan River.