A Role For Parasites in the Behavior of the Ozark Zigzag Salamander (Plethodon Angusticlavius)

Parasites can influence traits related to the fitness of the host, including host behavior. I studied the behavior of the Ozark zigzag salamander (Plethodon angusticlavius), that was naturally infected with the larval stage of an ectoparasitic mite (Hannemania eltoni) to determine if parasitism was associated with altered behavioral patterns. Experiments were designed to answer three specific questions: (1) Can level of parasitism be detected via chemical cues by conspecifics? (2) Does level of parasitism influence agonistic behavior of males in male-male interactions? and (3) Is parasitism associated with altered foraging behavior of females? In experiment 1, males and females were tested in separate two-choice experiments in the following test conditions: (a) fecal pellet of male with low parasite load versus fecal pellet of male with high parasite load, (b) fecal pellet of male with low parasite load versus control (chemical blank) pellet, and (c) fecal pellet of male with high parasite load versus control pellet. Non-parasitized females spent significantly more time near fecal pellets of males with low parasite loads in test condition (a). Males with low parasite loads spent significantly more time near control pellets, whereas males with high parasite loads spent significantly more time near fecal pellets of males with high parasite loads in test condition (c). Behavior of males and females was influenced by their levels of infection. In experiment 2, levels of aggression for males with low parasite loads were not different between symmetric and asymmetric contests (where the asymmetry was the level of parasitic infection). However, males with high parasite loads were significantly less aggressive in asymmetrical contests thatn in symmetrical contests. Furthermore, males with high parasite loads were overall less aggressive than males with low parasite loads. Finally, in experiment 3, the latency to first capture was significantly longer for infected females than non-infected females, although the total number of prey captured was not different between the two groups of females. These data taken together indicate that subtle alterations in behavior of infected individuals may have potential fitness consequences

Effect of histamine on lung contractile elements in growing cattle

peer reviewedaudience: researcher, professionalOBJECTIVE: To determine the effect of histamine on the contractile elements of the respiratory tract in neonatal calves and young adult cattle. SAMPLE POPULATION: Samples of trachealis muscle, bronchi, and intrapulmonary arteries and veins dissected from the respiratory tracts of healthy bovids (2 to 8 days and 16 to 20 months old). PROCEDURE: Histamine cumulative concentration-effect curves (10(-6) to 10(-3) M) were constructed in duplicate smooth muscle samples mounted in organ baths. Contractile responses to histamine were compared with reference contractions elicited by methacholine (10(-5) M) for airways or KCl (127 mM) for vessels. RESULTS: In young adult cattle, trachealis muscle had a substantial contractile response to histamine (84% of methacholine-induced contraction), whereas bronchi reacted slightly (15 and 20% for large and small bronchi, respectively). Although contractile responses to KCl were comparable in arteries and veins, histamine-induced contractions were greater for intrapulmonary veins than for arteries (202 vs 48% of KCl-induced contraction). In neonatal calves, histamine-induced contraction of veins also exceeded that of arteries (230 vs 54% of KCl-induced contraction); however, unlike in young adult cattle, histamine produced notable contraction of large and small bronchi (48 and 60% of methacholine-induced contraction, respectively). CONCLUSIONS AND CLINICAL RELEVANCE: Compared with intrapulmonary arteries, intrapulmonary veins have greater contractile responses to histamine in neonatal and young adult cattle. Data suggest loss of histamine responsiveness in bronchial smooth muscle as neonatal calves grow to young adults. Venodilation may be useful in treatment of lung edema in cattle

Food availability and parasite infection influence mating tactics in guppies (Poecilia reticulata)

Despite the important effects of diet and parasite infection on male reproductive behavior, few studies have simultaneously addressed their influence on intrasexual selection (male--male competition). We examined the synergistic effects of 2 naturally varying environmental factors, lifetime food intake and infection, with the monogenean parasite Gyrodactylus turnbulli on the mating tactics and foraging behavior of male guppies (Poecilia reticulata). We allowed fish to interact directly with each other during observations and found that unparasitized males won more intermale contests, courted females more frequently, and received positive responses to courtship displays more frequently than males that had been infected. Infected males devoted more time to foraging and less time to courtship and competition than uninfected males, suggesting that they were energetically limited and could not increase reproductive effort despite their reduced expected lifespan. This interpretation was supported by the observation that greater food intake ameliorated the negative effects of parasite infection on courtship effort. Our results have bearing on how natural variation in food availability and parasite prevalence influence geographic variation in reproductive behavior. Copyright 2009, Oxford University Press.