Batrachochytrium dendrobatidis is a chytrid fungus that causes the lethal skin disease chytridiomycosis in amphibians. It is regarded as an emerging infectious disease affecting diverse amphibian populations in many parts of the world. Because there are few model amphibian species for immunological studies, little is known about immune defenses against B. dendrobatidis. We show here that the South African clawed frog, Xenopus laevis, is a suitable model for investigating immunity to this pathogen. After an experimental exposure, a mild infection developed over 20 to 30 days and declined by 45 days postexposure. Either purified antimicrobial peptides or mixtures of peptides in the skin mucus inhibited B. dendrobatidis growth in vitro. Skin peptide secretion was maximally induced by injection of norepinephrine, and this treatment resulted in sustained skin peptide depletion and increased susceptibility to infection. Sublethal X-irradiation of frogs decreased leukocyte numbers in the spleen and resulted in greater susceptibility to infection. Immunization against B. dendrobatidis induced elevated pathogen-specific IgM and IgY serum antibodies. Mucus secretions from X. laevis previously exposed to B. dendrobatidis contained significant amounts of IgM, IgY, and IgX antibodies that bind to B. dendrobatidis. These data strongly suggest that both innate and adaptive immune defenses are involved in the resistance of X. laevis to lethal B. dendrobatidis infections.Batrachochytrium dendrobatidis is a newly described chytrid fungus that causes the lethal skin disease chytridiomycosis in amphibians (29). Growing evidence links amphibian declines in Australia, Central America, the western United States, Europe, and Africa to this emerging infectious disease (4, 9, 12, 26, 29, 34-36, 45, 65). B. dendrobatidis colonizes skin cells of adults and the keratinized mouth parts of tadpoles (3, 4, 29, 34) but does not invade other tissues. It is spread by waterborne zoospores that attach to the skin and migrate to the basal layer of the epidermis (3). The pathogen replicates within the epidermal cells and moves to the surface as the cells mature. Emerging zoospores may infect the same host or another nearby host (3,4,29,34). Recent evidence supports the hypothesis that death results from impaired retention of essential ions by the skin resulting in eventual cardiac arrest (63, 64). Some species of amphibians are very resistant to lethal infections of B. dendrobatidis, whereas others are more susceptible (4,26,27,38,(66)(67)(68), and the factors that determine resistance or susceptibility are not well understood. Although much is known about amphibian immunity in general (9, 14, 41), there is limited information about specific immune responses against B. dendrobatidis.We hypothesized that resistant species have antimicrobial peptides or antibodies in the mucus that limit initial infections by B. dendrobatidis zoospores and prevent the further colonization of the same host by zoospores emerging from the skin. Previous work has shown th...

General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. Full terms of use are available: http://www.bristol.ac.uk/pure/about/ebr-terms 1 Stereotypic route-tracing in captive Carnivora is predicted by species-typical 1 home range sizes and hunting styles 2 3 Abstract 4In captive conditions (e.g. zoos), some Carnivora species typically show negligible 5 stereotypic behaviour (SB) and reproduce successfully, while others tend to 6 reproduce poorly and be very stereotypic. We used comparative methods to identify 7 species-level risk factors for SB and captive infant mortality (CIM). Candidate 8 predictor variables were natural ranging behaviour, territoriality, aspects of natural 9 foraging, wild activity levels, cranial volume, and IUCN Red List status. Previous 10 research had identified naturally long daily travel distances, and being large-bodied 11 and wide-ranging, as SB risk factors. We nearly doubled the size of this original SB 12 database, and then imposed stricter quality controls (e.g. on minimum sample sizes 13 for inclusion). Analysing the resulting 23-species dataset confirmed naturally large 14 ranges and travel distances as risk factors. It also showed that the range size effect: 15 is independent of body mass (although body mass and range size together predicted 16 SB most strongly); is stronger for stereotypic route-tracing (e.g. pacing) than for all 17 SB forms combined; and explains the apparent daily travel distance effect (which 18 vanished when range size was controlled for). Furthermore, a new finding emerged: 19 that naturally long chase distances during hunts also predicted more severe route-20 tracing. Turning to CIM, previous research had also identified naturally long travel 21 distances and large home ranges as risk factors. We failed to replicate this, or to 22 confidently identify any species-level risk factor (despite CIM significantly varying 23 between related species, at least for Canidae and Ursidae

Depressive-like forms of waking inactivity have been recently observed in laboratory primates and horses. We tested the hypotheses that being awake but motionless within the home-cage is a depression-like symptom in mice, and that in impoverished housing, it represents an alternative response to stereotypic behaviour. We raised C57BL/6 ('C57') and DBA/2 ('DBA') females to adulthood in non-enriched (n=62 mice) or enriched (n=60 mice) cages, observing home-cage behaviour during the active (dark) phases. We predicted that being still but awake would be reduced by environmental enrichment; more pronounced in C57s, as the strain most prone to learned helplessness; negatively related to stereotypic behaviour; and positively related to immobility in Forced Swim Tests (FST). Compared to enriched mice, non-enriched subjects did spend more time spent being inactive but awake, especially if they displayed relatively little stereotypic behaviour. C57 mice also spent more time awake but motionless than DBAs. Furthermore, even after statistically controlling for housing type and strain, this behaviour very strongly tended to predict increased immobility in the FST, while high levels of stereotypic behaviours in contrast predicted low immobility in the FST. Being awake but motionless is thus a reaction to non-enriched housing that seems to be an alternative to stereotypic behaviour, and could reflect depression-like states.

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