Immunodepression reduces learning performance in male laboratory mice (Mus musculus).

Several theoretical and empirical studies have suggested that immunocompetence may act as a constraint on learning, due to a trade-off in investment in the two processes. Here we tested whether experimentally depressing immune responsiveness of male BKW mice using antithymocyte serum (ATS) would lead to reduced learning performance in a radial maze task. Correct choices in the maze were indicated by the presence of familiar odours, incorrect choices by unfamiliar odours. We showed that temporarily depressing cellular immunity led to a reduction in performance in terms of a reduced proportion of correct choices. We also found a positive relationship between the proportion of correct entries over the period of testing and haemagglutination titre, indicating that mice showing greater immune responsiveness performed better in the maze. We conclude that depressing the immune system reduces learning performance in a combined odour/spatial learning task, and that some individuals are better able to compensate for the experimental immunodepression. In contrast to previous studies, there was no evidence that the effect of ATS was mediated by associated changes in corticosterone or testosterone secretion. There were no significant effects of the presence of female odour on learning performance, and therefore no evidence that the down regulation of learning in relation to immune depression was influenced by apparent reproductive opportunity.

Temporal and between-site variation in helminth communities of bank voles ( Myodes glareolus) from N.E. Poland. 2. The infracommunity level.

The relative importance of temporal and spatial effects was assessed in helminth communities of bank voles (Myodes glareolus) in 3 woodland sites in N.E. Poland in the late summers of 1999 and 2002. Among common species the rank order of sites in relation to prevalence and abundance of infection was maintained between surveys. Site effects accounted for most of the deviance (in statistical models), and time was less important, so the exact location from which voles were sampled was of critical importance. The only exception was Syphacia petrusewiczi. In contrast, for derived measures such as species richness and diversity, most deviance was accounted for by host age, and the interaction between site and year was significant, implying that rank order of sites changed between years. Temporal effects on derived measures were generated primarily by a combination of relatively small changes in prevalence and abundance of the common, rather than the rare, species between the years of the study. In the medium-term, therefore, helminth communities of bank voles in N.E. Poland had a stable core, suggesting a substantial strong element of predictability.

Temporal and between-site variation in helminth communities of bank voles ( Myodes glareolus) from N.E. Poland. 1. Regional fauna and component community levels.

Helminth infections were studied in bank voles (Myodes glareolus) from 3 woodland sites in N.E. Poland in the late summers of 1999 and 2002, to assess the temporal stability of derived statistics describing the regional helminth fauna and component community structure, and spatial influence on the latter. Regional helminth fauna changed dramatically between the two years, primarily due to a fall in the abundance of Syphacia petrusewiczi but was partially compensated for by an increase in Mesocestoides lineatus and Cladotaenia globifera. It was dominated by nematodes overall, but more so in 1999 than in 2002 when larval cestodes were more frequent. Most derived parameters for component community structure varied considerably between sites and the two surveys, the hierarchical order for sites not being maintained between surveys. They were susceptible to the disproportionate influence of three relatively rare, unpredictable species with the greatest overall aggregated distribution among hosts. Jaccard's similarity index was less influenced by the rare species, showing greater stability between sites and across years. In conclusion, temporal variation confounded any site-specific characteristics of the summary measures quantified in this study and their usefulness is therefore restricted to the years in which the surveys were conducted.

Odour learning and immunity costs in mice.

There is accumulating evidence that learning is metabolically costly. One way in which this may manifest itself is in trade-offs between learning effort and immune function, with learning increasing susceptibility to infection. We tested this idea in the context of odour learning using outbred (BKW) male laboratory mice. Mice were exposed to three experimental treatments in which they were required to learn different numbers of urinary odours. While treatment affected the extent to which mice habituated to test odours during training, differences were not a simple function of the number of odours. The fact that there was also no significant effect of treatment on the degree of preference for novel over familiar odours in subsequent tests suggests mice retained learned odour profiles equally well regardless of the number of odours. That subsequent infection with Babesia microti increased with the number of odours mice had to learn is then consistent with an increased cost to learning effort when more odours were presented. Analysis within treatments, and relationships with the change in corticosterone concentration over the period of the experiment, suggested that it was a failure to learn, rather than maintaining learning performance, in more difficult learning tasks that led to greater infection. As in a previous study of maze learning in the strain, there was no direct relationship between infection and measures of peripheral antibody (total IgG) titre. The results are discussed in relation to studies in other learning contexts and reported relationships between glucocorticoid hormones and learning outcomes.

The consequences of inbreeding for recognizing competitors.

Extreme inbreeding will compromise an animal's ability to discriminate between individuals and, thus, assess familiarity and kinship with conspecifics. In rodents, a large component of individual recognition is mediated through chemical communication. The counter-marking of competitor males' scent marks provides a measure of discrimination between their own scent and that from other individuals. We investigated whether males in common outbred (ICR(CD-1) and TO) and inbred (BALB/c) strains of laboratory mice could recognize the urinary scents of other individuals by measuring their investigation and counter-marking responses. Dominant males of outbred strains investigated and counter-marked scents from other males, whether of the same or another strain. Dominant inbred BALB/c males investigated but did not counter-mark their own strain scents, counter-marking only those from another strain. They did not use environmentally induced status differences in odours to recognize scents from other males. The inability of the inbred mice to discriminate between their own scent marks and those of other males is likely to alter their competitive behaviour, which could influence responses in experiments and the welfare of caged laboratory mice.

Maternal effects on the development of social rank and immunity trade-offs in male laboratory mice (Mus musculus).

Social status in randomly constituted groups of male CFLP mice was predictable from early suckling behaviour and rate of weight gain in natal litters. High-ranking males were those that had suckled on more anterior teats and gained weight more quickly. Rank was not predicted by any measures of sibling interaction or hormone (testosterone, corticosterone) concentration. Aggressiveness in eventual high-rankers was associated negatively with the proportion of males in the litter at birth and the amount of maternal attention received. Aggressive social relationships within natal litters did not predict polarized rank relationships in randomized groups. Nevertheless, while still in their natal litters, and in the absence of aggressive rank relationships, eventual rank categories showed the same difference in modulation of testosterone concentration in relation to current immunocompetence (low-rankers modulating, high-rankers not), as has repeatedly been found in randomized groups by earlier studies. The role of maternal condition in determining rank-related life-history development in male mice is discussed.

The role of parasite-induced immunodepression, rank and social environment in the modulation of behaviour and hormone concentration in male laboratory mice (Mus musculus).

Peripheral immune responsiveness in male laboratory mice was reduced by infection with the trichostrongyloid nematode Heligmosomoides polygyrus. Responsiveness was also lower among high-ranking (aggressive) males regardless of infection status. Reduced responsiveness in both infected animals and high rankers was associated with elevated serum corticosterone concentration (a potential immunodepressant) and was compounded among high-ranking males by subsequent high aggressiveness. As in previous experiments, only low rankers modulated testosterone secretion in relation to current immunocompetence and corticosterone concentration. The lack of any downregulation of aggression in response to parasite-induced immunodepression contrasted with previous results using antithymocyte serum and may be due to the more localized nature of immunodepression during H. polygyrus infection. However, the additional increase in corticosterone concentration resulting from exposure to female odour and destabilized aggressive social relationships did result in downregulation of aggression among high rankers and of testosterone among mice generally, suggesting that modulation rules of thumb are at least partly dependent on the proximate cues associated with immunodepression.

Environmental enrichment, immunocompetence, and resistance to Babesia microti in male mice.

Groups of male CFLP mice housed in cages furnished with shelves and nestboxes showed increased aggression and reduced resistance to an experimental infection of Babesia microti when compared with groups in unfurnished cages. Both a bystander measure of immunocompetence (serum total IgG concentration) and resistance to B. microti decreased as the number of attacks received by mice increased, but increased with the number of times individuals were recorded on shelves or in nestboxes. Serum concentrations of testosterone and corticosterone were generally downregulated in furnished cages; the absence of hormone-related reduction in resistance may have been due partly to this, but partly also to the apparent modulation of hormone concentrations in relation to concurrent immunocompetence. Some welfare implications of the results are considered.

Immunity costs and behavioural modulation in male laboratory mice (Mus musculus) exposed to the odours of females.

In a previous study, male laboratory mice experimentally immunodepressed with anti-thymocyte serum (ATS) showed changes in behaviour (aggression, general locomotory activity, and sleeping) and testosterone that are consistent with decision-making being modulated adaptively with respect to immunocompetence. We tested this idea further by repeating the experiment with the addition of female odours (soiled sawdust) to the home cages of males following ATS/control treatment. We predicted that, in the presence of cues suggesting reproductive opportunity, immunodepressed males would trade off potential immunity costs by failing to modulate behaviour. This expectation was borne out in that ATS-treated mice showed no change in aggression, locomotory activity, mounting, or sleeping relative to control animals, and mice overall showed differences in behaviour in the expected direction compared with a previous study in which female odours were not presented. However, despite the lack of difference in behaviour between ATS and control treatments, there was still evidence of a degree of behavioural modulation in relation to measures of immunocompetence.

Modulation of behaviour and testosterone concentration in immunodepressed male laboratory mice (Mus musculus).

Recent ideas suggest that current immunocompetence may act as a constraint on behavioural and physiological decisions, where these risk imposing an additional burden on immune function. We tested this in the context of time budgeting and the secretion of the potentially immunodepressive hormones testosterone and corticosterone, by treating adult male CFLP laboratory mice with antithymocyte serum (ATS) to depress thymus-mediated immune function. In comparison with males given a naive rabbit serum (NRS) vehicle control, ATS-treated mice showed a reduction in serum testosterone concentration, aggressive behaviour, and general activity, and maintained time spent sleeping, relative to pretreatment levels. Behaviours that differed between treatments correlated with measures of immunodepression (reduction in relative thymus weight or serum total IgG concentration), but relationships with behavioural changes were independent of those with testosterone. There was little evidence that changes were affected by social status. The results are discussed in the context of the adaptive modulation of immune function and physiological and behavioural decision-making.

Flower choice by honey bees (Apis mellifera L.): sex-phase of flowers and preferences among nectar and pollen foragers.

Bees foraging for nectar should choose different inflorescences from those foraging for both pollen and nectar, if inflorescences consist of differing proportions of male and female flowers, particularly if the sex phases of the flowers differ in nectar content as well as the occurrence of pollen. This study tested this prediction using worker honey bees (Apis mellifera L.) foraging on inflorescences of Lavandula stoechas. Female flowers contained about twice the volume of nectar of male flowers. As one would predict, bees foraging for nectar only chose inflorescences with disproportionately more female flowers: time spent on the inflorescence was correlated with the number of female flowers, but not with the number of male flowers. Inflorescence size was inversely correlated with the number of female flowers, and could be used as a morphological cue by these bees. Also as predicted, workers foraging for both pollen and nectar chose inflorescences with relatively greater numbers of both male and female flowers: time spent on these inflorescences was correlated with the number of male flowers, but not with the number of females flowers. A morphological cue inversely associated with such inflorescences is the size of the bract display. Choice of flowers within inflorescences was also influenced predictably, but preferences appeared to be based upon corolla size rather than directly on sex phase.

Comparing behaviour in wild and laboratory strains of the house mouse: Levels of comparison and functional inference.

Many behavioural studies of laboratory house mice have sought functional explanations for their results. This raises the problem of the comparability of behaviour with that of wild house mice from whose naturally selected repertoire the behaviour of laboratory strains has been derived. This in turn requires careful choice of measures to ensure that subtle changes in response during the selection of laboratory strains are taken into account. A comparison of social behaviours showing kin bias in male mice of the CFLP laboratory strain shows that superficial measures based on totals over an arbitrary test period, a widely used procedure, can be misleading because they fail to control for differences in the tendency for CFLP and wild mice to encounter one another and the intensity of social responses when encounters do occur. Such differences may reflect different contexts and consequences of social responses in the two strains.

Why do male ICR(CD-1) mice perform bar-related (stereotypic) behaviour?

Prolonged interaction with cage bars by captive mammals (usually classed as stereotypic) may reflect poor welfare. Such behaviour may arise from motivation to investigate the external environment or to escape captivity. However, these hypotheses have not been explicitly tested. We raised mice, Mus musculus, to adulthood in modified laboratory cages with two sets of bars at the top and side of the cage. One set provided a potential escape route, and half of each set was backed by Perspex to reduce cues from the external environment. We predicted where mice should interact with the bars according to their motivational priorities. Body weights were recorded weekly to study the relationship between physical development and bar-related behaviour. Serum corticosterone was measured to monitor the effect of bar-related behaviour on stress physiology. Mice preferred to interact with bars where external cues were detectable. As adults, mice responded more to the bars providing a potential exit, though this was affected by the exit location. Corticosterone titres were higher in mice whose potential exit was situated at the cage top. Response to the bars was apparently restricted by the physical development of mice, particularly among those whose potential exit was situated in the cage top.

Complex osteocutaneous injuries--timing of reconstruction. A report of 3 cases.

Twenty-seven patients with osseous trauma and soft-tissue loss were subjected to a treatment protocol aimed at obtaining definitive wound coverage within 10 days of injury. Reconstructive procedures included 19 successful microvascular tissue transfers as well as 8 pedicle flaps. The rate of serious complications was 8%, and patient morbidity was significantly reduced compared with a previous regimen of late reconstruction. An outline of the protocol is presented and technical points, which might enhance results, are discussed.

Stasis: a coevolutionary model.

Traditional neo-Darwinian explanations for stasis involve limited variation, developmental constraints and stabilizing selection. Of these, stabilizing selection is regarded as the mechanism operating most widely. Arguments based on stabilizing selection, however, implicitly assume a one-way evolutionary relationship between organism and environment. In this paper, I suggest that stasis may arise in a number of different ways as a result of organism/environment coevolution. The chief causes of stasis may be the attainment of coadapted equilibria between organism and environment and periods of quiescence within and between arms races. I also suggest that many cases of stasis in the fossil records may be apparent rather than real due to a reliance on gross morphological trends and that apparently large environmental changes during which stasis persists may not reflect change in the coadapted components of the organisms' environment.

Acquisition of dominance status affects maze learning in mice.

Learning is likely to be costly and thus subject to trade-off with other components of life history. An obvious prediction, therefore, is that investment in learning, and thus learning performance, will vary with individual life history strategy and the reproductive value of the learning outcome. We tested this idea in the context of social dominance in male laboratory mice, using a simple radial maze paradigm to compare the ability of high- and low-ranking male mice to track changing food location. We tested animals in randomly selected pairs before and after establishing aggressive rank relationships to distinguish intrinsic differences in learning ability from those attributable to acquiring high or low rank. There was no difference in learning between later dominants and subordinates prior to establishing rank relationships. After pairing, however, dominants showed a significantly greater percentage of correct responses, with the difference being greatest earlier in a sequence of trials. The percentage of correct responses also increased with the amount of aggression initiated during pairing. The results thus appeared to reflect a state-dependent change in learning associated with the aggressive social relationships formed during pairing.

Of mice and kin: the functional significance of kin bias in social behaviour.

1. Sharing recent ancestry (kinship) increases the degree of genetic similarity between individuals, where genetic similarity could mean anything from sharing a particular allele to sharing an entire genome. 2. Genetic similarity can influence behavioural and other responses between individuals in a number of ways, discriminatory and non-discriminatory. All are likely to result in kin bias, because of the correlation between genetic similarity and kinship, but only some should be regarded as involving kin discrimination. 3. Non-discriminatory kin bias could arise through close relatives sharing, for instance, physical characteristics (such as those influencing competitive ability), thresholds of behavioural response or requirements for particular resources. 4. Discriminatory kin bias could arise through the direct perception of genetic similarity between individuals (direct similarity discrimination) or the use of cues likely to correlate with genetic similarity (indirect similarity discrimination--of which kin discrimination is one form). Alternatively, it could arise incidentally through mistaken identity or discrimination at some other level, such as species identification. 5. Experiments with laboratory and wild house mice have revealed kin bias in a number of contexts, including (a) parental and infanticidal behaviour, (b) sexual development and behaviour and (c) investigatory behaviour and passive body contact among juveniles and adults. 6. While kin bias in mice has been interpreted as evidence for kin discrimination, there are several problems with such an interpretation. These include (a) pronounced and complex effects of familiarity on discrimination, (b) a high risk of error-proneness in the indirect cues used in apparent kin discrimination and (c) weak and easily disrupted kin bias effects in certain contexts. 7. Consideration of social structure and discriminatory responses within populations of wild house mice leads to an alternative explanation for some kin bias in terms of incidental discrimination based on social group membership. 8. Several results from laboratory experiments suggest incidental discrimination is a more parsimonious explanation than kin discrimination for some intrasexual kin bias in behaviour. However, kin or direct similarity discrimination appears to be the most likely explanation for other aspects of intrasexual kin bias and for intersexual kin bias.