The less amorous Gammarus: predation risk affects mating decisions in Gammarus duebeni (Amphipoda)

We examined the trade-off between the behaviours associated with predator avoidance and mate acquisition in the mate-guarding amphipod crustacean Gammarus duebeni. We used laboratory experiments to investigate the impact of olfactory predator cues on activity, mate choice and mate-guarding behaviour of males and females. Pair formation declined under perceived risk of predation, reflecting reduced activity of both males and females and hence a reduced likelihood of encountering a mate. We also observed a reduction in the choosiness of both males and females. Under increased perceived predation risk, assessment of the female by the male was more likely to be followed by pair formation, and males showed a nonsignificant trend towards reduced discrimination in favour of large females and were less tenacious in their pair bond when they paired during exposure to predator cues. Females also showed less resistance behaviour, suggesting that both males and females trade off the costs of maximizing current reproductive success against the benefits of predator avoidance for survival and reproduction in the future. We discuss the implications of such context-dependent mating behaviours for ecological interactions between species and suggest that predators, via the effects of perceived predation risk on mate choice and mate guarding in the prey species, induce trait-mediated indirect effects with the potential to influence population dynamics and community structure. (C) 2008 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

Maternal effects on offspring size and packaging constraints in the whelk

Life-history theory predicts an optimal offspring size, irrespective of reproductive effort; however, in some species offspring size correlates positively with maternal size. We examine hypotheses for why this latter situation should occur in the whelk Buccinum undatum. The trade-offs between aspects of reproduction in whelks are complicated due to the provision of protective egg capsules. Many eggs are placed within each capsule but c. 99% of these eggs are consumed by the remaining developing young. Large maternal size results in more eggs, larger eggs, more eggs consumed per hatchling, more capsules, larger capsules, more eggs per capsule, a larger number of hatchlings per capsule and larger hatchlings. Increased intra-capsule and post-hatch sibling competition may decrease the marginal value for additional young and select for larger young, however, our data do not support this explanation. Instead, packaging constraints within each capsule limit the size of hatchlings but this constraint is relaxed for medium to large females because they produce large capsules. Small females appear to produce young below optimum size because of the space constraint thus explaining the correlation between maternal size and offspring size.

Assessment of fighting ability in animal contests

Selection should favour accurate information gathering regarding the likely costs and benefits of continued conflict. Here we consider how variation in the abilities of contestants to assess resource-holding potential (RHP) influences fights. This has been examined in various game theory models. However, discriminating between assessment strategies has proven difficult and has resulted in confusion. To add clarity, we group existing models into three main types that differ in the information about RHP that contestants are presumed to gather: (1) pure self-assessment, (2) cumulative assessment and (3) mutual assessment. Within this framework we outline methods advocated to discriminate successfully between the three main assessment models. We discuss support for each model, before highlighting a number of conflicting and inconclusive studies, leading us to consider alternative approaches to investigate assessment. Furthermore, we examine support for newly emerging concepts such as 'varying degrees of assessment', 'switching assessment' strategies and the possibility of contestants adopting different assessment strategies within a fight involving distinctive roles. We suggest future studies will benefit by judicious use of a battery of techniques to determine how animals settle contests. Finally, we highlight difficulties with current game theory models, and raise concerns regarding the use of certain behavioural criteria to accept or reject a model, particularly since this may conflict with evidence for a given assessment strategy. Furthermore, the failure of existing models to account for newly emerging concepts points to limitations of their use and leads us to challenge game theoreticians to develop upon them. (C) 2009 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

Information gathering and decision making about resource value in animal contests

Contestants are predicted to adjust the cost of a fight in line with the perceived value of the resource and this provides a way of determining whether the resource has been assessed. An assessment of resource value is predicted to alter an animal's motivational state and we note different methods of measuring that state. We provide a categorical framework in which the degree of resource assessment may be evaluated and also note limitations of various approaches. We place studies in six categories: (1) cases of no assessment, (2) cases of internal state such as hunger influencing apparent value, (3) cases of the contestants differing in assessment ability, (4) cases of mutual and equal assessment of value, (5) cases where opponents differ in resource value and (6) cases of particularly complex assessment abilities that involve a comparison of the value of two resources. We examine the extent to which these studies support game theory predictions and suggest future areas of research. (C) 2008 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

Clinical significance of sperm DNA damage in assisted reproduction outcome

Background: Sperm DNA damage shows great promise as a biomarker of infertility. The study aim is to determine the usefulness of DNA fragmentation (DF), including modified bases (MB), to predict assisted reproduction treatment (ART) outcomes. Methods: DF in 360 couples (230 IVF and 130 ICSI) was measured by the alkaline Comet assay in semen and in sperm following density gradient centrifugation (DGC) and compared with fertilization rate (FR), embryo cumulative scores (ECS1) for the total number of embryos/treatment, embryos transferred (ECS2), clinical pregnancy (CP) and spontaneous pregnancy loss. MB were also measured using formamidopyrimidine DNA glycosylase to convert them into strand breaks. Results: In IVF, FR and ECS decreased as DF increased in both semen and DGC sperm, and couples who failed to achieve a CP had higher DF than successful couples (+12.2 semen, P = 0.004; +9.9 DGC sperm, P = 0.010). When MB were added to existing strand breaks, total DF was markedly higher (+17.1 semen, P = 0.009 and +13.8 DGC sperm, P = 0.045). DF was not associated with FR, ECS or CP in either semen or DGC sperm following ISCI. In contrast, by including MB, there was significantly more DNA damage (+16.8 semen, P = 0.008 and +15.5 DGC sperm, P = 0.024) in the group who did not achieve CP. Conclusion: SDF can predict ART outcome for IVF. Converting MB into further DNA strand breaks increased the test sensitivity, giving negative correlations between DF and CP for ICSI as well as IVF. © 2010 The Author.