FREQUENCY‐DEPENDENT SOCIAL DOMINANCE IN A COLOR POLYMORPHIC CICHLID FISH

A mechanism commonly suggested to explain the persistence of color polymorphisms in animals is negative frequency‐dependent selection. It could result from a social dominance advantage to rare morphs. We tested for this in males of red and blue color morphs of the Lake Victoria cichlid, Pundamilia. Earlier work has shown that males preferentially attack the males of their own morph, while red males are more likely to win dyadic contests with blue males. In order to study the potential contribution of both factors to the morph co‐existence, we manipulated the proportion of red and blue males in experimental assemblages and studied its effect on social dominance. We then tried to disentangle the effects of the own‐morph attack bias and social dominance of red using simulations. In the experiment, we found that red males were indeed socially dominant to the blue ones, but only when rare. However, blue males were not socially dominant when rare. The simulation results suggest that an own‐morph attack bias reduces the social dominance of red males when they are more abundant. Thus, there is no evidence of symmetric negative frequency‐dependent selection acting on social dominance, suggesting that additional fitness costs to the red morph must explain their co‐existence.     

Leukaemia inhibitory factor (LIF) is functionally linked to axotrophin and both LIF and axotrophin are linked to regulatory immune tolerance

Axotrophin (axot) is a newly characterised stem cell gene and mice that lack axotrophin are viable and fertile, but show premature neural degeneration and defective development of the corpus callosum. By comparing axot+/+, axot+/- and axot-/- littermates, we now show that axotrophin is also involved in immune regulation. Both T cell proliferation and T cell-derived leukaemia inhibitory factor (LIF) were suppressed by axotrophin in a gene-dose-dependent manner. Moreover, a role for axotrophin in the feedback regulation of LIF is implicated. This is the first evidence that fate determination mediated by LIF maybe qualified by axotrophin.     

Studies on the interaction of extended terpyridyl and triazine metal complexes with DNA

The interaction with duplex DNA of a series of 12 previously synthesised ruthenium (II) complexes incorporating extended terpyridines or analogous ligands is reported. The interaction was investigated using absorption spectroscopy and also, when possible, luminescence spectroscopy. Binding parameters for the interactions were estimated using established models. It was found that binding affinities are relatively large and their magnitude is somewhat dependent on the metal centre attached to the ligand. Viscosity studies reveal that all the complexes interact with DNA through groove binding and not intercalation. The variation in binding affinities of these complexes is rationalised by a consideration of electrostatic and steric factors.     

The performance advantage of a high resting metabolic rate in juvenile salmon is habitat dependent

1.?Basal levels of metabolism vary significantly among individuals in many taxa, but the effects of this on fitness are generally unknown. Resting metabolic rate (RMR) in juvenile salmon and trout is positively related to dominance status and ability to obtain a feeding territory, but it is not clear how this translates into performance in natural conditions. 2.?The relationships between RMR, dominance, territoriality and growth rates of yearling Atlantic salmon Salmo salar were examined in relation to predictability in food supply and habitat complexity, using replicate sections of a large-scale controlled semi-natural stream. 3.?Estimated RMR was a strong predictor of dominance, and under conditions of a predictable food supply in a structurally simple habitat, high estimated RMR fish obtained the best feeding territories and grew faster. 4.?When the spatial distribution of food was made less predictable, dominant (high estimated RMR) fish were still able to occupy the most profitable feeding locations by periodically moving location to track the changes in food availability, but RMR was no longer a predictor of growth rate. Moreover, when a less predictable food supply was combined with a visually more complex (and realistic) habitat, fish were unable to track changes in food availability, grew more slowly and exhibited greater site fidelity, and there were no relationships between estimated RMR and quality of occupied territory or growth rate. 5.?The relative benefit of RMR is thus context dependent, depending on both habitat complexity and the predictability of the food supply. Higher habitat complexity and lower food predictability decrease the performance advantages associated with a high RMR.