International audienceCoral reef ecosystems are remarkable for their high productivity in nutrient-poor waters. A high proportion of primary production is consumed by the dominant herbivore assemblage, teleost fishes, many of which are the product of recent and rapid diversification. Our review and synthesis of the trophodynamics of herbivorous reef fishes suggests that current models underestimate the level of resource partitioning, and thus trophic innovation, in this diverse assemblage. We examine several lines of evidence including feeding observations, trophic anatomy, and biochemical analyses of diet, tissue composition and digestive processes to show that the prevailing view (including explicit models) of parrotfishes as primary consumers of macroscopic algae is incompatible with available data. Instead, the data are consistent with the hypothesis that most parrotfishes are microphages that target cyanobacteria and other protein-rich autotrophic microorganisms that live on (epilithic) or within (endolithic) calcareous substrata, are epiphytic on algae or seagrasses, or endosymbiotic within sessile invertebrates. This novel view of parrotfish feeding biology provides a unified explanation for the apparently disparate range of feeding substrata used by parrotfishes, and integrates parrotfish nutrition with their ecological roles in reef bioerosion and sediment transport. Accelerated evolution in parrotfishes can now be explained as the result of (1) the ability to utilize a novel food resource for reef fishes, i.e. microscopic autotrophs; and (2) the partitioning of this resource by habitat and successional stage

Alternative reproductive tactics may be a product of adaptive phenotypic plasticity, such that discontinuous variation in life history depends on both the genotype and the environment. Phenotypes that fall below a genetically determined threshold adopt one tactic, while those exceeding the threshold adopt the alternative tactic. We report evidence of genetic variability in maturation thresholds for male Atlantic salmon (Salmo salar) that mature either as large (more than 1 kg) anadromous males or as small (10-150 g) parr. Using a commongarden experimental protocol, we find that the growth rate at which the sneaker parr phenotype is expressed differs among pure-and mixed-population crosses. Maturation thresholds of hybrids were intermediate to those of pure crosses, consistent with the hypothesis that the life-history switch points are heritable. Our work provides evidence, for a vertebrate, that thresholds for alternative reproductive tactics differ genetically among populations and can be modelled as discontinuous reaction norms for age and size at maturity.

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Bartonella is a genus of pathogenic gram-negative bacteria that primarily parasitizes mammalian hosts and is understood to be the causative agent for a number of illnesses that affects humans and their companion animals. In Nova Scotia, Ixodes scapularis (Say) is the primary vector of Bartonella spp. Recent studies suggest that the presence of bacterial agents may influence the physiology and behaviour of these Ixodes ticks. Following in this research, the goal of the current study was to determine potential changes in physiology and behaviour in I. scapularis infected with Bartonella spp. For this purpose, I. scapularis ticks were collected in Nova Scotia and subjected to tests to determine temperature preference and supercooling point (SCP), followed by DNA extraction, PCR, and gel electrophoresis in order to detect the presence of the Bartonella spp. in the collected samples. 45.5% of the experimental population was determined to be infected with Bartonella spp., with males infected at a rate of 48.7% and females at a rate of 42.3%. Infected females demonstrated a preference for a lower average temperature (23.85°C ±2.41) than uninfected females (26.47°C ±2.90), however confidence intervals based on standard deviation around the mean suggests that this difference is not significant. No other significant difference was determined between the infected and uninfected populations. We therefore conclude that Bartonella spp. infection does not affect the behaviour or physiology of I. scapularis.