Conspicuous stripes on prey capture attention and reduce attacks by foraging jumping spiders.

Many animals avoid predation using aposematic displays that pair toxic/dangerous defences with conspicuous achromatic warning patterns, such as high-contrast stripes. To understand how these prey defences work, we need to understand the decision-making of visual predators. Here we gave two species of jumping spiders (Phidippus regius and Habronattus trimaculatus) choice tests using live termites that had their back patterns manipulated using paper capes (solid white, solid black, striped). For P. regius, black and striped termites were quicker to capture attention. Yet despite this increased attention, striped termites were attacked at lower rates than either white or black. This suggests that the termite's contrast with the background elicits attention, but the internal striped body patterning reduces attacks. Results from tests with H. trimaculatus were qualitatively similar but did not meet the threshold for statistical significance. Additional exploratory analyses suggest that attention to and aversion to stripes is at least partially innate and provide further insight into how decision-making played out during trials. Because of their rich diversity (over 6500 species) that includes variation in natural history, toxin susceptibility and degree of colour vision, jumping spiders are well suited to test broad generalizations about how and why aposematic displays work.

Comparative morphology of the mechanosensory lateral line system in a clade of New Zealand triplefin fishes.

The mechanoreceptive lateral line system in fishes detects hydrodynamic stimuli and plays a critical role in many fundamental behaviours, including orientation to water currents and the detection of stationary objects, prey and predators. Interspecific variation in lateral line structure may result from a process of functional adaptation, with the background level of hydrodynamic activity proposed as an important selective pressure. Here we use the eight species of the ecologically diverse New Zealand marine triplefin fish of the genus Forsterygion and one species from the sister genus Notoclinops to investigate interspecific differences in lateral line morphology and to assess the relationship between lateral line characteristics and exposure to wave energy (fetch/depth ratio). Overall, the results show that lateral line traits are divergent between species, and these differences could in part be related to the wave exposure of the habitats that the species occupy. Specifically, numbers of canal neuromasts differed significantly between species, and most canal groupings increased in neuromast number with fetch/depth ratio, while the number and area of some superficial neuromast groupings decreased significantly with exposure. Distribution of superficial neuromasts along the trunk in the semi-pelagic and paedomorphic species F. maryannae differed from the other, demersal species, which may be associated with the unique lifestyle of this species and/or developmental processes. Canal architecture also differed considerably between species, but displayed no relationship with fetch/depth ratio. The results from this study indicate that some interspecific differences in lateral line organs may be a by-product of selection for habitat divergence. Future work should explore additional causal factors that might have influenced the evolution of lateral morphology in these species, including phylogenetic and allometric effects.