Our review on the evolution of spider vision is now available online in The Biological Bulletin. Features a general overview of the topic, and original work comparing spider opsins and phototransduction genes with those of other arthropod lineages.
Our newest paper, with Sebastian Echeverri at the helm, covers the geometry of courtship interactions in colorful jumping spiders. While the male performs a spectacular mating dance, it is the female who drives the interaction. Read more in the current issue of Behavioral Ecology
During communication, alignment between signals and sensors can be critical. Signals are often best perceived from specific angles, and sensory systems can also exhibit strong directional biases. However, we know little about how animals establish and maintain such signaling alignment during communication. To investigate this, we characterized the spatial dynamics of visual courtship signaling in the jumping spider Habronattus pyrrithrix. The male performs forward-facing displays involving complex color and movement patterns, with distinct long- and short-range phases. The female views displays with 2 distinct eye types and can only perceive colors and fine patterns of male displays when they are presented in her frontal field of view. Whether and how courtship interactions produce such alignment between male display and female field of view is unknown. We recorded relative positions and orientations of both actors throughout courtship and established the role of each sex in maintaining signaling alignment. Males always oriented their displays toward the female. However, when females were free to move, male displays were consistently aligned with female principal eyes only during short-range courtship. When female position was fixed, signaling alignment consistently occurred during both phases, suggesting that female movement reduces communication efficacy. When female models were experimentally rotated to face away during courtship, males rarely repositioned themselves to re-align their display. However, males were more likely to present certain display elements after females turned to face them. Thus, although signaling alignment is a function of both sexes, males appear to rely on female behavior for effective communication.
Available now as a preprint in Arthropod Structure & Development: https://www.ncbi.nlm.nih.gov/pubmed/27664782
Insects live in a three-dimensional space, and need to be able to attach to different types of surfaces in a variety of environmental and behavioral contexts. Adult leaf beetles possess great attachment ability due to their hairy attachment pads. In contrast, their larvae depend on smooth pads to attach to the same host plant. We tested friction forces generated by larvae and adults of dock leaf beetles Gastrophysa viridula on different rough surfaces, and found that adults generate much higher attachment to various substrates than larvae, but are more susceptible to completely losing attachment ability on surfaces with "critical" roughness. Furthermore, sex-specific setal morphology has the effect that attachment forces of male adults are generally higher than those of females when adjusted for body weight. The results are discussed in the context of development, ecology, and changing behavioral strategies of successive life stages.
Here is the last dispatch from the field, this time from North Padre Island near Corpus Christi, TX. It covers the last part of our collecting trip taking us from Del Rio, TX along the Rio Grande and up the Gulf Coast. Thanks again to everyone who contributed to our crowdfunding campaign! https://experiment.com/projects/why-are-some-jumping-spiders-so-colorful
Our new paper just came out in Animal Behavior, link: http://dx.doi.org/10.1016/j.anbehav.2015.05.007. It's a review of the reproducibility of contemporary studies of biological coloration. We found that methodological details are often missing, and data are seldom publicly available. We present guidelines for methods reporting, and for improving reproducibility.
I'm currently hunting for Habronattus jumping spiders in the American Southwest. This month-long field trip has largely been funded by the public, via the crowdfunding website experiment.com. To keep backers in the loop about our field work, I produced a series of video dispatches as we travelled from Arizona to Texas. Here are the first four, more are coming as we're wrapping up.
This Monday, the paper that describes our discovery of spectral filters in jumping spider eyes came out in Current Biology. Here is the link to a free pdf reprint of the original paper:
The story got picked up by a large number of press outlets, here are writeups by National Geographic, Science, and the LA Times:
and some more in German, in Der Spiegel and Neue Zürcher Zeitung:
Some of my early work on the biomechanics of insect adhesive devices was published in a themed issue of Interface Focus this week. Leaf beetle larvae use 'smooth' attachment pads to adhere to their host plant, while their adults use 'hairy' pads for the same task. Link
Over a month ago, we set out to try our hand at crowdfunding a project on Experiment.com. Now, after a very exciting November, our next field trip and a bunch of state-of-the-art video equipment is supported by the public! Backers contributed over $7000 to this project. The campaign is over now, but the project site will remain online to keep our backers up to date on our progress. Read more over on Experiment.com, or in this write-up in Science(!).
New paper: Dynamic visual cues induce jaw opening and closing by tiger beetles during pursuit of prey
In dynamic locomotory contexts, visual cues often trigger adaptive behaviour by the viewer, yet studies investigating how animals determine impending collisions typically employ either stationary viewers or objects. We described a dynamic situation of visually guided prey pursuit in which both impending prey contact and escape elicit observable adaptive behaviours in the pursuing tiger beetle. We investigated which visual cues may independently control opening and closing of the beetle's jaws during chases of prey dummies. Jaw opening and closing typically occur when prey is within the 60° binocular field, but not at specific distances, angular sizes or time-to-collision. We show that a sign change in the expansion rate of the target image precedes jaw opening (16 ms) and closing (35 ms), signalling to the beetle that it is gaining on the target or that the target is getting away. We discuss the ‘sloppiness' of such variation in the lag of the behavioural response, especially jaw closing, as an adaptation to uncertainty about target position due to degradation of the target image by motion blur from the fast-running beetle.
Cornell Chronicle has a good summary of the paper, with an interview with Cole Gilbert.
DB Zurek, MQ Perkins, and C Gilbert (2014). Dynamic visual cues induce jaw opening and closing by tiger beetles during pursuit of prey. Biology Letters, 20140760