Flicker is part of a multi-cue response criterion in fiddler crab predator avoidance

The polarisation of light is used by many species of cephalopods and crustaceans to discriminate objects or to communicate. Most visual systems with this ability, such as that of the fiddler crab, include receptors with photopigments that are oriented horizontally and vertically relative to the outside world. Photoreceptors in such an orthogonal array are maximally sensitive to polarised light with the same fixed e-vector orientation. Using opponent neural connections, this two-channel system may produce a single value of polarisation contrast and, consequently, it may suffer from null points of discrimination. Stomatopod crustaceans use a different system for polarisation vision, comprising at least four types of polarisationsensitive photoreceptor arranged at 0, 45, 90 and 135 deg relative to each other, in conjunction with extensive rotational eye movements. This anatomical arrangement should not suffer from equivalent null points of discrimination. To test whether these two systems were vulnerable to null points, we presented the fiddler crab Uca heteropleura and the stomatopod Haptosquilla trispinosa with polarised looming stimuli on a modified LCD monitor. The fiddler crab was less sensitive to differences in the degree of polarised light when the e-vector was at −45 deg than when the e-vector was horizontal. In comparison, stomatopods showed no difference in sensitivity between the two stimulus types. The results suggest that fiddler crabs suffer from a null point of sensitivity, while stomatopods do not.

Section: Research Articlementioning

confidence: 99%

Null point of discrimination in crustacean polarisation vision

How

Christy

Roberts

et al. 2014

“…Visually elicited escape behavior has been extensively studied in fiddler crabs in the field, by using moving dummies to simulate predator stimuli (e.g. Hemmi, 2005;Smolka et al, 2013). After extensive studies in the laboratory (see below), field studies began to be performed on Neohelice using the same approach ( Fig.…”

Section: Introductionmentioning

confidence: 99%

The predator and prey behaviors of crabs: from ecology to neural adaptations

Tomsic

Sztarker

Astrada

et al. 2017

Predator avoidance and prey capture are among the most vital of animal behaviors. They require fast reactions controlled by comparatively straightforward neural circuits often containing giant neurons, which facilitates their study with electrophysiological techniques. Naturally occurring avoidance behaviors, in particular, can be easily and reliably evoked in the laboratory, enabling their neurophysiological investigation. Studies in the laboratory alone, however, can lead to a biased interpretation of an animal's behavior in its natural environment. In this Review, we describe current knowledge - acquired through both laboratory and field studies - on the visually guided escape behavior of the crab Analyses of the behavioral responses to visual stimuli in the laboratory have revealed the main characteristics of the crab's performance, such as the continuous regulation of the speed and direction of the escape run, or the enduring changes in the strength of escape induced by learning and memory. This work, in combination with neuroanatomical and electrophysiological studies, has allowed the identification of various giant neurons, the activity of which reflects most essential aspects of the crabs' avoidance performance. In addition, behavioral analyses performed in the natural environment reveal a more complex picture: crabs make use of much more information than is usually available in laboratory studies. Moreover, field studies have led to the discovery of a robust visually guided chasing behavior in Here, we describe similarities and differences in the results obtained between the field and the laboratory, discuss the sources of any differences and highlight the importance of combining the two approaches.

“…A visual system viewing a flickering light source has a critical flicker fusion (CFF) threshold, above which the flicker becomes too fast for the system to follow (Fritsches et al, 2005), and the light appears continuous to the animal, and not flashing. The CFF threshold varies between animals, and is often related to lifestyle and illumination level, being fast in rapidly moving organisms in bright light and slow in nocturnal slow-movers (Horodysky et al, 2008;Smolka et al, 2013). It is therefore likely that reduced CFF could impair the capacity to react to fast events such as prey capture and predator avoidance.…”

Section: Introductionmentioning

confidence: 99%

Ocean acidification slows retinal function in a damselfish through interference with GABAA receptors

Chung

Marshall

Watson

et al. 2014

117

Vision is one of the most efficient senses used by animals to catch prey and avoid predators. Therefore, any deficiency in the visual system could have important consequences for individual performance. We examined the effect of CO 2 levels projected to occur by the end of this century on retinal responses in a damselfish, by determining the threshold of its flicker electroretinogram (fERG). The maximal flicker frequency of the retina was reduced by continuous exposure to elevated CO 2 , potentially impairing the capacity of fish to react to fast events. This effect was rapidly counteracted by treatment with a GABA antagonist (gabazine), indicating that GABA A receptor function is disrupted by elevated CO 2 . In addition to demonstrating the effects of elevated CO 2 on fast flicker fusion of marine fishes, our results show that the fish retina could be a model system to study the effects of high CO 2 on neural processing.