Effects of stimuli shape and polarization in evoking deimatic patterns in the European cuttlefish, Sepia officinalis, under varying turbidity conditions.

Cuttlefish possess the complex ability to identify approaching threats and then to selectively express the appropriate defense. We examined the visual cues used by Sepia officinalis cuttlefish during predator detection and the responses they selected. Using computer-generated stimuli, we set out to quantitate the deimatic responses to artificial looming stimuli of different shapes and contrasts. Defensive behavior gradually intensified as geometrical shapes resembled an image of a fish. Therefore, in addition to an object's size or its sudden increase in size, cuttlefish use form recognition to identify a threat. Cuttlefish demonstrated equal performance in predator detection trough clear water when presented with intensity versus polarization contrasts. However, when the water turbidity increased, the cuttlefish still detected looming fish shapes based on polarization contrast even when intensity information alone did not suffice. These results demonstrate the interplay between intensity and polarization information transmission and processing in the spatial domain. As nectobenthic organisms, cuttlefish probably experience low visibility conditions on a regular basis. The ability to see further into turbid water and to better detect an approaching object would be beneficial for their survival.

Maturation of polarization and luminance contrast sensitivities in cuttlefish (Sepia officinalis).

Polarization sensitivity is a characteristic of the visual system of cephalopods. It has been well documented in adult cuttlefish, which use polarization sensitivity in a large range of tasks such as communication, orientation and predation. Because cuttlefish do not benefit from parental care, their visual system (including the ability to detect motion) must be efficient from hatching to enable them to detect prey or predators. We studied the maturation and functionality of polarization sensitivity in newly hatched cuttlefish. In a first experiment, we examined the response of juvenile cuttlefish from hatching to the age of 1 month towards a moving, vertically oriented grating (contrasting and polarized stripes) using an optomotor response apparatus. Cuttlefish showed differences in maturation of polarization versus luminance contrast motion detection. In a second experiment, we examined the involvement of polarization information in prey preference and detection in cuttlefish of the same age. Cuttlefish preferentially chose not to attack transparent prey whose polarization contrast had been removed with a depolarizing filter. Performances of prey detection based on luminance contrast improved with age. Polarization contrast can help cuttlefish detect transparent prey. Our results suggest that polarization is not a simple modulation of luminance information, but rather that it is processed as a distinct channel of visual information. Both luminance and polarization sensitivity are functional, though not fully matured, in newly hatched cuttlefish and seem to help in prey detection.

The "prawn-in-the-tube" procedure: what do cuttlefish learn and memorize?

For several decades the "prawn-in-the-tube" procedure has been extensively used in the exploration of behavioral plasticity and its neural correlates in cuttlefish. Although the nature of the task has been characterized, the effect of reinforcement and the extent of different cues cuttlefish can use to solve and memorize the task remain unclear. To determine whether cuttlefish learned to inhibit predatory behavior because of pain incurred when the tentacles hit the glass tube, the shrimp prey (typically attacked with a tentacle strike) was replaced by crabs (normally caught by a jumping strategy, using all eight arms together, which is thought less likely to be painful). We showed that the cuttlefish is still capable of learning inhibition of predatory behavior when it adopts another catching strategy, which suggests that pain from the tentacles hitting the tube has little effect on the learning process. The two latest experiments have shown that cuttlefish do not learn to inhibit predatory behavior towards a specific type of prey, but rather learn and memorize visual (light polarization) and tactile information from the glass tube. The "prawn-in-the-tube" procedure is a powerful and user-friendly tool in the investigation of the processing and retention of multisensory information in invertebrates. Our recent findings now open up new areas of investigation into the neural correlates of learning and memory processes in cuttlefish.

Cuttlefish rely on both polarized light and landmarks for orientation.

Cuttlefish are sensitive to linear polarization of light, a sensitivity that they use in predation and possibly in intraspecific communication. It has also been shown that cuttlefish are able to solve a maze using visual landmarks. In this study, cuttlefish were trained to solve a Y-maze with the e-vector of a polarized light and landmarks as redundant spatial information. The results showed that cuttlefish can use the e-vector orientation and landmarks in parallel to orient and that they are able to use either type of cue when the other one is missing. When they faced conflicting spatial information in the experimental apparatus, the majority of cuttlefish followed the e-vector rather than landmarks. Differences in response latencies in the different conditions of testing (training with both types of cue, tests with single cue or with conflicting information) were observed and discussed in terms of decision making. The ability to use near field and far field information may enable animals to interpret the partially occluded underwater light field.