Search

Embryos perceive environmental stimuli, thanks to their almost mature sensory systems. In cuttlefish, the embryonic development of Sepia officinalis and Sepia pharaonis is similar but the egg capsule transparency is different. S. officinalis' eggs are black (ink), which provide protection from predators. Conversely, those of S. pharaonis are translucent. The aim of this study was to test the visual and chemosensory perception abilities of these two cuttlefish embryos by observation of the ventilation rate (VR) before and after stimulation. Our results show that S. pharaonis responds to light at stage 22 and S. officinalis at stage 24. Conversely, S. pharaonis responds to predator odor at stage 23 and S. officinalis at stage 22. Both species are able to respond to these stimuli before hatching but do not have the same developmental schedule. Neither are the responses of the two cuttlefish exactly the same. In S. officinalis, VR increases after stimulations. In S. pharaonis, VR increases after light stimulation and decreases following the odor stimulation after stage 25. This result could reveal an ability to recognize stimuli at stage 25. The decrease could be identified as freezing-like behavior which would be more adaptive than an increase, since the embryos are visible., (© 2019 Wiley Periodicals, Inc.)

Number sense is a key cognitive function in animals. The biological functions of number discrimination have a wide range, including the selection of prey and social interaction. In a previous study, we have shown that cuttlefish are able to distinguish numerical differences among various integers, including 1 vs. 2, 2 vs. 3, 3 vs. 4, and 4 vs. 5. However, it is not known whether cuttlefish are able to discriminate various fractions, that is, various non-integer numbers. In addition, no study on invertebrates has examined fraction number sense. Using the active preying behavior of cuttlefish (Sepia pharaonis), we investigated the spontaneous preference for larger quantity by presenting two-alternative choice between 1 vs. 1.5, 1.5 vs. 2, 2 vs. 2.5, and 2.5 vs. 3. In this context, the quantity1.5 is composed of one large shrimp and one small shrimp, in which the size of the small shrimp is one-half of that of the large shrimp. The result shows that the cuttlefish chose larger quantity in the first three pairs, but they could not distinguish the pair 2.5 vs. 3. Despite that the absolute differences in these pairs are the same (0.5), the relative differences in these pairs decrease (0.5, 0.33, 0.25, and 0.2, respectively). This implies that the perceived difference in quantity is proportional to the initial quantity (Weber's law). Although the present study does not truly differentiate the number difference from the quantity difference, this result does raise the possibility that cuttlefish may be equipped with the primitive concept of fractions, and if so, the perceived just noticeable difference is similar for both integer and fraction number discrimination.

Cephalopods are renowned for their ability to adaptively camouflage on diverse backgrounds. Sepia officinalis camouflage body patterns have been characterized spectrally in the laboratory but not in the field due to the challenges of dynamic natural light fields and the difficulty of using spectrophotometric instruments underwater. To assess cuttlefish color match in their natural habitats, we studied the spectral properties of S. officinalis and their backgrounds on the Aegean coast of Turkey using point-by-point in situ spectrometry. Fifteen spectrometry datasets were collected from seven cuttlefish; radiance spectra from animal body components and surrounding substrates were measured at depths shallower than 5 m. We quantified luminance and color contrast of cuttlefish components and background substrates in the eyes of hypothetical di- and trichromatic fish predators. Additionally, we converted radiance spectra to sRGB color space to simulate their in situ appearance to a human observer. Within the range of natural colors at our study site, cuttlefish closely matched the substrate spectra in a variety of body patterns. Theoretical calculations showed that this effect might be more pronounced at greater depths. We also showed that a non-biological method ("Spectral Angle Mapper"), commonly used for spectral shape similarity assessment in the field of remote sensing, shows moderate correlation to biological measures of color contrast. This performance is comparable to that of a traditional measure of spectral shape similarity, hue and chroma. This study is among the first to quantify color matching of camouflaged cuttlefish in the wild.

Camouflage is the primary defense behavior in cephalopods. It is known that cuttlefish immediately after hatching are capable of showing various body patterns for concealing themselves, however recent studies suggest that maturation of camouflage body patterns is faster for cuttlefish (Sepia officinalis) reared in enriched environments than those reared in impoverished environments. Since camouflage patterning in cephalopods is predominately visually driven, this study specifically investigates effects of the rearing background contrast on the maturation of body patterns in cuttlefish (Sepia pharaonis). Newly hatched animals were separated into two cohorts, one reared in a uniform-gray background (low-contrast, or L group) and the other raised in a black/white checkerboard background (high-contrast, or H group). At Weeks 2, 4, 6, 8, 10, and 12, cuttlefish were placed individually either on uniform or checkerboard substrates to examine their body patterns. Animals from both L and H groups appear to show moderate disruptive patterns on the checkerboard and less disruptive on the uniform background at Week 2. Throughout development, however, cuttlefish from the H group showed stronger disruptive patterns than that of the L group on the checkerboard background at Weeks 10 and 12. In interesting findings, cuttlefish from both L and H groups showed similar strength but different disruptive components on the uniform background in later postembryonic stages. These results suggest that the maturation of camouflage body patterns in S. pharaonis is at least in part affected by visual contrast of their rearing backgrounds, although environmental complexity or social interaction is also likely to be involved in this process. This also implies that early visual experience could exert its effect on the seemingly preprogrammed behaviors such as camouflage body patterning in cephalopods., (2010 APA, all rights reserved)

Camouflage is the primary defense in cuttlefish. The rich repertoire of their body patterns can be categorized into three types: uniform, mottle, and disruptive. Several recent studies have characterized spatial features of substrates responsible for eliciting these body patterns on natural and artificial backgrounds. In the present study, we address the role of spatial scales of substrate texture in modulating the expression of camouflage body patterns in cuttlefish, Sepia officinalis. Substrate textures were white noise patterns first filtered into various octave-wide spatial frequency bands and then thresholded to generate binary (black/white) images. Substrate textures differed in spatial frequency but were identical in all other respects; this allowed us to examine the effects of spatial scale on body patterning. We found that as the spatial scale of substrate texture increased, cuttlefish body patterns changed from uniform, to mottle, to disruptive, as predicted from the camouflage mechanism of background matching. For substrates with spatial scales larger than skin patterning components, cuttlefish showed reduced disruptive patterning. These results are consistent with the idea that the body pattern deployed by a cuttlefish attempts to match the energy spectrum of the substrate, and underscore recent reports suggesting that substrate spatial scale is a key determinant of body patterning responses in cuttlefish.

The camouflaging abilities of cuttlefish (Sepia officinalis) are remarkable and well known. It is commonly believed that cuttlefish-although color blind-actively match various colors of their immediate surroundings, yet no quantitative data support this notion. We assembled several natural substrates chosen to evoke the three basic types of camouflaged body patterns that cuttlefish express (uniform/stipple, mottle, and disruptive) and measured the spectral reflectance of the camouflaged pattern and the respective background using a fiber optic spectrometer. We demonstrate that the reflectance spectra of cuttlefish skin patterns correlate closely with the spectra of these natural substrates. Since pigmented chromatophores play a key role in cephalopod color change, we also measured the spectral reflectance of individual cuttlefish chromatophores under the microscope, and confirm the results from a previous publication reporting three distinct colors of chromatophores (yellow, orange, and dark brown) on the animals' dorsal side. Taken together, our results show that the color variations in substrate and animal skin can be very similar and that this may facilitate color match on natural substrates in the absence of color vision.

Cephalopods are known for their ability to change camouflage body patterns in response to changes in the visual background. Recent research has used artificial substrates such as checkerboards to investigate some specific visual cues that elicit the various camouflaged patterns in cuttlefish. In this study, we took information from experiments on artificial substrates and assembled a natural rock substrate (fixed with glue) with those features that are thought to elicit disruptive coloration in cuttlefish. The central hypothesis is that light rocks of appropriate size, substrate contrast and edge characteristics will elicit disruptive camouflage patterns in cuttlefish. By adding graded light sand in successively greater quantities to this glued rock substrate, we predicted that disruptive camouflage patterns would be replaced by progressively more uniform patterns as the visual features of rock size, contrast and edges were altered by the addition of sand. By grading the degree of disruptiveness in the animals' body patterns, we found that the results support this prediction, and that there is a strong correlation between fine details of the visual background properties and the resultant body pattern shown by the cuttlefish. Specifically, disruptive coloration was elicited (1) when one or a few light rocks of approximately the size of the animal's White square skin component were in the surrounding substrate (dark rocks alone did not elicit disruptive coloration), (2) there was moderate-to-high contrast between the light rocks and their immediate surrounds, and (3) the rock edges were well defined. Taken together, the present study provides direct evidence of several key visual features that evoke disruptive skin coloration on natural backgrounds.