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  • 1
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    To be seen or to hide : visual characteristics of body patterns for camouflage and communication in the Australian giant cuttlefish Sepia apama (2011)
    University of Chicago
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © University of Chicago, 2011. This article is posted here by permission of University of Chicago for personal use, not for redistribution. The definitive version was published in American Naturalist 177 (2011): 681-690, doi:10.1086/659626.
    Description: It might seem obvious that a camouflaged animal must generally match its background whereas to be conspicuous an organism must differ from the background. However, the image parameters (or statistics) that evaluate the conspicuousness of patterns and textures are seldom well defined, and animal coloration patterns are rarely compared quantitatively with their respective backgrounds. Here we examine this issue in the Australian giant cuttlefish Sepia apama. We confine our analysis to the best-known and simplest image statistic, the correlation in intensity between neighboring pixels. Sepia apama can rapidly change their body patterns from assumed conspicuous signaling to assumed camouflage, thus providing an excellent and unique opportunity to investigate how such patterns differ in a single visual habitat. We describe the intensity variance and spatial frequency power spectra of these differing body patterns and compare these patterns with the backgrounds against which they are viewed. The measured image statistics of camouflaged animals closely resemble their backgrounds, while signaling animals differ significantly from their backgrounds. Our findings may provide the basis for a set of general rules for crypsis and signals. Furthermore, our methods may be widely applicable to the quantitative study of animal coloration.
    Description: S.Z. was supported by a Case award from the Biotechnology and Biological Sciences Research Council and QinetiQ and is currently supported by Office of Naval Research (ONR) grant N00014-09-1-1053. R.T.H. received partial support from ONR grant N0001406-1- 0202.
    Keywords: Camouflage ; Communication ; Signaling ; Image structure ; Cephalopods ; Vision
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
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  • 2
    Electronic Resource
    Electronic Resource
    VISION AND SENSORY PHYSIOLOGY The lateral line systems of three deep-sea fish (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 49 (1996), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The distribution and ultrastructure of the lateral line systems in three taxonomically dispersed deep-sea fish are described: Poromitra capito, Melanonus zugmayeri and Phrynichthys wedli. They are meso- to bathpelagic and are thought to feed on small crustaceans and fish. All possess highly developed lateral line systems, a feature associated with life in the deep sea. Poromitra capito and M. zugmayeri exhibit widened head canals which are connected to the outside by large pores and which contain around 60 large neuromasts. Each neuromast consists of a cupula, shield-shaped mantle and a sensory plate containing hundreds to thousands of hair cells. Direction of sensitivity is in the long axis of the canal (perpendicular to the long axis of the mantle). Depending on their position on the sensory plate, the hair cells have different morphologies. They fall into three basic classes which, from comparison with past work, may be tuned to different frequencies. Alternatively, the various hair cell morphologies could be interpreted as being members of a developmental or growth sequence. Phrynichthys wedli has no canal organs, these being replaced secondarily by many superficial neuromasts placed on prominent papillae in rows which cover much of the ‘head’ and body. Direction of sensitivity is along the axis of the neuromast row. An extreme proliferation of superficial neuromasts are also found on the heads of P. capito and M. zugmayeri and these are of a type not described before. They consist of stitches, raised on papillae in M. zugmayeri and several mm long in P. capito, in which continuous lines of hair cells, two to three cells wide, are embedded. Direction of sensitivity is perpendicular to the long axis of the stitch. Based on the structure and direction of sensitivity, possible functional implications of all the neuromast types described are compared and discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1996.tb06079.x
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  • 3
    Electronic Resource
    Electronic Resource
    The UV visual world of fishes: a review (1999)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 54 (1999), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Ultraviolet-A radiation (320–400 nm) is scattered rapidly in water. Despite this fact, UV is present in biologically useful amounts to at least 100 m deep in clear aquatic environments. Discovery of UV visual pigments with peak absorption at around 360 nm in teleost cone photoreceptors indicates that many teleost fishes may be adapted for vision in the UV range. Considering the characteristic absorption curve for visual pigments, about 18% of the downwelling light that illuminates objects at 30-m depth would be available to UV-sensitive cones. Strong scattering of UV radiation should produce unique imaging conditions as a very bright UV background in the horizontal view and a marked veiling effect that, with distance, obscures an image. Many teleosts have three, or even four, classes of cone cells mediating colour vision in their retina and one can be sensitive to UV. These UV-sensitive cones contain a visual pigment based on a unique opsin which is highly conserved between fish species. Several powerful methods exist for demonstration of UV vision, but all are rather demanding in terms of technique and equipment. Demonstration that the eye lacks UV-blocking compounds that are present in many fish eyes is a simpler method that can indicate the possibility of UV vision. The only experimental evidence for the use of UV vision by fishes is connected to planktivory: detection of UV-opaque objects at close range against a bright UV background is enhanced by the physical properties of UV light. Once present, perhaps for the function of detecting food, UV vision may well be co-opted through natural selection for other functions. Recent discovery that UV vision is critically important for mate choice in some birds and lizards is a strong object lesson for fish ecologists and behaviourists. Other possible functions amount to far more than merely adding a fourth dimension to the visible spectrum. Since UV is scattered so effectively in water, it may be useful for social signalling at short range and reduce the possibility of detection by other, illegitimate, receivers. Since humans are blind to UV light, we may be significantly in error, in many cases, in our attempts to understand and evaluate visual aspects of fish behaviour. A survey of the reflectance properties of skin pigments in fishes reveals a rich array of pigments with reflectance peaks in the UV. For example, the same yellow to our eyes may comprise two perceptually different colours to fish, yellow and UV-yellow. It is clearly necessary for us to anticipate that many fishes may have some form of UV vision.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1999.tb00848.x
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  • 4
    Electronic Resource
    Electronic Resource
    Solubility of Barium Sulphate in Sea Water (1968)
    [s.l.] : Nature Publishing Group
    Nature 217 (1968), S. 834-835 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] There is thus considerable interest in obtaining values for solubilities in sea water by direct measurement, especially for the less soluble compounds which may in some circumstances limit the concentrations of certain elements. This interest extends to a more diverse range of compounds when ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/217834a0
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  • 5
    Electronic Resource
    Electronic Resource
    Visual pigment diversity in two genera of mantis shrimps implies rapid evolution (Crustacea; Stomatopoda) (1996)
    Springer
    Journal of comparative physiology 179 (1996), S. 371-384 
    Details
    ISSN: 1432-1351
    Keywords: Visual pigment ; Stomatopoda ; Visual ecology ; Evolution ; Photoreceptor ; Retina
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract 1. Interspecific diversity in the visual pigments of stomatopod crustaceans was characterized using microspectrophotometry. We examined the 10 visual pigments in main rhabdoms in retinas of 3 species of each of two genera of stomatopod crustaceans of the superfamily Gonodactyloidea, Gonodactylus (G. oerstedii, G. aloha, and G. curacaoensis) and Odontodactylus (O. scyllarus, O. brevirostris, and O. “havanensis”). Species were selected to provide a matched diversity of habitats. 2. In each genus, visual pigments varied in λmax in several regions of the retina, as revealed by analysis of variance. The variation within closely related species of the same genus implies that visual pigments can evolve rapidly in stomatopods. 3. In photoreceptors of the peripheral retina, which are devoted to spatial vision, visual pigment λmax decreased as the depth range of the various species increased, a typical pattern for marine animals. In contrast, visual pigment λmax in photoreceptors of retinal regions devoted to polarization vision (midband Rows 5 and 6) is not obviously correlated with the spectral environment, implying that polarization information may be confined to particular spectral ranges. Visual pigments of the tiered rows of the midband, which are committed to spectral analysis, span a larger spectral range in shallow-water than deepwater species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00194991
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  • 6
    Electronic Resource
    Electronic Resource
    Behavioural evidence for colour vision in stomatopod crustaceans (1996)
    Springer
    Journal of comparative physiology 179 (1996), S. 473-481 
    Details
    ISSN: 1432-1351
    Keywords: Stomatopod ; Colour vision ; Crustacean behaviour
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract If an organism can be taught to respond in a particular way to a wavelength of light, irrespective of that light's intensity, then it must be able to perceive the colour of the stimulus. No marine invertebrate has yet been shown to have colour vision. Stomatopod crustaceans (mantis shrimps) are colourful animals and their eyes have many adaptations which indicate that they are capable of such spectral analysis. We adopted an associative learning paradigm to attempt to demonstrate colour vision. Stomatopods readily learnt to choose some colours from arrays of greys, even when the correct choice colours were darker than the ones they had been trained to. Possible mechanisms underlying colour vision in these animals, and their ecological significance are discussed. A simple model is presented which may help interpret the complex-stomatopod colour vision system and explain some of the learning anomalies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00192314
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  • 7
    Electronic Resource
    Electronic Resource
    Tetrachromacy, oil droplets and bird plumage colours (1998)
    Springer
    Journal of comparative physiology 183 (1998), S. 621-633 
    Details
    ISSN: 1432-1351
    Keywords: Key words Bird ; Colour ; Vision ; UV ; Plumage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract There is a growing body of data on avian eyes, including measurements of visual pigment and oil droplet spectral absorption, and of receptor densities and their distributions across the retina. These data are sufficient to predict psychophysical colour discrimination thresholds for light-adapted eyes, and hence provide a basis for relating eye design to visual needs. We examine the advantages of coloured oil droplets, UV vision and tetrachromacy for discriminating a diverse set of avian plumage spectra under natural illumination. Discriminability is enhanced both by tetrachromacy and coloured oil droplets. Oil droplets may also improve colour constancy. Comparison of the performance of a pigeon's eye, where the shortest wavelength receptor peak is at 410 nm, with that of the passerine Leiothrix, where the ultraviolet-sensitive peak is at 365 nm, generally shows a small advantage to the latter, but this advantage depends critically on the noise level in the sensitivity mechanism and on the set of spectra being viewed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003590050286
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  • 8
    Electronic Resource
    Electronic Resource
    Some optical features of the eyes of stomatopods (1993)
    Springer
    Journal of comparative physiology 173 (1993), S. 583-594 
    Details
    ISSN: 1432-1351
    Keywords: Stomatopod ; Vision ; Crustacean ; Optics ; Sensitivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Anatomical dimensions of individual ommatidia from various regions in the eyes of six species of stomatopod have been measured. Using these measurements, estimates of the sensitivity and acceptance angle of each ommatidium were calculated. The relationship between sensitivity distribution in various eye regions and habitat was examined. There is a good correlation between the sensitivity of eyes in the six species examined and their habitat or activity cycle. Animals living in deeper or more turbid water, or which are often active at night possess eyes with relatively high sensitivity. Ommatidia in six-row mid-bands are more sensitive than those in surrounding eye regions. This is achieved by enlarging ommatidial size or decreasing focal length. Increased light capture is necessary in these rows as they contain dense intrarhabdomal filters and tiered rhabdoms which drastically attenuate light as it passes down the rhabdom. Acute zone facets are larger, also for additional sensitivity. The way the image is sampled was studied by comparing acceptance angles to inter-ommatidial angles, measured previously. In most eye regions of most eyes these angles are matched. Where this is not the case (in the mid-band, near mid-band regions and the edge of the eye) an explanation can be found in the function of the region involved, or that of the closely adjacent regions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00197766
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  • 9
    Electronic Resource
    Electronic Resource
    Photoreceptor spectral diversity in the retinas of squilloid and lysiosquilloid stomatopod crustaceans (1993)
    Springer
    Journal of comparative physiology 172 (1993), S. 339-350 
    Details
    ISSN: 1432-1351
    Keywords: Photoreceptor ; Retina ; Spectral sensitivity ; Stomatopod ; Visual ecology ; Visual pigment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract 1. We examined the retinas of 2 species of stomatopods in the superfamily Squilloidea, Cloridopsis dubia and Squilla empusa, and 2 species of the super-family Lysiosquilloidea, Coronis scolopendra and Lysiosquilla sulcata, using microspectrophotometry in the visible region of the spectrum. 2. Retinas of all species included numerous photostable pigments, such as green reflecting pigment, hemocyanin, colored oil droplets, and vesicles. Both lysiosquilloid species also had intrarhabdomal filters within specialized photoreceptors of the midband. 3. Squilloid species contained a single visual pigment throughout all photoreceptors, with peak absorption at medium wavelengths (near 515nm). Retinas of lysiosquilloids contained a diversity of visual pigments, with estimated λmax values ranging from 397 to 551 nm. 4. Spectral sensitivity functions were estimated for the lysiosquilloid species based on estimates of visual pigment λnax, photoreceptor dimensions, and specific absorbances of the visual pigments and intrarhabdomal filters. Ommatidia of midband Rows 1 to 4 contained pairs of narrowly tuned spectral receptors, appropriate for spectral discrimination, while ommatidia of midband Rows 5 and 6, and all peripheral ommatidia, had broad spectral sensitivity functions. 5. Lysiosquilloid stomatopods have retinas that closely resemble those of gonodactyloids both structurally and in their visual pigment diversity. In contrast, squilloids have retinas that are much simpler. These differences appear to be related to the habitats and activity cycles of species belonging to the 3 major superfamilies of stomatopod crustaceans.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00216616
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  • 10
    Electronic Resource
    Electronic Resource
    The retinas of mantis shrimps from low-light environments (Crustacea; Stomatopoda; Gonodactylidae) (1994)
    Springer
    Journal of comparative physiology 174 (1994), S. 607-619 
    Details
    ISSN: 1432-1351
    Keywords: Photoreceptor ; Retina ; Spectral sensitivity ; Stomatopoda ; Visual ecology ; Visual pigment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract 1. We examined microspectrophotometrically the retinas of 3 species of stomatopods in the superfamily Gonodactyloidea, all of which live in environments that are reduced both in the intensity and spectral range of natural illumination. Species examined were Odontodactylus brevirostris, O. scyllarus, and Hemisquilla ensigera. 2. All 3 species had the typical gonodactyloid diversity of visual pigments, with 8 different photopigments residing in the 4 tiered rows of the midband and 2 additional types in the untiered classes of photoreceptors in the midband and peripheral retina. The spectral range covered by the λmax values of the visual pigments of each species was similar to that of other gonodactyloid and lysiosquilloid species. 3. Apparent retinal adaptations in species of Odontodactylus for vision in dimly lit, spectrally narrow photic environments were seen primarily as specializations of the intrarhabdomal filters. These were of reduced diversity, and had reduced absorption at long wavelengths compared to the filters of other gonodactyloid stomatopods. Retinas of H. ensigera lacked both proximal classes of intrarhabdomal filter, and had the smallest total range of visual pigment λmax yet observed in mantis shrimps. These modifications decrease the spectral range and number of types of narrow-band spectral classes of phooreceptors, while increasing their sensitivity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00217382
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