Book reviewFishes of the North-eastern Atlantic and the Mediterranean: Volume II. P.J.P. Whitehead, M.-L. Bauchot, J.-C. Hureau, J. Nielsen, E. Tortonese (Editors). UNESCO Press, Paris, 1986, pp. 510–1007, FF 250, Dfl 105.00, ISBN 92-3-002308-6

Bioluminescence spans all oceanic dimensions and has evolved many times— from bacteria to fish—to powerfully influence behavioral and ecosystem dynamics. New methods and technology have brought great advances in understanding of the molecular basis of bioluminescence, its physiological control, and its significance in marine communities. Novel tools derived from understanding the chemistry of natural light-producing molecules have led to countless valuable applications, culminating recently in a related Nobel Prize. Marine organisms utilize bioluminescence for vital functions ranging from defense to reproduction. To understand these interactions and the distributions of luminous organisms, new instruments and platforms allow observations on individual to oceanographic scales. This review explores recent advances, including the chemical and molecular, phylogenetic and functional, community and oceanographic aspects of bioluminescence.

/pdf/bioluminescence-in-the-sea-43cqr67xhm.pdf

Bioluminescence in the Sea

In underwater situations, clarity of images are degraded by light absorption and scattering. This causes one colour to dominate the image. In order to improve the perception of underwater images, we proposed an approach based on slide stretching. The objective of this approach is twofold. Firstly, the contrast stretching of RGB algorithm is applied to equalize the colour contrast in images. Secondly, the saturation and intensity stretching of HSI is used to increase the true colour and solve the problem of lighting. Interactive software has been developed for underwater image enhancement. Results of the software are presented in this paper.

/pdf/underwater-image-enhancement-using-an-integrated-colour-3epfncppsc.pdf

Underwater Image Enhancement Using an Integrated Colour Model

Although private communication is considered an important diversifying force in evolution, there is little direct behavioural evidence to support this notion. Here, we show that ultraviolet (UV) signalling in northern swordtails ( Xiphophorus ) affords a channel for communication that is not accessible to their major predator, Astyanax mexicanus , the Mexican tetra. Laboratory and field behavioural experiments with swordtails ( X. nigrensis ) and predators ( A. mexicanus ) demonstrate that male UV ornamentation significantly increases their attractiveness to females but not to this predator, which is less sensitive to UV. UV reflectance among swordtail species correlates positively with tetra densities across habitats, and visual contrast estimates suggest that UV signals are highly conspicuous to swordtails in their natural environment. Cross–species comparisons also support the hypothesis that natural selection drives the use of UV communication. We compared two species, one with high ( X. nigrensis ) and one with low ( X. malinche ) Mexican tetra densities. Xiphophorus nigrensis males reflect significantly more UV than X. malinche , exhibit significant UV sexual dimorphism, and UV is a salient component of the sexual communication system. In X. malinche , however, males reflect minimally in the UV, there is no UV sexual dimorphism, and UV does not play a part in its communication system.

/pdf/a-private-ultraviolet-channel-in-visual-communication-4ciisktbaf.pdf

A private ultraviolet channel in visual communication

https://devistuartfox.files.wordpress.com/2013/06/whiting_et_al_2006_anim_behav_flat_lizard_uv.pdf

Ultraviolet signals ultra-aggression in a lizard

Ultraviolet (UV) vision is well documented for many species of vertebrates. UV cues are known to be used in foraging, navigation and in mate choice. We conducted a series of behavioral experiments to investigate the role of UV perception in mate choice in both female and male guppies (Poecilia reticulata). In our experiments the visual appearance of potential mates was manipulated using either UV transmitting (UV+) or UV blocking (UV-) filters. Female guppies significantly preferred UV+ males. Male guppies tended to prefer UV- females, but their preferences were marginally nonsignificant. Further experiments investigating the role of luminance, indicate that UV wavelengths are probably being used for color discrimination rather than for detecting differences in brightness. These experiments raise the possibility that UV is used in mate assessment in different ways by male and female guppies. This may reflect the different strategies that the two sexes have in order to maximize reproductive success. To our knowledge, these are the first data showing that UV is used by any fish species in mate selection.

/pdf/ultraviolet-vision-and-mate-choice-in-the-guppy-poecilia-312mizdwkj.pdf

Ultraviolet vision and mate choice in the guppy (Poecilia reticulata)

Vision in lanternfish (Myctophidae): adaptations for viewing bioluminescence in the deep sea

Ultraviolet dermal reflexion and mate choice in the guppy, Poecilia reticulata

Spectral irradiance and foraging efficiency in the guppy, Poecilia reticulata

Microspectrophotometry (MSP) revealed the presence of a rod and at least two cone classes (mid- and long-wavelength sensitive) in the intertidal peacock blenny Salaria pavo. Both rhodopsin and porphyropsin based visual pigments were found in all fish, together with high individual variation in the chromophore ratio. The three morphs (females, males and sneaker males) differed in their spectral sensitivities (as measured with the optomotor response) with sneakers having higher sensitivity at long-wavelengths than either males or females. This long-wave displacement of peak sensitivity could be due to elevated proportions of porphyropsin visual pigments in the sneakers' retinae. The lenses of all morphs exhibited a short-wavelength cut-off and an unusual layer of carotenoid was found behind the retinal pigment epithelium and in the outer segments of some cones. These screening pigments could serve a photo-protective role or to improve visual contrast. No short-wave photoreceptors were located using MSP. This indicates that this cone class may be absent or present at very low numbers in the retina. This is the first in depth study of the visual system of a blenniid fish and indicates potential within-species visual variation that may be related to the species' habitat and morph-specific behavioural requirements.

/pdf/vision-and-visual-variation-in-the-peacock-blenny-ssyoo61u5u.pdf

Elizabeth M. White

Papers

Ultraviolet vision and mate choice in the guppy (Poecilia reticulata)

Vision in lanternfish (Myctophidae): adaptations for viewing bioluminescence in the deep sea

Ultraviolet dermal reflexion and mate choice in the guppy, Poecilia reticulata

Spectral irradiance and foraging efficiency in the guppy, Poecilia reticulata

Vision and visual variation in the peacock blenny