Visual pigments, oil droplets, ocular media and cone photoreceptor distribution in two species of passerine bird: the blue tit (Parus caeruleus L.) and the blackbird (Turdus merula L.)

The spectral absorption characteristics of the retinal photoreceptors of the blue tit (Parus caeruleus) and blackbird (Turdus merula) were investigated using microspectrophotometry. The retinae of both species contained rods, double cones and four spectrally distinct types of single cone. Whilst the visual pigments and cone oil droplets in the other receptor types are very similar in both species, the wavelength of maximum sensitivity (λ_max) of long-wavelength-sensitive single and double cone visual pigment occurs at a shorter wavelength (557 nm) in the blackbird than in the blue tit (563 nm). Oil droplets located in the long-wavelength-sensitivesingle cones of both species cut off wavelengths below 570–573 nm, theoretically shifting cone peak spectral sensitivity some 40 nm towards the long-wavelength end of the spectrum. This raises the possibility that the precise λ_max of the long-wavelength-sensitive visual pigment is optimised for the visual function of the double cones. The distribution of cone photoreceptors across the retina, determined using conventional light and fluorescence microscopy, also varies between the two species and may reflect differences in their visual ecology. Accepted: 8 January 2000     

Variation in ultraviolet reflectance by carotenoid-bearing feathers of tanagers (Thraupini: Emberizinae: Passeriformes)

Avian visual sensitivity encompasses both the human visible range (400–700 nm) and also near‐ultraviolet (UV) wavelengths (320–400 nm) invisible to normal humans. I used reflectance spectrophotometry to assess variation in UV reflectance for yellow, orange and red plumage in 67 species of tanager (Passeriformes). Previous chemical studies, and my analysis of reflectance minima, suggest that carotenoids are the dominant pigments in yellow, orange and red tanager plumage. Spectra recorded over the range of wavelengths to which birds are sensitive (320–700 nm) were invariably bimodal, with both a plateau of high reflectance at longer (> 500 nm) wavelengths and a distinct secondary peak at UV (< 400 nm) wavelengths. Within this overall framework, variation in UV reflectance was expressed within well‐defined quantitative limits: (1) peak reflectance was always lower than the corresponding plateau of reflectance at longer visible wavelengths; (2) the intensity of peak reflectance declined steadily below 350 nm; (3) wavelengths of peak reflectance clustered between 350 and 370 nm. Significant correlations were detected between various measures of total reflectance in the UV and visible wavebands, but not between various measures of spectral location of UV and visible reflectance. I propose that the strong absorption band at short visible wavelengths (～ 380–550 nm) responsible for bimodal spectra of carotenoids in vitro is also responsible for bimodal reflectance by carotenoid‐based plumage colours. The construction of the UV and visible reflectance bands from different sides of this same absorbance band provides a mechanism for the observed covariation between UV and visible wavelengths. Lack of an association between the spectral locations of the UV and visible reflectance bands may result from the limited variation in spectral location of the UV band. These patterns suggest that plumage colours are subject to constraints, just as are more traditional morphological characters. © 2005 The Linnean Society of London, Biological Journal of the Linnean Society, 2005, 84 , 243–257.     

Spectral sensitivity of the compound eye in butterflies (Heliconius)

Summary The spectral sensitivity of the compound eye in three butterfly species (Heliconius erato, H. numata, H, sara) was tested electrophysiologically in the wavelength region 310 to 650 nm. Sensitivity maxima were found at 370 to 390 nm, 450 to 470 nm, and 550 to 570 nm, for all species. The three sensitivity maxima are suggested to be due to different photoreceptor types effecting wave-length discrimination. An interspecies difference in spectral sensitivity was also found. The difference is suggested to be due to the relative number of photoreceptors of each type. In some of the present experiments a small discontinuity in sensitivity was found at 610 or 630 nm. It is probably caused by a selective reflection of these wavelengths from a tapetum.     

Spectral sensitivity and Color Vision in the Bottlenose Dolphin (Tursiops Truncatus)

Spectral sensitivity was measured in air in a bottlenose dolphin using a behavioral training technique. The spectral sensitivity curve shows two maxima in sensitivity, one in the near ultraviolet part of the spectrum and the other one in the bluegreen part at about 490 nm. Two wavelength discrimination tasks showed that the dolphin could discriminate two wavelengths from the peak regions of the two maxima of the spectral sensitivity function, but not between two wavelengths lying within the broad maximum of the curve in the bluegreen part of the spectrum. Possible underlying mechanisms for the shape of the function are discussed.     

Spectral sensitivity and Color Vision in the Bottlenose Dolphin ( Tursiops Truncatus )

Spectral sensitivity was measured in air in a bottlenose dolphin using a behavioral training technique. The spectral sensitivity curve shows two maxima in sensitivity, one in the near ultraviolet part of the spectrum and the other one in the bluegreen part at about 490 nm. Two wavelength discrimination tasks showed that the dolphin could discriminate two wavelengths from the peak regions of the two maxima of the spectral sensitivity function, but not between two wavelengths lying within the broad maximum of the curve in the bluegreen part of the spectrum. Possible underlying mechanisms for the shape of the function are discussed.     

Photopic spectral sensitivity of a teleost fish,the roach (Rutilus rutilus), with special reference to its ultraviolet sensitivity

Summary This study reports photopic spectral sensitivity curves (351–709 nm) for four individual roach,Rutilus rutilus, determined by two choice appetitive training. All four curves show four sensitivity maxima at 361–398 nm, 421–448 nm, 501–544 nm and 634–666 nm which are related to the four known roach photopic visual pigments (Avery et al. 1982). The overall shape of the curves at long wavelengths indicates inhibitory interactions between the red and green cone mechanisms. That the high behavioural sensitivity in the UV is caused by a specific ultraviolet visual pigment and is not due to aberrant stimulation of the other cone types is shown by the redetermination of spectral sensitivity at short wavelengths (351–501 nm) following the selective bleaching of the three longer wavelength visual pigments. This depresses the blue sensitivity to a greater degree than the relatively unaffected UV sensitivity maximum. Spectral transmission data from two corneas and four lenses show that they transmit considerable amounts of light in the near UV.     

Comparative studies of crustacean spectral sensitivity

Summary Spectral sensitivity of the lateral eyes of the isopodPorcellio scaber (wood louse) and the decapodsCallinectes sapidus (blue crab),Palaemonetes paludosus (Everglades prawn),Orconectes virilis, andO. immunis (crayfish) have been measured between 300 and 660 nm by determining the reciprocal number of photons required to evoke a constant size retinal action potential. Porcellio is maximally sensitive at 515 nm andCallinectes at 505 nm. Both species have a single pigment system, as spectral sensitivity is unchanged by red light adaptation. Palaemonetes appears to have a dichromatic color vision. Sensitivity of the dark-adapted eye is dominated by a receptor maximally sensitive at 550–555 nm, but red or yellow adaptation discloses a uv pigment with _max at about 380 nm. Present evidence suggests the 555 and 380 nm pigments are located in different receptor cells. Orconectes has peak sensitivity at 565 nm, but under red light adaptation and close to the electroretinographic threshold a second sensitivity maximum appears at 425 nm. As in the prawn, these peaks seem to indicate the presence of a two-receptor color vision system.The corneas ofOrconectes, Callinectes, andHomarus (lobster) are relatively thick, and microspectrophotometric measurements show near ultraviolet absorption as well as the protein peak at 280 nm. By contrast,Palaemonetes andMusca (housefly), species with near ultraviolet receptors, have thinner corneas which are transparent through the near ultraviolet. The crystalline cone ofPalaemonetes likewise shows no near ultraviolet absorption but a strong protein band at 280 nm.The scarcity of ultraviolet receptors in the compound eyes of crustacea, in contrast to their common occurrence in insects, is thought to be related to the relative absence of ultraviolet wavelengths in most aquatic environments.This work was supported in part by USPHS research grant NB 03333 to Yale University and postdoctoral fellowship NB 22,547 to H.R.F.     

Genetic variability of the sws1 cone opsin gene among New World monkeys

Vision is a major sense for Primates and the ability to perceive colors has great importance for the species ecology and behavior. Visual processing begins with the activation of the visual opsins in the retina, and the spectral absorption peaks are highly variable among species. In most Primates, LWS/MWS opsins are responsible for sensitivity to long/middle wavelengths within the visible light spectrum, and SWS1 opsins provide sensitivity to short wavelengths, in the violet region of the spectrum. In this study, we aimed to investigate the genetic variation on the sws1 opsin gene of New World monkeys (NWM) and search for amino acid substitutions that might be associated with the different color vision phenotypes described for a few species. We sequenced the exon 1 of the sws1 opsin gene of seven species from the families Callitrichidae, Cebidae, and Atelidae, and searched for variation at the spectral tuning sites 46, 49, 52, 86, 90, 93, 114, 116, and 118. Among the known spectral tuning sites, only residue 114 was variable. To investigate whether other residues have a functional role in the SWS1 absorption peak, we performed computational modeling of wild-type SWS1 and mutants A50I and A50V, found naturally among the species investigated. Although in silico analysis did not show any visible effect caused by these substitutions, it is possible that interactions of residue 50 with other sites might have some effect in the spectral shifts in the order of ~14 nm, found among the NWM. We also performed phylogenetic reconstruction of the sws1 gene, which partially recovered the species phylogeny. Further studies will be important to uncover the mutations responsible for the phenotypic variability of the SWS1 of NWM, and how spectral tuning may be associated with specific ecological features such as preferred food items and habitat use.     

Spectral sensitivity of vervet monkeys (Cercopithecus aethiops sabaeus) and the issue of catarrhine trichromacy

Several genera of platyrrhine monkeys show significant polymorphism of color vision. By contrast, catarrhine monkeys have usually been assumed to have uniform trichromatic color vision. However, the evidential basis for this assumption is quite limited. To study this issue further, spectral sensitivity functions were obtained from vervet monkeys (Cercopithecus aethiops sabaeus) using the technique of electroretinographic flicker photometry. Results from a chromatic adaptation experiment indicated that each of the twelve subjects had two classes of cone pigment in the 540/640 nm portion of the spectrum. That result strongly suggests that this species has routine trichromatic color vision. Comparison of the spectral sensitivity functions obtained from vervets and from similarly-tested humans further indicates that the cone complements of the two species are very similar. Results from this investigation add further support to the idea that there are fundamental differences in the genetic mechanisms underlying color vision in platyrrhine and catarrhine monkeys.     

Phototactic behaviour of the parasitoid Encarsia formosa (Hymenoptera: Aphelinidae)

We investigated the spectral sensitivity and response to light intensity of Encarsia formosa (Hymenoptera: Aphelinidae), which is a key natural enemy of the greenhouse whitefly, Trialeurodes vaporariorum, and the tobacco whitefly, Bemisia tabaci (Hemiptera: Aleyrodidae). To do so, we used 15 monochromatic lights (emitting various specific wavelengths from 340 to 649?nm) and white light. E. formosa adults, which are diurnal insects, showed a positive phototaxis to a broad spectrum of light, with peaks of sensitivity at 414, 340, 450, and 504?nm. These results show that this parasitoid is generally more sensitive to short wavelength lights than long wavelength lights across all spectral ranges tested. Furthermore, E. formosa adults showed an increased phototactic response at low intensities and a decreased response at high intensities, for both ultraviolet light and violet light. Thus, E. formosa showed both colour and intensity preferences. This experiment provides a scientific basis for the development of colour traps for insect pest management and improves understanding of the ecological significance of colour vision by E. formosa.     

Distribution and abundance of marine turtles in the Socialist Republic of Viet Nam

To establish baseline data on the distribution, abundance and threats to marine turtles in Viet Nam we conducted surveys with local fishers, community members and provincial Ministry of Fisheries staff from 17 of Viet Nam’s 29 coastal provinces. These data indicate that five species of marine turtle reside in Viet Nam’s waters (loggerhead, olive ridley, leatherback, green and hawksbill turtles), and four species nest on Viet Nam’s beaches (all of the above except the loggerhead turtle). It is evident from these data that significant declines have occurred in both foraging and nesting populations of all five marine turtle species found in Viet Nam. The greatest current threats to marine turtle populations in Viet Nam are habitat degradation, the accidental and opportunistic of turtles capture by fishers and the direct take of nesting females and their eggs. Successful conservation efforts have been made in recent years through collaboration between international Non Government Organisations and several Vietnamese Government Ministries. Continued success of these projects and the development and implementation of marine conservation policy will depend upon building awareness among Government employees, fishers and the general public about marine turtle biology, ecology, and the need to protect them.     

Photoreceptor Spectral Sensitivity in the Bumblebee,Bombus impatiens (Hymenoptera: Apidae)

The bumblebee Bombus impatiens is increasingly used as a model in comparative studies of colour vision, or in behavioural studies relying on perceptual discrimination of colour. However, full spectral sensitivity data on the photoreceptor inputs underlying colour vision are not available for B. impatiens. Since most known bee species are trichromatic, with photoreceptor spectral sensitivity peaks in the UV, blue and green regions of the spectrum, data from a related species, where spectral sensitivity measurements have been made, are often applied to B impatiens. Nevertheless, species differences in spectral tuning of equivalent photoreceptor classes may result in peaks that differ by several nm, which may have small but significant effects on colour discrimination ability. We therefore used intracellular recording to measure photoreceptor spectral sensitivity in B. impatiens. Spectral peaks were estimated at 347, 424 and 539 nm for UV, blue and green receptors, respectively, suggesting that this species is a UV-blue-green trichromat. Photoreceptor spectral sensitivity peaks are similar to previous measurements from Bombus terrestris, although there is a significant difference in the peak sensitivity of the blue receptor, which is shifted in the short wave direction by 12–13 nm in B. impatiens compared to B. terrestris.     

Tetranucleotide markers from the loggerhead sea turtle (Caretta caretta) and their cross-amplification in other marine turtle species

The loggerhead sea turtle (Caretta caretta) is a federally threatened species and listed as endangered by the World Conservation Union (IUCN). We describe primers and polymerase chain reaction (PCR) conditions to amplify 11 novel tetranucleotide microsatellite loci from the loggerhead sea turtle. We tested primers using samples from 22 females that nested at Melbourne Beach, Florida (USA). Primer pairs yielded an average of 11.2 alleles per locus (range of 4–24), an average observed heterozygosity of 0.83 (range 0.59–0.96), and an average polymorphic information content of 0.80 (range 0.62–0.94). We also demonstrate the utility of these primers, in addition to primers for 15 loci previously described, for amplifying microsatellite loci in four additional species representing the two extant marine turtle families: olive ridley (Lepidochelys olivacea), hawksbill (Eretmochelys imbricata), green turtle (Chelonia mydas), and leatherback (Dermochelys coriacea).     

Spectral sensitivity and photopigments of a nocturnal prosimian,the bushbaby (Otolemur crassicaudatus)

Earlier studies yielded conflicting conclusions on the types of photoreceptors and photopigments found in the eyes of nocturnal prosimians. In this investigation a noninvasive electrophysiological procedure, electroretinogram flicker photometry, was employed to measure scotopic and photopic spectral sensitivity in the thick-tailed bushbaby (Otolemur crassicaudatus). The scotopic spectral sensitivity function of the bushbaby has a peak of about 507 nm. Under photopic test conditions, spectral sensitivity shifts toward the longer wavelengths. The results from a series of adaptation experiments indicate that the cones of the bushbaby retina contain only a single type of cone photopigment (peak sensitivity at about 545 nm). One implication from this result is that these animals do not have color vision. The photopigment arrangement of the bushbaby is different from that earlier found in diurnal and crepuscular prosimians but is similar to that of the owl monkey, the only nocturnal simian. © 1996 Wiley-Liss, Inc.     

铜绿丽金龟对不同光谱的行为反应

【目的】旨在获得铜绿丽金龟 Anomala corpulenta Motschulsky敏感的波谱范围及性别差异。【方法】本研究利用室内行为学的方法,测试了在波长为340~610 nm的14个单色光刺激下铜绿丽金龟的趋、避光行为反应,并计算趋、避光反应率曲线。【结果】观测显示,各单色光均能引起铜绿丽金龟产生一定的趋、避光反应,其雌雄虫的趋光敏感光区位于紫外光（405 nm）、蓝光（460 nm）和绿光区（505和570 nm）,性别对趋光行为有一定的影响,但是仅存在于趋光反应率曲线波峰的大小,而对波峰的位置没有影响。铜绿丽金龟的避光行为反应,在雌雄之间无明显的性别分化,其避光敏感光谱为紫外光（380 nm）、蓝光（440 nm）和绿光区（492和505 nm）。【结论】铜绿丽金龟成虫对不同波长光的趋性存在差异,性别对其光谱行为反应有一定的影响。该研究结果为铜绿丽金龟光视觉的深入研究奠定必要的理论基础,也为利用其趋光性对该金龟甲进行综合治理提供科学依据。     

Vision in the common bed bug Cimex lectularius L. (Hemiptera: Cimicidae): eye morphology and spectral sensitivity

Bed bugs as pests of public health importance recently experienced a resurgence in populations throughout the U.S. and other countries. Consequently, recent research efforts have focused on improving understanding of bed bug physiology and behaviour to improve management. While few studies have investigated the visual capabilities of bed bugs, the present study focused specifically on eye morphology and spectral sensitivity. A 3‐D imaging technique was used to document bed bug eye morphology from the first instar through adult and revealed morphological characteristics that differentiate the common bed bug from the tropical bed bug as well as sex‐specific differences. Electrophysiological measurements were used to evaluate the spectral sensitivity of adult bed bugs. Male bed bugs were more responsive than females at some wavelengths. Electrophysiological studies provided evidence for at least one photoreceptor with a spectral sensitivity curve peak in the green (λ_max 520 nm) region of the spectrum. The broadened long wavelength portion of the spectral sensitivity curve may potentially indicate another photoreceptor in the yellow–green (λ_max 550 nm) portion of the spectrum or screening pigments. Understanding more about bed bug visual biology is vital for designing traps, which are an important component of integrated bed bug management.     

Spectral sensitivity of vertically migrating marine copepods

Light is a critical factor in the proximate basis of diel vertical migration (DVM) in zooplankton. A photobehavioral approach was used to examine the spectral sensitivity of four coastal species of calanoid copepod, representing a diversity of DVM patterns, to test whether species that migrate (nocturnal or reverse DVM) have response spectra that differ from non-migratory surface dwellers. The following species were given light stimuli at wavelengths from 350 to 740 nm, and their photoresponses were measured: Centropages typicus (nocturnal migrator), Calanopia americana (nocturnal migrator), Anomalocera ornata (reverse migrator), and Labidocera aestiva (non-migrator). Centropages typicus and A. ornata had peak responses at 500 and 520 nm, respectively, while Calanopia americana had maximum responses at 480 and 520 nm. Thus, the species that undergo DVM have peak photobehavioral responses at wavelengths corresponding to those available during twilight in coastal water, although the range of wavelengths to which they respond is variable. Non-migratory surface-dwelling L. aestiva had numerous response peaks over a broad spectral range, which may serve to maximize photon capture for vision in their broad-spectrum shallow-water habitat.     

The ontogeny of morphological defenses in Kemp's ridley (Lepidochelys kempii) and loggerhead (Caretta caretta) sea turtles

Marine turtles are large reptiles that compensate for high juvenile mortality by producing hundreds of hatchlings during a long reproductive lifespan. Most hatchlings are taken by predators during their migration to, and while resident in, the open ocean. Their survival depends upon crypticity, minimizing movement to avoid detection, and foraging efficiently to grow to a size too difficult for predators to either handle or swallow. While these behavioral antipredator tactics are known, changes in morphology accompanying growth may also improve survival prospects. These have been only superficially described in the literature. Here, we compare the similarities and differences in presumed morphological defenses of growing loggerhead (Caretta caretta) and Kemp's ridley (Lepidochelys kempii) posthatchlings, related species that differ in growth rate, timing of habitat shift (the return from oceanic to neritic locations), and size at maturity. In both species, vertebral spination and carapace widening increase disproportionally as small turtles grow, but later in ontogeny, the spines regress, sooner in ridley than in loggerhead turtles. Carapace widening occurs in both species but loggerheads are always longer than they are wide whereas in Kemp's ridley turtles, the carapace becomes as wide as long. Our analysis indicates that these changes are unrelated to when each species shifts habitat but are related to turtle size. We hypothesize that the spines function in small turtles as an early defense against gape‐limited predators, but changes in body shape function throughout ontogeny—initially to make small turtles too wide to swallow and later by presenting an almost flat and hardened surface that large predators (such as a sharks) are unable to grasp. The extremely wide carapace of the Kemp's ridley may compensate for its smaller adult size (and presumed greater vulnerability) than the loggerhead. J. Morphol. 276:929–940, 2015. © 2015 Wiley Periodicals, Inc.     

GLOBAL PHYLOGEOGRAPHY OF THE LOGGERHEAD TURTLE (CARETTA CARETTA) AS INDICATED BY MITOCHONDRIAL DNA HAPLOTYPES

Restriction-site analyses of mitochondrial DNA (mtDNA) from the loggerhead sea turtle (Caretta caretta) reveal substantial phylogeographic structure among major nesting populations in the Atlantic, Indian, and Pacific oceans and the Mediterranean sea. Based on 176 samples from eight nesting populations, most breeding colonies were distinguished from other assayed nesting locations by diagnostic and often fixed restriction-site differences, indicating a strong propensity for natal homing by nesting females. Phylogenetic analyses revealed two distinctive matrilines in the loggerhead turtle that differ by a mean estimated sequence divergence p = 0.009, a value similar in magnitude to the deepest intraspecific mtDNA node (p = 0.007) reported in a global survey of the green sea turtle Chelonia mydas. In contrast to the green turtle, where a fundamental phylogenetic split distinguished turtles in the Atlantic Ocean and the Mediterranean Sea from those in the Indian and Pacific oceans, genotypes representing the two primary loggerhead mtDNA lineages were observed in both Atlantic–Mediterranean and Indian-Pacific samples. We attribute this aspect of phylogeographic structure in Caretta caretta to recent interoceanic gene flow, probably mediated by the ability of this temperate-adapted species to utilize habitats around southern Africa. These results demonstrate how differences in the ecology and geographic ranges of marine turtle species can influence their comparative global population structures.     

Relative sensitivity of various spectral forms of photosynthetic pigments to leaf senescence in wheat (Triticum aestivum L.)

The change in the characteristics of the absorption spectrum of chloroplasts which were isolated from the mature and senescing primary wheat leaves, was examined at various wavelengths in which the photosynthetic pigments mostly absorb. Chlorophyll (Chl) a was observed to be relatively more sensitive to leaf senescence than Chl b and carotenoids. Furthermore, the various spectral in vivo forms of Chl a, did not degrade to a similar extent; the far red absorbing forms of Chl a including species that absorb maximally at 692 nm (Chl a-692), 700 nm (Chl a-700) and 708 nm (Chl a 708) were found to be extremely sensitive to senescence induced losses. Both attached and detached senscing primary wheat leaves exhibited nearly similar pattern in the loss of photosynthetic pigments which suggests that the loss in long wavelength absorbing forms of Chl a is a selective indicator of leaf senescence.