Persistent Halogenated Organic Pollutants in Deep-Water-Deposited Particulates from South China Sea.

POP data are limited in the marine environment; thus, this study aimed to investigate background persistent organic pollutant (POP) levels in oceanic deep-water-deposited particulates in the South China Sea (SCS). Six POPs, including polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs), dioxin-like polychlorinated biphenyls (DL-PCBs), polybrominated diphenyl ethers (PBDEs), polybrominated dibenzo-p-dioxins/dibenzofurans (PBDD/Fs), polychlorinated diphenyl ethers (PCDEs), and polybrominated biphenyls (PBBs), were investigated in eight pooled samples from the SCS from 20 September 2013 to 23 March 2014 and 15 April 2014 to 24 October 2014 at depths of 2000 m and 3500 m. PBDEs were the most predominant compounds, with the highest mean Σ14PBDE of 125 ± 114 ng/g dry weight (d.w.), followed by Σ17PCDD/F, Σ12PBDD/F, and Σ12DL-PCB (275 ± 1930, 253 ± 216, and 116 ± 166 pg/g d.w., respectively). Most PBDD/F, PBB, and PCDE congeners were below the detection limits. PCDDs had the highest toxic equivalency (TEQ), followed by PBDDs and DL-PCBs. Among the six POPs, PBDEs were the major components of the marine-deposited particles, regarding both concentrations and mass fluxes. Compared to 3500 m, PBDE levels were higher at a depth of 2000 m. PBDE mass fluxes were 20.9 and 14.2 ng/m2/day or 68.2 and 75.9 ng/m2/year at deep-water 2000 and 3500 m, respectively. This study first investigated POP levels in oceanic deep-water-deposited particles from existing global data.

Correlation Between Pathogenic Determinants Associated with Clinically Isolated Non-Typhoidal Salmonella.

Non-typhoidal and Typhoidal Salmonella are bacterial pathogens source of worldwide and major disease burden. Virulent determinants of specific serovars belonging to non-typhoidal Salmonella have been extensively studied in different models, yet the pathogenesis of this group of bacteria and the development of clinical symptoms globally remains underexplored. Herein, we implemented microbiological and molecular procedures to investigate isolate virulence traits and molecular diversity, likely in association with disease severity. Our results show that selected clinical isolates from a tertiary referring hospital, depending on the richness of the environment and isolate serotypes, exhibited different, and sometimes controversial, virulence properties. The tested strains were susceptible to Ceftriaxone (90%) with decreasing reactivity to Trimethoprim-Sulfamethoxazole (72%), Chloramphenicol (64%), Ampicillin (48%), Gentamicin (44%), and Ciprofloxacin (2%). Disc susceptibility results partially correlated with minimum inhibitory concentration (MIC); however, special attention must be given to antimicrobial treatment, as a rise in multi-resistant isolates to Trimethoprim-Sulfamethoxazole (2/38 µg/mL), Minocycline (8 µg/mL) and Ampicillin (16 µg/mL) has been noticed, with two isolates resistant to Ceftazidime (16 µg/mL). By comparison to previous molecular epidemiology studies, the variation in the gene profiles of endemic pathogens supports the need for continuous and up-to-date microbiological and molecular reports.

Neural processing of linearly and circularly polarized light signal in a mantis shrimp Haptosquilla pulchella.

Stomatopods, or mantis shrimp, are the only animal group known to possess circular polarization vision along with linear polarization vision. By using the rhabdomere of a distally located photoreceptor as a wave retarder, the eyes of mantis shrimp are able to convert circularly polarized light into linearly polarized light. As a result, their circular polarization vision is based on the linearly polarized light-sensitive photoreceptors commonly found in many arthropods. To investigate how linearly and circularly polarized light signals might be processed, we presented a dynamic polarized light stimulus while recording from photoreceptors or lamina neurons in intact mantis shrimp Haptosquilla pulchella The results indicate that all the circularly polarized light-sensitive photoreceptors also showed differential responses to the changing e-vector angle of linearly polarized light. When stimulated with linearly polarized light of varying e-vector angle, most photoreceptors produced a concordant sinusoidal response. In contrast, some lamina neurons doubled the response frequency in reacting to linearly polarized light. These responses resembled a rectified sum of two-channel linear polarization-sensitive photoreceptors, indicating that polarization visual signals are processed at or before the first optic lobe. Noticeably, within the lamina, there was one type of neuron that showed a steady depolarization response to all stimuli except right-handed circularly polarized light. Together, our findings suggest that, between the photoreceptors and lamina neurons, linearly and circularly polarized light may be processed in parallel and differently from one another.

Intracellular Recordings of Spectral Sensitivities in Stomatopods: a Comparison across Species.

Stomatopods (mantis shrimps) possess one of the most complex eyes in the world with photoreceptors detecting up to 12 different colors. It is not yet understood why stomatopods have almost four times the number of spectral photoreceptors compared with most other animals. It has, however, been suggested that these seemingly redundant photoreceptors could encode color through a new mechanism. Here we compare the spectral sensitivities across five species of stomatopods within the superfamily Gonodactyloidea using intracellular electrophysiological recordings. The results show that the spectral sensitivities across species of stomatopods are remarkably similar apart from some variation in the long-wavelength receptors. We relate these results to spectral sensitivity estimates previously obtained using microspectrophotometry and discuss the variation in the spectral sensitivity maxima (λmax) of the long-wavelength receptors in regard to the previous findings that stomatopods are able to tune their spectral sensitivities according to their respective light environment. We further discuss the similarities of the spectral sensitivities across species of stomatopods in regard to how color information might be processed by their visual systems.

Circularly polarized light detection in stomatopod crustaceans: a comparison of photoreceptors and possible function in six species.

A combination of behavioural and electrophysiological experiments have previously shown that two species of stomatopod, Odontodactylus scyllarus and Gonodactylaceus falcatus, can differentiate between left- and right-handed circularly polarized light (CPL), and between CPL and linearly polarized light (LPL). It remains unknown if these visual abilities are common across all stomatopod species, and if so, how circular polarization sensitivity may vary between and within species. A subsection of the midband, a specialized region of stomatopod eyes, contains distally placed photoreceptor cells, termed R8 (retinular cell number 8). These cells are specifically built with unidirectional microvilli and appear to be angled precisely to convert CPL into LPL. They are mostly quarter-wave retarders for human visible light (400-700 nm), as well as being ultraviolet-sensitive linear polarization detectors. The effectiveness of the R8 cells in this role is determined by their geometric and optical properties. In particular, the length and birefringence of the R8 cells are crucial for retardation efficiency. Here, our comparative studies show that most species investigated have the theoretical ability to convert CPL into LPL, such that the handedness of an incoming circular reflection or signal could be discriminated. One species, Haptosquilla trispinosa, shows less than quarter-wave retardance. Whilst some species are known to produce circularly polarized reflections (some Odontodactylus species and G. falcatus, for example), others do not, so a variety of functions for this ability are worth considering.

Three new records of Nannosquillidae from Taiwan with notes on their ecology (Crustacea, Stomatopoda, Lysiosquilloidea).

The genus Pullosquilla Manning, 1978, including P. litoralis, P. thomassini, and P. pardus, has been found in Taiwan for the first time. All three species live in a subtidal sand flat north of the Bitou fishing port within the Kenting National Park, Taiwan. Adult specimens were examined, illustrated, and photographed. The habitat, which all three species share, is described. The implication of such closely related species sharing the same habitat is discussed.

A shape-anisotropic reflective polarizer in a stomatopod crustacean.

Many biophotonic structures have their spectral properties of reflection 'tuned' using the (zeroth-order) Bragg criteria for phase constructive interference. This is associated with a periodicity, or distribution of periodicities, parallel to the direction of illumination. The polarization properties of these reflections are, however, typically constrained by the dimensional symmetry and intrinsic dielectric properties of the biological materials. Here we report a linearly polarizing reflector in a stomatopod crustacean that consists of 6-8 layers of hollow, ovoid vesicles with principal axes of ~550 nm, ~250 nm and ~150 nm. The reflection of unpolarized normally incident light is blue/green in colour with maximum reflectance wavelength of 520 nm and a degree of polarization greater than 0.6 over most of the visible spectrum. We demonstrate that the polarizing reflection can be explained by a resonant coupling with the first-order, in-plane, Bragg harmonics. These harmonics are associated with a distribution of periodicities perpendicular to the direction of illumination, and, due to the shape-anisotropy of the vesicles, are different for each linear polarization mode. This control and tuning of the polarization of the reflection using shape-anisotropic hollow scatterers is unlike any optical structure previously described and could provide a new design pathway for polarization-tunability in man-made photonic devices.

Atmospheric concentrations of persistent organic pollutants over the Pacific Ocean near southern Taiwan and the northern Philippines.

This study investigates the atmospheric occurrence of persistent organic pollutants (POPs) over the Pacific Ocean near southern Taiwan and the northern Philippines. We determined sixty-six compounds, including polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), dioxin-like polychlorinated biphenyls (DLPCBs), polybrominated diphenyl ethers (PBDEs), as well as polychlorinated diphenyl ethers (PCDEs), polybrominated dibenzo-p-dioxins and dibenzofurans (PBDD/Fs), and polybrominated biphenyls (PBBs), in air samples simultaneously collected from the offshore oceanic atmosphere (n=6) and over a rural area (n=2). We calculated the atmospheric World Health Organization 2005 toxic equivalency levels (WHO2005-TEQ), for the total dioxin-like POPs, including PCDD/Fs, DLPCBs, and PBDD/Fs, being 0.00612 pg WHO2005-TEQ/m(3) and 0.0138 pg WHO2005-TEQ/m(3) over the ocean and land, respectively. We found unexpected lower averaged atmospheric PBDE concentrations in the rural area (15.9 pg/m(3)) than over the ocean (31.1 pg/m(3)) due to higher levels of the BDE209 congener, although the difference was not statistically significant. We have compared and reported our field results with previously published datasets over the global oceans, which suggest PCBs and PBDEs are the dominant chemical contaminants in the global oceanic atmosphere among these halogenated POPs (e.g. PCBs and Σdi-hepta PBDEs could be found in the range of 0.09-48.7 and 8.07-94.0 pg/m(3), respectively, including our dataset). However, there are still very few investigations on the global atmospheric levels of PBDD/Fs, PCDEs and PBBs and our data sums to these earlier studies. Finally, we point out that the halogenated POPs originated from Taiwan or the continental East Asia which could easily reach remote ocean sites via atmospheric transport.

Spectral sensitivities and color signals in a polymorphic damselfly.

Animal communication relies on conspicuous signals and compatible signal perception abilities. Good signal perception abilities are particularly important for polymorphic animals where mate choice can be a challenge. Behavioral studies suggest that polymorphic damselflies use their varying body colorations and/or color patterns as communication signal for mate choice and to control mating frequencies. However, solid evidence for this hypothesis combining physiological with spectral and behavioral data is scarce. We investigated this question in the Australian common blue tail damselfly, Ischnura heterosticta, which has pronounced female-limited polymorphism: andromorphs have a male-like blue coloration and gynomorphs display green/grey colors. We measured body color reflectance and investigated the visual capacities of each morph, showing that I. heterosticta have at least three types of photoreceptors sensitive to UV, blue, and green wavelength, and that this visual perception ability enables them to detect the spectral properties of the color signals emitted from the various color morphs in both males and females. We further demonstrate that different color morphs can be discriminated against each other and the vegetation based on color contrast. Finally, these findings were supported by field observations of natural mating pairs showing that mating partners are indeed chosen based on their body coloration. Our study provides the first comprehensive evidence for the function of body coloration on mate choice in polymorphic damselflies.

A different form of color vision in mantis shrimp.

One of the most complex eyes in the animal kingdom can be found in species of stomatopod crustaceans (mantis shrimp), some of which have 12 different photoreceptor types, each sampling a narrow set of wavelengths ranging from deep ultraviolet to far red (300 to 720 nanometers). Functionally, this chromatic complexity has presented a mystery. Why use 12 color channels when three or four are sufficient for fine color discrimination? Behavioral wavelength discrimination tests (Δλ functions) in stomatopods revealed a surprisingly poor performance, ruling out color vision that makes use of the conventional color-opponent coding system. Instead, our experiments suggest that stomatopods use a previously unknown color vision system based on temporal signaling combined with scanning eye movements, enabling a type of color recognition rather than discrimination.

A novel function for a carotenoid: astaxanthin used as a polarizer for visual signalling in a mantis shrimp.

Biological signals based on color patterns are well known, but some animals communicate by producing patterns of polarized light. Known biological polarizers are all based on physical interactions with light such as birefringence, differential reflection or scattering. We describe a novel biological polarizer in a marine crustacean based on linear dichroism of a carotenoid molecule. The red-colored, dichroic ketocarotenoid pigment astaxanthin is deposited in the antennal scale of a stomatopod crustacean, Odontodactylus scyllarus. Positive correlation between partial polarization and the presence of astaxanthin indicates that the antennal scale polarizes light with astaxanthin. Both the optical properties and the fine structure of the polarizationally active cuticle suggest that the dipole axes of the astaxanthin molecules are oriented nearly normal to the surface of the antennal scale. While dichroic retinoids are used as visual pigment chromophores to absorb and detect polarized light, this is the first demonstration of the use of a carotenoid to produce a polarizing signal. By using the intrinsic dichroism of the carotenoid molecule and orienting the molecule in tissue, nature has engineered a previously undescribed form of biological polarizer.

Behavioural relevance of polarization sensitivity as a target detection mechanism in cephalopods and fishes.

Aquatic habitats are rich in polarized patterns that could provide valuable information about the environment to an animal with a visual system sensitive to polarization of light. Both cephalopods and fishes have been shown to behaviourally respond to polarized light cues, suggesting that polarization sensitivity (PS) may play a role in improving target detection and/or navigation/orientation. However, while there is general agreement concerning the presence of PS in cephalopods and some fish species, its functional significance remains uncertain. Testing the role of PS in predator or prey detection seems an excellent paradigm with which to study the contribution of PS to the sensory assets of both groups, because such behaviours are critical to survival. We developed a novel experimental set-up to deliver computer-generated, controllable, polarized stimuli to free-swimming cephalopods and fishes with which we tested the behavioural relevance of PS using stimuli that evoke innate responses (such as an escape response from a looming stimulus and a pursuing behaviour of a small prey-like stimulus). We report consistent responses of cephalopods to looming stimuli presented in polarization and luminance contrast; however, none of the fishes tested responded to either the looming or the prey-like stimuli when presented in polarization contrast.

Circular polarization vision in a stomatopod crustacean.

We describe the addition of a fourth visual modality in the animal kingdom, the perception of circular polarized light. Animals are sensitive to various characteristics of light, such as intensity, color, and linear polarization [1, 2]. This latter capability can be used for object identification, contrast enhancement, navigation, and communication through polarizing reflections [2-4]. Circularly polarized reflections from a few animal species have also been known for some time [5, 6]. Although optically interesting [7, 8], their signal function or use (if any) was obscure because no visual system was known to detect circularly polarized light. Here, in stomatopod crustaceans, we describe for the first time a visual system capable of detecting and analyzing circularly polarized light. Four lines of evidence-behavior, electrophysiology, optical anatomy, and details of signal design-are presented to describe this new visual function. We suggest that this remarkable ability mediates sexual signaling and mate choice, although other potential functions of circular polarization vision, such as enhanced contrast in turbid environments, are also possible [7, 8]. The ability to differentiate the handedness of circularly polarized light, a visual feat never expected in the animal kingdom, is demonstrated behaviorally here for the first time.

Spectral and spatial properties of polarized light reflections from the arms of squid (Loligo pealeii) and cuttlefish (Sepia officinalis L.).

On every arm of cuttlefish and squid there is a stripe of high-reflectance iridophores that reflects highly polarized light. Since cephalopods possess polarization vision, it has been hypothesized that these polarized stripes could serve an intraspecific communication function. We determined how polarization changes when these boneless arms move. By measuring the spectral and polarizing properties of the reflected light from samples at various angles of tilt and rotation, we found that the actual posture of the arm has little or no effect on partial polarization or the e-vector angle of the reflected light. However, when the illumination angle changed, the partial polarization of the reflected light also changed. The spectral reflections of the signals were also affected by the angle of illumination but not by the orientation of the sample. Electron microscope samples showed that these stripes are composed of several groups of multilayer platelets within the iridophores. The surface normal to each group is oriented at a different angle, which produces essentially constant reflection of polarized light over a range of viewing angles. These results demonstrate that cuttlefish and squid could send out reliable polarization signals to a receiver regardless of arm orientation.

Light habitats and the role of polarized iridescence in the sensory ecology of neotropical nymphalid butterflies (Lepidoptera: Nymphalidae).

The exploitation of polarized light may increase perceived visual contrast independent of spectrum and intensity and thus have adaptive value in forest habitats, where illumination varies greatly in brightness and spectral properties. Here we investigate the extent to which Costa Rican butterflies of the family Nymphalidae exhibit polarized wing reflectance and evaluate the types of habitats in which the trait is commonly found. We also examine the degree of polarized reflectance of wing patterns in representative species belonging to the nymphalid subfamilies Charaxinae, Heliconiinae, Morphinae and Nymphalinae. Polarized reflectance was evaluated using museum specimens illuminated with a light source that simulated the spectrum of ambient sunlight and viewed through a polarized filter. Of the 144 species examined, 75 species exhibited polarized reflectance patterns. These species were significantly more likely to occupy forest habitats than open habitats. A concentrated changes test performed on a phylogeny of the Nymphalidae, with the Papilionidae as an outgroup, provides further support for the correlated evolution of polarized iridescence and life in a forest light environment. These results are consistent with the hypothesis that the production and detection of polarized light may have adaptive communicative value in those species inhabiting forest habitats with complex light conditions. The potential utility of polarized iridescence and iridescent wing coloration within differing ambient spectral environments is discussed to provide a basis for future investigation of the polarized light ecology of butterflies.

Polarization vision and its role in biological signaling.

Visual pigments, the molecules in photoreceptors that initiate the process of vision, are inherently dichroic, differentially absorbing light according to its axis of polarization. Many animals have taken advantage of this property to build receptor systems capable of analyzing the polarization of incoming light, as polarized light is abundant in natural scenes (commonly being produced by scattering or reflection). Such polarization sensitivity has long been associated with behavioral tasks like orientation or navigation. However, only recently have we become aware that it can be incorporated into a high-level visual perception akin to color vision, permitting segmentation of a viewed scene into regions that differ in their polarization. By analogy to color vision, we call this capacity polarization vision. It is apparently used for tasks like those that color vision specializes in: contrast enhancement, camouflage breaking, object recognition, and signal detection and discrimination. While color is very useful in terrestrial or shallow-water environments, it is an unreliable cue deeper in water due to the spectral modification of light as it travels through water of various depths or of varying optical quality. Here, polarization vision has special utility and consequently has evolved in numerous marine species, as well as at least one terrestrial animal. In this review, we consider recent findings concerning polarization vision and its significance in biological signaling.