Localization of multiple opsins in ocular and non-ocular tissues of deep-sea shrimps and the first evidence of co-localization in a rhabdomeric R8 cell (Caridea: Oplophoroidea).

Bioluminescence is a prevalent phenomenon throughout the marine realm and is often the dominant source of light in mesophotic and aphotic depth horizons. Shrimp belonging to the superfamily Oplophoroidea are mesopelagic, perform diel vertical migration, and secrete a bright burst of bioluminescent mucous when threatened. Species in the family Oplophoridae also possess cuticular light-emitting photophores presumably for camouflage via counter-illumination. Many species within the superfamily express a single visual pigment in the retina, consistent with most other large-bodied mesopelagic crustaceans studied to date. Photophore-bearing species have an expanded visual opsin repertoire and dual-sensitivity visual systems, as evidenced by transcriptomes and electroretinograms. In this study, we used immunohistochemistry to describe opsin protein localization in the retinas of four species of Oplophoroidea and non-ocular tissues of Janicella spinicauda. Our results show that Acanthephyra purpurea (Acanthephyridae) retinas possess LWS-only photoreceptors, consistent with the singular peak sensitivity previously reported. Oplophoridae retinas contain two opsin clades (LWS and MWS) consistent with dual-sensitivity. Oplophorus gracilirostris and Systellaspis debilis have LWS in the proximal rhabdom (R1-7 cells) and MWS2 localized in the distal rhabdom (R8 cell). Surprisingly, Janicella spinicauda has LWS in the proximal rhabdom (R1-7) and co-localized MWS1 and MWS2 opsin paralogs in the distal rhabdom, providing the first evidence of co-localization of opsins in a crustacean rhabdomeric R8 cell. Furthermore, opsins were found in multiple non-ocular tissues of J. spinicauda, including nerve, tendon, and photophore. These combined data demonstrate evolutionary novelty and opsin duplication within Oplophoridae, with implications for visual ecology, evolution in mesophotic environments, and a mechanistic understanding of adaptive counter-illumination using photophore bioluminescence.

Comparative mitogenomic analysis of subterranean and surface amphipods (Crustacea, Amphipoda) with special reference to the family Crangonyctidae.

Mitochondrial genomes play important roles in studying genome evolution, phylogenetic analyses, and species identification. Amphipods (Class Malacostraca, Order Amphipoda) are one of the most ecologically diverse crustacean groups occurring in a diverse array of aquatic and terrestrial environments globally, from freshwater streams and lakes to groundwater aquifers and the deep sea, but we have a limited understanding of how habitat influences the molecular evolution of mitochondrial energy metabolism. Subterranean amphipods likely experience different evolutionary pressures on energy management compared to surface-dwelling taxa that generally encounter higher levels of predation and energy resources and live in more variable environments. In this study, we compared the mitogenomes, including the 13 protein-coding genes involved in the oxidative phosphorylation (OXPHOS) pathway, of surface and subterranean amphipods to uncover potentially different molecular signals of energy metabolism between surface and subterranean environments in this diverse crustacean group. We compared base composition, codon usage, gene order rearrangement, conducted comparative mitogenomic and phylogenomic analyses, and examined evolutionary signals of 35 amphipod mitogenomes representing 13 families, with an emphasis on Crangonyctidae. Mitogenome size, AT content, GC-skew, gene order, uncommon start codons, location of putative control region (CR), length of rrnL and intergenic spacers differed between surface and subterranean amphipods. Among crangonyctid amphipods, the spring-dwelling Crangonyx forbesi exhibited a unique gene order, a long nad5 locus, longer rrnL and rrnS loci, and unconventional start codons. Evidence of directional selection was detected in several protein-encoding genes of the OXPHOS pathway in the mitogenomes of surface amphipods, while a signal of purifying selection was more prominent in subterranean species, which is consistent with the hypothesis that the mitogenome of surface-adapted species has evolved in response to a more energy demanding environment compared to subterranean amphipods. Overall, gene order, locations of non-coding regions, and base-substitution rates points to habitat as an important factor influencing the evolution of amphipod mitogenomes.

Secondary not subordinate: Opsin localization suggests possibility for color sensitivity in salticid secondary eyes.

The principal eyes of jumping spiders (Salticidae) integrate a dual-lens system, a tiered retinal matrix with multiple photoreceptor classes and muscular control of retinal movements to form high resolution images, extract color information, and dynamically evaluate visual scenes. While much work has been done to characterize these more complex principal anterior eyes, little work has investigated the three other pairs of simpler secondary eyes: the anterior lateral eye pair and two posterior (lateral and median) pairs of eyes. We investigated the opsin protein component of visual pigments in the eyes of three species of salticid using transcriptomics and immunohistochemistry. Based on characterization and localization of a set of three conserved opsins (Rh1 - green sensitive, Rh2 - blue sensitive, and Rh3 - ultraviolet sensitive) we have identified potential photoreceptors for blue light detection in the eyes of two out of three species: Menemerus bivittatus (Chrysillini) and Habrocestum africanum (Hasarinii). Additionally, the photoreceptor diversity of the secondary eyes exhibits more variation than previous estimates, particularly for the small, posterior median eyes previously considered vestigial in some species. In all three species investigated the lateral eyes were dominated by green-sensitive visual pigments (RH1 opsins), while the posterior median retinas were dominated by opsins forming short-wavelength sensitive visual pigments (e.g. RH2 and/or RH3/RH4). There was also variation among secondary eye types and among species in the distribution of opsins in retinal photoreceptors, particularly for the putatively blue-sensitive visual pigment formed from RH2. Our findings suggest secondary eyes have the potential for color vision, with observed differences between species likely associated with different ecologies and visual tasks.

Molecular Evolution of Malacostracan Short Wavelength Sensitive Opsins.

Investigations of the molecular mechanisms behind detection of short, and particularly ultraviolet, wavelengths in arthropods have relied heavily on studies from insects due to the relative ease of heterologous expression of modified opsin proteins in model organisms like Drosophila. However, species outside of the Insecta can provide information on mechanisms for spectral tuning as well as the evolutionary history of pancrustacean visual pigments. Here we investigate the basis of spectral tuning in malacostracan short wavelength sensitive (SWS) opsins using phylogenetic comparative methods. Tuning sites that may be responsible for the difference between ultraviolet (UV) and violet visual pigment absorbance in the Malacostraca are identified, and the idea that an amino acid polymorphism at a single site is responsible for this shift is shown to be unlikely. Instead, we suggest that this change in absorbance is accomplished through multiple amino acid substitutions. On the basis of our findings, we conducted further surveys to identify spectral tuning mechanisms in the order Stomatopoda where duplication of UV opsins has occurred. Ancestral state reconstructions of stomatopod opsins from two main clades provide insight into the amino acid changes that lead to differing absorption by the visual pigments they form, and likely contribute the basis for the wide array of UV spectral sensitivities found in this order.

Relationships between local variability in parasite communities of the black-spotted croaker (Protonibea diacanthus) (Teleostei: Sciaenidae) and host population structure and seasonality.

We evaluated spatial and temporal variability in parasite communities from the commercially important tropical marine fish the black-spotted croaker (Protonibea diacanthus) (Teleostei: Sciaenidae) to examine its population structure off the coast of the Northern Territory, Australia. Differences in parasite assemblage between four locations, across three seasons of the year, were used to evaluate the degree of connectivity of the sciaenid across coastal study areas. Analysis of parasite prevalence and mean intensity in these fish suggested the four sampling sites are distinct host populations. Across time, parasite assemblages at the four sites were distinct during the mid-dry (April-August) and build-up (September-November) seasons. During the wet season (December-March) there was substantial overlap in the parasite assemblages at three of the four sites indicating that fish population mixing may be occurring. Parasite assemblages at one nearshore site remained distinct across spatial and temporal scales. Our findings support the utility of parasitic organisms for elucidating the population structure of host species and reiterate the need to account for both spatial and temporal variability when performing stock discrimination analyses.

Increasing complexity of opsin expression across stomatopod development.

Stomatopods are well studied for their unique visual systems, which can consist of up to 16 different photoreceptor types and 33 opsin proteins expressed in the adults of some species. The light-sensing abilities of larval stomatopods are comparatively less well understood with limited information about the opsin repertoire of these early-life stages. Early work has suggested that larval stomatopods may not possess the extensive light detection abilities found in their adult counterparts. However, recent studies have shown that these larvae may have more complex photosensory systems than previously thought. To examine this idea at the molecular level, we characterized the expression of putative light-absorbing opsins across developmental stages, from embryo to adult, in the stomatopod species Pullosquilla thomassini using transcriptomic methods with a special focus on ecological and physiological transition periods. Opsin expression during the transition from the larval to the adult stage was further characterized in the species Gonodactylaceus falcatus. Opsin transcripts from short, middle, and long wavelength-sensitive clades were found in both species, and analysis of spectral tuning sites suggested differences in absorbance within these clades. This is the first study to document the changes in opsin repertoire across development in stomatopods, providing novel evidence for light detection across the visual spectrum in larvae.

Description of two new species of Diplectanum Diesing, 1858 (Monogenea: Diplectanidae) collected from Protonibea diacanthus (Lacepède, 1802) (Teleostei: Sciaenidae) from waters off northern Australia.

Two new species of the family Diplectanidae Monticelli, 1903 from the gills of Protonibea diacanthus (Lacepède, 1802) (Teleostei: Sciaenidae) off the northern Australian coast are described. Previous studies have either morphological or genetic results, whereas this study combines morphological and advanced molecular methods to provide the first detailed descriptions for species of Diplectanum Diesing, 1858 from Australia utilising both methodologies. Two new species, Diplectanum timorcanthus n. sp. and Diplectanum diacanthi n. sp., are morphologically described and genetically characterised using the partial nuclear 28S ribosomal RNA gene (28S rRNA) and the internal transcribed spacer 1 (ITS1) partial sequence.

Physiological and behavioral evidence for multiple spectral channels in the larval stomatopod visual system.

Larval stomatopods have generally been described as having a typical larval crustacean compound eye, which lacks the visual pigment diversity and morphological specializations of the well-studied stomatopod adult eye. However, recent work has suggested that larval stomatopod eyes are more complex than previously described. In this study, we provide physiological and behavioral evidence of at least three distinct photoreceptor classes in three species of larval stomatopods: Gonodactylellus n. sp., Gonodactylaceus falcatus and Pullosquilla n. sp. First, electroretinogram recordings were used to measure the spectral sensitivity of each species. Evidence for at least three spectral classes were identified in each: an ultraviolet, peaking at 340-376 nm; a short-wavelength blue, peaking at 455-464 nm; and a long-wavelength orange, peaking at 576-602 nm. Next, the behavioral response to light was investigated. We found that each species demonstrated positive phototactic responses to monochromatic stimuli across the UV-visible spectrum. In wavelength preference trials, distinct preferences among species were identified when different colored light stimuli were presented simultaneously. All species displayed a strong response to the UV stimulus, as well as responses to blue and orange stimuli, although at different response strengths, but no response to green. The results of this study demonstrate that larval stomatopods not only have multiple physiologically active spectral classes but they also display clear and distinct responses to wavelengths across the spectrum. We propose that the spectral classes demonstrated in each are related to visually guided ecological tasks of the larvae, which may differ between species.

Genomic Comparisons Reveal Selection Pressure and Functional Variation Between Nutritional Endosymbionts of Cave-Adapted and Epigean Hawaiian Planthoppers.

Planthoppers in the family Cixiidae (Hemiptera: Auchenorrhyncha: Fulgoromorpha) harbor a diverse set of obligate bacterial endosymbionts that provision essential amino acids and vitamins that are missing from their plant-sap diet. "Candidatus Sulcia muelleri" and "Ca. Vidania fulgoroidea" have been associated with cixiid planthoppers since their origin within the Auchenorrhyncha, whereas "Ca. Purcelliella pentastirinorum" is a more recent endosymbiotic acquisition. Hawaiian cixiid planthoppers occupy diverse habitats including lava tube caves and shrubby surface landscapes, which offer different nutritional resources and environmental constraints. Genomic studies have focused on understanding the nutritional provisioning roles of cixiid endosymbionts more broadly, yet it is still unclear how selection pressures on endosymbiont genes might differ between cixiid host species inhabiting such diverse landscapes, or how variation in selection might impact symbiont evolution. In this study, we sequenced the genomes of Sulcia, Vidania, and Purcelliella isolated from both surface and cave-adapted planthopper hosts from the genus Oliarus. We found that nutritional biosynthesis genes were conserved in Sulcia and Vidania genomes in inter- and intra-host species comparisons. In contrast, Purcelliella genomes retain different essential nutritional biosynthesis genes between surface- and cave-adapted planthopper species. Finally, we see the variation in selection pressures on symbiont genes both within and between host species, suggesting that strong coevolution between host and endosymbiont is associated with different patterns of molecular evolution on a fine scale that may be associated with the host diet.

Investigation of the ultrastructures and retinal arrangements of larval stomatopod eyes.

Though the transparent apposition eyes of larval stomatopod crustaceans lack most of the unique retinal specializations known from their adult counterparts, increasing evidence suggests that these tiny pelagic organisms possess their own version of retinal complexity. In this paper, we examined the structural organization of larval eyes in six species of stomatopod crustaceans across three stomatopod superfamilies using transmission electron microscopy. The primary focus was to examine retinular cell arrangement of the larval eyes and characterize the presence of an eighth retinular cell (R8), which is typically responsible for UV vision in crustaceans. For all species investigated, we identified R8 photoreceptor cells positioned distal to the main rhabdom of R1-7 cells. This is the first evidence that R8 photoreceptor cells exist in larval stomatopod retinas, and among the first identified in any larval crustacean. Considering recent studies that identified UV sensitivity in larval stomatopods, we propose that this sensitivity is driven by this putative R8 photoreceptor cell. Additionally, we identified a potentially unique crystalline cone structure in each of the species examined, the function of which is still not understood.

Photonic tinkering in the open ocean.

Light-manipulating materials are discovered in the eyeglitter of pelagic crustaceans.

Genome Sequence of Arthrobacter Phage NathanVaag.

We report the genome sequence of bacteriophage NathanVaag, an actinobacteriophage isolated from soil in El Paso, Texas, that infects Arthrobacter sp. strain ATCC 21022. The 49,645-bp genome contains 73 predicted protein-coding genes. Based on gene content similarity to phages in the Actinobacteriophage Database, NathanVaag is assigned to phage cluster AO1.

Crustacean conundrums: a review of opsin diversity and evolution.

Knowledge of crustacean vision is lacking compared to the more well-studied vertebrates and insects. While crustacean visual systems are typically conserved morphologically, the molecular components (i.e. opsins) remain understudied. This review aims to characterize opsin diversity across crustacean lineages for an integrated view of visual system evolution. Using publicly available data from 95 species, we identified opsin sequences and classified them by clade. Our analysis produced 485 putative visual opsins and 141 non-visual opsins. The visual opsins were separated into six clades: long wavelength sensitive (LWS), middle wavelength sensitive (MWS) 1 and 2, short wavelength or ultraviolet sensitive (SWS/UVS) and a clade of thecostracan opsins, with multiple LWS and MWS opsin copies observed. The SWS/UVS opsins were relatively conserved in most species. The crustacean classes Cephalocarida, Remipedia and Hexanauplia exhibited reduced visual opsin diversity compared to others, with the malacostracan decapods having the highest opsin diversity. Non-visual opsins were identified from all investigated classes except Cephalocarida. Additionally, a novel clade of non-visual crustacean-specific, R-type opsins (Rc) was discovered. This review aims to provide a framework for future research on crustacean vision, with an emphasis on the need for more work in spectral characterization and molecular analysis. This article is part of the theme issue 'Understanding colour vision: molecular, physiological, neuronal and behavioural studies in arthropods'.

Colour vision in stomatopod crustaceans.

The stomatopod crustaceans, or mantis shrimps, are colourful marine invertebrate predators. Their unusual compound eyes have dorsal and ventral regions resembling typical crustacean apposition designs separated by a unique region called the midband that consists of from two to six parallel rows of ommatidia. In species with six-row midbands, the dorsal four rows are themselves uniquely specialized for colour analysis. Rhabdoms of ommatidia in these rows are longitudinally divided into three distinct regions: an apical ultraviolet (UV) receptor, a shorter-wavelength middle tier receptor and a longer-wavelength proximal tier receptor. Each of the total of 12 photoreceptors has a different spectral sensitivity, potentially contributing to a colour-vision system with 12 channels. Mantis shrimps can discriminate both human-visible and UV colours, but with limited precision compared to other colour-vision systems. Here, we review the structure and function of stomatopod colour vision, examining the types of receptors present in a species, the spectral tuning of photoreceptors both within and across species, the neural analysis of colour and the genetics underlying the multiple visual pigments used for colour vision. Even today, after many decades of research into the colour vision of stomatopods, much of its operation and its use in nature remain a mystery. This article is part of the theme issue 'Understanding colour vision: molecular, physiological, neuronal and behavioural studies in arthropods'.

Immediate effects of superficial dry needling of the trigeminal nerve innervation field for participants with cervicogenic headache. A randomized controlled trial.

BACKGROUND: Cervicogenic headache (CGH) is a common condition with a neuroanatomical basis involving the trigeminal nerve. Dry needling (DN) is a safe and effective treatment for CGH but most studies involve deep DN to cervical musculature. OBJECTIVE: The aim of this study was to investigate immediate effects of superficial DN of the trigeminal nerve innervation field on numeric pain rating scale (NPRS), flexion-rotation test (FRT), cervical range of motion (AROM), and pain-pressure threshold (PPT) of right (R) and left (L) supraorbital (SO), and right (R) and left (L) greater occipital (GO) nerves in participants with CGH. METHODS: A parallel controlled randomized design involving 30 participants with CGH received either superficial DN (N = 17) or sham DN (N = 13). Participants and outcome assessors were blind to group assignment. Wilcoxon signed rank analyzed within-group effects and Mann-Whitney U analyzed between-group. RESULTS: Statistically significant between-group differences were observed for NPRS (P < .001) and AROM (P < .006) favoring DN and were clinically meaningful. Right and left Flexion rotation tests (FRT) outcomes were non-significant (P = .137) but clinically meaningful. No differences were observed for PPT over: R SO (P = .187); L SO (P = .052); R GO (P = .187); or L GO (P = .052). Between-group effect sizes across variables were moderate to large (0.53-1.4) but confidence intervals were wide. CONCLUSION: Superficial DN targeting the innervation field of the trigeminal nerve improves clinical outcomes in patients with CGH. Only the immediate effects were analyzed and the sample size was small. Larger, longer-term assessments are needed comparing superficial DN of the trigeminal innervation field and other conservative interventions for CGH.

The complete mitochondrial genomes and phylogenetic analysis of two Nycteribiidae bat flies (Diptera: Hippoboscoidea).

We sequenced the complete mitochondrial genomes of two bat fly species within the Nycteribiidae (Diptera: Hippoboscoidea) - Dipseliopoda setosa (Cyclopodiinae) and Basilia ansifera (Nycteribiinae). Both mitogenomes were complete and contained 13 protein-coding genes, 22 tRNAs, and two rRNAs. Relative to the inferred ancestral gene order of dipteran mitochondrial genomes, no rearrangements were identified in either species. There were large differences in size between the two genomes, with D. setosa having a larger genome (19,164 bp) than B. ansifera (16,964 bp); both species had larger genomes than two previously published Streblidae bat fly species (e.g., Paradyschiria parvula and Paratrichobius longicrus). The increased genome sizes were due to expansions in the control region and the non-coding region downstream of the light-strand origin of replication. Additional differences between the two mitogenomes included a significantly longer cox3 gene in B. ansifera and a longer nad1 gene in D. setosa. Interestingly, both genomes also had the lowest GC content (D. setosa - 15.9%; B. ansifera - 17.0%) of any available Hippoboscoidea mitochondrial genome (18.8-23.9%). These mitogenomes represent the first sequences from species within the bat fly family Nycteribiidae. The sequence data here will provide a foundation for continued studies of genome evolution more generally within obligate blood-feeding ectoparasites, and specifically for the bat flies as vectors of significant 'bat-associated' viruses and microorganisms.

The Gluopsins: Opsins without the Retinal Binding Lysine.

Opsins allow us to see. They are G-protein-coupled receptors and bind as ligand retinal, which is bound covalently to a lysine in the seventh transmembrane domain. This makes opsins light-sensitive. The lysine is so conserved that it is used to define a sequence as an opsin and thus phylogenetic opsin reconstructions discard any sequence without it. However, recently, opsins were found that function not only as photoreceptors but also as chemoreceptors. For chemoreception, the lysine is not needed. Therefore, we wondered: Do opsins exists that have lost this lysine during evolution? To find such opsins, we built an automatic pipeline for reconstructing a large-scale opsin phylogeny. The pipeline compiles and aligns sequences from public sources, reconstructs the phylogeny, prunes rogue sequences, and visualizes the resulting tree. Our final opsin phylogeny is the largest to date with 4956 opsins. Among them is a clade of 33 opsins that have the lysine replaced by glutamic acid. Thus, we call them gluopsins. The gluopsins are mainly dragonfly and butterfly opsins, closely related to the RGR-opsins and the retinochromes. Like those, they have a derived NPxxY motif. However, what their particular function is, remains to be seen.

Genome Sequence of Arthrobacter globiformis Phage KeAlii from Hawai'i.

Here, we report the genome sequence of bacteriophage KeAlii, a Siphoviridae that infects Arthrobacter globiformis strain B-2979, from Honolulu, Hawai'i. The 41,850-bp genome contains 66 predicted protein-coding genes and 1 gene that encodes a tRNA for tryptophan. Genome comparisons suggest KeAlii is closely related to actinobacteriophage Adolin.

Complete mitochondrial genomes and phylogenetic analysis of the Hawaiian planthoppers Iolania perkinsi and Oliarus cf. filicicola (Hemiptera: Cixiidae).

We sequenced the complete mitochondrial genomes of one Iolania perkinsi (Kirkaldy 1902) and one Oliarus cf. filicicola (Kirkaldy 1909) planthopper (Hemiptera: Fulgoroidea: Cixiidae) from Volcano Village, located on the eastern flank of Mauna Loa. The I. perkinsi complete mitogenome is 14,949 bp in length and contains 13 protein-coding genes, 22 tRNAs and 2 rRNAs. The O. cf. filicicola nearly complete mitogenome is 15,196 bp in length due to an expanded (but incomplete) control region, and contains all of the typical metazoan genes: 13 protein-coding genes, 22 tRNAs and two rRNAs. Relative to the inferred ancestral gene order of insect mitochondrial genomes, no rearrangements were identified in either species. In addition to the shorter control region in I. perkinsi, the differences between the two mitogenomes consist of longer cox1, cox2, cob, nad1, nad5, nad6 genes but shorter nad4 gene in I. perkinsi relative to O. cf. filicicola. These mitogenomes represent the first sequences from species within the Hawaiian Cixiidae. The sequence data here will provide a foundation for continued studies of speciation patterns and dynamics of evolutionary radiation across Hawaiian planthoppers.