A genetically tractable jellyfish model for systems and evolutionary neuroscience.

Jellyfish are radially symmetric organisms without a brain that arose more than 500 million years ago. They achieve organismal behaviors through coordinated interactions between autonomously functioning body parts. Jellyfish neurons have been studied electrophysiologically, but not at the systems level. We introduce Clytia hemisphaerica as a transparent, genetically tractable jellyfish model for systems and evolutionary neuroscience. We generate stable F1 transgenic lines for cell-type-specific conditional ablation and whole-organism GCaMP imaging. Using these tools and computational analyses, we find that an apparently diffuse network of RFamide-expressing umbrellar neurons is functionally subdivided into a series of spatially localized subassemblies whose synchronous activation controls directional food transfer from the tentacles to the mouth. These data reveal an unanticipated degree of structured neural organization in this species. Clytia affords a platform for systems-level studies of neural function, behavior, and evolution within a clade of marine organisms with growing ecological and economic importance.

High concentrations of floating neustonic life in the plastic-rich North Pacific Garbage Patch.

Floating life (obligate neuston) is a core component of the ocean surface food web. However, only 1 region of high neustonic abundance is known so far, the Sargasso Sea in the Subtropical North Atlantic gyre, where floating life provides critical habitat structure and ecosystem services. Here, we hypothesize that floating life is also concentrated in other gyres with converging surface currents. To test this hypothesis, we collected samples through the eastern North Pacific Subtropical Gyre in the area of the North Pacific "Garbage Patch" (NPGP) known to accumulate floating anthropogenic debris. We found that densities of floating life were higher inside the central NPGP than on its periphery and that there was a positive relationship between neuston abundance and plastic abundance for 3 out of 5 neuston taxa, Velella, Porpita, and Janthina. This work has implications for the ecology of subtropical oceanic gyre ecosystems.

Isolation and Characterization of Feeding-Deficient Strains in Inbred Lines of the Hydrozoan Jellyfish Cladonema pacificum.

Feeding behavior in cnidarians has been studied as a model experimental system in physiology and neurobiology. Although the feeding response in cnidarians, such as Hydra, is triggered by chemical signals, the underlying molecular mechanisms that ensure their precise execution are not well understood. It could be largely due to the lack of genetic analysis in cnidarian experimental systems. Cladonema pacificum is a hydrozoan jellyfish that is easy to maintain and cross for genetic analysis in the laboratory. To establish C. pacificum as a model experimental animal in cnidarians, we have been inbreeding strains of jellyfish. Here, we document our progress in developing C. pacificum inbred lines and feeding-defective strains that we isolated in the course of inbreeding. In the inbred lines, an increasing number of feeding-defective strains appeared as descending generations and finally all the F5 progeny showed a feeding-deficient phenotype presumably owing to inbreeding depression. Feeding behaviors of these strains were analyzed by video microscopy and we found that the feeding-defective strains captured prey, but could not kill them. After trapping prey, wild-type medusae contracted their tentacles tightly and then bent the tentacles to bring the prey to the mouth; however, feeding-defective medusae rarely contracted their tentacles and did not bend. These feeding-defective phenotypes are caused by lack of stinging nematocytes in their tentacle batteries. These findings furnish a clue to the regulatory aspects of feeding behavior, but also reveal the mechanisms of stinging nematocyte transport in tentacles.

Differential gene expression between functionally specialized polyps of the colonial hydrozoan Hydractinia symbiolongicarpus (Phylum Cnidaria).

BACKGROUND: A colony of the hydrozoan Hydractinia symbiolongicarpus comprises genetically identical yet morphologically distinct and functionally specialized polyp types. The main labor divisions are between feeding, reproduction and defense. In H. symbiolongicarpus, the feeding polyp (called a gastrozooid) has elongated tentacles and a mouth, which are absent in the reproductive polyp (gonozooid) and defensive polyp (dactylozooid). Instead, the dactylozooid has an extended body column with an abundance of stinging cells (nematocysts) and the gonozooid bears gonophores on its body column. Morphological differences between polyp types can be attributed to simple changes in their axial patterning during development, and it has long been hypothesized that these specialized polyps arose through evolutionary alterations in oral-aboral patterning of the ancestral gastrozooid. RESULTS: An assembly of 66,508 transcripts (>200 bp) were generated using short-read Illumina RNA-Seq libraries constructed from feeding, reproductive, and defensive polyps of H. symbiolongicarpus. Using several different annotation methods, approximately 54% of the transcripts were annotated. Differential expression analyses were conducted between these three polyp types to isolate genes that may be involved in functional, histological, and pattering differences between polyp types. Nearly 7 K transcripts were differentially expressed in a polyp-specific manner, including members of the homeodomain, myosin, toxin and BMP gene families. We report the spatial expression of a subset of these polyp-specific transcripts to validate our differential expression analyses. CONCLUSIONS: While potentially originating through simple changes in patterning, polymorphic polyps in Hydractinia are the result of differentially expressed functional, structural, and patterning genes.The differentially expressed genes identified in our study provide a starting point for future investigations of the developmental patterning and functional differences that are displayed in the different polyp types that confer a division of labor within a colony of H. symbiolongicarpus.

The fouling hydroid Ectopleura larynx: a lack of effect of next generation antifouling technologies.

The hydroid Ectopleura larynx is one of the main fouling organisms on salmon aquaculture cages in Norway; this study investigated novel surface materials and microtopographies to deter its settlement. The settlement preferences of hydroid larvae for 12 materials with wettabilities ranging from hydrophobic (54°) to hydrophilic (112°) were tested in a no-choice bioassay. Although settlement differed between materials, with the highest average settlement on polytetrafluoroethylene (95%) and the lowest on untreated polyurethane (53%), no trend regarding the tested wettabilities could be found and none of the tested materials was able to reduce average settlement below 50%. Furthermore, nine high-density polyethylene (HDPE, 100-600 µm microtopographies) and seven polydimethylsiloxane (PDMS; 40-400 µm microtopographies) microtextured surfaces were tested. There was no systematic effect of microtopography on the settlement of E. larynx larvae. However, there was a preference for settlement in channels on PDMS microtopographies between 80 and 300 µm. Similarly, there were no preferences for any of the examined microtopographies in a 12-day field test using PDMS surfaces at a commercial fish farm. The study indicated that neither surface wettability (hydrophilicity-phobicity) nor microtopographies were effective at deterring the settlement of the hydroid E. larynx. The high plasticity of the aboral pole and the hydrorhiza of the hydroids may explain settlement even under unfavourable conditions, highlighting the successful colonisation traits of this dominant biofouling species.

New record and a new species of Lissosabinea Christoffersen, 1988 (Decapoda: Caridea: Crangonidae) from Brazil.

Lissosabinea tridentata (Pequegnat, 1970) known hitherto from the Gulf of Mexico off Florida (24N) and only western Atlantic representative of the genus, is reported here for the first time from much further south, Brazil off the coast of Esprito Santo, Vitria-Trindade Seamount Chain, Montague Bank (20S), between 310 and 391 m. A second western Atlantic species, Lissosabinea christofferseni sp. nov., is described here as new from material collected in the Abrolhos Bank, at depth between 340360 m. One exuviae and one damaged specimen, reported in 1988 from off the coast of Chu, Brazil (34S) (at that time mistakenly referred to as Uruguay) and attributed to Lissosabinea cf. tridentata are herein referred to the new species. It has been clarified that Lissosabinea christofferseni sp. nov. and L. tridentata have a transverse row of teeth adjacent to the posterior margin of the sixth pleonal sternite; in crangonids, such a feature is so far known only in Placopsicrangron formosa Komai Chan, 2009.

Artificial structures as biological "influencers": Hydrozoa and Anthozoa diversity in a Colombian Caribbean Marina.

The Puerto Velero Marina, located on the central Caribbean coast of Colombia, is an example of an artificial structure that serves as a substrate for a vulnerable community such as cnidarians (Hydrozoa and Anthozoa). This study provides the first assessment of corals and other cnidarians inhabiting artificial marine habitats in a marginal environment of the Caribbean of Colombia. The Puerto Velero Marina was built into a 7 km2 sand spit generated by sedimentation at the mouth of the Magdalena River. In this study were recorded 14 cnidarian species, among which were found 48 small colonies of scleractinian corals such as Porites, Siderastrea, Phyllangia, and Astrangia. This initial biodiversity assessment of the artificial structure provides a baseline that highlights the importance of further monitoring programs to identify non-native species that could reach this kind of hard structures.

The abundance of microplastics in cnidaria and ctenophora in the North Sea.

Microplastic (MP) ingestion has been widely recorded in aquatic organisms, but few studies focus on cnidarians and ctenophores, which form a significant contribution to marine trophic interactions. Scyphozoans (Cyanea capillata, C. lamarckii and Aurelia aurita), hydrozoan (Cosmetira pilosella) and ctenophores (Beroe cucumis and Pleurobrachia bachei) collected opportunistically from Orkney, Shetland and the North Sea were thermally disintegrated, with a subsample of ingested plastics analysed using FTIR. A total of 1,986 MPs were counted (94% fibres), the majority (84.4%) in the four cnidarian species. Highest MP concentrations were recorded in B. cucumis (0.956 ml-1), whilst C. pilosella yielded the lowest (0.014 ml-1). The main polymers in digestate were PET and PP, with 27% discounted as non-plastics. In feeding trials, A. aurita ingested a greater quantity of PET fibres (60-80%), compared to nylon (0%) and HDPE fibres (0%). This study demonstrates cnidarians and ctenophores, a largely overlooked group, are a potential route for MPs entry into food webs.

Photochromic Conjugated Microporous Polymer Manifesting Bio-Inspired pcFRET and Logic Gate Functioning.

Design and synthesis of solid-state photochromic materials remain a challenge because of high structural constrain. However, this can be mitigated in attaining structural flexibility by introducing permanent porosity into the system. Here, we report for the first time the design and synthesis of a photochromic conjugated microporous polymer (pcCMP) by assembling photochromic dithienylethene aldehyde and benzene-1,3,5-tricarbohydrazide. The yellow photo-isomer pcCMP-O gets converted to a deep-green photo-isomer pcCMP-C by UV-light irradiation, which can be reverted to pcCMP-O by visible light or thermal treatment. Owing to the thermo-irreversible nature, the pcCMP is found to be suitable for designing an INH functioning logic gate. pcCMP-C shows highly enhanced conductivity (92 times) because of enhanced conjugation compared to pcCMP-O. Furthermore, we demonstrate the bio-inspired photo-switchable pcFRET process by encapsulation of a red-emissive green fluorescent protein (gfp) chromophore analogue into the pcCMP. This material shows high processibility and has been exploited further for secret writing.

Two new species of Bargmannia (Pyrostephidae, Physonectae, Siphonophorae).

Two new deep-living species of the genus Bargmannia (Siphonophorae, Physonectae, Pyrostephidae) are described based, almost exclusively, on the nectophores of single specimens collected by ROVs off the west coast of California. The nectophores of B. stenotes sp. nov. were relatively small, up to 11.4 mm in length and, in the preserved condition had very narrow nectosacs. There was a marked bend in the distal part of the preserved nectophore, resulting in the ostium opening upwards. The mature nectophores of B. profunda sp. nov. were almost twice as long as those of B. stenotes and were characterised by the fact that the lower lateral ridges did not join, distally, with the meso-lateral ones. This feature also was present in smaller nectophores of B. amoena but those of B. stenotes, at that stage, did not have a mouth-plate.

Two new species of Hippolyte from the Tropical Central and East Atlantic (Crustacea, Decapoda, Caridea).

Two new species of the caridean shrimp genus Hippolyte Leach, 1814 [in Leach, 1813-14] are described from the Tropical Central and East Atlantic. Hippolyte cedrici sp. nov., from Príncipe and São Tomé, can be distinguished from both the related H. holthuisi Zariquey Álvarez, 1953 and H. varians Leach, 1814 on the basis of rostral dentition, as well as meristics of the ambulatory pereiopods. Hippolyte karenae sp. nov., from St. Helena, is morphologically similar to H. coerulescens (Fabricius, 1775) and H. obliquimanus Dana, 1852, by having a well-developed tooth on the outer angle of the first peduncular article of the antennula. It differs from these species, amongst other characters, primarily in the armature of the ambulatory dactyli. Specimens were collected from hydrozoan, antipatharian and alcyonarian cnidarians.

Rapid and ultrasensitive detection of active thrombin based on the Vmh2 hydrophobin fused to a Green Fluorescent Protein.

A fusion protein designed in order to combine the fluorescence emission of the Green Fluorescent Protein (GFP) with the adhesion ability of the class I hydrophobin Vmh2 was heterologously produced in the yeast Pichia pastoris. The Vmh2-GFP fusion protein has proven to be a smart and effective tool for the study of Vmh2 self-assembling. Since the two proteins were linked by the specific cutting site of the thrombin, the fusion protein was used as the active biological element in the realization of a thrombin biosensor. When the thrombin present in the target solution specifically hydrolyzed its cleavage sequence, a consequent decrease in the fluorescence intensity of the sample could be observed. The Vmh2-GFP based assay allowed quantification of thrombin in solution with a detection limit of 2.27aM. The specificity of the assay with respect to other proteases and proteins granted the measurement of thrombin added to healthy human plasma with same high sensitivity and a limit of detection of 2.3aM. Further advantages of the developed biosensor are the simplicity of its design and preparation, and the low requirements in terms of samples, reagents and time.

Structural but not functional conservation of an immune molecule: a tachylectin-like gene in Hydractinia.

Tachylectin-related proteins are a recently characterized group of pattern recognition molecules, functioning in the innate immunity of various animals, from the ancient sponges to vertebrates. Tachylectins are characterized by six internal tandem repeats forming beta-propeller domains. We have identified and characterized a tachylectin-related gene in the colonial marine hydroid, Hydractinia echinata. The predicted gene product, termed CTRN, contained an N-terminal signal peptide and had a well-conserved tachylectin-like structure. RT-PCR analyses revealed only post-metamorphic expression while no mRNA was detected during embryonic development or in planula larvae. Exposure of colonies to LPS under conditions known to activate an immune response in Hydractinia did not result in upregulation of the gene. In situ hybridization analysis of metamorphosed animals detected CTRN transcripts only in a small subpopulation of neurons and their precursor cells, localized in a ring-like structure around the mouth of polyps. The same ring-like structure of CTRN expressing neurons was also observed in young polyp buds, predicting the position of the future mouth. This type of expression pattern can hardly be attributed to an immune-relevant gene. Thus, despite high structural similarity to tachylectins, this cnidarian member of this group seems to be an exception to all other tachylectins identified so far as it seems to have no function in cnidarian innate immunity.

Drag of Clean and Fouled Net Panels--Measurements and Parameterization of Fouling.

Biofouling is a serious problem in marine aquaculture and it has a number of negative impacts including increased forces on aquaculture structures and reduced water exchange across nets. This in turn affects the behavior of fish cages in waves and currents and has an impact on the water volume and quality inside net pens. Even though these negative effects are acknowledged by the research community and governmental institutions, there is limited knowledge about fouling related effects on the flow past nets, and more detailed investigations distinguishing between different fouling types have been called for. This study evaluates the effect of hydroids, an important fouling organism in Norwegian aquaculture, on the forces acting on net panels. Drag forces on clean and fouled nets were measured in a flume tank, and net solidity including effect of fouling were determined using image analysis. The relationship between net solidity and drag was assessed, and it was found that a solidity increase due to hydroids caused less additional drag than a similar increase caused by change in clean net parameters. For solidities tested in this study, the difference in drag force increase could be as high as 43% between fouled and clean nets with same solidity. The relationship between solidity and drag force is well described by exponential functions for clean as well as for fouled nets. A method is proposed to parameterize the effect of fouling in terms of an increase in net solidity. This allows existing numerical methods developed for clean nets to be used to model the effects of biofouling on nets. Measurements with other types of fouling can be added to build a database on effects of the accumulation of different fouling organisms on aquaculture nets.

Apparent membrane pore-formation by Portuguese Man-of-war (Physalia physalis) venom in intact cultured cells.

Intracellular, ratiometric microfluorimetry with fura-2 reveals that low doses of Portuguese Man-of-war (Physalia physalis) venom cause a linear increase in intracellular calcium accumulation by cultured L-929 cells. The influx of calcium is preceded by a lag period that is relatively independent of venom concentration, except at very low concentrations. Electron micrographs of negatively stained preparations of membranes from venom-treated L-929 and GH(4)C(1) cells exhibit 10-80 nm diameter lesions. The number and diameter of these lesions correlate with venom concentration. The venom forms lesions in GH(4)C(1) cells at much lower concentrations than in L-929 cells. Osmotic protectants such as sucrose and polyethylene glycol (PEG), reduce the extent of lactate dehydrogenase (LDH) release from venom-treated cells with the higher molecular weight PEG causing a greater inhibition of LDH release than sucrose. These results imply that Man-of-war venom produces pore-like structures in the membranes of target cells, which leads to colloid osmotic swelling with subsequent release of intracellular proteins and cell lysis.

A gene family of putative immune recognition molecules in the hydroid Hydractinia.

Animal taxa display a wide array of immune-type receptors that differ in their specificities, diversity, and mode of evolution. These molecules ensure effective recognition of potential pathogens for subsequent neutralization and clearance. We have characterized a family of putative immune recognition molecules in the colonial hydroid Hydractinia symbiolongicarpus. A complementary DNA fragment with high similarity to the sea urchin L: -rhamnose-binding lectin was isolated and used to screen 9.5 genome equivalents of a H. symbiolongicarpus bacterial artificial chromosome library. One of the resulting 19 positive clones was sequenced and revealed the presence of a 5,111-bp gene organized in 13 exons and 12 introns. The gene was predicted to encode a 726-amino acid secreted modular protein composed of a signal peptide, an anonymous serine-rich domain, eight thrombospondin type 1 repeats, and a L: -rhamnose-binding lectin domain. The molecule was thus termed Rhamnospondin (Rsp). Southern hybridization and sequence analyses indicated the presence of a second Rsp gene. The cDNA from both Rsp genes was sequenced in 18 individuals, revealing high levels of genetic polymorphism. Nucleotide substitutions were distributed throughout the molecule and showed a significantly higher number of synonymous substitutions per synonymous sites than its nonsynonymous counterparts. Whole-mount in situ hybridization and semi-quantitative reverse transcription polymerase chain reaction of microorganism-challenged colonies indicated that Rsp molecules were specifically and constitutively expressed in the hypostome of gastrozooids' mouth. Thus, the combination of (1) comparative analysis on domain composition and function, (2) polymorphism, and (3) expression patterns, suggest that Rsp genes encode a family of putative immune recognition receptors, which may act by binding microorganisms invading the colony through the polyp's mouth.