Pedal Disc Research Articles

Ectodermal origin and tissue dedifferentiation in the podocyst production by the polyps of the Asian moon jelly (Aurelia coerulea).

The histological origin of podocysts in scyphozoans has long been undetermined, with uncertainty whether they arise from mesenchymal amoebocytes or stalk and pedal disc ectoderm in polyps. Histological investigation on the pedal disc was difficult due to the settlement of polyps on hard substrates. In this study, we investigated the histological characteristics of polyps during podocyst production in Asian moon jelly (Aurelia coerulea) with utilizing those attached on thin polystyrene substrates. Fine histological features of the pedal disc became possible after the substrates were decomposed during histological processing. Our findings unequivocally demonstrate that the cell mass of podocysts originates from the ectoderm of the pedal disc and the stalk without the involvement of amoebocytes in the mesoglea. Preceding the podocyst formation, the pedal disc undergoes enlargement facilitated by the elongated stalk ectodermal cells, which attach to a substrate. Subsequently, the pedal disc ectoderm give rise to the primary podocyst cells with accumulating nutrient granules in the cytoplasm and forming the cyst capsule cooperatively with the invaginated pedal disc ectoderm. Direct transformation from the ectodermal cells to podocyst cells suggests that podocyst formation involves tissue dedifferentiation. Throughout the period of podocyst production, the gastrodermis of polyps is physically separated from the ectoderm by the mesoglea and shows no histological changes, and no amoebocytes appear in the mesoglea. These histological properties are totally different from those in other modes of asexual reproduction, which incorporate the endoderm of polyps, suggesting the developmental and evolutionary differences between these asexual reproductions and podocyst production in Scyphozoa.

Effect of fragment size on growth and survival rate of Sarcophyton sp.

The Sarcophyton sp. are very strong and dominant in many coral reef areas. Sarcophyton species are characterized by a distinct sterile stalk, a broad, flared, smooth, mushroom-shaped top, with a wide distribution and dominance in numerous coral reef areas extending from the Red Sea and eastern Africa to the western Pacific Ocean. They are cherished in marine aquariums for their diverse colors and adaptability. However, their excessive exploitation has significantly impacted resources and disrupted the balance of the soft coral biome that inhabits coral reefs. The objective of the current study was to assess the impact of fragment size (0.5 × 0.5; 1.0 × 1.0; 1.5 × 1.5; 2.0 × 2.0, and 2.5 × 2.5 cm) on survival rate, growth rate and time of attachment of coral Sarcophyton sp. in a closed seawater system. Each treatment involved three replicates with 20 cuttings per replicate, and the experimental period was 90 days. The experiment showed that the fragment size did not influence the growth rate of oral disc diameter, pedal disk diameter, and the time attachment of Sarcophyton sp. However, the size of the fragment affects the survival rate, height growth rate, and weight of Sarcophyton sp. colonies. These findings collectively suggest that the initial coral fragment size of 1.5 cm was suitable in laboratory conditions.

Spatial Distribution and Biochemical Characterization of Serine Peptidase Inhibitors in the Venom of the Brazilian Sea Anemone Anthopleura cascaia Using Mass Spectrometry Imaging.

Sea anemones are known to produce a diverse array of toxins with different cysteine-rich peptide scaffolds in their venoms. The serine peptidase inhibitors, specifically Kunitz inhibitors, are an important toxin family that is believed to function as defensive peptides, as well as prevent proteolysis of other secreted anemone toxins. In this study, we isolated three serine peptidase inhibitors named Anthopleura cascaia peptide inhibitors I, II, and III (ACPI-I, ACPI-II, and ACPI-III) from the venom of the endemic Brazilian sea anemone A. cascaia. The venom was fractionated using RP-HPLC, and the inhibitory activity of these fractions against trypsin was determined and found to range from 59% to 93%. The spatial distribution of the anemone peptides throughout A. cascaia was observed using mass spectrometry imaging. The inhibitory peptides were found to be present in the tentacles, pedal disc, and mesenterial filaments. We suggest that the three inhibitors observed during this study belong to the venom Kunitz toxin family on the basis of their similarity to PI-actitoxin-aeq3a-like and the identification of amino acid residues that correspond to a serine peptidase binding site. Our findings expand our understanding of the diversity of toxins present in sea anemone venom and shed light on their potential role in protecting other venom components from proteolysis.

Clarification of the diagnosis of the genus Loxosoma s.l. (Entoprocta; Loxosomatidae) based on morphological and molecular data.

Loxosomatidae are solitary entoprocts associated with various types of invertebrate hosts. Two genera are distinguished in the family Loxosomatidae, Loxosomella and Loxosoma, that have clear morphological differences in the attachment structures. Loxosoma attaches to the substratum by a muscular sucking pedal disk, which allows moving. Both kidneys and adults are thought to have a pedal disc throughout their lives. In August 2021, several specimens of loxosomatids were found in the White Sea at a depth of 3070 m on a polychaete Laonice sp. (Spionidae), which were investigated using light and electron microscopy as well as molecular phylogenetic analysis. These loxosomatids were identified as Loxosomella aripes Nielsen, although a stalk of large buds of the specimens from the White Sea terminate with a pedal disc typical of Loxosoma. Molecular phylogenetic analysis of two markers [28S rRNA (~380bp) and 18S rRNA (in three parts totaling ~1850bp)] confirms the affinity of the species to Loxosoma s.l. and does not confirm monophyly of the genera Loxosoma and Loxosomella, indicating that the entire system of loxosomatids requires revision. Here, we redescribe the species Loxosomella aripes as Loxosoma s.l. aripes. The diagnosis of the genus Loxosoma s.l. is supplemented with the observation that the structure of the attachment organ can change after anchoring to the substrate. A list of species currently assigned to Loxosomella that may in fact belong to the genus Loxosoma s.l. is also given.

An abundant sea anemone from the Carboniferous Mazon Creek Lagerstӓtte, USA

AbstractSea anemones (Actiniaria) are among the rarest of recognized fossil organisms, even rarer than jellyfish. Here we demonstrate that the most abundant fossil in the Pennsylvanian Mazon Creek Lagerstätte of Illinois, Essexella asherae, is an infaunal or semi‐infaunal anemone. Essexella is redescribed based on a taphonomic analysis of thousands of specimens, as well as associated medusae and trace fossils. Specimens of Essexella (also known as the ‘blobs’) were long believed to be medusae, but we reassign Essexella to the order Actiniaria and reinterpret the putative jellyfish Reticulomedusa as the pedal or oral disc of Essexella. We also implicate Essexella as a producer of Conostichus, a widespread plug‐shaped trace fossil that occurs in coeval strata in the same region. Radiate structures comparable to the bases of Conostichus and the ichnofossil Bergaueria, as well as the pedal discs of modern anemones, characterize Reticulomedusa. Bona fide medusae are present in the Mazon Creek biota, and include Anthracomedusa turnbulli and Octomedusa pieckorum, whereas the soft‐bodied fossil Lascoa mesostaurata is referred to Problematica.

Cell volume maintenance capacity of the sea anemone Bunodosoma cangicum: the effect of copper.

Cell volume regulation is an essential strategy for the maintenance of life under unfavorable osmotic conditions. Mechanisms aimed at minimizing the physiological challenges caused by environmental changes are crucial in anisosmotic environments. However, aquatic ecosystems experience multiple stressors, including variations in salinity and heavy metal pollution. The accumulation of heavy metals in aquatic ecosystems has a significant effect on the biota, leading to impaired function. The aim of this study was to investigate the capacity of volume regulation in isolated cells of the sea anemone Bunodosoma cangicum exposed to nominal copper (Cu) concentrations of 5 and 50µg L-1, associated or not with hypoosmotic (15‰) or hyperosmotic (45‰) shock for 15min. In the absence of the metal, our results showed volume maintenance in all osmotic conditions. Our results showed that cell volume was maintained under all osmotic conditions in the absence of Cu. Similarly, no significant differences were observed in cell volumes under isosmotic and hyperosmotic conditions in the presence of both Cu concentrations. A similar homeostatic response was observed under the hypoosmotic condition with 5µg L-1 Cu. Our results showed an increase in cell volume with exposure of the cells to the hypoosmotic condition and 50µg L-1 Cu. The response could be associated with the increased bioavailability of Cu, reduced ability to resist multixenobiotics and their efflux pathways, and the impairment of water efflux in specialized transmembrane proteins. Therefore, B. cangicum pedal disk cells can tolerate osmotic variations in aquatic ecosystems. However, the capacity to regulate cell volume under hypoosmotic conditions can be affected by the presence of a metal contaminant (50µg L-1 Cu), which could be due to the inhibition of water channels.

Cascade effects of seafloor litter on benthic ecosystems in the northern Yellow Sea

The accumulation of seafloor litter changes the habitats of benthic organisms and thus affects their spatial distribution. Previous studies suggested that the accumulation of seafloor litter might contribute to the bloom of Metridium senile fimbriatum, given that seafloor litter could serve as “vectors” for M. senile dispersal and provide with “natural habitat” for their settlement. As a common fouler and invader, M. senile bloom will inevitably affect the benthic ecosystems. The cascading effects of seafloor litter on benthic ecosystems can be explored by studying the interactions between this litter-associated anemone and other co-occurred species. Therefore, this study uses stable isotope analysis to study the food composition of M. senile attached to the seafloor litter and the niche relationship with co-occurred species. First, by comparing the stable isotope ratios of the pedal disc and tentacle of M. senile, it was found that the δ15N of the foot disc is more stable than that of the tentacle, so the pedal disc was chosen as the sampling tissue. The mean δ13C value of M. senile was -19.34 ± 0.86‰, which ranged from -22.30‰ to -18.17‰. For δ15N, the mean value was 12.02 ± 0.95‰, which ranged from 9.22‰ to 13.31‰. Then, we quantified the contribution of the potential food resources of M. senile using the SIMMR model. M. senile has the highest feeding proportion to crustaceans, followed by juvenile fish, zooplankton and other macrobenthos. Meanwhile, M. senile has high uncertainty in the feeding proportion of crustaceans and juvenile fish. In addition, the trophic niche overlap between different functional groups was calculated by the SIBER model, and the results showed that the isotopic niche of M. senile was overlapped with different functional groups, ranging from 34.29 to 35.25%. Therefore, this study suggests that M. senile, as litter-associated carnivorous anemone, interacts with other components in the ecosystems through predation and competition, which also reveals the cascade effect of seafloor litter on the benthic ecosystems of the northern Yellow Sea.

Tentacle patterning during Exaiptasia diaphana pedal lacerate development differs between symbiotic and aposymbiotic animals.

Exaiptasia diaphana, a tropical sea anemone known as Aiptasia, is a tractable model system for studying the cellular, physiological, and ecological characteristics of cnidarian-dinoflagellate symbiosis. Aiptasia is widely used as a proxy for coral-algal symbiosis, since both Aiptasia and corals form a symbiosis with members of the family Symbiodiniaceae. Laboratory strains of Aiptasia can be maintained in both the symbiotic (Sym) and aposymbiotic (Apo, without algae) states. Apo Aiptasia allow for the study of the influence of symbiosis on different biological processes and how different environmental conditions impact symbiosis. A key feature of Aiptasia is the ease of propagating both Sym and Apo individuals in the laboratory through a process called pedal laceration. In this form of asexual reproduction, small pieces of tissue rip away from the pedal disc of a polyp, then these lacerates eventually develop tentacles and grow into new polyps. While pedal laceration has been described in the past, details of how tentacles are formed or how symbiotic and nutritional state influence this process are lacking. Here we describe the stages of development in both Sym and Apo pedal lacerates. Our results show that Apo lacerates develop tentacles earlier than Sym lacerates, while over the course of 20 days, Sym lacerates end up with a greater number of tentacles. We describe both tentacle and mesentery patterning during lacerate development and show that they form through a single pattern in early stages regardless of symbiotic state. In later stages of development, Apo lacerate tentacles and mesenteries progress through a single pattern, while variable patterns were observed in Sym lacerates. We discuss how Aiptasia lacerate mesentery and tentacle patterning differs from oral disc regeneration and how these patterning events compare to postembryonic development in Nematostella vectensis, another widely-used sea anemone model. In addition, we demonstrate that Apo lacerates supplemented with a putative nutrient source developed an intermediate number of tentacles between un-fed Apo and Sym lacerates. Based on these observations, we hypothesize that pedal lacerates progress through two different, putatively nutrient-dependent phases of development. In the early phase, the lacerate, regardless of symbiotic state, preferentially uses or relies on nutrients carried over from the adult polyp. These resources are sufficient for lacerates to develop into a functional polyp. In the late phase of development, continued growth and tentacle formation is supported by nutrients obtained from either symbionts and/or the environment through heterotrophic feeding. Finally, we advocate for the implementation of pedal lacerates as an additional resource in the Aiptasia model system toolkit for studies of cnidarian-dinoflagellate symbiosis.

First record of a sea anemone of genus Bunodosoma with two oral discs: a clue to asexual reproduction?

Different reproductive strategies (both sexual and asexual) that may occur in individuals of the same species may explain the success of sea anemones (Cnidaria:Actiniaria) in colonizing different ecosystems around the planet. Here we provide the first record of a Bunodosoma specimen with two oral discs and discuss the possibility of asexual reproduction in this genus. One individual of Bunodosoma cangicum was found in Carneiros beach (Pernambuco state, Brazil) with two fully individualized oral discs but with column and pedal disc still connected. Our finding may represent a clue to longitudinal fission in Bunodosoma. Yet, despite the number of different studies carried out so far, the absence of data regarding asexual reproduction in Bunodosoma suggests that it might be rare in this genus, occurring only in sporadic cases such as recovery from injury.

Reproduction in the tropical frilly sea anemone Phymanthus pinnulatus (Cnidaria, Actiniaria)

AbstractOur understanding of how sea anemones reproduce in the equatorial Central Indo‐Pacific region remains poor compared to other marine regions. Here we report the gametogenic cycles of Phymanthus pinnulatus, a zooxanthellate sea anemone found throughout the Indo‐Pacific tropics. Observations were based on 41 individuals collected in Singapore. We found P. pinnulatus to be gonochoric, with an equal sex ratio of 1:1. Phases of oogenesis and spermatogenesis were detailed for the first time in P. pinnulatus, and were consistent with phases in other actiniarians. Females with pedal disc diameters <10 mm were found to asynchronously produce oocytes. We also found that trophonemata were associated with both oocytes and spermaries during gametogenesis. In Singapore, the periods during which gametes matured in each sex of P. pinnulatus appeared to overlap. We were unable distinguish whether spawning was annual or continuous in P. pinnulatus. Our observations on the occurrence of maturing and matured gametes in P. pinnulatus were similar to those reported for other species within the Central Indo‐Pacific. It also coincided with the multispecies spawning of scleractinian corals in Singapore. This study contributes to the growing body of work focused on the biology of tropical actiniarians in the Central Indo‐Pacific region.

Sea anemones (Exaiptasia pallida) use a secreted adhesive and complex pedal disc morphology for surface attachment

BackgroundThe mechanism by which sea anemones attach to surfaces underwater remains elusive, which is surprising given their ubiquitous distribution in the world’s oceans and tractability for experimental biology. Their adhesion is mechanically interesting, bridging the interface between very hard and soft materials. The Cnidaria are thought to have evolved adhesion to surfaces at least 505 Ma ago implying that, among the Metazoa, only Porifera developed this capability earlier. The purpose of this study was primarily to address an existing hypothesis, that spirocysts (a sticky class of cnidocyst) facilitate adhesion to surfaces, as observed during prey capture.ResultsWe demonstrated conclusively that spirocysts were not involved in the pedal disc adhesion of Exaiptasia pallida. Second, we applied a variety of imaging methods to develop an understanding of the true adhesion mechanism. Morphological studies using scanning electron microscopy identified a meshwork of adhesive material, unique to the pedal disc. Serial block-face SEM highlighted four classes of cells that could secrete the adhesive from the pedal disc ectoderm. A variety of histochemical techniques identified proteins, glycans and quinones in the cell contents and secreted adhesive, with variation in contents of specific cell-types in different areas of the body.ConclusionsSpirocysts are not used by Exaiptasia pallida for adhesion to surfaces. Instead, a structurally and compositionally complex secreted glue was observed, firmly attaching the animals underwater. The results of this study provide a basis for further investigations of adhesion in Cnidaria, and establish E. pallida as a new model organism for bioadhesion research.

The sea anemone Bunodosoma cangicum as a potential biomonitor for microplastics contamination on the Brazilian Amazon coast

This study reports for the first time the ingestion of meso- (5.01–25 mm) and microplastics (1 μm–5 mm) by the sea anemone Bunodosoma cangicum, the most abundant actiniarian species on the Amazon coast. At three sites on the coast of Pará, Brazil, anemones were collected from beachrocks in the intertidal zone (30 at each site), measured (pedal disc diameter, mm) and weighed (wet weight, g). The contents of the gastrovascular cavity were extracted and analyzed under a stereoscope. The recovered plastic particles were characterized by Fourier Transform Infrared (FTIR) spectroscopy. Overall, 139 microplastic and 2 mesoplastic items were identified in 68 individuals (75.6%) among the 90 examined, with a mean of 1.6 (±1.5) items per individual. Plastic fibers comprised about 84% of the ingested plastics, followed by fragments (∼12%) and films (∼4%). Particle diameters ranged from 0.10 to 9.17 mm (1.57 ± 1.23 mm). A weak positive correlation was found between the weight of anemones and the number of plastic particles in the gastrovascular cavity (p = 0.03) and between the number of prey items and the number of plastic particles in the gastrovascular cavity (p < 0.01). The main polymers identified by FTIR analysis were polyethylene terephthalate (PET), polypropylene (PP), polyamide (PA), polyurethane (PU), polyethylene (PE), acrylonitrile butadiene styrene (ABS), polystyrene (PS) and rayon. Sea anemones ingested significantly more plastic debris at the most urbanized and populous sampling sites. This study provides the first evidence of microplastics contamination of marine invertebrates from the Amazon coast. Abundant species such as B. cangicum have the potential to monitor the levels of plastic contamination in the region. Our results support this potential, as the species showed a high frequency of plastic ingestion and allowed detection of plastic contamination even in the best-preserved area where anemones were collected.

Origin and evolution of the symbiosis between sea anemones (Cnidaria, Anthozoa, Actiniaria) and hermit crabs, with additional notes on anemone-gastropod associations

The anemone-crab mutualism is ubiquitous in temperate and tropical marine environments. In this symbiosis, one or more anemones live on a shell inhabited by a hermit crab and reciprocal phoretic, trophic, and defensive benefits are exchanged between the partners. Sea anemone-hermit crab symbionts belong to three families: Hormathiidae (Calliactis and Paracalliactis), Sagartiidae (Carcinactis and Verrillactis), and Actiniidae (Stylobates). Hermit crabs establish most partnerships by detaching anemones and placing them on their shell; sea anemones can also mount shells unaided, triggered by a mollusc-derived substance in the periostracum of the shell. At least partial cooperation by the anemones is necessary for successful establishment of the symbiosis. Here, we expand the evolutionary framework for hormathiid symbionts by generating a phylogeny with at least one member of each actiniarian symbiotic genus with hermit crabs using five molecular markers (16S, 12S, 18S, 28S, CO3). We not only corroborated the results from a previous study by finding two origins of hermit crab symbiosis within Hormathiidae, but also found additional origins for hermit crab symbiosis within Actiniaria. We provide for the first time evidence of a close relationship between symbionts Carcinactis dolosa and V. paguri. The ability to secrete chitin by the ectoderm of the column is inferred to be broadly convergent within Actiniaria whereas the secretion of a chitinous carcinoecium by the pedal disc is a distinct but convergent morphological adaptation of several lineages within Actiniaria. Our finding of multiple origins for both the hermit crab and gastropod symbioses suggests that the shell-mounting behavior might only have been the precursor of the hermit crab association among Calliactis spp.

Discovery and characterization of tyrosinases from sea anemone pedal disc

The formation of underwater adhesion is a complicated physiological process and many different types of enzymes are found to be essential apart from structural proteins. Previous studies have shown that various tyrosinases were present in marine adhesives, but little information is available about the over-expression and enzymatic characterization of these enzymes. Specifically, this study first identified four significantly up-regulated tyrosinases in the pedal disc of Haliplanella luciae by means of multi-omics technology, and made preliminary bioinformatics predictions. Sequence alignment showed that the Tyr1_Hl contained six conserved His residues that bind to copper ions, of which a tyrosinase with diphenolase activity named as Tyr1_HlΔ, was expressed in Escherichia coli BL21 (DE3) cells and purified by affinity chromatography. Enzymatic characterization showed that the activity of Tyr1_HlΔ was Cu2+ dependent and maximum catalytic activities were in 20 mM Tris–HCl (pH 8.0) at 37 °C. In summary, we identified novel tyrosinases in the pedal disks of sea anemone for the first time and the Tyr1_HlΔ was successfully recombinant expressed. Our study will provide basis for future exploration of bio-adhesion mechanism and design of bio-adhesives derived from sea anemones.

About the Cover

Next article FreeAbout the CoverPDFPDF PLUSFull Text Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinked InRedditEmailQR Code SectionsMoreCoverThe cover features the introduced anemone Sagartia elegans on fouling panels in Salem Harbor, Massachusetts. One of the two adults has visibly ripe female reproductive tissue (salmon colored) that can be seen through the translucent oral disk. Alongside these adults are many asexually produced pedal lacerates, which are produced by contraction and tearing of the pedal disk. Through this method of asexual reproduction, anemone populations exponentially increase and take over hard-bottom substrata. Sagartia elegans is native to western Europe and was introduced to Salem Harbor before the year 2000. The population was restricted to Salem Harbor in the western Atlantic and would increase in summer and fall but disappear every winter. In the winter of 2010, the population in Salem Harbor disappeared and has since never been seen again, despite intensive efforts to locate this species.On pages 283–291, Wells and Harris test hypotheses for the local extinction of this species and bring context to this failed invasion, a highly understudied topic despite the prevalence of introduced species in marine habitats. They report that the mechanism for its failed invasion is likely a mismatch between the thermal tolerance of this population and the winter temperatures. In both laboratory and field experiments, anemones died well above temperatures experienced in Salem Harbor, suggesting a warm-water refuge. Another contributor to the fate of this population was the apparent lack of genetic diversity; they observed only females, and all individuals within the population were the same color, which is uncharacteristic of this species in its native range.Credits: Photo, Christopher D. Wells, University at Buffalo. Cover design, Jeannie Harrell, University of Chicago. Next article DetailsFiguresReferencesCited by The Biological Bulletin Volume 237, Number 3December 2019 Published in association with the Marine Biological Laboratory Article DOIhttps://doi.org/10.1086/708139 © 2019 by The University of Chicago. All rights reserved.PDF download Crossref reports no articles citing this article.

Reproduction of the anthozoan Anemonia sulcata (Pennant, 1777) in southern Spain: from asexual reproduction to putative maternal care

Anemonia sulcata (Pennant, 1777) is a common shallow water cnidarian from rocky platform and boulder beaches in southern Spain, where it is a popular seafood item with an increasing fishery. To aid in the management of a sustainable fishery, a study on the reproduction of A. sulcata in the littoral of Malaga (southern Spain) was performed from November 2014 to September 2015, using histological methods. A total of 123 specimens were examined, with a size range (as diameter of the pedal disc) from 1.1 to 48.2 mm. The sex ratio was significantly biased to females, with 1.7 females: 1 male (χ2 = 4.45, p < 0.01). The spermatozoids and oocytes arise from the endodermal cells. The mature oocytes receive nutritive filaments (trophonema) from the endoderm cells. There were zooxanthellae in the mesenteries, tentacles and also inside the oocytes. A gastrula was observed in one individual, as well as several planula larvae in different degree of development in others. Asexual reproduction by internal budding was observed in some individuals. The studied population showed an extended reproductive cycle with a peak of spawning in April. The size and weight of sexual maturity of the studied population were 21.5 mm and 16.5 g, respectively. A positive significant correlation was observed between size and weight of individuals. We suggest that the diameter of the pedal disc should be used as the legal parameter for the management of this fishery, as this measurement is easier to take by fishermen at sea than the weight, the current legal parameter.

Transcriptional characterisation of the Exaiptasia pallida pedal disc

BackgroundBiological adhesion (bioadhesion), enables organisms to attach to surfaces as well as to a range of other targets. Bioadhesion evolved numerous times independently and is ubiquitous throughout the kingdoms of life. To date, investigations have focussed on various taxa of animals, plants and bacteria, but the fundamental processes underlying bioadhesion and the degree of conservation in different biological systems remain poorly understood. This study had two aims: 1) To characterise tissue-specific gene regulation in the pedal disc of the model cnidarian Exaiptasia pallida, and 2) to elucidate putative genes involved in pedal disc adhesion.ResultsFive hundred and forty-seven genes were differentially expressed in the pedal disc compared to the rest of the animal. Four hundred and twenty-seven genes were significantly upregulated and 120 genes were significantly downregulated. Forty-one condensed gene ontology terms and 19 protein superfamily classifications were enriched in the pedal disc. Eight condensed gene ontology terms and 11 protein superfamily classifications were depleted. Enriched superfamilies were consistent with classifications identified previously as important for the bioadhesion of unrelated marine invertebrates. A host of genes involved in regulation of extracellular matrix generation and degradation were identified, as well as others related to development and immunity. Ab initio prediction identified 173 upregulated genes that putatively code for extracellularly secreted proteins.ConclusionThe analytical workflow facilitated identification of genes putatively involved in adhesion, immunity, defence and development of the E. pallida pedal disc. When defence, immunity and development-related genes were identified, those remaining corresponded most closely to formation of the extracellular matrix (ECM), implicating ECM in the adhesion of anemones to surfaces. This study therefore provides a valuable high-throughput resource for the bioadhesion community and lays a foundation for further targeted research to elucidate bioadhesion in the Cnidaria.

Morphotypes of the common beadlet anemone Actinia equina (L.) are genetically distinct

Anemones of the genus Actinia are ecologically important and familiar organisms on many rocky shores. However, this genus is taxonomically problematical and prior evidence suggests that the North Atlantic beadlet anemone, Actinia equina, may actually consist of a number of cryptic species. Previous genetic work has been largely limited to allozyme electrophoresis and there remains a dearth of genetic resources with which to study this genus. Mitochondrial DNA sequencing may help to clarify the taxonomy of Actinia. Here, the complete mitochondrial genome of the beadlet anemone Actinia equina (Cnidaria: Anthozoa: Actinaria: Actiniidae) is shown to be 20,690 bp in length and to contain the standard complement of Cnidarian features including 13 protein coding genes, two rRNA genes, two tRNAs and two Group I introns, one with an in-frame truncated homing endonuclease gene open reading frame. However, amplification and sequencing of the standard mtDNA barcoding region of the cytochrome oxidase I gene revealed only two haplotypes, differing by a single base pair, in widely geographically separated A. equina and its congener A. prasina. COI barcoding shows that whilst A. equina and A. prasina share the common mtDNA haplotype, haplotype frequency differed significantly between A. equina with red/orange pedal discs and those with green pedal discs, consistent with the hypothesis that these morphotypes represent incipient species.

Tenactisgen. nov. (Actiniaria, Haloclavidae) a new genus of sea anemones from the Gulf of California, Mexico

We describe and illustrate a new genus and species of sea anemone from the intertidal in the Gulf of California (Mexico).Tenactisgen. nov. is characterized by mesenteries decamerously arranged, a single pair of directives attached to a single and strong siphonoglyph, small conchula, endodermal marginal sphincter muscle, pedal disc with basilar muscles, cinclides in pedal disc and proximal column, column with verrucae and pseudoacrorhagi, and a cnidom withp-mastigophores A2 andp-mastigophores B1 and B2a.Tenactis riosmenaigen. et sp. nov. is characterized by having a column not divisible into regions with longitudinal rows of verrucae distally and pseudoacrorhagi forming spherical structures at the tip, only 10 pairs of perfect mesenteries, diffuse endodermal marginal sphincter muscle andp-mastigophores A2 andp-mastigophores B1 and B2a in the filaments. Because of the decamerous arrangement of the mesenteriesTenactisgen. nov. most closely resembles some members of Actiniidae, Haloclavidae, Minyadidae, Oractiidae and Limnactinidae (Actinioidea), Halcampidae (Metridioidea) and Halcuriidae (Actinernoidea). However, the combination of having a decamerous arrangement of mesenteries, single siphonoglyph, conchula and cinclides indicate this new genus belongs to Haloclavidae. Additionally, the presence of a diffuse endodermal marginal sphincter muscle, basilar muscles, a single pair of directives, column with longitudinal rows of verrucae distally and pseudoacrorhagi,p-mastigophores A2, andp-mastigophores B1 and B2a in the filaments distinguishTenactis riosmenaigen. et sp. nov. within Haloclavidae. This is the first record of the family Haloclavidae for the Gulf of California.

Symbiont Identity Influences Patterns of Symbiosis Establishment, Host Growth, and Asexual Reproduction in a Model Cnidarian-Dinoflagellate Symbiosis.

The genus Symbiodinium is physiologically diverse and so may differentially influence symbiosis establishment and function. To explore this, we inoculated aposymbiotic individuals of the sea anemone Exaiptasia pallida (commonly referred to as "Aiptasia"), a model for coral symbiosis, with one of five Symbiodinium species or types (S. microadriaticum, S. minutum, phylotype C3, S. trenchii, or S. voratum). The spatial pattern of colonization was monitored over time via confocal microscopy, and various physiological parameters were measured to assess symbiosis functionality. Anemones rapidly formed a symbiosis with the homologous symbiont, S. minutum, but struggled or failed to form a long-lasting symbiosis with Symbiodinium C3 or S. voratum, respectively. Symbiodinium microadriaticum and S. trenchii were successful but reached their peak density two weeks after S. minutum. The spatial pattern of colonization was identical for all Symbiodinium taxa that were ultimately successful, starting in the oral disk and progressing to the tentacles, before invading the column and, finally, the pedal disk. In all cases, proliferation through the anemone's tentacles was patchy, suggesting that symbionts were being expelled into the gastrovascular cavity and re-phagocytosed by the host. However, the timing of these various spatial events differed between the different Symbiodinium taxa. Furthermore, S. microadriaticum and S. trenchii were less beneficial to the host, as indicated by lower rates of photosynthesis, anemone growth, and pedal laceration. This study enhances our understanding of the link between symbiont identity and the performance of the overall symbiosis, which is important for understanding the potential establishment and persistence of novel host-symbiont pairings. Importantly, we also provide a baseline for further studies on this topic with the globally adopted "Aiptasia" model system.