Bellactis lux n. sp. (Cnidaria: Anthozoa: Actiniaria: Aiptasiidae), a new sea anemone from the Gulf of Mexico.

Here we describe a new species of sea anemone from the family Aiptasiidae based on specimens collected from the Gulf of Mexico (USA: Florida & Alabama). Accounts of this species have been known since the early 1990s, primarily from an underwater field guide and hobbyist aquarium literature under the name Lightbulb Anemone. We describe it as a new species from the genus Bellactis based on anatomy, histology, and cnidom. Members of this species are small in size, with a smooth, typically contracted column divided into regions based on color and bearing rows of two or three elevated cinclides in the mid column. Their tentacles are distinctive, translucent, distally inflated and can be bulbous in shape, with sub annular rings. This description synthesizes information about Bellactis and contextualizes what is known about its diversity in light of other members of the Aiptasiidae.

Phylogeny and taxonomy of Haloclavidae (Verrill, 1899) with a redescription of the parasitic, burrowing sea anemone, Peachia chilensis Carlgren, 1931.

Haloclavidae Verrill, 1899 is a family of burrowing sea anemones grouped within the superfamily Actinioidea (Rafinesque, 1815). Currently, it includes 30 species in 10 genera. Characters given for this family in descriptions of its taxa have not been consistent, with numerous exceptions to the expectations of the familial diagnosis. Previous phylogenetic analyses have shown that Haloclavidae is potentially a polyphyletic group, but resolution of relationships of the few representatives of Haloclavidae included in analyses has been problematic. Here we address questions of monophyly and affinity of Haloclavidae using three mitochondrial and two nuclear markers. We assess the monophyly of Haloclavidae in the context of all major lineages of Actiniaria Hertwig, 1882, emphasizing diversity of superfamily Actinioidea. We use parsimony-based character optimization to interpret the distribution of key traits in the superfamily. We find that Haloclavidae is not monophyletic and propose two new families, Peachiidae fam. nov. and Harenactidae fam. nov., while also retaining some species in the family Haloclavidae, so that taxonomy better reflects relationships and diversity of the group. In addition, we redescribe a species within the newly created Peachiidae, Peachia chilensis Carlgren, 1931. We use recent larval samples obtained in Antofagasta, Chile, and the histological slides from the original description to redescribe P. chilensis, to provide a complete account of cnidae, external, and internal morphology. Finally, we compare P. chilensis to other burrowing anemones found in Chile and provide an understanding of the genus Peachia that reflects recent phylogenetic perspective on diversity of anemones previously assigned to family Haloclavidae.

Intertidal sea anemones (Cnidaria: Actiniaria) from the west coast of the Peninsula of Baja California, Mexico.

Nine species of sea anemones are documented from the west coast of the Peninsula of Baja California. Short descriptions of Anthopleura artemisia (Pickering in Dana, 1846), A elegantissima (Brandt, 1835), A. sola Pearse Francis, 2000 and Epiactis prolifera Verrill, 1869 are provided, including images of the external and internal anatomy, as well as cnidae. In addition, an updated list of the sea anemone species recorded in Mexico, including both the Pacific and Atlantic regions, is provided. The northern species A. artemisia and E. prolifera are recorded for the first time in Mexico. With these new records, the number of sea anemone species known in the Mexican Pacific increases to 35, and to 57 for the entire country.

Tentacle Morphological Variation Coincides with Differential Expression of Toxins in Sea Anemones.

Phylum Cnidaria is an ancient venomous group defined by the presence of cnidae, specialised organelles that serve as venom delivery systems. The distribution of cnidae across the body plan is linked to regionalisation of venom production, with tissue-specific venom composition observed in multiple actiniarian species. In this study, we assess whether morphological variants of tentacles are associated with distinct toxin expression profiles and investigate the functional significance of specialised tentacular structures. Using five sea anemone species, we analysed differential expression of toxin-like transcripts and found that expression levels differ significantly across tentacular structures when substantial morphological variation is present. Therefore, the differential expression of toxin genes is associated with morphological variation of tentacular structures in a tissue-specific manner. Furthermore, the unique toxin profile of spherical tentacular structures in families Aliciidae and Thalassianthidae indicate that vesicles and nematospheres may function to protect branched structures that host a large number of photosynthetic symbionts. Thus, hosting zooxanthellae may account for the tentacle-specific toxin expression profiles observed in the current study. Overall, specialised tentacular structures serve unique ecological roles and, in order to fulfil their functions, they possess distinct venom cocktails.

Cnidarian-bilaterian comparison reveals the ancestral regulatory logic of the ß-catenin dependent axial patterning.

In animals, body axis patterning is based on the concentration-dependent interpretation of graded morphogen signals, which enables correct positioning of the anatomical structures. The most ancient axis patterning system acting across animal phyla relies on ß-catenin signaling, which directs gastrulation, and patterns the main body axis. However, within Bilateria, the patterning logic varies significantly between protostomes and deuterostomes. To deduce the ancestral principles of ß-catenin-dependent axial patterning, we investigate the oral-aboral axis patterning in the sea anemone Nematostella-a member of the bilaterian sister group Cnidaria. Here we elucidate the regulatory logic by which more orally expressed ß-catenin targets repress more aborally expressed ß-catenin targets, and progressively restrict the initially global, maternally provided aboral identity. Similar regulatory logic of ß-catenin-dependent patterning in Nematostella and deuterostomes suggests a common evolutionary origin of these processes and the equivalence of the cnidarian oral-aboral and the bilaterian posterior-anterior body axes.

Transcriptional characterisation of the Exaiptasia pallida pedal disc.

BACKGROUND: Biological 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. RESULTS: Five 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. CONCLUSION: The 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.

First Detailed Record of Symbiosis Between a Sea Anemone and Homoscleromorph Sponge, With a Description of Tempuractis rinkai gen. et sp. nov. (Cnidaria: Anthozoa: Actiniaria: Edwardsiidae).

A new species in a new genus of sea anemone, Tempuractis rinkai gen. et sp. nov., was discovered at several localities along the temperate rocky shores of Japan. The new species is approximately 4 mm in length and has been assigned to family Edwardsiidae, because it has eight macrocnemes, lacks sphincter and basal muscles, and possesses rounded aboral end. The sea anemone, however, also has a peculiar body shape unlike that of any other known taxa. This new species resembles some genera, especially Drillactis and Nematostella, in smooth column surface without nemathybomes or tenaculi, but is distinguishable from them by several morphological features: the presence of holotrichs and absence of nematosomes. Furthermore, this edwardsiid species exhibits a peculiar symbiotic ecology with sponges. Therefore, a new genus, Tempuractis, is proposed for this species. In the field, T. rinkai sp. nov. was always found living inside homosclerophorid sponge of the genus Oscarella, which suggests a possible obligate symbiosis between Porifera and Actiniaria. The benefit of this symbiosis is discussed on the basis of observations of live specimens, both in the aquarium and field. This is the first report of symbiosis between a sea anemone and a homoscleromorph sponge.

Histological study on maturation, fertilization and the state of gonadal region following spawning in the model sea anemone, Nematostella vectensis.

The starlet sea-anemone Nematostella vectensis has emerged as a model organism in developmental biology. Still, our understanding of various biological features, including reproductive biology of this model species are in its infancy. Consequently, through histological sections, we study here key stages of the oogenesis (oocyte maturation/fertilization), as the state of the gonad region immediately after natural spawning. Germ cells develop in a secluded mesenterial gastrodermal zone, where the developing oocytes are surrounded by mucoid glandular cells and trophocytes (accessory cells). During vitellogenesis, the germinal vesicle in oocytes migrates towards the animal pole and the large polarized oocytes begin to mature, characterized by karyosphere formation. Then, the karyosphere breaks down, the chromosomes form the metaphase plate I and the eggs are extruded from the animal enclosed in a sticky, jelly-like mucoid mass, along with numerous nematosomes. Fertilization occurs externally at metaphase II via swimming sperm extruded by males during natural spawning. The polar bodies are ejected from the eggs and are situated within a narrow space between the egg's vitelline membrane and the adjacent edge of the jelly coat. The cortical reaction occurs only at the polar bodies' ejection site. Several spermatozoa can penetrate the same egg. Fertilization is accompanied by a strong ooplasmatic segregation. Immediately after spawning, the gonad region holds many previtellogenic and vitellogenic oocytes, though no oocytes with karyosphere. Above are the first histological descriptions for egg maturation, meiotic chromosome's status at fertilization, fertilization and the gonadal region's state following spawning, also documenting for the first time the ejection of the polar body.

New records of the deep-sea anemone Phelliactis callicyclus Riemann-Zurneck, 1973 (Cnidaria, Actiniaria, Hormathiidae) from the Gulf of California, Mexico.

Specimens of a deep-sea anemone were observed in photographs and video footage taken with the Remotely Operated Vehicle JASON (WHOI Deep Submergence Laboratory) in the Gulf of California, Mexico, in May 2008. Comparison of our material with photographs and description of this species available in literature indicate that the sea anemones filmed during the JASON survey are most likely to represent Phelliactis callicyclus Riemann-Zurneck, 1973. This species has previously been reported from a locality in the Gulf of California near the present record. During the JASON survey, 28 specimens of P. callicyclus were spotted in 27 locations during six dives. The specimens occurred on angular rock outcrops along the escarpments of the transform faults of the Gulf of California, between depths of 993-2543 m and at temperatures ranging from 2.3 to 4.5°C. Based on these new records, Phelliactis callicyclus appears to be widely spread in the Gulf of California.

The 'Antenna Balloon Anemone' Found in the Seto Inland Sea: New Genus and Species of Sea Anemone, Antennapeachia setouchi (Cnidaria, Actinaria, Haloclavidae).

In the present study, we report the identification of a sea anemone, Antennapeachia setouchi, collected in the Seto Inland Sea, which represents a new genus and new species. This new species has unusual tentacle and mesenterial arrangements that have not been observed in other species of Haloclavidae. There are 12 regular marginal tentacles and two 'antenna tentacles,' with the latter always rising upward and located on the oral disk near the mouth; the species is also characterized by its peculiar mesenterial pairs, consisting of a macrocneme and a microcneme. Furthermore, this species shows an interesting behavior: it can inflate its body like a balloon, lift above the seafloor, and drift with the sea current. The presence of a single, strong siphonoglyph, physa-like aboral end, and the lack of sphincter muscle classify this sea anemone within Haloclavidae. It resembles Peachia species, but cannot be classified in this genus as the new species has two pairs of mesenteries, consisting of a macrocneme and a microcneme, and irregular antenna tentacles. Therefore, we propose a new genus Antennapeachia to accommodate this species.

Paraphelliactis tangi n. sp. and Phelliactis yapensis n. sp., two new deep-sea species of Hormathiidae (Cnidaria: Anthozoa: Actiniaria) from a seamount in the tropical Western Pacific.

Two new species of hormathiid actiniarians, Paraphelliactis tangi n. sp. and Phelliactis yapensis n. sp., are described from a seamount near the Yap Trench in the tropical Western Pacific. Paraphelliactis tangi n. sp. has a thick cuticle, a tuberculated column divisible into scapus and scapulus, a complete fifth cycle of mesenteries, an equal number of mesenteries at the margin and at the limbus, and up to 192 tentacles without aboral mesogloeal thickenings that are hexamerously arranged in six cycles. This species differs distinctly from the three known species of Paraphelliactis by the above mentioned features (vs. an incomplete fifth cycle of mesenteries, usually more mesenteries at the margin than at the limbus, and the tentacles with aboral mesogloeal thickenings). So far, it is the only member of the genus Paraphelliactis found in the Western Pacific. Phelliactis yapensis n. sp. has an asymmetric bilobed oral disc and column, tuberculated scapus and scapulus, an incomplete fifth cycle of mesenteries, and up to 162 tentacles with aboral mesogloeal thickenings that are alternately arranged in two cycles. In comparison with other Phelliactis species, the basitrichs of mesenterial filaments of Ph. yapensis are distinctly larger. Phelliactis yapensis n. sp. is the fourth species of Phelliactis found in the Western Pacific.

Metapeachia schlenzae sp. nov. (Cnidaria: Actiniaria: Haloclavidae) a new burrowing sea anemone from Brazil, with a discussion of the genus Metapeachia.

The diversity of burrowing sea anemones from Brazil is poorly known with only three species recorded. Metapeachia schlenzae sp. nov. is described from specimens collected in the intertidal zone of São Sebastião and Cabo Frio in the southeastern coast of Brazil. Metapeachia schlenzae sp. nov. is the second species described for the genus and the second haloclavid recorded from Brazil. A comparison between Metapeachia schlenzae sp. nov. and Metapeachia tropica, the type species of the genus, is included. The two valid species of Metapeachia differ in the morphology of the conchula, internal anatomy, cnidae and geographical distribution.

Elucidating the evolutionary relationships of the Aiptasiidae, a widespread cnidarian-dinoflagellate model system (Cnidaria: Anthozoa: Actiniaria: Metridioidea).

Sea anemones of the family Aiptasiidae sensu Grajales and Rodríguez (2014) are conspicuous members of shallow-water environments, including several species widely used as model systems for the study of cnidarian-dinoflagellate symbiosis and coral bleaching. Although previously published phylogenetic studies of sea anemones recovered Aiptasiidae as polyphyletic, they only included a sparse sample in terms of its taxonomic diversity and membership of the family had not been yet revised. This study explores the phylogenetic relationships of this family using five molecular markers and including newly collected material from the geographical distribution of most of the currently described genera and species. We find a monophyletic family Aiptasiidae. All the currently proposed genera were recovered as monophyletic units, a finding also supported by diagnostic morphological characters. Our results confirm Bellactis and Laviactis as members of Aiptasiidae, also in agreement with previous morphological studies. The monophyly of the group is congruent with the morphological homogeneity of the members of this family. The obtained results also allow discussing the evolution of morphological characters within the family. Furthermore, we find evidence for and describe a new cryptic species, Exaiptasia brasiliensis sp. nov., based on molecular data, geographical distribution, and the identity of its endosymbiotic dinoflagellate.

Characterization of Morphological and Cellular Events Underlying Oral Regeneration in the Sea Anemone, Nematostella vectensis.

Cnidarians, the extant sister group to bilateria, are well known for their impressive regenerative capacity. The sea anemone Nematostella vectensis is a well-established system for the study of development and evolution that is receiving increased attention for its regenerative capacity. Nematostella is able to regrow missing body parts within five to six days after its bisection, yet studies describing the morphological, cellular, and molecular events underlying this process are sparse and very heterogeneous in their experimental approaches. In this study, we lay down the basic framework to study oral regeneration in Nematostella vectensis. Using various imaging and staining techniques we characterize in detail the morphological, cellular, and global molecular events that define specific landmarks of this process. Furthermore, we describe in vivo assays to evaluate wound healing success and the initiation of pharynx reformation. Using our described landmarks for regeneration and in vivo assays, we analyze the effects of perturbing either transcription or cellular proliferation on the regenerative process. Interestingly, neither one of these experimental perturbations has major effects on wound closure, although they slightly delay or partially block it. We further show that while the inhibition of transcription blocks regeneration in a very early step, inhibiting cellular proliferation only affects later events such as pharynx reformation and tentacle elongation.

A new species of Diadumene (Actiniaria: Diadumenidae) from the subtropical coast of Brazil.

Diadumene paranaensis n. sp., collected from the Yacht Club of Paranaguá (Paranaguá Bay, Paraná State, southern Brazil), is described as a new species of sea anemone, based on external and internal morphology, cnidome, and molecular data for 16S/CO3 mitochondrial DNA. This species is partially similar to D. cincta due to the presence of macrobasic p-amastigophores in the tentacles, but is distinguished by the cinclides arranged in longitudinal rows and microbasic p-amastigophores in the acontia.

Morphological Variability and Distinct Protein Profiles of Cultured and Endosymbiotic Symbiodinium cells Isolated from Exaiptasia pulchella.

Symbiodinium is a dinoflagellate that plays an important role in the physiology of the symbiotic relationships of Cnidarians such as corals and sea anemones. However, it is very difficult to cultivate free-living dinoflagellates after being isolated from the host, as they are very sensitive to environmental changes. How these symbiont cells are supported by the host tissue is still unclear. This study investigated the characteristics of Symbiodinium cells, particularly with respect to the morphological variability and distinct protein profiles of both cultured and endosymbiotic Symbiodinium which were freshly isolated from Exaiptasia pulchella. The response of the cellular morphology of freshly isolated Symbiodinium cells kept under a 12 h L:12 h D cycle to different temperatures was measured. Cellular proliferation was investigated by measuring the growth pattern of Symbiodinium cells, the results of which indicated that the growth was significantly reduced in response to the extreme temperatures. Proteomic analysis of freshly isolated Symbiodinium cells revealed twelve novel proteins that putatively included transcription translation factors, photosystem proteins, and proteins associated with energy and lipid metabolism, as well as defense response. The results of this study will bring more understandings to the mechanisms governing the endosymbiotic relationship between the cnidarians and dinoflagellates.

Evolution of anthozoan polyp retraction mechanisms: convergent functional morphology and evolutionary allometry of the marginal musculature in order Zoanthidea (Cnidaria: Anthozoa: Hexacorallia).

BACKGROUND: Retraction is among the most important basic behaviors of anthozoan Cnidaria polyps and is achieved through the coordinated contraction of at least six different muscle groups. Across the Anthozoa, these muscles range from unrecognizable atrophies to massive hypertrophies, producing a wide diversity of retraction abilities and functional morphologies. The marginal musculature is often the single largest component of the retraction mechanism and is composed of a diversity of muscular, attachment, and structural features. Although the arrangements of these features have defined the higher taxonomy of Zoanthidea for more than 100 years, a decade of inferring phylogenies from nucleotide sequences has demonstrated fundamental misconceptions of their evolution. RESULTS: Here we expand the diversity of known marginal muscle forms from two to at least ten basic states and reconstruct the evolution of its functional morphology across the most comprehensive molecular phylogeny available. We demonstrate that the evolution of these forms follows a series of transitions that are much more complex than previously hypothesized and converge on similar forms multiple times. Evolution of the marginal musculature and its attachment and support structures are partially scaled according to variation in polyp and muscle size, but also vary through evolutionary allometry. CONCLUSIONS: Although the retraction mechanisms are diverse and their evolutionary histories complex, their morphologies are largely reflective of the evolutionary relationships among Zoanthidea higher taxa and may offer a key feature for integrative systematics. The convergence on similar forms across multiple linages of Zoanthidea mirrors the evolution of the marginal musculature in another anthozoan order (Actiniaria). The marginal musculature varies through evolutionary allometry of functional morphologies in response to requirements for additional force and resistance, and the specific ecological and symbiotic functions of individual taxa.

Absence of consistent genetic differentiation among several morphs of Actinia (Actiniaria: Actiniidae) occurring in the Portuguese coast.

Actinia equina, the beadlet sea anemone, is a very labile species, displaying variable colour patterns, broad habitat choice and diverse modes of reproduction. Historically, studies using genetic markers such as allozymes and differences in habitat choice lead several authors to propose that different colour morphs could represent different species. One of the species defined was A. fragacea. In this paper, the relationships between brown, red and green colour morphs of A. equina and A. fragacea were studied, using two DNA fragments (one mitochondrial and one nuclear). Individuals were sampled from three different areas in Portugal separated by a maximum distance of 500 km. This is the first study applying direct sequencing of selected gene fragments to approach the validity of Actinia morphs as different genetic entities. The results show that, at least in the Portuguese coast, these colour morphs do not correspond to the two valid species recognized in the literature. The existence of cryptic species is discussed. 

Morphological revision of the genus Aiptasia and the family Aiptasiidae (Cnidaria, Actiniaria, Metridioidea).

Sea anemones of the genus Aiptasia Gosse, 1858 are conspicuous members of shallow-water environments worldwide and serve as a model system for studies of cnidarian-dinoflagellate symbiosis. However, to date there have been no comprehensive analyses investigating the systematics of the group. In addition, previously published phylogenetic studies of sea anemones have shown that the genus is not monophyletic. Herein we revise the genus Aiptasia and the family Aiptasiidae Carlgren, 1924 using newly-collected material. We find that the formerly-named A. pallida (Agassiz in Verrill, 1864) (now Exaiptasia pallida comb. nov.) encompasses a single, widespread species from the tropics and subtropics; we erect a new genus, Exaiptasia gen. nov., for this species primarily based on cnidae, mode of asexual reproduction and symbionts. We also find morphological evidence that supports splitting A. mutabilis into two species: A. couchii (Cocks, 1851) and A. mutabilis. In addition, we find Bellactis Dube, 1983 (formerly placed within Sagartiidae Gosse, 1858) and Laviactis gen. nov. (formerly known Ragactis Andres, 1883, whose familial placement was previously uncertain) belonging within Aiptasiidae. Aiptasiidae is a morphologically homogeneous family whose members (those species in genera Aiptasia, Aiptasiogeton Schmidt, 1972, Bartholomea Duchassaing de Fombressin & Michelotti, 1864, Bellactis, Exaiptasia gen. nov., and Laviactis gen. nov.) are characterized by ectodermal longitudinal muscles in the distal column, rows of cinclides in mid-column, microbasic b-mastigophores in the column, and acontia with basitrichs and microbasic p-amastigophores.

The bilaterian head patterning gene six3/6 controls aboral domain development in a cnidarian.

The origin of the bilaterian head is a fundamental question for the evolution of animal body plans. The head of bilaterians develops at the anterior end of their primary body axis and is the site where the brain is located. Cnidarians, the sister group to bilaterians, lack brain-like structures and it is not clear whether the oral, the aboral, or none of the ends of the cnidarian primary body axis corresponds to the anterior domain of bilaterians. In order to understand the evolutionary origin of head development, we analysed the function of conserved genetic regulators of bilaterian anterior development in the sea anemone Nematostella vectensis. We show that orthologs of the bilaterian anterior developmental genes six3/6, foxQ2, and irx have dynamic expression patterns in the aboral region of Nematostella. Functional analyses reveal that NvSix3/6 acts upstream of NvFoxQ2a as a key regulator of the development of a broad aboral territory in Nematostella. NvSix3/6 initiates an autoregulatory feedback loop involving positive and negative regulators of FGF signalling, which subsequently results in the downregulation of NvSix3/6 and NvFoxQ2a in a small domain at the aboral pole, from which the apical organ develops. We show that signalling by NvFGFa1 is specifically required for the development of the apical organ, whereas NvSix3/6 has an earlier and broader function in the specification of the aboral territory. Our functional and gene expression data suggest that the head-forming region of bilaterians is derived from the aboral domain of the cnidarian-bilaterian ancestor.