The Morphology of the Phoronid Phoronopsis harmeri

We studied the morphology and gross anatomy of the phoronid Phoronopsis harmeriusing light microscopy and scanning electron microscopy. The body of Ph. harmeriis subdivided into several regions: a lophophore, a head, anterior, and posterior parts of the body, and an ampulla. The lophophore is spiral and comprises 0.5 turns. In males, there are lophophoral organs in the tentacular crown; under the lophophore, there is an epithelial fold or collar. The internal organization shows partitioning into three coeloms: the coelom of the epistome, the tentacular coelom, and the trunk coelom. The trunk coelom is divided into a series of chambers by a complex system of mesenteries. The intestine is U-shaped, and the epistome is located above the mouth opening. The circulatory system is closed and consists of the following vessels: the efferent and afferent circular, left and right lateral (efferent), and medial (afferent) vessels. In Ph. harmeri, there is a dorsolateral (afferent) vessel running through the ampulla and the lower part of the posterior trunk region. The excretory system is composed of paired metanephridia that resemble asymmetrical U-shaped tubes. Sexual dimorphism is characteristic of the structure of the distal part of the nephridium, which opens into the body cavity. The nervous system consists of a dorsal nervous field, a circular nerve plexus, and a giant left nerve fiber. Ph. harmeriis a dioecious species; the gametes develop in a vasoperitoneal tissue that envelops the intestine in the posterior part of the trunk region.     

Filter feeding mechanism in the phoronid <Emphasis Type="Italic">Phoronopsis harmeri</Emphasis> (Phoronida,Lophophorata)

Phoronids, like other Lophophorata (Bryozoa and Brachiopoda) are filter feeders. The lophophore performs various functions, the most important of which is the collection and sorting of food particles. The mechanism of sorting has been well studied for many other groups of invertebrate, but until now it has remained obscure for phoronids. With the help of functional morphology data we are proposing a possible scheme of sorting in phoronids on the example of Phoronopsis harmeri. The lower limit of the particle size is defined by the distance between laterofrontal cilia of tentacles and equals 1.2 μm. Larger particles are transferred by frontal cilia to the basis of the tentacles, where they pass into the lophophoral groove. The distance between the epistome and the external row of tentacles regulates the upper limit of the particle size that are suitable for food. Only particles whose size does not exceed 12 μm get into the lophophoral groove and further into the mouth. Larger particles collect in the space above the epistome and are removed from the lophophore. The size of the food particles that phoronids consume by filtration lies in a range 1.2–12 μm. These are bacteria and small phytoplankton organisms. At the same time the significant individual mobility of the phoronid tentacles plays an important role in the expansion of the pabular spectrum to large inactive zooplankton and phytoplankton organisms reaching a size of 50–100 μm.     

Inter‐ and intraspecific plasticity in distribution patterns of immunoreactive compounds in actinotroch larvae of Phoronida (Lophotrochozoa)

Recent molecular data place Phoronida within the protostome superclade Lophotrochozoa, where they have been suggested to form a monophyletic assemblage with Brachiopoda and/or Nemertea. Herein, the anatomy of the nervous system and the structure of the apical organ are described for two larval stages of Phoronis muelleri in order to contribute to the discussion concerning the evolution of lophotrochozoan nervous systems. Specimens were investigated by confocal laser scanning microscopy using antibodies against the serotonin‐like immunoreactive (serotonin‐lir), the FMRF‐amide‐like immunoreactive (FMRFamide‐lir) and the small cardioactive peptide B‐like immunoreactive (small cardioactive peptide B‐lir) compounds of the nervous system. Consistent with larvae of other phoronid species, we found a complex apical organ that consists of numerous serotonin‐lir flask‐shaped cells, additional bi‐ or multipolar serotonin‐lir cells and several FMRFamide‐lir perikarya. A detailed comparison between our results and those of a previous study on the same species shows significant differences in the innervation of the preoral lobe, the tentacles and the telotroch. Our work is the first to prove the presence of small cardioactive peptide B in phoronids. In larvae of P. muelleri, it is expressed in neurites along the margin of the preoral hood, in the mesosome, in the tentacles, in the trunk as well as in the apical organ. A positive signal for this peptide is also known from molluscs, annelids and arthropods, indicating that it was also part of the protostomian groundplan. In contrast to a recent study on another phoronid species, Phoronopsis harmeri, we did not find a ventral neurite bundle in the larval stages investigated herein, thus leaving the question open whether this structure was part of the phoronid groundplan or evolved de novo in P. harmeri.     

The effect of a tube-building phoronid on associated infaunal species diversity, composition and community structure

Habitat modifying organisms can alter the distribution of associated species. We surveyed soft-sediment patches in Bodega Harbor, California and found that patches with high densities of the phoronid Phoronopsis harmeri (Pixell, 1912), a chemically-defended tube-building lophophorate, have higher infaunal abundance and richness than similar patches with low densities of P. harmeri. To determine whether this difference was driven by P. harmeri and whether this difference is attributable to the activities of the organism, or simply its physical structure, we conducted a field experiment with four treatments: live phoronids, mimics of phoronid structure, phoronid-free sediments (bare) and unmanipulated sediments. Although the field experiment did not detect differences in the overall abundance or richness of infauna among the manipulated treatments, some of the individual species did show a positive response to the presence of phoronids and phoronid structure (i.e., mimics). In particular, the polychaete Boccardia proboscidea, the amphipod Monocorophium uenoi, and harpacticoid copepods were facilitated by the presence of phoronids and phoronid structure when there was sediment disturbance. The inconsistency between the results of the survey and of the manipulative experiment may be largely driven by the disturbance caused by the manipulation. However, where P. harmeri has an effect, it is generally positively associated with infaunal abundance that may be attributable to the stabilization of sediments.     

Cucumaria anivaensis (Holothuroidea: Dendrochirotida)—A New Species of Holothurians from the Coastal Waters of Sakhalin

Cucumaria anivaensis sp. nov. is described from Aniva Bay (Sakhalin). This species is characterized by having large lengthened plates in the body skin with large apertures in the medial region and small apertures at both edges, very long plates with an outgrowth on one side in the tentacles, and an expanded basis of the radial plates of the pharyngeal ring. Some plates of the oral disk have strong enlargement in the medial region.     

Ultrastructure of the Blood System in the Phoronid Phoronopsis harmeri Pixell, 1912: 1. Capillaries

Four types of blood capillaries of the phoronid Phoronopsis harmeri are described. These are capillaries of the tentacles, of the body, of the stomach plexus, and of the vasoperitoneal tissue. The wall of capillary consists of cells of the coelomic lining, a layer of extracellular matrix, and separate endothelial cells. Myoepithelial coelomic cells of tentacle capillaries contain cross-striated fibers. In capillaries of the body and the stomach plexus, the myofilaments are smooth. In the cells of the wall of vasoperitoneal tissue capillaries, myofilaments are lacking. The cells of the vessel wall of the tentacles, the body, and the vasoperitoneal tissue bear a single cilium. The cells of capillaries of the stomach plexus lack a cilium. The ultrastructure of erythrocytes and amebocytes is described. In the cytoplasm of erythrocytes, there is a basal body. It is assumed that erythrocytes originated from the ciliary cells of the wall of the blood vessels.     

Modern Data on the Innervation of the Lophophore in Lingula anatina (Brachiopoda) Support the Monophyly of the Lophophorates

Evolutionary relationships among members of the Lophophorata remain unclear. Traditionally, the Lophophorata included three phyla: Brachiopoda, Bryozoa or Ectoprocta, and Phoronida. All species in these phyla have a lophophore, which is regarded as a homologous structure of the lophophorates. Because the organization of the nervous system has been traditionally used to establish relationships among groups of animals, information on the organization of the nervous system in the lophophore of phoronids, brachiopods, and bryozoans may help clarify relationships among the lophophorates. In the current study, the innervation of the lophophore of the inarticulate brachiopod Lingula anatina is investigated by modern methods. The lophophore of L. anatina contains three brachial nerves: the main, accessory, and lower brachial nerves. The main brachial nerve is located at the base of the dorsal side of the brachial fold and gives rise to the cross neurite bundles, which pass through the connective tissue and connect the main and accessory brachial nerves. Nerves emanating from the accessory brachial nerve account for most of the tentacle innervation and comprise the frontal, latero-frontal, and latero-abfrontal neurite bundles. The lower brachial nerve gives rise to the abfrontal neurite bundles of the outer tentacles. Comparative analysis revealed the presence of many similar features in the organization of the lophophore nervous system in phoronids, brachiopods, and bryozoans. The main brachial nerve of L. anatina is similar to the dorsal ganglion of phoronids and the cerebral ganglion of bryozoans. The accessory brachial nerve of L. anatina is similar to the minor nerve ring of phoronids and the circumoral nerve ring of bryozoans. All lophophorates have intertentacular neurite bundles, which innervate adjacent tentacles. The presence of similar nerve elements in the lophophore of phoronids, brachiopods, and bryozoans supports the homology of the lophophore and the monophyly of the lophophorates.     

First Records of Dinoflagellates Alexandrium margalefi Balech, 1994 and A. tamutum Montresor, Beran et John, 2004 in the Seas of the Russian Far East

New records of two Alexandrium species are reported for the Russian seas. A. margalefi Balech was found in Peter the Great Bay (Sea of Japan), and A. tamutum Montresor, Beran et John was found in Aniva and Sakhalinskii bays (Sea of Okhotsk). Both species were observed in summer in small numbers at water temperatures of 22– 24°C and 8.6–11°C, respectively. Data on the morphology and distribution of the species is provided.Original Russian Text Copyright © 2005 by Biologiya Morya, Selina, Morozova.     

The fauna of the South China Sea include unknown phoronid species: new records of larvae and adults

The Phoronida is a phylum of marine invertebrates that have a worldwide distribution and that form huge benthic aggregations in many aquatic areas. Although there are only 11 recognized species of phoronids, many species clearly remain to be described. The matching of larval and adult stages of the same species will help indicate which larvae belong to described species and which represent undescribed species whose adults have yet to be found. Larvae of four phoronid species were collected in Nha Trang Bay and investigated by light microscopy and molecular methods. Three of the described larvae belong to new phoronid species that have yet to be named. These larvae have unique morphological features and occupy separate positions on the phylogenetic tree of phoronids. One of the described larvae belongs to Phoronis hippocrepia or to a closely related species. Observations made with a new macrophotographic method indicated that Phoronopsis californica also occurs in Nha Trang Bay. Thus, according to records of larvae and adults, Nha Trang Bay contains at least nine phoronid species: Phoronopsis californica, Phoronopsis malakhovi, Phoronis australis, Phoronis hippocrepia (or a closely related species), three unknown phoronid species whose larvae have unique morphological features and that apparently belong to the genus Phoronis, and two species, whose adults have unique set of morphological features. The richness of phoronids in this area suggests that the Indo-Pacific is a centre of phoronid biodiversity.     

Ciliary feeding structures and particle capture mechanism in the freshwater bryozoan Plumatella repens (Phylactolaemata)

Abstract. In contrast to marine bryozoans, the lophophore structure and the ciliary filter‐feeding mechanism in freshwater bryozoans have so far been only poorly described. Specimens of the phylactolaemate bryozoan Plumatella repens were studied to clarify the tentacular ciliary structures and the particle capture mechanism. Scanning electron microscopy revealed that the tentacles of the lophophore have a frontal band of densely packed cilia, and on each side a zigzag row of laterofrontal cilia and a band of lateral cilia. Phalloidin‐linked fluorescent dye showed no sign of muscular tissue within the tentacles. Video microscopy was used to describe basic characteristics of particle capture. Suspended particles in the incoming water flow, set up by the lateral ‘pump’ cilia on the tentacles, approach the tentacles with a velocity of 1–2 mm s^‐1. Near the tentacles, the particles are stopped by the stiff sensory laterofrontal cilia acting as a mechanical sieve, as previously seen in marine bryozoans. The particle capture mechanism suggested is based on the assumed ability of the sensory stiff laterofrontal cilia to be triggered by the deflection caused by the drag force of the through‐flowing water on a captured food particle. Thus, when a particle is stopped by the laterofrontal cilia, the otherwise stiff cilia are presumably triggered to make an inward flick which brings the restrained particle back into the downward directed main current, possibly to be captured again further down in the lophophore before being carried to the mouth via the food groove. No tentacle flicks and no transport of captured particles on the frontal side of the tentacles were observed. The velocity of the metachronal wave of the water‐pumping lateral cilia was measured to be ～0.2 mm s^‐1, the wavelength was ～7 μm, and hence the ciliary beat frequency estimated to be ～30 Hz (～20 °C). The filter feeding process in P. repens reported here resembles the ciliary sieving process described for marine bryozoans in recent years, although no tentacle flicks were observed in P. repens. The phylogenetic position of the phylactolaemates is discussed in the light of these findings.     

Phoronid phylogenetics (Brachiopoda; Phoronata): evidence from morphological cladistics,small and large subunit rDNA sequences,and mitochondrial cox1

A matrix of 24 morphodevelopmental characters and an alignment of small subunit (SSU) and large subunit (LSU) rDNA nuclear and cox1 mitochondrial gene sequences (～4500 sites) were compiled from up to 12 phoronids including most named taxa, but probably constituting only a portion of worldwide diversity. Morphological data were analysed by weighted parsimony; sequence data by maximum and Bayesian likelihood, both with Phoronis ovalis as the local outgroup. Morphological and sequence‐based phylogenies were similar, but not fully congruent. Phoronid rDNAs were almost free from mutational saturation, but cox1 showed strong saturation unless distant outgroups and P. ovalis were omitted, suggesting that many phoronid divergences are old (≥100 Myr). rDNA divergence between named phoronid taxa is generally substantial, but Phoronopsis harmeri (from Vladivostock) and Phoronopsis viridis (from California) are genetically close enough to be conspecific. In another alignment, of 24 taxa, phoronid rDNAs were combined with data from brachiopods and distant (molluscan) outgroups. The relative ages of divergence between phoronids and their brachiopod sister‐groups, of the split between the P. ovalis and non‐ovalis lineages, and of other phoronid splits, were estimated from this alignment with a Bayesian lognormal uncorrelated molecular clock model. Although confidence limits (95% highest probability density) are wide, the results are compatible with an Early Cambrian split between phoronids and brachiopods and with the Upper Devonian latest age suggested for the P. ovalis/non‐ovalis split by the putative phoronid ichnofossil, Talpina. Most other ingroup splits appear to be ～50–200 Myr old. Inclusion of phoronids with brachiopods in the crown clade pan‐Brachiopoda suggests that a distinctive metamorphosis and absence of mineralization are ancestral phoronid apomorphies. Worldwide diversity and possible associations between character‐states and life‐history attributes deserve comprehensive further study.     

Fouling community of the red king crab, <Emphasis Type="Italic">Paralithodes camtschaticus</Emphasis> (Tilesius 1815), in a subarctic fjord of the Barents sea

We examined the species composition of red king crab (Paralithodes camtschaticus) fouling communities in Dolgaya Bay, a small fjord of the Barents Sea, in August 2005 and 2006. In total, there were 13 species observed on 301 crabs collected from water depths of 5–90 m. Barnacles (Balanus crenatus; prevalence 42.9%) and blue mussels (Mytilus edulis; 11.6%) were the most common epibionts, while amphipods (Ischyrocerus commensalis) were the most common symbionts (28.6%). Infestation rates in Dolgaya Bay were different from those in an “open” area of the Barents Sea (Dalnezelenetskaya Bay), probably due to differences in hydrodynamic conditions. Differences in infestation prevalence and intensity were detected neither between male and female crabs nor between crabs collected at 5–35 m versus 90 m depths. Prevalence of common fouling species increased with host size. Amphipods I. commensalis colonized the carapace and limbs in Dolgaya Bay less frequently than in Dalnezelenetskaya Bay, probably due to interspecific competition with barnacles occupying the dorsal parts of the host. Juvenile barnacles and mussels dominated the fouling communities on the crabs. The age of barnacles did not exceed 2–4 months. However, the presence of 4-year-old mussels suggests that these older mollusks have been directly transferred from mussel beds to the hosts. Our results indicate that colonization by epibionts and symbionts is generally not disadvantageous for the crab hosts, except for some possible negative impacts of amphipods occupying the gills.     

The species composition and quantitative distribution of the diatom genus Pseudo-nitzschia H. Peragallo, 1990 in Russian waters of the Sea of Japan and the Sea of Okhotsk

This paper studies the species composition and quantitative distribution of diatoms that belong to the genus Pseudo-nitzschia in the Russian waters of the Sea of Japan and the Sea of Okhotsk. In total, 11 species of this genus were found in the area, including 7 that are known as being potentially toxic. The highest concentrations of Pseudo-nitzschia microalgae (1.4 × 10⁶–2.7 × 10⁶ cells/L) were found in the summer and autumn in the Peter the Great Bay of the Sea of Japan and the lowest concentrations (2.5 × 10²–1 × 10⁴ cells/L) were found in the Sakhalinsky and Akademiya bays of the Sea of Okhotsk. The species diversity of potentially toxic diatoms was greatest (seven species) and the cell concentrations highest (over 6 × 10⁵ cells/L) in the Peter the Great Bay, Sea of Japan, and in the Aniva Bay, Sea of Okhotsk. The density of potentially toxic species was highest near the northeastern coast of Sakhalin Island, in the Amur River estuary, and in adjacent waters. This paper also presents geographical distribution maps of Pseudo-nitzschia species and maps of the density distribution of potentially toxic microalgae over the studied area and identifies potential amnesic shellfish poisoning areas.     

Genus Alexandrium Halim, 1960 (Dinophyta) from the Pacific coast of Russia: Species composition, distribution, and dynamics

At present 8 species of Alexandrium genus have been found in seas and adjacent waters of Russia: A. acatenella, A. catenella, A. insuetum, A. margalefii, A. ostenfeldii, A. pseudogonyaulax, A. tamarense, and A. tamutum. The distribution and population density of Alexandrium species varied within the surveyed area of the Pacific: in the Sea of Japan and Sea of Okhotsk, 7 species were recorded; 3 species were recorded along the Pacific coast of Kamchatka; and 2 species were found in the Bering Sea. A. tamarense was the most widespread and abundant species over the area. A. insuetum was recorded only in the Sea of Japan, and A. catenella, in the Sea of Okhotsk (Terpeniya Bay). The highest concentration of Alexandrium spp. (2–7 million cells/l) was recorded along the Pacific coast of Kamchatka and in the Bering Sea; in the Sea of Okhotsk, a rather high concentration (51000 cells/l) was registered in Aniva Bay; in the Sea of Japan, the highest concentration was recorded in Peter the Great Bay (6000 cells/l). The distribution of cysts (spores) in surface sediments of the Pacific coast of Russia as a whole reflected the pattern of distribution of vegetative cells of Alexandrium. Cysts of Alexandrium cf. tamarense prevailed all over the area, with the maximum concentration along the Pacific coast of Kamchatka. Beyond that type of cysts, insignificant numbers of cysts of Alexandrium cf. minutum were recorded in Peter the Great Bay and Aniva Bay. Analysis of seasonal dynamics revealed that cells of Alexandrium spp. occurred in Peter the Great Bay from June up to September, and along the Pacific coast of Kamchatka from April to October. In the first region, the maximum density was recorded in August; it was provided by A. pseudogonyaulax (59% of the total density of Alexandrium), A. tamarense (35%), and A. insuetum (6%). In the second region, it was recorded in July, thanks only to development of A. tamarense.     

Architecture and function of the lophophore in the problematic brachiopod Heliomedusa orienta (Early Cambrian, South China)

The detailed structure of the lophophore is a key diagnostic character in the definition of higher brachiopod taxa. The problematic Heliomedusa orienta Sun and Hou, from the Lower Cambrian Chengjiang Lagerstätte of Yunnan, southwestern China, has a well-preserved lophophore, which is unlike that of any known extant or extinct brachiopods. Based on a comparative study of lophophore disposition in H. orienta and the extant discinid Pelagodiscus atlanticus, the in- and excurrent pattern and shell orientation of H. orienta are described and discussed. Reconstructions of lophophore shape and function are based on numerous specimens and comparison with P. atlanticus. The lophophore is composed of a pair of lophophoral arms that freely arch posteriorly rather than coiling anteriorly as commonly seen in fossil and recent lingulids. The lophophore is attached to the dorsal lobe of the mantle; it has neither calcareous nor chitinous supporting structures, and is disposed symmetrically on either side of the valve midline. The mouth can be inferred to be located at the base of the two brachial tubes, slightly posterior to the anterodorsal projection of the body wall. The lophophoral arms bear laterofrontal tentacles with a double row of cilia along their lateral edge, as in extant lingulid brachiopods. The main brachial axes are also ciliated, which presumably facilitated transport of mucous-bound nutrient particles to the mouth. The unique organization of the lophophore in Heliomedusa is not like any known fossil and living brachiopods. This clearly demonstrates that H. orienta is not a member of any crown group. It is here considered as a member of the brachiopod stem group, which challenges recent interpretations of a close discinid affinity.     

Ultrastructure of the body cavities in Phylactolaemata (Bryozoa)

Only species belonging to the bryozoan subtaxon Phylactolaemata possess an epistome. To test whether there is a specific coelomic cavity inside the epistome, Fredericella sultana, Plumatella emarginata, and Lophopus crystallinus were studied on the ultrastructural level. In F. sultana and P. emarginata, the epistome contains a coelomic cavity. The cavity is confluent with the trunk coelom and lined by peritoneal and myoepithelial cells. The lophophore coelom extends into the tentacles and is connected to the trunk coelom by two weakly ciliated coelomic ducts on either side of the rectum. The lophophore coelom passes the epistome coelom on its anterior side. This region has traditionally been called the forked canal and hypothesized to represent the site of excretion. L. crystallinus lacks an epistome. It has a simple ciliated field where an epistome is situated in the other species. Underneath this field, the forked canal is situated. Compared with the other species, it is pronounced and exhibits a dense ciliation. Despite the occurrence of podocytes, which are prerequisites for a selected fluid transfer, there is no indication for an excretory function of the forked canal, especially as no excretory porus was found. J. Morphol. 2009. © 2008 Wiley‐Liss, Inc.     

Two new species of <Emphasis Type="Italic">Paraliparis</Emphasis> (Scorpaeniformes: Liparidae) from the Ross Sea (Antarctica)

Liparidae from stomachs of Antarctic toothfish Dissostichus mawsoni Norman, 1937 (Nototheniidae) caught in the Ross Sea (Pacific sector of Antarctica) have been identified. Two new species of deep-water liparids of the genus Paraliparis Collett, 1879—P. caninus sp. nov. (at a depth of 1182–1651 m) and P. vipera sp. nov. (1700 m)—were described. Both species that turned out to be most similar to P. neelovi Andriashev, 1982, from the Kerguelen area (the Indo-Oceanic sector of the South Ocean) are combined with it into a species group “P. neelovi.” According to meristic characters, pattern of dentition, and the size of gill opening, species of “P. neelovi” are close to the species group “P. copei.” In collections from a depth of 1700 m, also two individuals of P. andriashevi Stein et Tompkins, 1989, known previously from only two types from the northern boundary of the Ross Sea were found. The new finding supports species validity and extends the known limits of its range. The wide distribution of bathybenthal Paraliparis having low fecundity and leading a near-bottom mode of life can be explained by the presence of mesopelagic juveniles and their dispersal via currents.