Biochemical genetics and taxonomy in Plumatella fungosa and P. repens (Bryozoa: Phylactolaemata)

SUMMARY. Some authors have recently concluded that, using morphological criteria, the freshwater bryozoans Plumatella repens and P. fugosa cannot be separated and should be regarded as conspecific. To test this conclusion, electrophoretic techniques have been used to examine genetic differences between the two nominate species at several enzyme loci. Significant variation at a malate dehydrogenase locus and three aminopeptidase loci establish beyond doubt that P. repens and P. fugosa are separate but related species. No significant variation was found between two populations of P. repens . Morphological characters for the distinction of the two species are discussed and evaluated.     

Biochemical genetics and taxonomy in Plumatella emarginata and P. repens (Bryozoa: Phylactolaemata)

SUMMARY. Although morphological distinctions are well documented, many authors have regarded the freshwater bryozoan Plumatella emarginata as a variety of P. repens. Differences between the two nominate species have been studied by the electrophoretic examination of genetic variation at enzyme loci. Genetic identity (Nei, 1972) was 0.286, a value well below that expected for conspecific allopatric populations. The results leave little doubt that specimens of the two species are from quite distinct and separate gene pools, with an unexpectedly high level of genetic differentiation. It is therefore concluded that P. emarginata is a valid species and is not merely a variety of P. repens. Morphological differences between the two species are also discussed.     

Ultrastructural study of metamorphosis in the freshwater bryozoan Plumatella fungosa (Bryozoa,Phylactolaemata)

Summary

At metamorphosis the attachment of the Plumatella larva to the substrate is effected by secretions from glandular cells in the apical plate, the leading pole during swimming. The larval mantle folds back and slides down towards the substrate. By ciliary activity an adhesive secretion is spread over the metamorphosing larva and the attachment area. Two polypides appear through the larval terminal opening. The mantle fold, together with gland cells, nerve cells, sensory cells, and muscle cells from the larva form a nutritive cell mass. Reduction of this nutritive cell mass is accomplished by autolysis and phagocytosis. An invaginated area of the nutritive cell mass is provided with a dense layer of microvilli, which seem to have an absorbtive function. The nutritive cell mass consisting of transitory larval tissues provides a significant source of nutrient for the developing polypide buds.     

Novel morphological and genetic tools to discriminate species among the family Plumatellidae (Phylactolaemata,Bryozoa)

Some species of the freshwater bryozoans (Bryozoa, Phylactolaemata) belonging to the genus Plumatella are remarkably difficult to identify because of the large similarity of superficial architecture of their statoblasts. The examination of statoblasts by scanning electron microscope (SEM) has in fact resolved only some taxonomic questions. In this article, the authors report on novel morphological and molecular traits to discriminate among ten species of Plumatellidae (P. viganoi, P. repens, P. geimermassardi, P. rugosa, P. reticulata, P. casmiana, P. fungosa, P. emarginata, P. vaihiriae, and Hyalinella punctata). The former traits are based on shape, number, and position of annular chamber pores, whereas the latter reside on amplification and sequence analysis of the Internal Transcribed Spacer (ITS) region of nuclear rDNA. The successful amplification of ITS region from statoblasts and zooidial tubules allowed us to sequence this region on all the species investigated. The ITS sequences showed the presence of sufficient and informative polymorphisms to discriminate among morphologically similar species. It is noteworthy that the resulting ITS phylogenetic tree largely corroborated the distinction of at least two groups of freshwater bryozoans inferred on the basis of the annular chamber pore morphology. This study provides innovative approaches to reliably characterize freshwater bryozoans species and gain more insight into their taxonomy, phylogenetic relationship, and biodiversity.     

Sequential development of Buddenbrockia plumatellae (Myxozoa: Malacosporea) within Plumatella repens (Bryozoa: Phylactolaemata)

Colonies of the freshwater bryozoan Plumatella repens collected from a river in the UK were found to be infected with the myxozoan parasite Buddenbrockia plumatellae following laboratory maintenance. Optimisation of the bryozoan diet allowed maintenance of infected colonies for 90 d, permitting observation by light and electron microscopy of the sequential parasitic developmental cycle. Parasite stages were associated with host peritoneum, identifying the primary developmental phase. The association of B. plumatellae cells with peritoneal basal lamina and morphological similarities between parasite and host suggested that the parasite remodelled host tissue. Progressive expansion and elongation of individual parasites led to the release of freely floating vermiform stages within the host coelomic cavities. Within these 'worms', intraluminal masses developed, resulting in the formation of spores. Upon maturation, the 'worms' ruptured, releasing many spores within the host that were subsequently discharged. Although parasitism led to increased bryozoan fragmentation and lowered statoblast production, some colonies did survive, resulting in repeated waves of infection. Long-term laboratory maintenance of infected bryozoan colonies could provide a means of maintaining B. plumatellae for study until the full life cycle is ascertained.     

Development and molecular characterisation of the microsporidian Schroedera airthreyi n. sp. in a freshwater bryozoan Plumatella sp. (Bryozoa: Phylactolaemata)

The development of a new species of microsporidian, infecting a freshwater Plumatellid bryozoan, is described. The small-subunit rDNA, internal transcribed spacer region (ITS), and partial large-subunit rDNA genes were sequenced. Phylogenetic analysis demonstrated that the parasite clustered with Schroedera plumatellae. However, while there were morphological affinities with this species, significant differences were also observed. The infection initially appeared as a roughening of the peritoneum lining the metacoelom of the bryozoan. This roughening resolved into meront-infected syncytia, composed of interconnected cells of the body wall that detached to float in the coleomic cavity. Spores were observed to develop within these syncytia. All stages of development were diplokaryotic in contrast to S. plumatellae, which has a distinct monokaryotic merogony preceding sporogony. The infection was pathogenic to the host. Direct bryozoan-bryozoan transmission was not observed. We propose to name the microsporidian Schroedera aithreyi n. sp.     

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.     

Stereoscan studies of phylactolaemate bryozoan statoblasts including a key to the statoblasts of the British and European Phylactolaemata

The stereoscan electron microscope has been used to study morphological features of the statoblasts of nine phylactolacmate species. Pores present in the walls of annulus chambers of floating statoblasts are fully described for the first time. The taxonomic significance of surface patterning is assessed, and a key to the species found in Britain and Europe is included.     

Freshwater bryozoans (Bryozoa) of Norway III: distribution and ecology of Plumatella fruticosa

Bryozoans were investigated during field studies of 601 lakes and other surface water bodies throughout Norway from 1960 to 1978. The frequency of occurrence of Plumatella fruticosawas evaluated in relation to 12 environmental variables. Statistically significant deviations from the frequencies expected on the basis of random distribution were described using the categories preference, avoidance, and absence. According to our material P. fruticosais one of the most common bryozoan species in Norwegian fresh water, represented in samples from 251 localities. This species occurred frequently all over the country, north to 71° 06 N (the northernmost record globally). Maximum elevation above sea level was 1179 m (maximum for Northern Europe).In most studies of freshwater bryozoans from the holarctic region, Plumatella fruticosahas been reported as widely distributed, but locally rare. In Norway, however, P. fruticosa is frequently found all over the country, even far to the north. The species apparently finds an optimal climate in the cold temperate and cold regions of Norway. Plumatella fruticosapreferred lakes, avoided slow-flowing rivers and ponds, and was absent in smaller water bodies. The species preferred somewhat higher elevation (400–900 m above sea level), but avoided lakes with the lowest summer temperatures (below 11 °C). P. fruticosa also preferred oligotrophic conditions with poor aquatic vegetation, stony shores, lakes poor in calcium and magnesium (sometimes almost comparable with distilled water), where the water was clear and colourless, and slightly acidic to neutral. The species also preferred lakes surrounded by Sphagnum bogs and was absent when pH was below 5.2. P. fruticosa avoided eutrophic conditions with rich aquatic vegetation, alkaline water (pH above 7.0), lakes with a higher content of calcium and magnesium and those with strongly coloured water (above 100 mg Pt l^–1). In spite of its preference for ion-poor conditions, it was also found in a brackish water lake. For most environmental variables, the species had a wider tolerance range than reported from elsewhere.     

Ultrastructure of Buddenbrockia allmani n. sp. (Myxozoa, Malacosporea), a parasite of Lophopus crystallinus (Bryozoa, Phylactolaemata)

Development of a new species of malacosporean myxozoan (Buddenbrockia allmani n. sp.) in the bryozoan Lophopus crystallinus is described. Early stages, represented by isolated cells or small groups, were observed in the host's body wall or body cavity. Multiplication and rearrangement of cells gave an outer cell layer around a central mass. The outer cells made contact by filopodia and established adherens junctions. Sporoplasmosomes were a notable feature of early stages, but these were lost in subsequent development. Typical malacosporean sacs were formed from these groups by attachment of the inner (luminal) cells by a basal lamina to the outer layer (mural cells). Division of luminal cells gave rise to a population of cells that was liberated into the lumen of the sac. Mitotic spindles in open mitosis and prophase stages of meiosis were observed in luminal cells. Centrioles were absent. Detached luminal cells assembled to form spores with four polar capsules and several valve cells surrounding two sporoplasms with secondary cells. Restoration of sporoplasmosomes occurred in primary sporoplasms. A second type of sac was observed with highly irregular mural cells and stellate luminal cells. A radially striated layer and dense granules in the polar capsule wall, and previous data on 18 rDNA sequences enabled assignment of the species to the genus Buddenbrockia, while specific diagnosis relied on the rDNA data and on sac shape and size.     

Transmission of Tetracapsuloides bryosalmonae (Myxozoa: Malacosporea) to Fredericella sultana (Bryozoa: Phylactolaemata) by various fish species

Tetracapsuloides bryosalmonae is a myxozoan parasite of salmonids and freshwater bryozoans, which causes proliferative kidney disease (PKD) in the fish host. To test which fish species are able to transmit T. bryosalmonae to bryozoans, an infection experiment was conducted with 5 PKD-sensitive fish species from different genera. Rainbow trout Oncorhynchus mykiss, brown trout Salmo trutta, brook trout Salvelinus fontinalis, grayling Thymallus thymallus and northern pike Esox lucius were cohabitated with T. bryosalmonae-infected Fredericella sultana colonies and then subsequently cohabitated with statoblast-reared parasite free Bryozoa. Statoblasts from infected colonies were tested by PCR to detect cryptic stages of T. bryosalmonae, which may indicate vertical transmission of the parasite. In this study, brown trout and brook trout were able to infect Bryozoa, while there was no evidence that rainbow trout and grayling were able to do so. Few interstitial kidney stages of the parasite were detected by immunohistochemistry in brown trout and brook trout, while rainbow trout and grayling showed marked proliferation of renal interstitial tissue and macrophages with numerous parasite cells. Intraluminal stages in the kidney tubules were only detected in brown trout and rainbow trout. In contrast to previous observations, pike was not susceptible to PKD in these trials according to the results of T. bryosalmonae-specific PCR. No DNA of T. bryosalmonae was detected in any statoblast.     

Proliferative, presaccular stages of Tetracapsuloides bryosalmonae (Myxozoa: Malacosporea) within the invertebrate host Fredericella sultana (Bryozoa: Phylactolaemata)

Proliferative kidney disease (PKD), caused by the malacosporean parasite, Tetracapsuloides bryosalmonae, is a major disease of salmonid culture both in western Europe and North America. The fish are infected from spores that develop within freshwater bryozoans and are released into the water column. Although sporogenesis has been studied in the bryozoan host and occurs within sacs, the formation of these sacs from presaccular stages has only been hypothesized. Examination of infected bryozoans by using a range of techniques identified proliferating, presaccular amoeboid stages of T. bryosalmonae on the body wall of the bryozoan Fredericella sultana. These stages possessed unique electron-dense bodies and were observed as aggregating within the bryozoan metacoel, differentiating to form spore sacs. Spore sac growth was associated with the assimilation of the presaccular parasites rather than through cryptomitosis of sac mural cells. This sac formation through aggregation and assimilation suggests an intriguing mechanism by which T. bryosalmonae can cross-fertilize.     

Plumatella nitens, a new species of freshwater bryozoan from North America (Ectoprocta: Phylactolaemata), previously misidentified

Plumatella nitens is a newly recognized species of phylactolaemate bryozoan in North America. It has previously been combined with either P. repens or P. fungosa, from which it differs primarily by the floatoblast. In P. nitens the ventral floatoblast annulus is uniformly narrow with no significant widening at the poles. The dorsal floatoblast fenestra is conspicuously larger than in either P. repens or P. fungosa. Reticulated ridges on the dorsal fenestra are weak along the margins, becoming unusually prominent in the center. The sessoblast is densely covered with uneven papillae. Spotty sampling so far shows a distribution only in the northern half of North America, including Massachusetts, Michigan, Minnesota, Wisconsin, Ontario, and the northern regions of Illinois, Indiana, and Ohio.     

Phylogeny and taxonomy of Phylloporia (Hymenochaetales): new species and a worldwide key to the genus

Species of Phylloporia (Hymenochaetales, Basidiomycota) are polypores with tiny, yellowish and thick-walled basidiospores and are highly divergent in morphology. The monophyly of 35 cosmopolitan isolates of Phylloporia was strongly supported based on analysis of the nLSU rDNA gene but with exclusion of P. resupinata. Among the 19 lineages recognized in the nLSU rDNA phylogeny five new species from China, Phylloporia crataegi, P. fontanesiae, P. gutta, P. nandinae and P. oreophila, were revealed and these species are introduced with additional morphological evidence. A diagnostic key to all 23 thus far accepted species in Phylloporia is provided.     

Phylogeny, classification and taxonomy of European dragonflies and damselflies (Odonata): a review

Although Europe is the cradle of dragonfly systematics and despite great progress in the last 2 decades, many issues in naming its species and understanding their evolutionary history remain unresolved. Given the public interest, conservation importance and scientific relevance of Odonata, it is time that remaining questions on the species?? status, names and affinities are settled. We review the extensive but fragmentary literature on the phylogeny, classification and taxonomy of European Odonata, providing summary phylogenies for well-studied groups and an ecological, biogeographic and evolutionary context where possible. Priorities for further taxonomic, phylogenetic and biogeographic research are listed and discussed. We predict that within a decade the phylogeny of all European species will be known.     

Freshwater bryozoans (Bryozoa) of Norway IV: Distribution and ecology of four species of Plumatella with notes on Hyalinella punctata

Bryozoans were investigated during field studies of 601 lakes and other surface water bodies throughout Norway from 1960 to 1978. The frequency of occurrence of Plumatella repens was evaluated in relation to 12 environmental variables. Statistically significant deviations from the frequencies expected on the basis of random distribution were described using the categories preference, avoidance and absence. P. repens is one of the most common bryozoan species in Norway. It is represented at 227 localities in our material and by 29 additional records. The species occurred frequently all over the country, north to 71°09N (the northernmost record on the European mainland). Maximum elevation above sea level was 1052 m (maximum for Northern Europe). P. repens preferred lakes, avoided rivers, and was absent from the smallest water bodies. The species preferred (1) low elevation (2–200 m above sea level), (2) medium water temperature, (3) rich aquatic vegetation (eutrophic conditions), (4) small wave action, (5) high content of calcium and magnesium, (6) pH 6.4–9.6, and (7) rather high water colour. Otherwise P. repens avoided (1) habitats above 500 m but occurred up to 1052 m, (2) the lowest water temperature intervals, (3) sites with poor aquatic vegetation and stony shores, (4) medium wave action, (5) sites with a low calcium and magnesium content, (6) lakes of low water colour, and (7) lakes with pH below 6.6: it was absent from lakes with pH below 5.2. For many environmental variables, the species had a wider tolerance range than reported from elsewhere. P. fungosa, P. casmiana, and P. emarginata are all rare in Norway. The total numbers of known localities, with our records in (), are 18 (11), 7 (7), and 7 (5), respectively. These sites are all from lowland areas up to 133 m above sea level. Environmental variables in the habitats are described. P. fungosa was represented by a single floatoblast in each of the four northernmost lakes where it was recorded. One of these lakes was in North Norway some 1000 km away from the nearest known sites with living colonies. The presence of large colonies of P. fungosa in some parts of southern Norway and only `single floatoblast lakes' further north is discussed in relation to the equilibrium theory of island biogeography: birds facilitate immigration by carrying floatoblasts and environmental conditions prevent their germination and the development of living colonies. All records of P. casmiana and P. emarginata were from South Norway. Results for P. fruticosa have been published previously. Notes are given on an old and now missing sample from ca. 1900, identified by Lacourt (1968) as Hyalinella punctata – the only record of this species from Norway.     

The genera Cribrilina and Collarina (Bryozoa, Cheilostomatida) in the British Isles and North Sea Basin, Pliocene to present day

Seven species assigned to the genus Cribrilina are illustrated by scanning electron microscopy (SEM) and redescribed. At the present day, three species occur in the area studied: C. punctata (Hassall), C. cryptooecium Norman and C. annulata (Fabricius). The presence of Collarina balzaci (Audouin), which has previously been confused with Cribrilina punctata , is also reported. The following species of Cribrilina are known as Pliocene and Pleistocene fossils: C. punctata, C. cryptooecium, C. watersi Andersson, C. puncturata (Wood) and C. mucronata Canu & Lecointre. In addition, C. annulata and C. spitsbergensis Norman have been reported as fossils, but these occurrences could not be confirmed here by the examination of actual material. Lectotypes are selected for C. spitsbergensis, C. watersi, C. puncturata and C. mucronata. Type material of the American fossil C. marylandica , which has been synonymised with C. punctata , is illustrated.     

Unexpectedly high diversity of Monoporella (Bryozoa: Cheilostomata) in the Aleutian Islands, Alaska: taxonomy and distribution of six new species

The cheilostome bryozoan genus Monoporella is poorly resolved taxonomically; only four Recent species have been formally described, though several undescribed species have been reported in the literature. The literature indicates no more than five species in the genus occurring in any local region of the world, with one to three species in most regions where the genus has been reported. I examined bryozoans from 52 trawl catches in the western and western-central Aleutian Islands, Alaska, and found specimens of Monoporella in 12 of these samples. Study of these specimens by scanning electron microscopy (SEM) revealed six new species that are described herein: M. flexibila, M. elongata, M. gigantea, M. ellefsoni, M. seastormi, and M. aleutica. Two of the species have erect colony morphologies, a condition not previously reported in Monoporella. The species diversity of Monoporella appears to be greater in the Aleutians than in any other part of the world adequately surveyed. I discuss whether this apparent high diversity is an artifact due to insufficient sampling in the deep shelf zone, and present two hypotheses to explain this high diversity should it prove not to be an artifact: 1) the present high local diversity represents a relict of past high diversity occurring broadly around the North Pacific rim; and 2) a local radiation of Monoporella occurred in the Aleutian archipelago.