Timothy S. Wood

Ultrastructure of Buddenbrockia identifies it as a myxozoan and verifies the bilaterian origin of the Myxozoa.

The phylogenetic affinities of Buddenbrockia, a nematode-like parasite of freshwater bryozoans, have remained unknown since it was first reported in the nineteenth century. The discovery of Buddenbrockia parasitic in Hyalinella punctata in Ohio and Plumatella repens in France has provided material for the first ultrastructural study of this animal. This has revealed the presence of polar capsules, diagnostic myxozoan features, in the body wall. Other features, which place Buddenbrockia firmly among tetracapsulid myxozoans in the Class Malacosporea, are the unusual morphology of the polar capsules, the absence of the external tube in capsulogenesis, the body wall with its unusual cell junctions and utilization of freshwater bryozoans as hosts. The ultrastructural study has established the triploblastic organization of Buddenbrockia by confirmation of the presence of an inner layer of cells and 4 sets of longitudinal muscles. Our studies have, thus, simultaneously revealed that Buddenbrockia is a myxozoan and that the myxozoans are derived from bilaterians. The latter conclusion resolves the ongoing controversy over the triploblastic versus diploblastic nature of the Myxozoa. Our studies also provide evidence that bryozoans are ancestral hosts for the myxozoans and that loss of triploblast features has characterized the major radiation of the better known endoparasites of fish and worms in the Class Myxosporea.

Ectoproct Bryozoans of Ohio

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Freshwater bryozoans of New Zealand: A preliminary survey

Five bryozoan species were encountered in a 15-day survey of freshwater habitats in New Zealand. Listed in order of decreasing frequency these were: Fredericella sultana, Plumatella repens, P. emarginata, Paludicella articulata, and one plumatellid species not previously described. Micro- structural features of the floatoblast annulus separate the P. repens specimens into two distinct varieties, named here P. repens typica and P. repens rugosa. Paludicella, reported almost 100 years ago from the City of Dunedin waterworks, was still found only in a single reservoir of that city. Species distribution did not correlate significantly with water tempera- ture, current velocity, pH, or total dissolved solids. Two additional species believed to occur in New Zealand, Fredericella australiensis and Plumatella fungosa, were not seen in this brief survey. An iden- tification key is provided for New Zealand bryozoans.

Three new species of plumatellid bryozoans (Ectoprocta:Phylactolaemata) defined by statoblast nodules

Three new species of plumatellid (Phylactolaemata) bryozoans are distinguished largely by the presence of tiny, rash-like nodules on the floatoblast surface. Nodules are integral parts of the sclerotized floatoblast envelope, and they persist through generations of laboratory rearing. These minute structures are best detected by scanning electron microscopy. In Plumatella bushnelli, n. sp., nodules are densely distributed on the floatoblast annulus. Notable in this species are floatoblast dimensions: the dorsal fenestra measures >½ the overall length of 400 μm. The species is known only from single sites in North Carolina and New Zealand. Plumatella nodulosa, n. sp., bears nodules over the entire floatoblast surface, not just the annulus; otherwise, the species most resembles the widespread P. rugosa (Wood, Wood, Geimer, Massard, 1998). Plumatella nodulosa is reported from 5 lentic sites in Illinois, Ohio, and western New York. In Plumatella similirepens, n. sp., the floatoblast has a paved annulus with widely scattered nodules; unlike the European species, P. repens (L., 1758), the floatoblast suture lacks the row of prominent tubercles on either side. Plumatella similirepens is confirmed from 2 sites in Illinois. Contrary to numerous published works, P. repens is unknown in North America.

Biofouling of wastewater treatment plants by the freshwater bryozoan, Plumatella vaihiriae (Hastings, 1929)

Abstract We report large growths of a phylactolaemate bryozoan, Plumatella vaihiriae [Hastings, A. (1929) Notes on some little-known phylactolaematous polyzoa and description of a new species from Tahiti. Ann. Mag. Nat. Hist., 10(3), 300–311], from three widely separated domestic wastewater treatment plants in the United States. This relatively uncommon species is previously known only from Tahiti, Hawaii, Utah, and Argentina. The bryozoan colonies are capable of plugging pipes and filters. Free statoblasts are suspected of interfering with ultraviolet disinfection of wastewater. Laboratory reared specimens exhibit rapid, aggressive growth and produce vast quantities of free statoblasts which either float or sink. Devising effective control methods is impeded by limited knowledge of bryozoan physiology. Given the widespread distribution of known wastewater treatment facilities affected by the bryozoan, the problem is probably a common one.

Myoanatomy and serotonergic nervous system of the ctenostome Hislopia malayensis: evolutionary trends in bodyplan patterning of ectoprocta

BackgroundEctoprocta is a large lophotrochozoan clade of colonial suspension feeders comprising over 5.000 extant species. Their phylogenetic position within the Lophotrochzoa remains controversially discussed, but also the internal relationships of the major ectoproct subclades -Phylactolaemata, Stenolaemata, and Gymnolaemata - remains elusive. To gain more insight into the basic configuration of ectoproct muscle systems for phylogenetic considerations, we analysed the adult myoanatomy and the serotonergic nervous system as well as myogenesis in budding stages of the ctenostome Hislopia malayensis.ResultsIn adults, the serotonergic nervous system is restricted to the lophophoral base with a high concentration in the cerebral ganglion and serotonergic perikarya between each pair of tentacles. Prominent smooth apertural muscles extend from the basal cystid wall to each lateral side of the vestibular wall. The musculature of the tentacle sheath consists of regular strands of smooth longitudinal muscles. Each tentacle is supplied with two bands of longitudinal muscles that show irregular striation. At the lophophoral base several muscles are present: (i) Short muscle fibres that proximally diverge from a single point from where they split distally into two separate strands. (ii) Proximally of the first group are smooth, longitudinal fibres that extend to the proximal-most side of the lophophoral base. (iii) Smooth muscle fibres, the buccal dilatators, traverse obliquely towards the pharynx, and (iv) a circular ring of smooth muscle fibres situated distally of the buccal dilatators. Retractor muscles are mainly smooth with short distal striated parts. The foregut consists mainly of striated ring musculature with only few longitudinal muscle fibres in the esophagus, while the remaining parts of the digestive tract solely exhibit smooth musculature. During budding, apertural and retractor muscles are first to appear, while the parietal muscles appear at a later stage.ConclusionsThe apertural muscles show high similarity within Ectoprocta and always consist of two sets of muscles. Gymnolaemates and Phylactolaemates show clear differences within their digestive tract musculature, the former showing smooth and longitudinal muscles to a much greater extent than the latter. The complex musculature at the lophophoral base appears promising for inferring phylogenetic relationships, but sufficient comparative data are currently lacking.

Differentiation of North American and European forms of Fredericella sultana(Blumenbach) (Ectoprocta : Phylactolaemata)

Fredericella sultana (Blumenbach, 1779) has long been considered one of the few freshwater bryozoan species with a truly cosmopolitan distribution. However, chromosome spreads from European material show 2n = 16 compared to 2n = 14 in North American specimens. In laboratory rearing the two forms are morphologically indistinguishable except for the surface texture of their statoblasts. Smooth statoblasts of European colonies match early illustrations of the species, while the densely pitted statoblasts of the North American form resemble those of F. indica Annandale 1909. On the basis of these observations we tentatively designate the North American ‘F. sultana’ as F. indica. The only known American species with smooth statoblasts is F. australiensis Goddard 1909, in which the 2n = 16 karyotype is similar or identical to European F. sultana; however, despite this karyotypic similarity the two species retain their distinguishing morphology when reared together in the laboratory. Two enzymes from a single specimen of European F. sultana were electrophoretically distinct from the corresponding enzymes present in samples of both F. australiensis and North American ‘F. sultana’. Four phosphoglucose isomerase alleles were present in North American ‘F. aultana’ from four geographically separated collection sites, although only one genotype for this locus was observed in material from any one site. These genetic findings are consistent with a relatively short-range dispersal potential in this species as compared to Plumatella species.

Organogenesis during budding and lophophoral morphology of Hislopia malayensis Annandale, 1916 (Bryozoa, Ctenostomata)

BackgroundBryozoans represent a large lophotrochozoan phylum with controversially discussed phylogenetic position and in group relationships. Developmental processes during the budding of bryozoans are in need for revision. Just recently a study on a phylactolaemate bryozoan gave a comprehensive basis for further comparisons among bryozoans. The aim of this study is to gain more insight into developmental patterns during polypide formation in the budding process of bryozoans. Particular focus is laid upon the lophophore, also its condition in adults. For this purpose we studied organogenesis during budding and lophophoral morphology of the ctenostome bryozoan Hislopia malayensis.ResultsPolypide buds develop on the frontal side of the developing cystid as proliferation of the epidermal and peritoneal layer. Early buds develop a lumen bordered by the inner budding layer resulting in the shape of a two-layered sac or vesicle. The hind- and midgut anlagen are first to develop as outpocketing of the prospective anal area. These grow towards the prospective mouth area where a comparatively small invagination marks the formation of the foregut. In between the prospective mouth and anus the ganglion develops as an invagination protruding in between the developing gut loop. Lophophore development starts with two lateral ridges which form tentacles very early. At the lophophoral base, intertentacular pits, previously unknown for ctenostomes, develop. The ganglion develops a circum-oral nerve ring from which the tentacle nerves branch off in adult zooids. Tentacles are innervated by medio-frontal nerves arising directly from the nerve ring, and medio-frontal and abfrontal nerves which originate both from an intertentacular fork.ConclusionsWe are able to show distinct similarities among bryozoans in the formation of the different organ systems: a two-layered vesicle-like early bud, the ganglion forming as an invagination of the epidermal layer in between the prospective mouth and anal area, the digestive tract mainly forming as an outpocketing of the prospective anal area, and the lophophore forming from two lateral anlagen that first fuse on the oral and afterwards on the anal side. Future studies will concentrate on cyclostome budding to complement our knowledge on developmental patterns of bryozoans.

Plumatella geimermassardi, a newly recognized freshwater bryozoan from Britain, Ireland, and continental Europe (Bryozoa: Phylactolaemata)

Plumatella geimermassardi is a newly recognized species of phylactolaemate bryozoan. Its known range extends from Ireland east through southern Norway and south into Italy. Colonies grow close to the substrate with little free branching; the body wall is mostly transparent and without an obvious raphe. Floatoblasts are broadly oval and relatively small, with distinctively large dorsal fenestra and uniformly narrow ventral annulus. The sessoblast basal valve is low and dish-shaped; the annulus bears tubercles which vary in their prominence. This species brings to 14 the number of phylactolaemate bryozoans known in the region.

Loxosomatoides sirindhornae, new species, a freshwater kamptozoan from Thailand (Entoprocta)

A new species of freshwater kamptozoan (Entoprocta) is described from the Mae Klong and Prachin Buri Rivers in central Thailand. This brings to two the number of known entoproct species occurring in fresh water. The new species, Loxosomatoides sirindhornae, grows as stolonate colonies; each diminutive zooid has a muscular, unsegmented stalk, and an obliquely oriented calyx. A well-formed hibernaculum originates from a short, lateral stolon at the base of certain zooids. The calyx bears a rigid shield with a conspicuous aboral carina extending along the entire length. Colonies have been found only in fully freshwater habitats and appear not to tolerate salinities higher than 1.0 ppt.