Skeletal Ultrastructures in some Cerioporine Cyclostome Bryozoans

Abstract The ultrastructure of the calcareous skeleton is described in nine species of Recent cyclostome bryozoans belonging to the suborder Cerioporina. Two species of Heteropora have interior zooecial walls comprising a granular precursory layer followed by a thick layer of transverse fibres and a subordinate foliated fabric with, in mature proximal walls, a semi-nacreous layer. The remaining seven species have interior walls with no transverse fibres and instead predominantly comprise a distally-imbricated, regularly foliated fabric overlying a granular precursory layer. Older, proximal surfaces often have abundant screw dislocations, but true semi-nacre is absent. Basal walls comprise an outer finely granular precursory fabric and planar spherulitic layer, succeeded by the same ultrastructural succession seen in the interior zooecial walls of the respective groups. Exterior walled diaphragms, peristomes and gonozooids similarly comprise an external fabric of planar spherulitic calcite, lined internally by the predominant fabric seen in the interior walls. Ultrastructurally, therefore, cerioporines may be split into two groups with different fabric suites, the first resembling cinctiporids and many tubuliporines in having interior walls with fabrics of transverse fibres, foliated crystallites and semi-nacre; and the second resembling the rectangulates Lichenopora and Disporella in having interior walls comprising only the foliated fabric. These findings support the close phylogenetic relationship between cerioporines and other cyclostomes but suggest that the cerioporines may constitute either a diphyletic or a paraphyletic group.     

Skeletal Ultrastructure in the Cyclostome Bryozoan Hornera

Abstract Scanning electron microscopy of calcified walls in two species of the cyclostome bryozoan Hornera has revealed previously undescribed details of skeletal morphology and growth. The calcitic interior walls of both H. robusta MacGillivray and H. squamosa Hutton have a laminated structure. Walls are extended at distal growing edges where the formation of new crystallites is concentrated and wall fabric is nacreous or semi-nacreous. New crystallites are seeded on the surface of existing crystallites as six-sided rhombs. At the centres of the rhombs in H. robusta there are often three ‘spikes' which point towards alternate sides of the rhomb. Screw dislocations resulting in spiral overgrowths are also common at these distal wall edges. Wall thickening occurs further proximally where walls develop a regularly foliated structure of imbricated laths growing towards the colony base. Although often thought to be ubiquitous in cyclostomes, the division of walls into three layers (an inner, primary layer flanked on both sides by secondary layers) is absent in Hornera. Wall ultrastructure contrasts strongly with the lamellar–fibrous–lamellar structure recently described from cinctiporid cyclostomes. The c-axes of the crystallites are orientated perpendicular to the wall surface in Hornera, unlike cinctiporids in which they are orientated within the plane of the wall. Apparent similarities in ultrastructure suggest that Hornera may provide a good model for wall growth in extinct trepostome bryozoans.     

Ultrastructure and Development of the Ooecial Walls in Some Calloporid Bryozoans (Gymnolaemata: Cheilostomata)

In the brood chambers (ovicells) of six calloporid cheilostomes studied each skeletal wall consists of four calcified layers: (1) a very thin superficial layer of planar spherulitic crystallites, (2) an upper (outer) layer with wall-perpendicular prismatic ultrastructure, (3) an intermediate lamellar layer, and (4) a lower (inner) wall-perpendicular prismatic layer. Comparative studies of both the ovicell wall ultrastructure and early ovicell formation showed a hypothetical opportunity for evolving complex (multilayered) skeletal walls by fusion of the initially separated gymnocystal and cryptocystal calcifications in Cheilostomata. In two species studied, a bilobate pattern in the final stage of the formation of the ooecial roof was encountered in specimens with the cuticle preserved. A possible explanation to this finding is discussed – the bilobate pattern is suggestive of the hypothetical origin of the brood chamber from (1) two flattened spines, or (2) reduction in spine number of an originally multispinous ovicell.     

Skeletal morphogenesis in some living collosphaerid Radiolaria

Two major patterns of shell morphogenesis occurring in varying proportions among species were identified by examining skeletons from five species of living collosphaerid, colonial Radiolaria: Collosphaera huxleyi, Acrosphaera cyrtodon, Acrosphaera spinosa, Siphonosphaera tubulosa and Siphonosphaera socialis. Skeletons possessing large open-lattice structures characterized by ellipsoidal to polygonal pores separated by narrow bars are produced by repeated subdivision of large pores into smaller pores. A bridge-like bar grows across the pore and subdivides it into two or more smaller pores. In skeletons with small, nearly circular pores and occasionally elongated tubular rims, the pores appear to be developed by rim thickening. Silica is deposited at the perimeter of the pore, thus decreasing its diameter and increasing the bar width between pores. In some species exhibiting intermediate types of skeletal morphology, there appears to be varying amounts of both bridge growth and rim growth. These data are used to explore possible phylogenetic pathways for a variety of collosphaerid species and to elucidate the processes of skeletal deposition in Radiolaria.     

Ultrastructure of nuchal organs in some marine polychaetes

Polychaetes normally possess one pair of nuchal organs at the posterior edge of the prostomium or peristomium. They have been regarded as chemosensory organs. The nuchal organs of four marine polychaete species with different habits were investigated by electron microscopy. Although the shapes of nuchal organs can vary greatly from simple ciliary bands (Scolelepis squamata, Spionidae) to retractile tongue-like, piston- or finger-shaped forms (Eteone longa, Anaitides mucosa, Phyllodocidae; Heteromastus filiformis, Capitellidae), the structural components, including the ciliated supporting cells, sensory cells, and nuchal epidermal cells, are essentially similar. The differences basically concern 1) the position of the sensory cells with relation to the ciliated supporting cells, 2) the location and structure of the nuchal nerve, and 3) the structure of the nuchal cuticle. The diverging nature of this modified cuticle is described and discussed in detail. Comparisons are made with the fine structure of nuchal organs of other polychaete species. Similarities of cellular components of nuchal organs are found not only in the four species studied here but also in all nuchal organs investigated so far. This is hypothesized to be due to the fact that the polychaete stem species already possessed nuchal organs with the respective cell types. Differences in the number and distribution of cellular components and in the overall shape of nuchal organs are thought to have evolved in correlation with the equipment of other cephalic appendages and with different habits and modes of nutrition.     

Systematics and Biogeography of Burrowing Bryozoans

Current investigations of the three principal families of ectoproctbryozoan burrowers has shown that while two of the families,the Terebriporidae and the Immergentiidae, belong to the minorOrder Ctenostomata, the third family, Penetrantiidae, previouslyconsidered a ctenostome, actually belongs to the major OrderCheilostomata. The implications of this are important; we haveconsidered the burrowing bryozoans to be a small obscure group,specialized for the burrowing mode of existence. We must nowconsider the possibility that there may be many more speciesof burrowing bryozoans as yet undiscovered, that they occurin at least two of the three bryozoan orders, and that burrowingconstitutes an important ecological niche or mode of adaptationfor the bryozoans. While such a change may seem to be merelya taxonomic maneuver, itmay also serve to emphasize the diversityof the ectoproct bryozoan groups which do burrow, and perhapsencourage research on them. At present we are making progressdescribing the living species, their anatomy and histology.We still know almost nothing about how they penetrate the substrate,nothing about possible effects upon the host organism, and nothingabout their means of geographical distribution, although theyseem to occur worldwide, burrowing primarily in molluscan shells.     

Microarchitecture of Body Wall of Extant Cyclostome Ectoprocts

Scanning electron microscope and light microscope studies ofthe body wall in cyclostome stenolaemate ectoprocts show thatthis wall has a distinctive microarchitecture. The microstructuresconsist of a linear series of longitudinal canals in the centralregion. Adjoining regions on either side have laminae of overlappingcalcareous tablets. In some cyclostomes at certain stages ofgrowth, laminae may show a less orderly meshwork pattern nearthe canals. The laminate layers of calcareous tablets are enclosedin an organic matrix and are penetrated by tubuli which passfrom the inner part of the body wall to the canals and alsolink the canals. The canals with organic and mineralized matricesopen into pores in the body wall. This elaborate meshwork andcanal and pore system provide the framework for growth and resorptionof the body wall and facilitate transport of cellular materialsfrom one zooid to another in a colony. Calcification at thedistal part of a colony seems to proceed in a series of stagesaround sites of calcification. The pattern of the body wallof the cyclostome ectoproct does not parallel a molluscan patternof skeletal growth as previously proposed. The hypothesis ofa hypostegal coelom in some cyclostome ectoprocts is rejected.     

Ultrastructure of the ascospores of some species of the Torulaspora group

Development and germination of the ascospores in species of the Torulaspora group of yeasts have been described. Most species had warty spores which, in sections, showed a dark outer layer consisting of the outer unit membrane of the prospore wall and a layer underneath formed at an early stage of development of the spores. In mature spores the light inner layer of the wall was delimited at the outside by a thin dark layer. The warts often contained dark material. The ascospores of two Pichia and three Debaryomyces species were studied for comparison; they differed in sections from the Torulaspora spores. The taxonomic implications of the ultrastructural observations have been discussed.     

Ultrastructure of resting cells of some non-spore-forming bacteria

Using electron microscopy (ultrathin sections and freeze-fractures), we investigated the ultrastructure of the resting cells formed in the cultures of Micrococcus luteus, Arthrobacter globiformis, and Pseudomonas aurantiaca under conditions of prolonged incubation (up to 9 months). These resting cells included cyst-like forms that were characterized by complex cell structure and the following ultrastructural properties: (i) a thickened or multiprofiled cell wall (CW), typically made up of a layer of the preexisting CW and one to three de novo synthesized murein layers; (ii) a thick, structurally differentiated capsule; (iii) presence of large intramembrane particles (d = 180-270 A), occurring both on the PF and EF sides of the membrane fractures of M. luteus and A. globiformis; (iv) a peculiar structure of the cytoplasm, which was either fine-grained or lumpy (coarse-grained) in different parts of the cell population; and (v) a condensed nucleoid. Intense formation of cyst-like cells occurred in aged (2- to 9-month-old) bacterial cultures grown on diluted complex media or on nitrogen-, carbon-, and phosphorus-limited synthetic media, as well as in suspensions of cells incubated in media with sodium silicate. The general morphological properties, ultrastructural organization, and physiological features of cyst-like cells formed during the developmental cycle suggest that constitutive dormancy is characteristic of non-spore-forming bacteria.     

Cyclostome embryology and early evolutionary history of vertebrates

Modern agnathans include only two groups, the lampreys and thehagfish, that collectively comprise the group Cyclostomata.Although accumulating molecular data support the cyclostomesas a monophyletic group, there remain some unsettled questionsregarding the evolutionary relationships of these animals inthat they differ greatly in anatomical and developmental patternsand in their life histories. In this review, we summarize recentdevelopmental data on the lamprey and discuss some questionsrelated to vertebrate evolutionary development raised by thelimited information available on hagfish embryos. Comparisonof the lamprey and gnathostome developmental patterns suggestssome plesiomorphic traits of vertebrates that would have alreadybeen established in the most recent common ancestor of the vertebrates.Understanding hagfish development will further clarify the,as yet, unrecognized ancestral characters that either the lampreysor hagfishes may have lost. We stress the immediate importanceof hagfish embryology in the determination of the most plausiblescenario for the early history of vertebrate evolution, by addressingquestions about the origins of the neural crest, thyroid, andadenohypophysis as examples.     

五列木科和肋果茶科花粉外壁超微结构及其与山茶科的系统学关系

借助光学显微镜、扫描电镜和透射电镜对五列木科Ｐｅｎｔａｐｈｙｌａｃａｃｅａｅ和肋果茶科Ｓｌａｄｅｎｉａｃｅａｅ花粉进行了观察,并与山茶科Ｔｈｅａｃｅａｅ若干属的花粉进行了详细的比较,同时参考了猕猴桃科Ａｃｔｉｎｉｄｉａｃｅａｅ的花粉特征。研究表明,肋果茶科的花粉与山茶科的花粉具有较多的相似性,如其形状和大小与山茶科中厚皮香亚科的几乎一致;而花粉的表面纹饰（粗糙至模糊的皱波状纹饰）则与山茶属,Ｆｒｅｚｉｅｒａ属和厚皮香亚科部分属的花粉纹饰相类似。从花粉外壁的结构看,肋果茶的花粉与石笔木属和山茶属的更接近,表现为：花粉外壁层次分化明显,复盖层和柱状层均较厚,外壁内层薄。而五列木科花粉除了形状和萌发孔类型与山茶科的相似外,其纹饰特征和外壁结构均与山茶科的差异较大,如五列木科花粉表面近光滑,外壁覆盖层较簿,柱状层很不发达,外壁内层相对较厚等。孢粉学上认为,肋果茶科与山茶科具有更为密切的关系,五列木科则与山茶科较疏远。支持把肋果茶科作为一个属置于山茶科内或作为山茶科的一个亚科     

Distribution of Mammalian-Like Melanopsin in Cyclostome Retinas Exhibiting a Different Extent of Visual Functions

Mammals contain 1 melanopsin (Opn4) gene that is expressed in a subset of retinal ganglion cells to serve as a photopigment involved in non-image-forming vision such as photoentrainment of circadian rhythms. In contrast, most nonmammalian vertebrates possess multiple melanopsins that are distributed in various types of retinal cells; however, their functions remain unclear. We previously found that the lamprey has only 1 type of mammalian-like melanopsin gene, which is similar to that observed in mammals. Here we investigated the molecular properties and localization of melanopsin in the lamprey and other cyclostome hagfish retinas, which contribute to visual functions including image-forming vision and mainly to non-image-forming vision, respectively. We isolated 1 type of mammalian-like melanopsin cDNA from the eyes of each species. We showed that the recombinant lamprey melanopsin was a blue light-sensitive pigment and that both the lamprey and hagfish melanopsins caused light-dependent increases in calcium ion concentration in cultured cells in a manner that was similar to that observed for mammalian melanopsins. We observed that melanopsin was distributed in several types of retinal cells, including horizontal cells and ganglion cells, in the lamprey retina, despite the existence of only 1 melanopsin gene in the lamprey. In contrast, melanopsin was almost specifically distributed to retinal ganglion cells in the hagfish retina. Furthermore, we found that the melanopsin-expressing horizontal cells connected to the rhodopsin-containing short photoreceptor cells in the lamprey. Taken together, our findings suggest that in cyclostomes, the global distribution of melanopsin in retinal cells might not be related to the melanopsin gene number but to the extent of retinal contribution to visual function.     

Variable Myopathic Presentation in a Single Family with Novel Skeletal RYR1 Mutation

We describe an autosomal recessive heterogeneous congenital myopathy in a large consanguineous family. The disease is characterized by variable severity, progressive course in 3 of 4 patients, myopathic face without ophthalmoplegia and proximal muscle weakness. Absence of cores was noted in all patients. Genome wide linkage analysis revealed a single locus on chromosome 19q13 with Zmax = 3.86 at θ = 0.0 and homozygosity of the polymorphic markers at this locus in patients. Direct sequencing of the main candidate gene within the candidate region, RYR1, was performed. A novel homozygous A to G nucleotide substitution (p.Y3016C) within exon 60 of the RYR1 gene was found in patients. ARMS PCR was used to screen for the mutation in all available family members and in an additional 150 healthy individuals. This procedure confirmed sequence analysis and did not reveal the A to G mutation (p.Y3016C) in 300 chromosomes from healthy individuals. Functional analysis on EBV immortalized cell lines showed no effect of the mutation on RyR1 pharmacological activation or the content of intracellular Ca²⁺ stores. Western blot analysis demonstrated a significant reduction of the RyR1 protein in the patient’s muscle concomitant with a reduction of the DHPRα1.1 protein. This novel mutation resulting in RyR1 protein decrease causes heterogeneous clinical presentation, including slow progression course and absence of centrally localized cores on muscle biopsy. We suggest that RYR1 related myopathy should be considered in a wide variety of clinical and pathological presentation in childhood myopathies.     

Ultrastructure and some other properties of inverted thyroid follicles in suspension culture

Separated thyroid follicles in suspension culture invert in 5% serum. In some, the inversion is not complete in that a small normal follicle persists completely in the interior of an inverted follicle. In inverted follicles the lumens are distended and electron lucent. The bounding epithelial cells are stretched, have relatively few microvilli on the surface toward the medium but they have bundles of oriented microfilaments usually located near the lumen. The cells are connected together by tight junctions. When inverted follicles are punctured, the lumen shrinks, the cells retract and become cuboidal and microvilli reappear. Microfilaments persist at the luminal surface but no longer in oriented bundles. No appreciable extracellular matrix is present at the basal cell surface in contact with the lumen, but matrix is occasionally observed between cells. Since bundles of microfilaments like stress fibers are observed in the cells in suspension culture, the presence of stress fibers in cells in monolayer culture is probably not dependent on attachment but might be a reflection of the spreading of the attached cells.     

Ultrastructure of the spines in the copulatory organ of some Monocelididae (Turbellaria,Proseriata)

Summary A comparative ultrastructural study of the copulatory organ was carried out in four genera of Turbellaria-Monocelididae. In all four genera the male copulatory organ is of the conjuncta-duplex type and has a cirrus armed with spines. Fine-structural analysis of the cirrus spines reveals that these structures are specializations within the basement lamina of the cirrus. In this part of the male canal the basement lamina has a trilamellar structure. The spines are formed by a local thickening of the middle electron-dense layer and show a structural similarity in all the Monocelididae investigated.The systematic value of this character within the family Monocelididae is discussed.Abbreviations b bacteria - bl basement lamina - cr cell remnants - g granules of prostate glands - hd hemidesmosomes - l lumen of cirrus - m _c muscles of cirrus - m _b muscles of bulbus - mi mitochondria - p parenchymal elements - s spine - sp septum - st stylet - sz spermatozoa     

Ultrastructure of chitosan and some gel-forming,branched-chain chitosan derivatives

Chitosan flakes from shrimp shells and xerogels derived from branched 1-deoxyglycit-1-yl chitosan derivatives were examined by scanning electron microscopy; the former displayed relatively large, dome-shaped orifices and the latter were found to exhibit a wide variety of ultrastructures, ranging from smooth, nonporous to microporous and microfibrillar. Some correlation between the chemical structure of the side chains of the chitosan derivatives and their microarchitecture could be established.     

α-Proteobacterial Symbionts of Marine Bryozoans in the Genus Watersipora

Bacterial symbionts that resembled mollicutes were discovered in the marine bryozoan Watersipora arcuata in the 1980s. In this study, we used PCR and sequencing of 16S rRNA genes, specific fluorescence in situ hybridization, and phylogenetic analysis to determine that the bacterial symbionts of “W. subtorquata” and “W. arcuata” from several locations along the California coast are actually closely related α-Proteobacteria, not mollicutes. We propose the names “Candidatus Endowatersipora palomitas” and “Candidatus Endowatersipora rubus” for the symbionts of “W. subtorquata” and “W. arcuata,” respectively.