Multizooidal Budding in Parasmittina trispinosa (Johnston) (Bryozoa,Cheilostomata)

Two principally different wall types occur in the bryozoan colony: Exterior walls delimiting the super-individual, the colony, against its surroundings and interior walls dividing the body cavity of the colony thus defined into units which develop into sub-individuals, the zooids. In the gymnolaemate bryozoans generally, whether uniserial or multiserial, the longitudinal zooid walls are exterior, the transverse (proximal and distal) zooid walls interior ones. The radiating zooid rows grow apically to form “tubes” each surrounded by exterior walls but subdivided by interior (transverse) walls. The stenolaemate bryozoans show a contrasting mode of growth in which the colony swells in the distal direction to form one confluent cavity surrounded by an exterior wall but internally subdivided into zooids by interior walls. In the otherwise typical gymnolaemate Parasmittina trispinosa the growing edge is composed of a series of “giant buds” each surrounded by exterior walls on its lateral, frontal, basal and distal sides and forming an undifferentiated chamber usually 2–3 times as broad and 3 or more times as long as the final zooid. Its lumen is subdivided by interior walls into zooids 2–3, occasionally 4, in breadth. This type of zooid formation is therefore similar to the “common bud” or, better-named, “multizooidal budding” characteristic of the stenoleamates but has certainly evolved independently as a special modification of the usual gymnolaemate budding.     

COMPARATIVE DEVELOPMENT OF SECRETORY CAVITIES IN THE TRIBES AMORPHEAE AND PSORALEEAE (LEGUMINOSAE: PAPILIONOIDEAE)

The tribes Amorpheae and Psoraleeae of the Leguminosae (Papilionoidae) share the characteristics of one-seeded fruits and gland-dotted foliage. Because of this, they traditionally have been considered closely related (either a single tribe or two closely related tribes). However, Barneby (1977) has suggested that the Amorpheae and Psoraleeae are not close but previously had been combined on the basis of a superficial resemblance. This paper describes the structure of the secretory cavities responsible for the gland dots. Approximately 50% of the species of each tribe were surveyed for cavity structure with leaflet clearings. Eight species were then chosen for developmental studies of their glands. Several distinct kinds of secretory cavities are present in these plants. Trabeculate cavities (found only in the Psoraleeae) are traversed by many elongated cells. This type of cavity and nontrabeculate cavities of the Psoraleeae initiate with localized dorsiventral elongation of protodermal cells to form a hemispherical protuberance on the leaf primordium surface. Development proceeds with separation of the cells of a protuberance along their lateral walls facing the protuberance center. As the leaf expands, the protuberance sinks until its apex is flush with the leaf surface. The result is a cavity lined by an epithelium of modified epidermal cells. Trabeculate cavities have more cells in the initial protodermal bump than nontrabeculate “epidermal” cavities, and the central cells of the protuberance are not involved in epithelium formation, but become separated from other cells on all lateral sides, transversing the cavity as trabeculae. Cavities of the Amorpheae are all nontrabeculate and subepidermal. They initiate with periclinal divisions of protodermal cells that result in two cell layers. The exterior layer differentiates into epidermis, while the interior layer divides to produce a small spherical group of cells (“epithelial initials”). Schizogeny occurs in the center of these cells to produce an epithelium-lined cavity. Previous studies of cavity development in the Amorpheae described lysigenous and schizo-lysigenous cavities for most species. These early reports are reviewed, and the possible role of preparation artifacts in producing images of lysigenous development in general is discussed.     

Neuronal organization of the accessory olfactory bulb of the lizard Podarcis hispanica: Golgi study

The neuronal organization of the accessory olfactory bulb (AOB), which receives sensory information from the vomeronasal organ, was described in a squamate reptile (Podarcis hispanica) by means of light microscopy. Using the Golgi-impregnation method, seven neuronal types could be distinguished: Periglomerular cells constitute a morphologically heterogeneous population of small neurons located between and around the glomeruli. The mitral cells are diffusely distributed in the AOB. Their cell bodies are usually located within the mitral cell layer, but some of them could be also observed in the plexiform layers. Mitral cells were classified into three subgroups on the basis of their sizes and dendritic tree morphologies. Thus, the “outer mitral cells” have the biggest cell bodies, and their distal secondary dendrites are mainly distributed rostrocaudally in the external plexiform layer. The “inner mitral cells” have large cell bodies, and their secondary dendrites are distributed dorsoventrally and are located deeper than those of the other two subgroups. The third type, the “small mitral cells,” is the smallest one among mitral cells in the AOB, and from their cell bodies, only two main dendritic trunks arise. The granule cells are composed of several categories based on their different cell body locations and dendritic tree morphologies. Thus, the “superficial granule cells” are located exclusively in the external plexiform layer and have small dendritic fields. The “middle granule cells” have fusiform cell bodies—situated in the internal plexiform layer—and present a wide dendritic projection area. Finally, the “deep granule cells” are distributed throughout the granule cell layer and include a great variety of dendritic tree morphologies. The distribution and morphological features of all neuronal types constituting the AOB of Podarcis were compared with those reported on other vertebrates. The results suggest that the lamination pattern and neuronal organization of the AOB in lizards are more similar to that of mammals than to that of the remaining vertebrates.     

THE ULTRASTRUCTURE OF SCENEDESMUS (CHLOROPHYCEAE). I. SPECIES WITH THE “RETICULATE” OR “WARTY” TYPE OF ORNAMENTAL LAYER1

The ultrastructure of the wall layers and ornamentative features of Scenedesmus pannonicus and S. longus are described using carefully correlated freeze-etched replicas, thin sections and scanning electron micrographs. The two species arc enclosed by different types of ornamented layers, S. pannonicus by the tightly filling, “warty” layer and S. longus by the loosely fitting, “reticulate” layer, held off the coenobium by 2 types of tubular propping spikelets and rosettes. The reticulate layer has an intricate substructure, especially when studied with freeze-etching. Its inner and outer surfaces appear different, as is its attachment to the 2 types of spikelets. Whole cells of S. longus subjected to acetolysis lack the cellulose wall and cytoplasm, but all other surface features survive, including the Trilaminar Sheath (TLS); this ornamentation cannot be “pectic.” The cellulose wall and ornamentation is unaffected by boiling water alone. Boiling in 6n NaOH removes the surface ornamentation, but the TLS and wall remain; the possibility that these features contain silica is discussed. The terminal spines of both species consist of closely packed spikelets enclosed within a skin of hexagonally-packed subunits. Similar subunits are seen in the propping spikelets of S. longus, and in the rows or “combs” of laterally fused spikelets of S. pannonicus. The warty layer of S. pannonicus is tightly appressed to the TLS except close to where the cells are joined, where it is suspended free. It is composed of a layer of globular subunits, and small indentations form the warts. Single, evenly distributed warts characterize the freely suspended sections of the warty layer, and the layer that encloses young coenobia soon after they have been formed: in contrast, the warts are clumped over the surface of older and larger colonies. Some of the single warts form characteristic double rows, but these latter remain single even on older cells. The surface structure of the warty layer, TLS, and plasmalemma are revealed by the freeze-etching process.     

Siphonariid development: Quintessential euthyneuran larva with a mantle fold innovation (Gastropoda; Panpulmonata)

Recent phylogenetic revisions of euthyneuran gastropods (“opisthobranchs” and “pulmonates”) suggest that clades with a planktotrophic larva, the ancestral life history for euthyneurans, are more widely distributed along the trunk of the euthyneuran tree than previously realized. There is some indication that the planktotrophic larva of euthyneurans has distinctive features, but information to date has come mainly from traditional “opisthobranch” groups. Much less is known about planktotrophic “pulmonate” larvae. If planktotrophic larvae of “pulmonates” share unique traits with those of “opisthobranchs,” then a distinctive euthyneuran larval-type has been the developmental starting template for a spectacular amount of evolved morphological and ecological disparity among adult euthyneurans. We studied development of a siphonariid by preparing sections of larval and postmetamorphic stages for histological and ultrastructural analysis, together with 3D reconstructions and data from immunolabeling of the larval apical sensory organ. We also sought a developmental explanation for the unusual arrangement of shell-attached, dorso-ventral muscles relative to the mantle cavity of adult siphonariids. Adult siphonariids (“false limpets”) have a patelliform shell but their C-shaped shell muscle partially embraces a central mantle cavity, which is different from the arrangement of these components in patellogastropods (“true limpets”). It is not obvious how shell muscles extending into the foot become placed anterior to the mantle cavity during siphonariid development from a veliger larva. We found that planktotrophic larvae of Siphonaria denticulata are extremely similar to previously described, planktotrophic “opisthobranch” larvae. To emphasize this point, we update a list of distinctive characteristics of planktotrophic euthyneuran larvae, which can anchor future studies on the impressive evolvability of this larval-type. We also describe how premetamorphic and postmetamorphic morphogenesis of larval mantle fold tissue creates the unusual arrangement of shell-muscles and mantle cavity in siphonariids. This result adds to the known postmetamorphic evolutionary innovations involving mantle fold tissue among euthyneurans.     

An anatomical investigation of calcicolous endolithic lichens from the Trieste karst (NE Italy)

ABSTRACT

The anatomy of five endolithic lichens (Acrocordia conoidea, Petractis clausa, Rinodina immersa, Verrucaria baldensis, and V. marmorea) from the Trieste Karst (north-eastern Italy) was thoroughly investigated. Samples already used in previous ecophysiological studies were examined by histological and mineralogical techniques, and by SEM. Biomineralisation products were searched for by X-ray diffractometry, X-ray microdiffractometry, and Fourier Transformed Infrared spectrophotometry. The results confirm that the photobiont layer is located approximately at the same depth in the substratum, although the species occur in habitats with strongly different light regimes; the thallus development is relatively constant within populations of a single species, but differs considerably among species. Several peculiarities of each species were revealed, such as the presence of large clews of hyphae in the inner layer of P. clausa, forming large voids in the substratum, or the development of morphologically different oil-hyphae. Calcium oxalate crystals were not detected. Some terms currently used to describe the anatomy of endolithic lichens are critically discussed, and the new term “lithocortex” and “pseudo-medulla” are introduced.     

Ultrastructural Changes During Encystment of Schizopyrenus russelli*

Ultrastructural changes associated with the encystment of Schizopyrenus russelli have been studied by electron microscopy. Before encystment small “black bodies” appear in the cytoplasm and later migrate toward the periphery. The outer cyst wall is secreted at this stage as a thin discontinuous layer which thickens and subsequently becomes continuous. Concomitant with this, the endoplasmic reticulum surrounds the mitochondria. The inner cyst wall later appears as a multilayered structure which presumably is cast off from the plasma membrane. Between the inner and outer layers of the cyst wall, there is a middle, less electron-dense layer wherein extruded cytoplasmic material is found embedded at certain places.     

Olfactory metamorphosis in the coastal tailed frog Ascaphus truei (Amphibia,Anura, Leiopelmatidae)

The structure of the olfactory organ in larvae and adults of the basal anuran Ascaphus truei was examined using light micrography, electron micrography, and resin casts of the nasal cavity. The larval olfactory organ consists of nonsensory anterior and posterior nasal tubes connected to a large, main olfactory cavity containing olfactory epithelium; the vomeronasal organ is a ventrolateral diverticulum of this cavity. A small patch of olfactory epithelium (the “epithelial band”) also is present in the preoral buccal cavity, anterolateral to the choana. The main olfactory epithelium and epithelial band have both microvillar and ciliated receptor cells, and both microvillar and ciliated supporting cells. The epithelial band also contains secretory ciliated supporting cells. The vomeronasal epithelium contains only microvillar receptor cells. After metamorphosis, the adult olfactory organ is divided into the three typical anuran olfactory chambers: the principal, middle, and inferior cavities. The anterior part of the principal cavity contains a “larval type” epithelium that has both microvillar and ciliated receptor cells and both microvillar and ciliated supporting cells, whereas the posterior part is lined with an “adult‐type” epithelium that has only ciliated receptor cells and microvillar supporting cells. The middle cavity is nonsensory. The vomeronasal epithelium of the inferior cavity resembles that of larvae but is distinguished by a novel type of microvillar cell. The presence of two distinct types of olfactory epithelium in the principal cavity of adult A. truei is unique among previously described anuran olfactory organs. A comparative review suggests that the anterior olfactory epithelium is homologous with the “recessus olfactorius” of other anurans and with the accessory nasal cavity of pipids and functions to detect water‐borne odorants. J. Morphol. 2011. © 2011 Wiley Periodicals, Inc.     

THE CELL WALL OF SCENEDESMUS QUADRICAUDA

Bisalputra, T., and T. E. Weier. (U. California, Davis.) The cell wall of Scenedesmus quadricauda. Amer. Jour. Bot. 50(10): 1011–1019. Illus. 1963.—Fine structure of the cell wall of Scenedesmus quadricauda fixed in both KMnO₄ and osmium tetroxide is described. The cell wall consists of 3 layers: the inner cellulosic layer which delimits individual cells; the outer pectic layer which binds the cells of the coenobium together; and a thin middle layer, bounded by membranes on either side, which is electron-dense in osmium-fixed material but of medium electron density in KMnO₄. The structure of the outer pectic layer is similar in both fixatives; it consists of a hexagonal network of electron-dense material on the surface, and a system of tubules or “props” which radiate out from the middle layer of the wall to support the net. The pectic layer appears in the daughter coenobia before their liberation from the parent colony.     

DIFFUSION RESISTANCE IN LEAVES AS RELATED TO THEIR STOMATAL ANATOMY AND MICRO-STRUCTURE

Transpiration from a plant leaf depends upon the water vapor pressure gradient between the substomatal cavity and the free air beyond the leaf. Transpiration also depends inversely on the resistance of the diffusion pathway through the substomatal cavity, stomate, and surface boundary layer. The value of the diffusion resistance is derived mathematically for Zebrina pendula, Medicago sativa, and Pinus resinosa. The vapor pressure gradient depends on the leaf temperature and therefore is related to the energy budget of the leaf. The exact solution of the diffusion equation is described and limiting examples discussed. The so-called “diameter law” is a special case which is distinctly limited in its application.     

Neuronal connections and the function of the corpora pedunculata in the brain of the American cockroach,Periplaneta americana (L.)

The fiber constituents and connections of the calyces — the input-receiving regions — of the corpora pedunculata (“mushroom bodies”) were studied in reduced silver preparations from the American cockroach, Periplaneta americana (L.). In the outer synaptic layer of the calyces five fiber classes were distinguished, the first three of which arise outside the mushroom body. (1) Four highly similar neurons with somata near the optic lobe branch into different parts of the ipsiateral protocerebrum, including both calyces. Their fibers are highly constant in arrangement and position and contain small nucleus-like bodies. (2) The tractus olfactorio-globularis (sensu lato) emits fiber groups which course along the calycal walls as “calycal tracts” before ultimately dissipating into the synaptic layer. Variability within these tracts is described. (3) Fibers of undertermined origin outside the mushroom body radiate from the calycal center outwards through the synaptic layer. (4) From the inner calycal layer of neurites belonging to intrinsic mushroom-body neurons, perpendicular collaterals enter the synaptic layer. (5) Intrinsic-neuron somata near the calycal rim emit fibers which course tangentially within the synaptic layer from calycal rim to center. These fibers form a special peripheral zone in the pedunculus. The predominant presumably afferent calycal fiber class is that derived from the tractus olfactorio-globularis. No evidence was found for tracts from optic lobe to calyces. On this basis, and in light of the experimental and comparative anatomical literature, it is suggested that the corpora pedunculata of P. americana and other pterygotes are fundamentally second-order antennal sensory processing centers. Conflicting observations in earlier reports are critically discussed.     

Eimeria ochrogasteri n. sp. from the Prairie Vole Microtus ochrogaster*

SYNOPSIS. Eimeria ochrogasteri n. sp. (Coccidia, Eimeriidae) from a prairie vole Microtus ochrogaster (Rodentia, Cricetidae) is described. This is the first recorded coccidium in prairie voles. Sporulated oocysts spherical to ellipsoidal, mean 24.0 by 20.5 μ. Oocyst wall double, outer layer thick, yellow-brown, deeply pitted, inner layer clear. Oocyst residuum varies from many small globules to a coalesced group of large and/or small globules. Polar granule present. Micropyle absent. Sporocysts ovoid with “capped” Stieda body, mean 12.3 by 8.2 μ. Sporocyst residuum present. Sporozoites average 14.9 by 2.9 μ with spherical anterior and oblong posterior refractile globules. This species was found in 1 of 71 voles from Weld county, Colorado.     

Ultrastructure and Development of Oil Idioblasts in Annona muricata L.

The ultrastructure and development of oil idioblasts in theshoot apex and leaves in Annona muricata L. are described, andthree arbitrary developmental stages are distinguished: cellsin which no additional cell wall layers have been depositedagainst the initial primary cell wall, possessing an electron-translucentcytoplasm and distinct plastids which lack thylakoids (stage1); cells in which a suberized layer has been deposited againstthe primary wall (stage 2, the cytoplasm resembles that of thepreceding stage), and cells in which an additional inner walllayer has been deposited against the suberized layer, whichincreases in thickness with development (stage 3). In this stagean oil cavity is formed, surrounded by the plasmalemma, andattached to a bell-like protrusion of the inner wall layer,the cupule. A complex membranous structure occurs next to thecupule. Smooth tubular endoplasmic reticulum (ER), appearingas linearly arranged tubules, and groups of crystalline bodieswith an almost hexagonal outline are present. The final stagewas further subdivided into three subgroups (a, b, c) basedon the extent of the oil cavity, its contents, and the compositionof the cytoplasm, and increasing thickness of the inner walllayer. The oil is probably synthesized in the plastids, releasedinto the cytoplasm, and then passed through the plasmalemmasurrounding the oil cavity. Oil idioblasts, Annona muricata L., suberized layer, inner wall layer, oil cavity, cupule, smooth tubular ER, crystalline bodies     

The Embryonic Origin of Neurosensory Cells and the Role of Nerve Cells in Metamorphosis in Phialidium gregarium (Cnidaria,Hydrozoa)

Summary

The embryonic origin of the nervous system in Phialidium gregarium was investigated. Entoderm-free planulae, surgically produced by bisection at mid-gastrulation, and normal planulae were examined by light and electron microscopy to determine their cellular composition. The cell types that occur in the epidermis of the normal planula were described. The entoderm-free planulae were found to be devoid of interstitial cells and their derivatives, the nematocytes and ganglion cells. Neurosensory cells were present, however, indicating that they are derivatives of the ectodermal epithelium.

The role of nerve elements in the initiation of metamorphosis was also examined. Normal and entoderm-free planulae treated for four hours with 0.4% colchicine at two, three, or four days of development fail to undergo cesium-induced metamorphosis. Since such treatment in other hydrozoans eliminates interstitial cells and their derivatives [1-3], it might be argued that ganglion cells are necessary to initiate metamorphosis. The observation that entoderm-free planulae, devoid of interstitial cell derivatives, are capable of responding to induction by bacteria or cesium, however, indicates that in Phialidium the colchicine effect is on other cell types. The results are compared with findings for other Cnidaria.     

Comparative fine structural studies of planulae and primary polyps of identical age of the sea pen,Ptilosarcus gurneyl

Electron microscopic study of an 18-day-old planulae and primary polyps of the sea pen, Ptilosarcus gurneyi, reveals 14 cell types: sustentacular cell A, sustentacular cell B, nerve cell, sensory cell, cnidoblast, interstitial cell, five types of gland cell (A, B, C, D and E), amoebocyte, style cell and endodermal cell. Of these, 9 are found in the planula, 12 in polyps and 7 are common to both stages. The fine structure of all cell types is described. Since the planulae and polyps in this study were identical in age of development, the gaining and losing of certain types of cells in the polyp are attributed to changes associated with settlement and metamorphosis. Modifications of the seven common cell types during metamorphosis can also be attributed to the change of life style from pelagic to benthic.     

Pollen of the Butomaceae and Alismataceae

When the microspores of B. umbellatus are released from the tetrad the developing wall consists only of muri and pilae (bacula). A basal layer is subsequently formed on unitmembrane-like strands. The latter appear to be formed de novo in association with the microspore cell membrane. As a basal layer develops an outer consolidated and an inner stranded layer are differentiated. These are considered ontogenetically equivalent and no terminological distinction appears justified. The basal layer and sexine are not differentiated by basic fuchsin or electron stains. Thus, the stranded (or nonhomogeneous) and amorphous-granular (or homogeneous) types of exine fine structure are histochemically indistinguishable in this species. Concomitant cytoplasmic activity, particularly in the peripheral region of the cell, may be related to substrate or enzyme synthesis, transport, and deposition. Several “unusual” vesicle types are tentatively related to other phases of morphogenetic activity in the protoplast.     

A Histochemical Study of Cytoplasmic Changes During Wall Layer Formation in the Oospore of Albugo candida

The young multinucleate oogonium in Albugo is double-walled with an outer layer exhibiting a negative staining reaction for insoluble polysaccharides and an inner layer which is strongly PAS-positive. The oogonial nuclei exhibit an unusual staining behaviour with aniline blue showing an outer dark blue sheath of proteins surrounding a central hyaline nuclear core. Various histochemical localizations were performed for tracing the chronological sequence of development of the wall layers of the oospore. The first wall of the fertilized oospore was laid at the interphase of the periplasm and the ooplasm. Subsequent wall layers were formed both on the inner and outer side of the first oosporic wall. The second oosporic wall was formed just internal to the first one and exhibited faint PAS positivity. The third wall of the oospore was formed external to the first one and the PAS-negative material for this was apparently contributed by the periplasm. This wall layer at later stages acquired a ridged appearance and these ridges in a mature oospore appear as distinct “pegs”. The last wall to be formed is the innermost one and it completely surrounds the central ooplasm. This wall layer is callosic in nature.     

狗脊孢壁发育超微结构的研究

鳞毛蕨型孢子类型众多,初步研究表明形态相似的孢子类型其孢壁发育特征存在差异,因此有必要对各代表类群的孢壁发育进行深入地研究。该文利用透射电镜对乌毛蕨科(Blechnaceae)狗脊(Woodwardia japonica)孢壁结构和发育的超微结构进行研究。结果表明:(1)狗脊孢子囊的结构由外向内分别为孢子囊壁细胞、两层绒毡层细胞和孢子母细胞;(2)狗脊孢子具乌毛蕨型(Blechnoid type)外壁,表面光滑,由两层构成,裂缝区域具辐射状的槽;(3)周壁属于空心型(cavity type),由四层构成,从内向外分别为P1、P2、P3和P4层,前三层叠合在一起,层间有不同程度的空隙,P4层与前三层之间具有明显而连续的空腔,并隆起形成片状褶皱纹饰;(4)有小球体和小杆共同参与孢子周壁的形成,周壁部分或全部来源于孢子囊壁细胞。综上所述,狗脊孢子与同属于鳞毛蕨型的贯众(Cyrtomium fortunei)和朝鲜介蕨(Dryoathyrium coreanum)孢壁的发育在周壁结构、周壁各层的发育顺序、周壁来源和参与成壁的特征物质等方面存在差异。该研究有利于进一步理解蕨类植物孢壁所蕴含的分类和演化上的科学意义和价值。     

Embryonic Stem Cells: Spontaneous and Directed Differentiation

The specific structural features of embryonic stem cells and embryoid bodies and mechanisms of their differentiation in different cell types are considered. The mouse embryonic stem cells (line R1) formed multilayer colonies which enlarged as a result of fast cell division. Embryoid bodies that derived from embryonic stem cells consisted of an outer layer, an inner layer, and an internal cavity. The structure of cells of the outer and inner layers markedly differed. Spontaneous and directed differentiation of embryoid bodies is determined by some unspecific and specific factors (growth and differentiation factors and extracellular matrix proteins). Retinoic acid, the most commonly used inducer of differentiation of the embryonic stem cells, induces different types of differentiation when applied at different concentrations. The sequence of expression of tissue specific genes and proteins during differentiation of the embryonic stem cells in vitrois similar to that in vivo.