Ultrastructural features of the epidermis of the planarian Artioposthia triangulata (Dendy)

The epidermis of the land planarian Arthioposthia triangulatawas examined by scanning and transmission electron microscopy. Thisinvestigation revealed that the flatworm was covered entirely withcilia and was especially densely populated on the ventral surface.In all regions the epidermis consisted of a one-layered columnarepithelium resting on a prominent basement membrane, but lacking aterminal web. Various secretions were found in the epidermistogether with epidermal rhabdoids. Below the basement membraneother secretory material was visible and this included thecytoplasmic lamellated granules and adenal rhabdites. The basementmembrane consisted of fibrils with a beaded appearance and thesewere arranged parallel to the epidermal layer but did not displaycross-banding. The secretory cells above and below the basementmembrane were compared and their products characterized on thebasis of shape, size and location. Their possible function isdiscussed.     

斜口涡虫(原卵黄目,斜口科)的生物学特性

摘要：本文报道了采自广东惠州市东江支流(23°09′00. 31"N,114°22′26.59″E)的中国涡虫一新纪录目原卵黄目(Prolecithophora)斜口涡虫(Plagiostomum sp.)。该虫体长4.51 ～6.00 mm,体被不规则的褐色细网纹,头钝圆,尾圆锥形,体中部圆柱状,眼点4只。该涡虫运动...     

New model for the formation and function of sagittocysts: Symsagittifera corsicae n. sp. (Acoela)

Abstract. This study is focused on the formation and function of sagittocysts, which are secretions typical of members of the acoel family Sagittiferidae. The needle-shaped sagittocysts are produced in specialized gland cells (sagittocytes) whose distal necks are often surrounded by muscle mantles. Contraction of the muscle mantle ejects the sagittocyst. We establish a model for the development of sagittocytes and muscle mantles out of the stem cell pool of the new acoel species Symsagittifera corsicae . We used various techniques, especially interference and phase-contrast microscopy of living specimens as well as labeling of the body-wall musculature, for species characterization. In addition to the morphological features, we provide the third complete sequence of the 18S rDNA gene in the family Sagittiferidae.     

An electron microscope study of primary epidermis formation in freshwater planarian embryos

Early development in freshwater planarians is generally considered to be highly modified to the point of being unique. A careful examination by TEM, however, suggests that the primary epidermis (Skaer, 1965) is formed in a rather regular manner but is partially inverted with respect to the definitive body axes. After formation of the yolk cell syncytium, the blastomeres enclosed within it increase in number in the central area. Some of these blastomeres then move peripherally as a group and fuse to form another syncytium, the primordium of the primary epidermis. This primordium contacts the surface of the yolk-cell syncytium at the place where the primordium will subsequently flow out. The primordium spreads to the opposite pole through the spaces among the syncytial and non-syncytial yolk cell masses.     

Phylogenetic relationships of the Temnocephaloidea (Platyhelminthes)

Temnocephala novaezealandiae (family Temnocephalidae) and Troglocaridicola mrazeki and Scutariella georgica (family Scutariellidae) were studied by electron microscopy in an attempt to reveal characters that would indicate their phylogenetic relationship to other members of the Platyhelminthes. Ultrastructural features of the epidermis in these temnocephaloideans are like those of the neoophoran turbellarians. The epidermis is syncytial, is honeycombed by a multitude of gland necks whose secretions produce an epidermal surface film, and is underlaid by a thick basement membrane. Some cells in the parenchyma are compartmentalized by intrusive cell processes from neighboring parenchymal cells in a fashion similar to parenchymal structure in the Monogenea and Digenea. The spermatozoa have a pair of free 9+1 flagella and contain aligned dense bodies. The Temnocephaloidea is evidently derived from an early rhabdocoel-turbellarian-like ancestor.     

Characters of the female gonad and the phylogeny of Platyhelminthes

The female gonad of Platyhelminthes shows a wide variability in its anatomical and cellular organization and submicroscopic structure, and some characteristics may be useful for elucidating the questioned monophyly of some taxa and reconstructing the phylogenetic tree of the group. The morphological characters of the female gonad have been subdivided into three levels: macroscopic, microscopic and ultrastructural, and some examples with potential phylogenetic value are presented for each level. This revised version was published online in July 2006 with corrections to the Cover Date.     

Ultrastructural features of cocoon-shell globules in the vitelline cells of neoophoran platyhelminths

The Neoophora is characterized by the presence of complex female gonads composed of both germaria and vitellaria. The vitellaria are made up of vitelline cells that differentiate to produce and accumulate reserve substances (proteins, lipid, glycogen) and precursors of the egg capsule or cocoon shell (phenolic proteins). A comparative ultrastructural and cytochemical investigation of shell-forming globules from the vitelline cells of some neoophoran platyhelminths shows that the internal structures of the shellforming globules can be grouped into two (or three) main types. In the first, globule content is characterized by a more or less homogeneous electron-dense substructure evidently arising from repeated coalescence of small vesicles produced by the rough endoplasmic reticulum and Golgi complex. A variant of this type of globule shows intermingling (or concentric) electron-dense and translucent areas producing a pattern resembling brain convolutions (convoluted pattern). The second type of shell-globule structure shows a multigranular pattern, presumably resulting from repeated fusions of Golgian vesicles followed by incomplete coalescence of the electron-dense content. Comparison of shell-globule structure in different taxa could be useful in elucidating some complex and still-unclear phylogenetic relationships among Platyhelminthes.     

Ultrastructural and cytochemical studies of the female gonad of Prorhynchus sp. (Platyhelminthes,Lecithoepitheliata)

The female gonad of Prorhynchus is heterocellular (neoophoran organization) and consists of an unpaired, elongate germovitellarium enveloped by a finely granular extracellular lamina. It is composed of a posterior germinative area where early oocytes are randomly associated with differentiating vitellocytes and a growth area with follicular organization. In each follicle a single oocyte is surrounded by a layer of vitellocytes. By electron microscopy, the oocytes showed features typical of non-vitellogenic germ cells; they had chromatoid bodies, annulate lamellae, lipid droplets and R.E.R. and Golgi complexes producing small granules with a multilamellar pattern. Vitellocytes showed features typical of secretory cells with the R.E.R. and Golgi complex developed to a great extent and involved in the production of type A and type B globules, respectively. We speculate that type A globules are shell-globules and type B globules are yolk. The structure, composition and role of vitellocyte globules of Prorhynchus are compared with those of homologous inclusions from other Platyhelminthes.Abbreviations A type A globule - B type B globule - ECL extracellular lamina - GC Golgi complex - L lipid - RER rough endoplasmic reticulum - O oocyte - V vitellocyte     

Primary homology assessment of structures in the female atrial system among species of the Polycystididae (Rhabditophora, Eukalyptorhynchia)

Abstract. The female atrial system of members of the Polycystididae has been studied at the light microscopical level and compared among the constituent taxa. Based on the criteria of position and conjunction, hypotheses of homology are put forward and compared with the assessments of homology found in earlier literature. Contradictory terminology is synonymized and adapted to fit new findings that recognize homology among structures in different taxa. Based on differences in position and structure, 2 types of female duct are recognized: female duct type I and female duct type II. The term “female bursa” is restricted to a sperm resorbing organ at the proximal end of the female duct type I and/or at the end of a common oviduct. Some species have bundles of glands at the place where the oviduct(s) enter the female duct type I, which are considered homologous among these species. Different types of seminal receptacles are recognized. The term “insemination duct” is restricted to the ducts which in some species, in addition to the oviducts, connect the ovaries with the female duct type I. A single muscular duct, the common oviduct, connects the joined oviducts with the female duct type I in species of Duplacrorhynchus and is considered homologous with the similar duct present in some other species. A uterus is always present, entering the common genital atrium through its frontal wall, or entering a female duct type II. This morphological review of the female atrial system reveals a mosaic distribution of characters if applied to previous phylogenies that are based primarily on the male reproductive system.     

Ultrastructure of the epidermis of adult and embryonic Paravortex species (Turbellaria,Eulecithophora)

The epidermis and associated structures of adult and embryonic Paravortex cardii and Paravortex karlingi, internal parasites of Cerastoderma edule, have been examined using scanning and transmission electron microscopy. The cellular epidermis of adult Paravortex bears cilia and microvilli which differ in number and distribution between P. karlingi and P. cardii. Cellular organelles include mitochondria, lipid bodies, Golgi bodies, and ultrarhabdites. Epidermal nuclei are located in the proximal portion of the cells. The development of the tegument of embryo Paravortex has been described and a possible origin for the embryo capsule is suggested. These findings are discussed in relation to the phylogenetic status of the Turbellaria in relation to other Platyhelminthes and in the functional adaptation of the epidermis for a parasitic mode of life.Abbreviations bb- basal bodies - bl- basal lamella - c- cilia - cp- capsule - dc- dark cells - e- embryos - ep- epidermis - g- Golgi bodies - int- interdigitation (of cells) - l- lipid - lf- lamellar fold - mc- migrating cell - mf- membranous folds - mt- mitochondria - mv- microvilli - n- nucleus - nb- neoblasts - p- projections of epidermis - par- parenchyma of mother - pr- primary rootlet - rc- rhabditogen cells - sr- secondary rootlet - ur- ultrarhabdites - vt- vitelline material     

Comparative structure of the epidermis in polychaetes (Annelida)

The polychaete epidermis generally consists of a single layer of supportive cells, gland cells and sensory cells. Except for the latter, this paper reviews the recent literature on the annelid epidermis, focussing on the mentioned cell types and the cuticle. The annelid epidermis is compared to that of Sipuncula, Echiura and Myzostomida. Supportive cells predominate in the polychaete epidermis. They show a high structural diversity even within single specimens. Ciliated cells are usually multiciliary and only two cases of monociliary epidermis cells are known. Unambigous epithilio-muscle cells are only described in feeding palps of a Magelona species. Secretory cells release a large number of gland products and some of them are essential for tube secretion. Rather pecularities of the cells and its arrangement within glands than the ultrastructure of the secretions is useful for phylogenetic considerations. One of the main components of the cuticle is collagen. Recent studies indicate that annelid cuticular collagen differs in several aspects from collagen of the connective tissue and might be of interest for systematics.     

Structure and evolution of the pharynx simplex in acoel flatworms (Acoela)

The homology of pharynges within the mostly pharynx‐less Acoela has been a matter of discussion for decades and even the basic question of whether a pharynx is a primitive trait within the Acoela and homologous to the pharynx of platyhelminth turbellarians is open. By using fluorescence staining of musculature, as well as conventional histological techniques and transmission electron microscopy, the present study sets focus on the mouth and pharynx (where present) of seven species of Acoela within Paratomellidae, Solenofilomorphidae, Hofsteniidae, Proporidae, and Convolutidae, as well as one species of Nemertodermatida and Catenulida, respectively. It is shown that among the investigated families of acoels there is a great variability in muscle systems associated with the mouth and pharynx and that pharynx histology and ultrastructural characters are widely diverse. There are no close similarities between the acoel pharynges and the catenulid pharynx but there is a general resemblance of the musculature associated with the mouth in the representatives of Paratomellidae and Nemertodermatida. On the basis of the profound differences in pharynx morphology, three major conclusions are drawn: 1) the pharynges as present in Recent acoels are not homologous to the pharynx simplex characteristic for Catenulida and Macrostomida within the Platyhelminthes; 2) the different muscular pharynx types of acoels are not homologous between higher taxa and thus a single acoel‐type pharynx simplex cannot be defined; 3) the presence of a muscular pharynx most likely does not represent the ancestral state. J. Morphol, 2009. © 2008 Wiley‐Liss, Inc.     

The adult musculature of two pseudostomid species reveals unique patterns for flatworms (Platyhelminthes,Prolecithophora)

We analyzed the adult musculature of two prolecithophoran species, Cylindrostoma monotrochum (von Graff, 1882) and Monoophorum striatum (von Graff, 1878) using a phalloidin-rhodamine technique. As in all rhabdithophoran flatworms, the body-wall musculature consisted of three muscle layers: on the outer side was a layer of circular muscle fibers and on the inner side was a layer of longitudinal muscle fibers; between them were two different types of diagonally orientated fibers, which is unusual for flatworms. The musculature of the pharynx consisted of a basket-shaped grid of thin longitudinal and circular fibers. Thick anchoring muscle fibers forming a petal-like shape connected the proximal parts of the pharynx with the body-wall musculature. Male genital organs consisted of paired seminal vesicles, a granular vesicle, and an invaginated penis. Peculiar ring-shaped muscles were only found in M. striatum, predominantly in the anterior body part. In the same species, seminal vesicles and penis only had circular musculature, while in C. monotrochum also longitudinal musculature was found in these organs. Female genital organs were only present in M. striatum, where we characterized a vagina interna, and a bursa seminalis. Transverse, crossover, and dorsoventral muscle fibers were lacking in the middle of the body and greatly varied in number and position in both species.     

Production and characterisation of cell- and tissue-specific monoclonal antibodies for the flatworm<Emphasis Type="Italic"> Macrostomum</Emphasis> sp.

Monoclonal antibodies (mABs) against various cell types of the basal free-living flatworm Macrostomum sp. were produced by immunising Balb/c mice with cell suspensions of disintegrated animals. We identified 360 positive supernatants with specific staining of various tissues, cell types, patterns or structures. Here we report immunocytochemical characterisation, histological stainings and isotyping of 11 mABs specific for muscle cells (MMu-1, MMu-2, MMu-3, MMu-4), digestive and prostate glands (MDr-1 and MDr-2, MPr-1), epidermal cells (MEp-1), the ventral nerve cord including neuron clusters (MNv-1), gastrodermal cells (MDa-1) and spermatids (MSp-1). Confocal microscopy, histological techniques, electron microscopy and immunoblotting were applied to demonstrate stainings in juveniles, adults, starved or well-fed animals. Considering the current lack of specific markers the obtained mABs will be particularly helpful studying embryonic and postembryonic development, pattern formation, cell differentiation, regeneration and reproductive allocation in Macrostomum sp., and possibly other basal flatworms. The small size, ease of culturing, short generation time, transparency and the basal phylogenetic position specify Macrostomum sp. as a suitable model organism for comparative analyses within Platyhelminthes and to Drosophila and C. elegans.     

中国涡虫一新纪录科肠口涡虫属一新纪录种格氏肠口涡虫(原卵黄目, 柱口科)

原卵黄目(Prolecithophora)柱口科(Cylindrostomidae)肠口涡虫属(Enterostomula)为海栖涡虫,全球记录3种,在中国未见报道。作者在广东省深圳市深圳湾海边(22°31'N,113°56'E)采集到一种海栖涡虫。本文对该种涡虫进行了较为详细的比较研究,鉴定为柱口科肠口涡虫属格氏肠口涡虫(E.graffi de Beauchamp,1913),为中国新纪录科新纪录属一新纪录种。该种涡虫多数个体背部具2条黑色横纹,部分个体背部花纹有明显变化。眼点2对。雌雄同体,精巢、卵巢各1个。受精囊位于卵巢与子宫之间;子宫位于体末端,后接一微小的外阴道。本文发现:①该涡虫的尾部腹面具有一个交配囊及一根雌性生殖管,交配囊是一个由肌肉层组成的袋状囊,同时与子宫、雌性生殖管相连;②雌性生殖管外围有明显的生殖腺包裹;③雌性生殖管孔、阴茎孔与口孔一起通往体外;④此种涡虫喜分泌黏液将微小杂质粘结呈半球状窝,虫体隐藏于窝内。     

Septate junctions in the cephalic epidermis of turbellarians (Bipalium)

Summary In the epidermis of turbellarians septate junctions of the pleated sheet type have been demonstrated in conventional thin sections and freeze fractured preparations. The structure of these junctions entirely agrees with that found in molluscs and arthropods.Financially supported by DFG (Sto 75/3,4; We 380/5)     

Keratinization of the epidermis of the Australian lungfish Neoceratodus forsteri (dipnoi)

The differentiation of the epidermis in sarcopterigian fish may reveal some trend of keratinization followed by amphibian ancestors to adapt their epidermis to land. Therefore, the process of keratinization of the epidermis of the Australian lungfish Neoceratodus forsteri was studied by histochemistry, electron microscopy, and keratin immunocytochemistry. The epidermis is tri-stratified in a 2-3-month-old tadpole but becomes 6-8 stratified in young adults. Keratin filaments increase from basal to external cells where loose tonofilament bundles are present. This is shown also by the comparison of positivity to sulfhydryl groups and increasing immunoreactivity to alpha-keratins in more external layers of the epidermis. Two broad-spectrum anti alpha-keratin monoclonal antibodies (AE1 and AE3) stain all epidermal layers as they do in actinopterigian fish. In the adult epidermis, but not in that of the larva, the AE2 antibody (a marker of keratinization in mammalian epidermis) often immunolabels more heavily the external keratinized layers where sulfhydryl groups are more abundant. Mucous granules are numerous and concentrate on the external surface of the epidermis to be discharged and contribute to cuticle formation. Keratin is therefore embedded in a mucus matrix, but neither compact keratin masses nor cell corneous envelope were seen in external cells. It is not known whether specific matrix proteins are associated with mucus. There was no immunolocalization of the keratin-associated proteins, filaggrin and loricrin, which suggests that the epidermis of this species lacks the matrix and cell corneus envelope proteins characteristic of that of amniotes. In conclusion, while specific keratins (AE2 positive) are probably produced in the uppermost layers as in amphibian epidermis, no interkeratin, matrix proteins seem to be present in external keratinocytes of the lungfish other than mucus.     

Unciliated body surface in three species of the Umagillidae (Dalyellioida,Platyhelminthes)

Anoplodiera voluta Westblad, Seritia elegans (Westblad) and Wahlia macrostylifera Westblad are species of the family Umagillidae living in the intestine of the holothurian Parastichopus tremulus. In all three species, part of the epidermis is unciliated, but unlike unciliated epidermis in the major parasitic flat-worm groups, it is cellular and has intraepithelial nuclei. The surface of the unciliated cells in A. voluta is convex with the cells separated by lateral gaps. The cells have two distinct regions: the basal, organelle-rich part and the apical part which contains few identifiable organelles except vesicles. In W. macrostylifera the unciliated cells have a flat surface and, between them, narrower gaps that in some cases widen to paracellular compartments below the cell surface. Apically the cells contain electron-dense vesicles, often in contact with the surface. S. elegans has unciliated cells separated by gaps. In all these species, apical vesicles indicate secretory activity. Comparison of the epidermis of these three species with the neodermis of the major parasitic flatworm groups within the Neodermata does not support a close relationship of the three to the Neodermata.     

Ultrastructural investigations on the differentiation of genital hard structures in free-living platyhelminths and their phylogenetic significance

Ultrastructure and differentiation of penis stylets and stylet needles have been investigated in representatives of various groups of free-living platyhelminths, viz. the Acoela, Macrostomida, Typhloplanoida, Kalyptorhynchia, and Dalyellioida. In all these groups, the differentiation of such hard parts occurs intracellularly but in different ways in the different groups. The ultrastructure of the bursal mouth piece in an acoel platyhelminth is not comparable to the hard structures in male copulatory organs. The presence of penial copulatory organs having intracellular hard structures appears to be an autapomorphy of the Euplatyhelminthes. Several characters in the ultrastructure and development of these structures can be used as autapomorphies for various platyhelminth groups.     

Ultrastructure of the protonephridial system of Dactylogyrus sp. and an unidentified ancyrocephaline (Monogenea: Dactylogyridae)

The ultrastructure of the flame bulbs and capillaries of the protonephridia of Dactylogyrus (probably anchoratus) from Carassius auratus in southeastern Australia, and of an unidentified ancyrocephaline from the marine teleost Priacanthus macracanthus in southern Queensland is described. The cilia of the flame are anchored in the terminal cell by means of basal bodies without distinct rootlets. The nucleus of the terminal cell is basal, and (in Dactylogyrus) partly lateral to the basal bodies. The weir consists of a row of internal and a row of external ribs (rods) connected by a ‘membrane’. The external ribs are continuations of the cytoplasm of a thick-walled ‘cytoplasmic cylinder’ (proximal canal cell) which tightly surrounds most of the flame and contains a septate junction; the internal ribs are continuous with the terminal cell. Internal leptotriches arise from the perikaryon of the terminal cell, and, in the ancyrocephaline, also from the internal ribs. The wall of the protonephridial capillaries contains a septate junction, a reticulum of interconnected spaces and, in the ancyrocephaline, also lamellae. Lateral flames are common in the capillaries of Dactylogyrus.