Anatomical and ultrastructural study of the pharyngeal bulb in Protodrilus (Polychaeta, Archiannelida). I. Muscles and myo-epithelial junctions

The pharyngeal bulb of Protodrilus is both a muscular and an epithelial organ whose function is the drawing up of food particles. The muscular system of the bulb is formed of tightly connected antagonistic muscles: the bulbus muscle and the sagittal and ‘grating plate’ muscles. All of them are composed of obliquely striated fibers whose ultrastructural characteristics are similar to those of Hirudina and even more to those of epitokous forms of Nereidae and Syllidae. Myo-epithelial cells do not exist in the pharyngeal bulb of Protodrilus contrary to what was previously thought; the muscles and the stomodeal epithelium are united by junction areas on both sides of the basal lamina. These myo-epithelial junctions may be compared to the myoepidermic junctions known in several Arthropods. A comparison of the ultrastructural features of the bulbus muscle fibers of Protodrilus (Protodrilidae) and Trilobodrilus (Dinophilidae) shows that the Protodrilus fiber clearly belongs to the obliquely striated type classically found in Polychaeta, while the Trilobodrilus fiber is a very peculiar type of obliquely striated fiber. These differences do not agree with Jägersten's hypothesis on the unity of the Archiannelida established on the basis of a structural similarity of the bulbus muscles.     

An ultrastructural analysis of the cuticle,epidermis and esophageal epithelium of Eisenia foetida (Oligochaeta)

The epidermis of Eisenia is covered by a cuticle and rests on a basement lamella. The cuticle, which is resistant to a variety of enzymes, is composed of non-striated, bundles of probable collagen fibers that are orthogonally oriented and are embedded in a proteoglycan matrix. The basement lamella consists of striated collagen fibers with a 560 Å major periodicity. Proximity and morphology suggest that the epidermis may contribute to both the cuticle and the basement lamella — that is, the single tissue may synthesize at least two types of collagen. The epidermis is a pseudostratified epithelium containing three major cell types (columnar, basal and gland) and a rare fourth type with apical cilia. The esophagus is lined by a simple cuticulated epithelium composed predominantly of a single cell type, which resembles the epidermal columnar cell. Rare gland cells occur in the esophageal epithelium, but basal cells are lacking.     

A preliminary ultrastructural study of Phragmatopoma (Polychaeta) gametes

Summary

The mature sperm morphology of this sabellariid polychaete most strongly resembles that of certain mussel sperm, with weaker resemblances to other polychaete and mollusc sperms. Sperm-egg binding appears to be aided by a filament, present in the mature unreacted sperm, which lengthens during the acrosome reaction, passes through the egg vitelline envelope, and binds within a few minutes of insemination to the egg plasma membrane.     

The ultrastructure of the cuticle of Nematoda. II. The cephalic cuticle of Stilbonematinae (Adenophorea,Desmodoridae)

Summary  The ultrastructure of the cephalic cuticle of 6 of 7 representative genera of Stilbonematinae (Eubostrichus, Catanema, Laxus, Robbea, Leptonemella, Stilbonema) is investigated using SEM and TEM techniques. Additionally, one species of Spirinia (Spiriniinae) and one of Desmodora (Desmodorinae) were studied for outgroup comparison. Most of the studied species show modifications of the cephalic cuticle. Furthermore, at least four different pathways have been developed to reinforce the head within Stilbonematinae. Species with a coarsely annulated somatic cuticle (Leptonemella sp., Stilbonema majum, and Desmodora ovigera) developed a rigid, non-annulated cephalic capsule by modifying the main constructing element of the median zone, the ’’ring body.’’ In faintly annulated Laxus oneistus, the annulated cephalic capsule results from a newly inserted ’’block layer’’ between the median and basal zone. The non-annulated cephalic capsule of Robbea sp. is formed by both the block layer and the ring body element. The annulated capsule of Catanema sp. stems from a doubled number of fiber layers within the basal zone. In Spirinia sp., only the amphidial region is strengthened in what could be termed an amphidial shield. All forms with cephalic capsules show mechanisms to keep the oral region pliable. Only Eubostrichus topiarius lacks a reinforcement of the cephalic cuticle. A comparison with the literature is made to elucidate corresponding structures within the cephalic capsules of representatives of Desmodorida. It is demonstrated that the presence of a cephalic cuticle is of no systematic value above the genus level. Accepted: 3 March 1996     

An ultrastructural study of the cuticle in the marine annelid Heterodrilus (Tubificidae, Clitellata)

The ultrastructure of the cuticle in four species of the marine Heterodrilus (H. paucifascis, H. pentcheffi, H. flexuosus, H. minisetosus) is investigated with transmission electron microscopy. The noncellular cuticle consists of several parts; closest to the epidermis is a thick zone of collagen fibers embedded in a matrix. The matrix continues outside the fiber zone, forming a layered epicuticle. The external surface of the epicuticle is covered by evenly distributed, membrane-bound bodies, termed epicuticular projections. The epicuticular projections have their longitudinal axis perpendicular to the surface of the cuticle and are attached to the surface by either the surrounding membrane itself or by short pedestals. Microvilli, extensions from the epidermal cells, penetrate and sometimes pass completely through the cuticle. There is interspecific variation in the morphology of the cuticle. The four studied species differ in the arrangement of the collagen fibers, from irregularly distributed fibril bundles to orthogonally arranged fiber layers, as well as in the number and density of layers in the epicuticle. One of the studied species, H. paucifascis, shows intraspecific variation, which is associated with sample locality. The Bahamian specimens of H. paucifascis have four layers in the epicuticle, club-shaped epicuticular projections, and collagen fibers forming a less defined orthogonal grid, while the Belizean specimens have three layers in the epicuticle, epicuticular projections with a bulging part at midlevel, and a distinct orthogonal grid. Based on these findings the variation in the morphology of the cuticle appears to be dependent on both phylogenetic constraints, and functional and environmental factors.     

Comparative ultrastructural study of the cuticle and spermatozoa in Propappus volki Michaelsen, 1916 (Annelida: Clitellata)

The ultrastructure of the cuticle and mature spermatozoa of the oligochaete Propappus volki Michaelsen, 1916 is described with the aim of providing additional data for clarifying the systematic position of the taxon. P. volki is a fresh-water species living in streams, and is easily recognized by its proboscis on the pre-segmental prostomium and, in mature specimens, by a clitellum covering the segments XII–XIV. The cuticle is composed of a proximal fibre zone and a distal layered epicuticle covered with membrane-bound epicuticular projections. The fibre zone consists of collagenous fibres in a matrix, arranged in either densely packed parallel layers with the fibres oriented in the same direction, or with more loosely distributed fibres, although with the same main orientation. The epicuticular projections are pyramidal with the base leaning on the outer surface of the epicuticle. The cuticle covering the proboscis differs in morphology from that of the rest of the worm; the fibre zone is composed of thin and short fibrils running in all directions, and the epicuticular projections are longer and more narrow than the projections in other regions of the worm.

The spermatozoa are filiform cells formed, in sequence, by an acrosome, an elongated nucleus, a long midpiece, and a flagellum. The acrosomal tube is short and straight with a completely external acrosomal vesicle. Following the acrosome is a apically corkscrew-shaped and basally straight nucleus. The midpiece is twisted and formed by five mitochondria. The flagellum shows a prominent central sheath arrangement.

A comparison with ultrastructurally described cuticles and spermatozoa from other clitellate species reveals most similarities with enchytraeids.     

The opercular moult in Spirorbis spirorbis (L.) and S. pusilloides Bush (Polychaeta: Serpulidae)

Opercular moult has been examined in two spirorbids, the tube-incubating Spirorbis spirorbis (L.) and the opercular incubating Spirorbis pusilloides Bush. In both species epithelial ingrowth cuts off the old operculum and a new one differentiates on the proximal side of the constriction. The immediate fate of the severed tissues differs in the two species; in S. spirorbis the epithelia slowly wither as the platelike operculum finally breaks away by rupture of the cuticle while in S. pusilloides there is a cataclysmic autolysis of the epithelial tissues although the cuticle is retained and functions as an incubation chamber which ruptures at the close of incubation to release the larvae and is then shortly discarded.Opercular moult, rare in the immature animal in either species, normally begins with the onset of breeding. In S. pusilloides it is an essential preliminary to brooding and throughout the breeding season opercular moult rigidly alternates with brood incubation to produce a new incubation chamber for each successive brood. In S. spirorbis there is also some evidence of a partial correlation between brooding and opercular moult but the two events overlap and moulting is less frequent than the production of broods. A brief consideration is given to the evolution of the brooding habit and the tentative conclusion reached that opercular incubation has evolved twice in the Spirorbinae.     

Fate of resting cysts of Alexandrium spp. ingested by Perinereis nuntia (Polychaeta) and Theola fragilis (Mollusca)

The ingestion of resting cysts of Alexandrium spp. by Perinereis nuntia (Polychaeta) and Theola fragilis (Mollusca) was experimentally examined in the laboratory. P. nuntia and T. fragilis were cultured in bottom sediment containing a high density of Alexandrium cysts under dark conditions. Moreover, to evaluate the degree and consequence of being ingested, the density of cysts in the control sediment (no macrobenthic organisms) and the germination capability of the cysts in the faecal pellets of the two species of macrobenthos were examined.Cysts in the culture sediment were found to be ingested by both P. nuntia and T. fragilis. No difference in the density of cysts between the sediments cultured with and without P. nuntia was observed. However, the density of cysts in the sediments with T. fragilis decreased by 24% compared to the density in the control sediment. It is possible that most of the cysts ingested were digested by T. fragilis. The rate of Alexandrium cyst digestion by this species is estimated 594 cysts/individual/day. It is estimated that 91% of the cysts ingested by T. fragilis were partially or totally digested and only 9% were excreted in a viable state during the experiment. Thus, T. fragilis has a stronger affect on the abundance of Alexandrium cysts compared with P. nuntia.No significant difference was observed between the germination success of the cysts from faecal pellets of P. nuntia and T. fragilis compared to the cysts in the control sediment. If, however, the necessary light for the cysts to germinate is cut off by being enclosed within the faecal pellet, the germination rate of cysts from the faecal pellets may be suppressed.     

Histochemical study of distribution of esterases in the pharyngeal bulb of earthworms.

The esterases are studied histochemically in the pharyngeal bulb of local earthworms using tweens, naphthols and indoxyl substrates. Lipase and esterases are located mainly in the pharyngeal epithelial cells and chromophill cells. No activity is seen in the nonchromophill cells. The connective tissue and musculo-vascular tissue contain some esterases activity. Possible role of the esterases in the cellular elements of pharynx has been discussed.     

Anatomical aspects of the gynoecium of species of Anthurium sect. Urospadix Engl. (Araceae,Alismatales)

Anthurium sect. Urospadix includes approximately 70 species differently distributed in Eastern Brazil, Western South America, and Central America. The present work studied the gynoecia of species of section Urospadix to describe their anatomical features. In all the species studied, the apical portion of the gynoecium differentiates into a stigma covered with short trichomes and an adjacent region formed by isodiametric cells. The stylar canal comprises short, unicellular secretory trichomes extending up to the ovarian aperture. Carpels are apically symplicate and basally synascidiate with a septum that does not reach the apical portion of the locule. The apical portion of the septum differentiates into long, secretory trichomes while the subapical one differentiates into the placenta. Locules are filled with mucilage. Since the epidermis of the region adjacent to the stigma, the length of the stylar portion, and the number of cell layers of the ovarian septum vary among the species studied, they may be useful for further taxonomic and systematic purposes. The present work is the first detailed report of trichome location and distribution on the gynoecia of Anthurium.     

Atherospio guillei (Laubier and Ramos, 1974) comb. nov. (Polychaeta: Spionidae) and closest relatives

Atherospio guillei (Laubier and Ramos, 1974) comb. nov. is redescribed based on new material collected during a benthic survey in the German Bight, North Sea. Main characteristics of this species are a deeply incised prostomium, modified neurochaetae on chaetiger 5 superior to a small bundle of capillaries, branchiae fully fused to notopodial lamellae with digitiform distal process from chaetiger 7 over a limited number of succeeding chaetigers, predominately unidentate curved hooks with closely applied sheath from chaetiger 13-15 and a pygidium surrounded by several pairs of lateral cirri. Atherospio is closely related to Pygospiopsis and Pseudatherospio. Interrelationships of these genera are discussed.     

Description of Trichotokara nothriae n. gen. et sp. (Apicomplexa, Lecudinidae) - An intestinal gregarine of Nothria conchylega (Polychaeta, Onuphidae)

The trophozoites of a novel gregarine apicomplexan, Trichotokara nothriae n. gen. et sp., were isolated and characterized from the intestines of the onuphid tubeworm Nothria conchylega (Polychaeta), collected at 20 m depth from the North-eastern Pacific Coast. The trophozoites were 50-155 μm long with a mid-cell indentation that formed two prominent bulges (anterior bulge, 14-48 μm wide; posterior bulge, 15-55 μm wide). Scanning electron microscopy (SEM) demonstrated that approximately 400 densely packed, longitudinal epicytic folds (5 folds/μm) inscribe the surface of the trophozoites, and a prominently elongated mucron (14-60 μm long and 6-12 μm wide) was covered with hair-like projections (mean length, 1.97 μm; mean width, 0.2 μm at the base). Although a septum occurred at the junction between the cell proper and the mucron in most trophozoites, light microscopy (LM) demonstrated that the cell proper extended into the core of the mucron as a thin prolongation. A spherical nucleus (8-20 μm) was situated in the middle of the trophozoites, and gamonts underwent caudal syzygy. The small subunit (SSU) rDNA sequence and molecular phylogenetic position of T. nothriae was also characterized. The sequence from this species was the most divergent of all SSU rDNA sequences currently known from gregarines and formed a weakly supported clade with Lecudina polymorpha, which also possesses densely packed epicyctic folds (3-5 folds/μm) and a prominently elongated mucron.     

Fine structure of the pharyngeal bulb in Trilobodrilus and its phylogenetic significance within archiannelida.

Transmission electron microscopical studies of the pharyngeal bulb in the archiannelid Trilobodrilus sp. proved the presence of two opposing myofilament systems in the plate muscle cells forming this bulb. These muscles are obliquely striated. The significance as well as the origin of this specialized plate-muscle cells in the pharyngeal bulb of archiannelids is discussed in the light of their controversial phylogenetic and systematic position. In addition a hypothesis is suggested to explain the origin of the special arrangement of two opposing systems of myofilaments in one single muscle cell.     

The epidermis of Timarete filigera (Polychaeta, Cirratulidae): histochemical and ultrastructural analysis of the gland cells

The aim of this study was to verify whether different living conditions of Polychaeta are correlated with morphological and functional differences in the organization of the integument. For this purpose, we decided to study the epidermis of Timarete filigera, a non-tubicolous polychaete. With this objective in mind, we have identified the various cellular types responsible for mucous secretion in the epidermis of this species and defined the histochemical composition of the mucus produced by different types of gland cells. Three types of gland cells have been identified by histochemical and ultrastructural studies in the epidermis of this polychaete. The histochemistry was carried out using standard techniques and peroxidase-labelled lectins. In type 1 cells, the secretory granules contain neutral glycoproteins with glucosidic residues of GalNAc, Galbeta 1,3 GalNAc, glucosidic and/or mannosidic residues. In type 2 cells, the secretory granules contain acid glycoproteins mainly sulphated with glucosidic residues of GalNAc, Galbeta 1,3 GalNAc, glucosidic and/or mannosidic residues, and some terminal sialic acid. In type 3 cells, the residual granules have the same chemical composition as that of granules present in type 2 cells. The secretion of these glandular mucous cells consists of mainly sulphated acidic glycoproteins and GAG resistant to testis jaluronidase. In these cells, the residual granules have the same chemical composition as that of their secretion. The heterogeneity of mucus composition may be correlated with its different functions.     

A study on the cuticle of Stegoalpheon kempi Chopra (Isopoda: Crustacea) in relation to its parasitic mode of life

Histological, histochemical, and possible functional properties of the cuticle in the bopyrid isopod parasite Stegoalpheon kempi Chopra are described. In the male, the epi- and the procuticle show similar histochemical characters. The protein constituent of the cuticle suggests a similarity to collagen and its significance is discussed in relation to the parasitic mode of life.In the female, the epicuticle is fuchsin-positive in Mallory's Triple and Masson's Trichrome stains, positive to tests for aromatic amino acids, but negative to tests for phenol, phenol oxidase, and quinone. In addition, the epicuticle shows auto-fluorescence and investigations on the fluorescent compounds present in the epicuticle protein show the presence of di- and tri-tyrosine. The function of these two unusual amino acids as possible cross links is discussed.The cuticle covering the pleopods lacks epicuticle, but it has a simple protein positive to the biuret test, and also a protein containing sulphydryl groups, perhaps as an adaptation for providing respiratory exchanges of gases through cuticle.     

Anatomical study of an aquatic mustard: Subularia aquatica (Brassicaceae)

Subularia aquatica is a small annual aquatic plant in the family Brassicaceae with unique leaf morphology. Its anatomical features were studied using light microscopy. We show that the leaves of S. aquatica are bifacial dorsiventral phyllodes, having adaxial-abaxial polarity, rather than the alternative unifacial type. This morphology is also manifested in the collaterally arranged vascular bundles, which are clearly bifacial. The roots exhibit typical anatomical features of an aquatic plant, including prominent aerenchyma. Although unique within the Brassicaceae, S. aquatica displays many of the same morphological characteristics as other Isoetid life-forms.     

Pilgerodendron uviferum（柏科）及其相关类群叶角质层微形态特征的比较研究

在扫描电镜下观察了分布于南半球的柏科Cupressaceae单种属Pilgerodendron u viferum及其相关类群的代表种Austrocedrus chilensis、Libocedrus plumosa和Papuacedr us papuana叶角质层内外表面的微形态特征。发现Pilgerodendron uviferum叶角质层外表面 光滑,不具Florin环,而其余3个属的代表种均有明显的Florin环;且仅L.plumosa叶角质层外 表面有乳状突起。观察结果支持传统的观点,即将P.uviferum作为独立的属;不支持基于DNA 分析的结果,即将P.uviferum归并到Libocedrus属。发现Papuacedrus papuana叶角质层外表 面有许多明显的小凹陷,与其相对应的叶角质层内表面有凹陷的小狭缝,该性状以前未见报 道。     

Histochemical and ultrastructural analysis of the epidermal gland cells of Branchiomma luctuosum (Polychaeta, Sabellidae)

Abstract. This histochemical and ultrastructural study describes the epidermal gland cells of a tubicolous polychaete, Branchiomma luctuosum . The histochemistry was carried out using standard techniques and FITC-labelled lectins. Four types of secretory cells were identified in two categories: orthochromatic cells (Type 1) and metachromatic cells (Types 2, 3, and 4). The secretory product of the Type-1 orthochromatic cells contains neutral glycoproteins with Galβ1,3GalNAc residues. Metachromatic cells produce acidic, mainly sulfated, glycoconjugates with Galβ1,3GalNAc residues (Type 2) or glucosidic and/or mannosidic residues (Types 3 and 4). In sialylated chains, terminal sialic acid is bound to the penultimate GalNAc and Galβ1,3GalNAc residues. The complex composition of the mucus produced by epidermal gland cells of B. luctuosum may be correlated with its different functions. Ultrastructural studies of the epidermal gland cells showed differing morphology, and the presence in the gland cells of Types 3 and 4 of a funnel-shaped structure for the extrusion of the secretory material.