Carbaryl-induced behavioural and reproductive abnormalities in the earthworm Metaphire posthuma: a sensitive model

Carbaryl, an N-methyl carbamate insecticide, is used in India to control foliar insects, but, due to soil contamination, it also adversely affects non-target organisms such as earthworms. This paper deals with the toxic effects of carbaryl on the behavioural and reproductive profiles of the earthworm, Metaphire posthuma. Locomotion and geotaxis were significantly affected, even after a 20-minute exposure to 0.125ppm carbaryl. The hatching of cocoons was altered at 0.5ppm, whereas cocoon production was retarded even at 0.125ppm carbaryl. No cocoon production was observed at 2.0ppm carbaryl. Sperm head abnormalities were reported even at the lowest test concentration of 0.125ppm. Wavy head abnormalities were observed at 0.125ppm carbaryl, whereas at 0.25ppm and 0.5ppm, the sperm heads became amorphous and the head nucleus was turned into granules deposited within the wavy head. It is concluded that the earthworm could be used as an ecosystem model for the initial toxicity testing of environmental pollutants.     

Secretory cells in the clitellar epithelium of Eisenia foetida (Annelida,Oligochaeta): A histochemical and ultrastructural study

Eight secretory cell types are identified in the clitellar epithelium of Eisenia foetida, of which five have been described in detail previously (i.e., the large granular, fine granular, metachromatic, orthochromatic, and small granular proteinacecus cells). The remaining three secretory cell types are mucus-producing cells specific to the clitellar epithelium (type 3), cells associated with the chaetal follicles (type 4), and cells that occur exclusively in the tubercula pubertatis (type 5). Type 3 cells secrete a mucus containing neutral and acid mucosubstances. Ultrastructurally, type 3 cells are characterized by membrane-bound globules 0.4 to 3.7 μm in diameter. The contents of the globules have a finely reticulate appearance. The secretion of type 4 cells contains a collagenlike protein and neutral and sulfated acid mucosubstances. Type 4 cell secretory granules are membrane bound and range in diameter from 0.8 to 1.6 μm. They contain large, electron-dense, spheroid cores which are surrounded by parallel orientated microfibrils 14 nm in diameter. Type 5 cells give variable responses to the histochemical techniques used in the present study. An elastinlike protein is detected in about half of the type 5 cells and acid and neutral mucosubstances in the remainder. At the ultrastructural level the secretory granules vary in shape from spheroid to polygonal. Their finely, electron-dense contents exhibit progressive swelling which results in the eventual rupture of the limiting membranes of the granules. The necks of types 3, 4, and 5 cells contain a peripheral ring of microtubles (20 ± 1 nm in diameter).     

An ultrastructural study of the prostate gland of megascolicid earthworm Lampito mauritii (Kinberg)

The ultrastructure of prostate gland of Lampito mauritii revealed two types of secretory cells. Type 1 cells with a broad basal region and a long apical region contain electron dense oval secretory granules with an increased density at the core region. Numerous electron lucent granules with fine filamentous and electron dense amorphous materials also occur at the basal region of these cells. Type 2 cells contain electron lucent mucous-like secretory granules. This cell type contains exceptionally large Golgi complexes having 20-23 stacked cisternae. Both cell types open into a common lumen and numerous microtubules are visible at the apical end. Junctional complexes, such as desmosomes and septate junctions, are observed in this glandular tissue.     

An ultrastructural study of osmiophilia in normal human oesophageal epithelium

Summary Oesophageal biopsies were obtained from patients with normal oesophagi during fibre-optic endoscopy for upper gastro-intestinal symptoms. They were studied with the prolonged osmication technique. The forming face of the Golgi apparatus was demonstrated in the basal and lower prickle cells. These cells also showed osmium deposition in their mitochondria, endoplasmic reticulum, perinuclear cisternae and lysosomes. The capillary endothelial cells also showed osmium deposition in their Golgi apparatus and endoplasmic reticulum.     

Cloning, expression, and characterization of cadmium-induced metallothionein-2 from the earthworms Metaphire posthuma and Polypheretima elongata

In this study we report the sequences of MT-2 cDNA from two species of Megascoleidae earthworms, Metaphire posthuma and Polypheretima elongata, by mRNA differential display after exposure of the organisms to cadmium. Complementary (c)DNA was verified as the MT-2 gene by the characteristics of its predicted translation product, namely a high cysteine content, conserved CXC motifs, and a molecular weight of around 8 kDa. Amino acid sequence alignment revealed a conserved TKCCG in the cloned MT-2 of both megascolecid earthworms instead of the corresponding conserved TQCCG found in lumbricid earthworms. The cDNAs corresponding to the two megascolecid MT-2 genes were expressed, and the MT-2 proteins were purified for biochemical characterization. The binding of Cu2+ exhibited monophasic kinetics and those of Zn2+ and Cd2+ biphasic kinetics. The proteins bound more tightly to Cd2+ than to Zn2+ and more tightly still to Cu2+. Zn-MT and apo-MT were the most effective at scavenging free radicals, followed by Cd-MT. In conclusion, MT-2s from M. posthuma and P. elongata showed unique sequence features compared to those of lumbricid earthworms. These earthworms could be used to evaluate heavy-metal pollution in soil due to the inducible MT-2 by cadmium exposure.     

An ultrastructural study of bruising in stored potato (Solarium tuberosum L.) tubers

Potato tubers of the cultivar Pentland Dell were investigated for ultrastructural changes following impact. Studies were carried out on tubers after 12 and 24 wk of storage using a falling bolt delivering 0.7 J of energy. Ultra-thin sections were examined by light and transmission electron microscopy. Tubers stored for 12 wk exhibited no visual bruise formation, whereas visible bruising resulted following impact of tubers stored for 24 wk. An ultrastructural sequence of events during bruising was established as (1) a collapse of intracellular compartmentation, (2) increased ribosomal and mitochondrial abundance within the cytoplasm, (3) increased density of cytoplasm adjacent to the cell wall and surrounding amyloplasts, and (4) the development of melanin in bruised cells. These observations are discussed in relation to tuber turgor and physiology during storage.     

An ultrastructural study of the dorsal lingual epithelium of the crab-eating frog,Rana cancrivora

The amphibian tongue contains two types of papilla which are believed to function in gustation and in the secretion of salivary fluid. Scanning electron microscopy reveals that columnar, filiform papillae are compactly distributed over nearly the entire dorsal surface of the tongue of the frog, Rana cancrivora, and fungiform papillae are scattered among the filiform papillae. Microridges and microvilli are distributed on the epithelial cell surface of the extensive area of the filiform papillae. Light microscopy shows that the apex of each filiform papilla is composed of stratified columnar and/or cuboidal epithelium and its base is composed of simple columnar epithelium. Transmission electron microscopy reveals that most of the epithelium of the filiform papillae is composed of cells that contain numerous round electron-dense granules 1–3 μm in diameter. Cellular interdigitation is well developed between adjacent cells. On the free-surface of epithelial cells, microridges or microvilli are frequently seen. Between these granular cells, a small number of ciliated cells, mitochondria-rich cells and electron-lucent cells are inserted. In some cases, electron-dense granules are present in the ciliated cells. At higher magnification, the electron-dense granules appear to be covered with patterns of spots and tubules. Overall, the morphology and ultrastructure of the lingual epithelium of the three species of Rana that have been studied are quite similar, but they can be easily distinguished from those of Bufo japonicus. Therefore, it appears that lingual morphology is phylogenetically constrained among members of the predominantly freshwater genus Rana to produce uniformity of papillary structure and this morphology persists in Rana cancrivora despite the distinct saline environment in which it lives. © 1993 Wiley-Liss, Inc.     

An ultrastructural study of the viscin tissue ofPhthirusa pyrifolia (H.B.K.) Eichler (Loranthaceae)

Summary The viscin tissue ofPhthirusa pyrifolia consists at maturity of two different cell types. The first of these (viscin cells) are greatly elongated and have massive secondary walls, the microfibrils of which are arranged strictly transversely, and are soaked with mucilaginous noncellulosic polysaccharides. The second type of cells (vesicular cells) is much broader, with a very extensive vacuolar system and thin primary cell walls only. Viscin cells are capable of being stretched very greatly, the microfibrils of the secondary wall then becoming oriented more or less longitudinally. In nature, this corresponds to the time of attachement to the host surface, and is followed by drying and, possibly, shortening of the viscin cells. Developmental study of the tissue suggests that Golgi bodies are the major organelles participating in polysaccharide production. The actual mucilage seems to originate from three sources: an unorganized substance which accumulates between the plasmalemma and compound middle lamella; spherical vacuoles which seem to be embedded in the central vacuole, some of which are seen open to the outside of the cell; and from the dissolution at maturity of the compound middle lamella. It is suggested that the two types of cells may correspond to the two major functions of viscin, viz., host attachment (viscin cells) and nutrition of the disseminator (vesicular cells).     

An ultrastructural and immunohistological study of the rat olfactory epithelium: Unique properties of olfactory sensory cells

The olfactory epithelium contains three cell types: basal cells, supporting cells and sensory neurons. Electron microscopy as well as immunofluorescence microscopy with intermediate-filament antibodies were used to study the rat olfactory epithelium in order to obtain more information about these different cell types and to try to investigate their histogenetic origins. We found mitoses in the basal-cell layer, as well as multiple centrioles and tonofilaments in some basal cells. As revealed by electron microscopy, the supporting cells contained tonofilaments and reacted strongly with antibodies to keratin, in line with their known epithelial nature. When antibodies to other intermediate-filament types were used, i.e. glial fibrillary acidic protein, vimentin, desmin and neurofilaments, no reaction was seen in the cells of the olfactory epithelium, with the exception of occasional staining of a few axons in the subepithelial layer by neurofilament antibodies. In particular, the cell bodies, dendrites and most axons of the sensory neurons were negative for a variety of antibodies against neurofilaments. Olfactory sensory neurons therefore belong to the very few cells in adult animals which seem to lack intermediate filaments. We discuss whether this finding is related to the fact that these cells are also unique among neurons in that they are not permanent cells but constantly turn over.     

An ultrastructural study of spermatogenesis and sperm morula breakdown inArenicola marina (L.) (Annelida: Polychaeta)

Spermatogenesis in the lugwormArenicola marina, in common with other members of Arenicolidae, occurs in the coelomic fluid and results in the formation of discs of mature spermatozoa known as a morulae. Within a morula, individual spermatozoa are connected by a common mass of cytoplasm called the cytophore and therefore make up a syncitium. Immediately prior to spawning, and in response to an endocrine substance known as “Sperm Maturation Factor” (SMF), the structure of the sperm morulae breaks down and free spermatozoa are liberated. These are subsequently spawned from the body cavity. The investigation described here uses transmission electron microscopy to investigate the ultrastructural changes, which accompany spermatogenesis and the breakdown of sperm morulae in response to SMF in vitro. The study demonstrates that the cytophore appears to have a key role both during spermatogenesis and during sperm morula breakdown. The ultrastructure of sperm morulae and of mature spermatozoa is described. The structure of spermatozoa is shown to be primitive with a single flagellum which appears to be coiled at its distal end. The phagocytosis of free spermatozoa by coelomocytes is also described and it is suggested that these may play a role in the resorption of unspawned gametes in vivo.     

An immunocytochemical and ultrastructural study of the nervous and muscular systems of Xenoturbella westbladi (Bilateria inc. sed.)

The phylogenetic position of the Xenoturbellida is highly disputed. Are they primitive flatworms? Are they related to Deuterostomia? Do they form a sister taxon to other Bilateria? Are they bivalve molluscs? In order to provide more data for this discussion, a study of the nervous system of Xenoturbella westbladi and its relation to the musculature was performed, using 5-HT and FMRFamide immunocytochemistry, TRITC-conjugated phalloidin fluorescence for staining of F-actin filaments, confocal scanning laser microscopy and transmission electron microscopy. The nervous system comprises solely an intraepidermal net of nerve cells and processes. No ganglia or any other internal nervous structures could be detected. No evidence of 5-HT- or FMRFamide-immunoreactive innervation below the subepidermal membrane complex was obtained. The 5-HT and FMRFamide immunoreactivity occurs in separate sets of neurones. On the ultrastructural level, three types of neurones were observed: (1) the predominating ”light” neurones, (2) the smaller ”dark” neurones and (3) the bipolar sensory neurones bearing a single cilium with a long bipartite rootlet. Non-synaptic, paracrine, release sites are common and synapses are inconspicuous. In the layer of epidermal cells, close to the lateral furrow, F-actin filaments were observed. They reach from the basal membrane to the surface. The organisation of the nervous system appears very simple. Our results are compatible with the hypothesis of Xenoturbellida forming a sister taxon to Bilateria. No evidence was obtained for inclusion of X. westbladi in either the Mollusca or Plathelminthes.     

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.     

Postnatal development of the vomeronasal epithelium in the rat: an ultrastructural study

Three basic types of cells are distinguished in the rat vomeronasal epithelium at birth: bipolar neurons, supporting cells, and basal cells. Neurons at this time include both immature and differentiated cells. By the end of the first postnatal week, all neurons show morphological signs of maturity in their cytoplasm, including abundant granular and smooth endoplasmic reticulum, neurotubules, dense lamellar bodies, apical centrioles, and tufts of microvilli. During the third week microvilli are more frequently encountered and appear to be longer and more branched. Supporting cells appear well-developed by the second day after birth. During the first ten days of life, supporting cells lose their centrioles and all of the complex associated with ciliary generation in the apical zone. Basal cells appear to be more numerous in newborns than in older animals. Protrusions projecting into the lumen are frequently observed in the epithelium of newborn animals, both on the dendrites of neurons and on supporting cells. After the third week, such protrusions are only observed in the transitional zone between the sensory and the non-sensory epithelia of the vomeronasal tubes. In this transitional zone, a fourth cell type showing apical protrusions with microvilli differentiates. Cytoplasm in this type resembles that of neighboring ciliated cells but has no cilia or centrioles. These transitional cells are considered to be cells in an intermediate state of differentiation, between that of the differentiated neurons and supporting cells of the sensory epithelium and that of the predominate ciliated cells of the non-sensory epithelium. The results suggest that by the end of the third week the vomeronasal epithelium is morphologically mature.