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The aminergic nature of the CV neurons present in the genital segments of the nerve cord of Eisenia foetida is demonstrated by fluorescence microscopy and by the chromaffin reaction modified for electron microscopy.
The endothelia of Tubifex tubifex Müller consist of myoendothelial cells, chloragocytes, or podocytes. The latter seem to occur only as windows on the ventral vessel which has an endothelium of myoendothelial cells elsewhere. The podocytes are large cells, with several processes on the inner side which ramify into several pedicels. These are aligned upon the outside of the basement membrane which lines the inside of the endothelium. The gaps between adjacent pedicels are about 40 nm wide. In capillaries fenestrated endothelia occur with irregular spacings measuring up to 0.4-1 micron. A diaphragm in podocytes or capillary fenestrations do not seem to exist. The basement membrane is the only continuous layer lining the blood vessels and capillaries of Tubifex with a rather uniform diameter in the range of 50nm. It is the only permeability barrier between blood and coelomic fluid.
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The first species belongs to the genus Pleurocystis (in the Oligocheta host, Eiseniella tetraedra). It is characterized by early syzygies with lateral connection and navicular sporocysts with similar poles. It differs from the only species already described of the genus and is named Pleurocystis eiseniellae n. sp. The second one is related to the genus Pterospora (in the Polychaeta host, Petaloproctus terricola) but differs from the three species already known by its size and number of terminal digitations in specimens always found in syzygy. The sporocysts with dissimilar poles (one rounded, the other neck-shaped) show a loose epispore. This Gregarine in named Pterospora petaloprocti n. sp.
The effect of short term influence of different concentrations of Pb(NO3)2 in the soil on the accumulation and localization of lead in the body wall cells of the earthworm Eisenia foetida (Savigny), Oligocheta, was studied histochemically. The experimental animals displayed the presence of lead deposits in the cytoplasm and vacuols of the epithelial gland cells which also showed morphological changes indicative of their increased secretory activity. Furthermore, a considerable accumulation of lead was found in the sarcoplasm and particularly in the sarcoplasmic reticulum of the muscle cells in the body wall. The histochemical data show that the most intense accumulation of lead is found in animals kept in an environment containing 0-05 mg Pb per 1 g of the soil. At this concentration of lead noteworthy morphological changes together with deposits of this metal are found in the mitochondria. This mitochondrial changes occurred together with the above mentioned, lead induced cytological deviations. They did not appear in other groups of experimental animals.
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The in vivo cumulation of neutral red, methylene blue and acriflavine in the body wall, midgut epithelium and chloragosomes of Lumbricus terrestris L. and Octolasium transpadanum Rosa, and the discharge of these dyes by chloragosomes was investigated by spectrophotometry. The chloragosomes cumulated the largest amount of the ingested dyes. Electron microscopy displayed the activation of the chloragogen cells and an increased chloragosome formation on the first days of dye intake. In dye-free environment, the dye content of the chloragosomes decreased rapidly. The above properties of the chloragogen cells indicate the role of these cells in the defence mechanism against the toxic effect of certain cationic xenobiotics ingested via the intestinal tract.
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The ventral nerve cord of Branchiobdella pentodonta consists of paired ganglia containing three different types of neurons, a central neuropil showing characteristic synapses and of an intersegmental apparatus made up of two large lateral connectives and a smaller ventral one. Some remarkable differences exist between the ventral nerve cord and that found in other oligochaetes; these include the presence of a large dorsal blood vessel, two dorsal muscular cells per metamere, and supportive glial cells ventral to the neuropil which have long transverse processes coming into contact with the segmental nerves.
Data are given on the larvogenesis of the diplocyst of Aploparaksis furcigera. The invagination process of the metamere is described. The external layer of duplicature (exocyst) of the diplocyst has been shown to be a derivate of typical cerecomere. Due to this the larvogenesis of the diplocyst of A. furcigera is regarded as a cystocercoid larvogevesis changed by the adaptation to parasitism in polymyarian intermediate hosts (Oligochaeta). The origin of protective cenogeneses of diplocyst is a response to mechanical effects of the cutaneous-muscular sac of Oligochaeta upon the developing larvocyst.
Nexuses have been demonstrated between glial cell processes in the earthworm ventral nerve cord. The nexuses have been demonstrated by freeze-cleavage to be A-type neuxuses, thus demonstrating for the first time the type of nexus present in the Annelida. If the nexal cleavage pattern has physiological significance then the results suggest that physiologically the nexuses of the earthworm may be similar to those of vertebrates.
The dorsal openings in the myelin sheath of the median giant fiber (MGF) of the earthworm (Lumbricus terrestris L.) have been studied with electronmicroscopical and electrophysiological methods. The fine structure of the dorsal nodes (DN) resembles in many aspects the Ranvier nodes in vertebrate and crustacean nerve fibers. The nodal membrane directly faces the extracellular collagenous capsule of the ventral cord and displays a conspicuous electrondense undercoat. The myelin sheath of the paranode shows a characteristic differentiation into large desmosomal contracts. Recordings of the transmembrane and longitudinal surface currents along the dorsal side of the MGF during spike propagation support the view that an active inward current is restricted there to the DN. The inward current density in the DN reaches outstandingly high values similar to those measured in vertebrate nodes of Ranvier. The nodal activity can be blocked by application of tetrodotoxin and local anaesthetics. Local electrical stimulation of only one DN may suffice to elicit propagated actions potentials up and down the MGF. It is concluded that the dorsal nodes of the median giant fiber of the earthworm are highly specialized excitable structures mediating saltatory impulse conduction in these fibers.
Graft rejection in the earthworm, Lumbricus terrestris, is mediated by granulocytic coelomocytes (neutrophils, by light microscopy). Within 1--3 days post-transplantation of body-wall xenografts, granulocytic coelomocytes migrate to the transplant site, penetrate the graft matrix, and actively phagocytize viable muscle fibers. Destruction of muscle tissues may be augmented by lymphocytic coelomocytes (basophils, by light microscopy), but these cells participate in a minor way and do so very late in the rejection process (days 11--13). Xenografts, autografts and sham-operated controls display generalized inflammatory reactions, including coelomyocyte infiltration into the grafted tissues. In autografts, however, granulocytes only penetrate the inner longitudinal muscle layers and extensive infiltration, persistence and complete destruction never occur. Lymphocytic coelomocytes are not observed in autografts or sham-operated controls. Grafts rejection by leukocytes in an advanced invertebrate confirms that aspects of cell-mediated immunity evolved early in phylogenetic history.
The mature annelid cuticle contains orthogonally oriented collagen in a matrix capped superficially by a dense epicuticle with external corpuscles. The underlying epidermis is a simple columnar epithelium with two major cell types, mucous-secreting cells which secrete through channels in the cuticle to the exterior of the worm, and "supportive" cells which presumably produce and increase the cuticle by secreting into it. The structures of supportive cells, previously interpreted as specialized for establishing interfibrillar collagen order, are revealed by glutaraldehyde fixation as common cellular components without the qualities deemed useful to align collagen. Cell processes which penetrate and sometimes pass completely through the cuticle are not stable, not in geometric order, and lack cilia-like structure. Cilia, unlike the ubiquitous cellular processes, are highly restricted to regions of the epidermis with specialized functions. Cellular control, or other control, of collagen fibrillogenesis remains unestablished.