Ultrastructure of the crayfish antennal gland revealed by scanning and transmission electron microscopy combined with ultrasonic microdissection

The antennal gland of the crayfish Pacifasticus leniusculus was studied using standard techniques for scanning electron microscopy as well as newer procedures for ultrasonic microdissection. To clarify relationships in the nephron tubule, transmission electron microscopy was employed. The coelomosac contains elongated cells (podocytes) displaying microvilli and extensive apical blebbing. A smooth basal lamina lines the blood space that furnishes hemolymph to the coelomosac. The labyrinth consists of tall columnar cells displaying apical microvilli, numerous blebs that seem to represent an expansion of apical plasma membrane, and lateral interdigitations. The nephron tubule consists of two distinctly different areas: a proximal region of flattened cells with extensive intercellular fusions, and a distal segment of separate, dome-shaped cells. Despite many similarities between the crayfish kidney and the vertebrate nephron, there are striking differences. The amount of surface blebbing that occurs in the coelomosac and labyrinth far exceeds that of the vertebrate nephron and may reflect its importance in the function of the crayfish kidney. The cells of the coelomosac are taller than are the vertebrate podocytes and possess less obvious arms and pedicels. In addition, the proximal segment of the nephron tubule is notable for its intercellular fusions, which are not present in the vertebrate nephron. Although the function of the intercellular fusions is unknown, they may play a role in cellular communication or the redistribution of fluids or electrolytes between cells.     

Ultrastructure of the crayfish kidney--coelomosac, labyrinth, nephridial canal

Regions of the crayfish kidney were examined by electron microscopy. Coelsmosac cells are loosely bound together by desmosome-like spot junctions, and connected to the basal lamina via characteristic pedicels. The cytoplasm contains numerous vesicles and vacuoles of various sizes and is often crowded with large, lysosome-like granules or dense bodies. The morphology suggests a filtration mechanism with reabsorption of materials such as protein from the filtrate and secretion of other substances into the lumen. The labyrinth is composed of cuboidal to columnar cells which possess a brush border, long and narrow intercellular spaces, basal plasmalemmal invaginations and typical cytoplasmic components. Two sub-regions are distinguishable. The morphology of labyrinth I suggests that these cells move fluid isotonically across the epithelium. Labyrinth II, in addition to isotonic transport, appears to be more active in the endocytic uptake and intracellular digestion of large molecules such as protein. The nephridial canal consists of cells which lack a brush border, but display extensive basal invaginations associated with elongated mitochondria. A proximal and distal region are cytologically distinguishable. Proximally, the cells are small and filled with mitochondria throughout. Scattered within the cytoplasm are vesicles, vacuoles, diffuse glycogen, free ribosomes, dense bodies and some rough endoplasmic reticulum. Distally, the cells are less compact, larger, and cuboidal to columnar in shape. The cytoplasm is similar to that of the proximal cells, but the basal invaginations are even larger and more extensive. The morphology of cells in both regions of the nephridial canal is highly suggestive of active solute reabsorption, probably occurring against an osmotic gradient.     

Ultrastructural studies and Na+,K+-ATPase immunolocalization in the antennal urinary glands of the lobster Homarus gammarus (Crustacea, Decapoda).

Unlike in crustacean freshwater species, the structure and ultrastructure of the excretory antennal gland is poorly documented in marine species. The general organization and ultrastructure of the cells and the localization of Na(+),K(+)-ATPase were examined in the antennal gland of the adult lobster Homarus gammarus. Each gland is composed of a centrally located coelomosac surrounded ventrally by a labyrinth divided into two parts (I and II) and dorsally by a voluminous bladder. There is no differentiated nephridal tubule between them. The labyrinth and bladder cells have in common a number of ultrastructural cytological features, including basal membrane infoldings associated with mitochondria, apical microvilli, and cytoplasmic extrusions, and a cytoplasm packed with numerous vacuoles, vesicles, lysosome-like bodies, and swollen mitochondria. Each type of cell also presents distinctive characters. Na(+),K(+)-ATPase was detected through immunofluorescence in the basal part of the cells of the labyrinth and in the bladder cells with an increasing immunostaining from labyrinth I to the bladder. No immunoreactivity was detected in the coelomosac. The cells of the labyrinth and of the bladder present morphological and enzymatic features of ionocytes. The antennal glands of the lobster thus possess active ion exchanges capabilities.     

Immunocytochemical demonstration of carbonic anhydrase in human epithelial cells

Human tissues obtained early postmortem were immunostained to demonstrate carbonic anhydrase (CA) and, in some instances, to differentiate CA I and CA II, employing an immunoglobulin-peroxidase bridge method. Optimal immunostaining was obtained in tissues fixed a few hours in Carnoy's fluid or a buffered HgCl2 solution. Specimens fixed 1/2 to 2 hr with buffered formalin or Bouin's fluid stained less well but better than those fixed 24 hr with formalin. In tracheobronchial glands, serous acini and demilunes exhibited intense immunoreactivity demonstrative of the isozyme CA II. In kidney, all cells of the distal convoluted tubules were strongly positive for CA and cortical collecting tubule cells stained strongly but with some variability among individual cells. Cells in medullary collecting tubules ranged from intensely to negligibly reactive. Proximal convoluted tubules and thick ascending limbs showed moderate to light, uniform staining, but the thin limbs of the loop of Henle were negative. Renal cell immunoreactivity occurred only with antiserum to CA II. Seromucous acini in submandibular glands stained strongly and selectively for CA. Ducts in liver and pancreas showed strong selective immunostaining. The most superficial columnar cells lining the main lumen of the colon and appendix displayed strong reactivity, as did columnar cells lining the gall bladder.     

Ontogeny of the antennal glands in the crayfish Astacus leptodactylus (Crustacea, Decapoda): immunolocalization of Na+,K+-ATPase

The involvement of the antennal urinary glands in the ontogeny of osmoregulatory functions was investigated during the development of Astacus leptodactylus by measurements of hemolymph and urine osmolality in juvenile and adult crayfish and by the immunodetection of the enzyme Na⁺,K⁺-ATPase. In stage II juveniles, 1-year-old juveniles, and adults, all of which were maintained in freshwater, urine was significantly hypotonic to hemolymph. In adults, chloride and sodium concentrations were much lower in urine than in hemolymph. During embryonic development, Na⁺,K⁺-ATPase was detected by immunocytochemistry in ionocytes lining the tubule and the bladder, at an eye index (EI) of 220–250 m, and in the labyrinth, at EI 350 m. In all regions, immunofluorescence was mainly located at the basolateral side of the cells. No immunofluorescence was detected at any stage in the coelomosac. In late embryonic stages (EI 410–440 m), in stage I juveniles, and in adults, strong positive immunofluorescence was found from the labyrinth up to and including the bladder. These results show that, as early as hatching, juvenile crayfish are able to produce dilute urine hypotonic to hemolymph. This ability originates from the presence of Na⁺,K⁺-ATPase in ion-transporting cells located in the labyrinth, the tubule, and the bladder of the antennal glands and constitutes one of the main adaptations of crayfish to freshwater.We thank the University of Tarbiat Modarres and Ministry of Science, Research and Technology, Islamic Republic of Iran for financial aid and support. Special thanks are also due to the Société Française dExportation des Ressources Educatives (SFERE) for the scholarship to S.K.     

Protonephridial organs in Myzostoma cirriferum (Myzostomida)

Myzostoma cirriferum Leuckart, 1836 possesses five paired, serially arranged, blindending nephridial organs which are described for the first time. Ultrastructural investigations reveal that each nephridium is composed of three terminal cells and one tubular cell that forms the emission tubule. The central lumen of the individual terminal cells contains six to nine flagella, each of which is surrounded regularly by cytoplasmic rods arranged in parallel. Weir-like fenestrations in the peripheral wall of the terminal cells make up the connection between the central lumina and the extracellular space around the nephridial organ. The canal of the emission tubule possesses cilia, microvilli and cytoplasmic structures, suggesting involvement of this cell with active transport and storage. It opens into the cuticle at the ventral surface of the animal.     

Studies on vertebrate kidney. V. PAS-positive lipids in kidneys of fishes from different habitats.

Five fish species living in different habitats, i.e. fresh water, estuarine and marine, were studied for the distribution of PAS-positive materia in various regions of the kidney, 10 minutes' oxidation with 0-5 per cent. HIO4 being employed prior to treatment with Schiff's reagent. PAS-positive material was detected in different sites of the kidney, i.e. brush border of proximal tubules, proximal tubule cells' cytoplasm, distal tubule cells' cytoplasm, glomerulus, basal cell border of proximal tubules and the interstitial cells. Of these sites, the brush border of the proximal tubule of Scoliodon sorrakowah showed the presence of PAS-positive lipids. Elsewhere the PAS-positive reaction was due to carbohydrates. Free aldehyde groups were absent. In Tilapia mossambica and Labeo rohita, PAS staining was enhanced after chloroform-methanol extraction, particularly in the brush border of the proximal tubule. The significance of these findings is discussed.     

Regional specialization in the malpighian tubules of the new zealand glow-worm Arachnocampa luminosa (diptera: Mycetophilidae). The structure and function of type I and II cells

The Malpighian tubules of the glow-worm Arachnocampa luminosa are divided into four morphologically distinct regions (Parts 1--4) each comprised of a different cell type (Types I--IV). The ultrastructure of Type II cells is indicative of a transport function. The basal cell surface is highly invaginated and at the apical surface the lumen is lined with microvilli about 80% of which contain mitochondria. Spherites contained in these cells are formed from small vesicles produced by the Golgi apparatus. They have a central uric acid core enclosed by laminations of phosphates of calcium and magnesium. Cells of Part 2 of the tubule secrete a fluid high in potassium (173 mM) and low in sodium (18 mM). The cell is 30 mV negative and the lumen 44 mV positive to the bathing solution. This is consistent with the proposal of an apical cation pump. The secretion produced by Part 2 of the tubules is modified by the Type I cells by the reabsorption of potassium (162 mM) and the addition of sodium (24 mM) to the primary excretory fluid. Type I cells are 20 mV negative and the lumen 22 mV positive with respect to the bathing medium. From ultrastructural observations, Type I cells exhibit features characteristic of transporting cells thought to have an absorptive function. The basal and apical cell surfaces are extensively folded, and mitochondria are found in bands above the basal infoldings and below the microvilli. Mitochondria do not penetrate the microvilli. On comparative grounds, the fine structure of Type I cells suggest that they reabsorb ions from the tubule lumen. Energy for these processes may come from the breakdown of lipids by microperoxisomes contained within these cells. Alternatively, the fluid produced by Part 2 of the tubule may be modified passively by diffusional processes across Type I cells.     

Ultrastructure of the metanephridia of Terebratulina retusa and Crania anomala (Brachiopoda)

Adult specimens of Terebratulina retusa and Crania anomala have one pair of metanephridia. Each metanephridium is composed of a ciliated nephridial funnel (nephrostome) and an outleading nephridial canal, thus, these organs are open ducts connecting the metacoel of the animal with the outer medium. In both species, the inner side of a nephrostome is lined by a columnar monociliated epithelium which contacts the coelothel within one of the two ileoparietal bands. The coelothel contains basal filaments (in C. anomala these are definite myofilaments). The canal epithelium also consists of monociliated columnar cells which differ from the nephrostome epithelial cells in size and some cell components. Within the nephropore, the canal epithelium makes contact with the so-called inner mantle epithelium which lines the mantle cavity. The nephrostome epithelial cells and the canal epithelial cells never contain any contractile filaments. There are always continuous transitions between these different epithelia and distinct borders cannot be observed. The present results, especially in comparison to Phoronida, do not contradict the hypothesis of a coelothelially derived nephridial funnel and an ectodermal nephridial duct in Brachiopoda. But with regard to the differences between Phoronida and Brachiopoda (larval protonephridia and podocytes in the adults are unknown in Brachiopoda), further investigations have to be done to test the hypothesis of such heterogeneously assembled metanephridia.     

Histochemical demonstration of peptidases in the human kidney

The localization of several peptidases in the human kidney was investigated histochemically. The membrane-bound peptidases, aminopeptidase A (APA), aminopeptidase M, gamma-glutamyltransferase (gamma-GT) and dipeptidylpeptidase IV, were mainly demonstrable in the brush border of the proximal tubule. In addition, APA was found in the glomeruli, while gamma-GT was found in the basal labyrinth of the proximal tubule. The lysosomal peptidases, dipeptidylpeptidase I and cathepsin B, were most strongly concentrated in the different-sized lysosomes of the proximal tubule, but they were also found in the small lysosomes of the distal tubule. Dipeptidylpeptidase II showed only a weak reaction in lysosomes of the proximal tubule. It is concluded that, in comparison with other previously studied species, the human kidney has a well-developed equipment with membrane-bound and lysosomal peptidases.     

Morphological regional differences of epithelial cells along the midgut in Diatraea saccharalis Fabricius (Lepidoptera: Crambidae) larvae

The sugarcane borer, Diatraea saccharalis Fabricius, is a pest to sugarcane and many other crops. This work aims to characterize morphological variability in the epithelial cells (columnar, goblet and regenerative) along the midgut of D. saccharalis larvae. Fragments of the midgut (anterior, middle and posterior regions) were fixed and processed by light and scanning electron microscopy. There are both cytochemical and ultrastructural differences in the morphology of the epithelial cells, depending on their localization along the midgut. The apical surface of columnar cells shows an increase in both number and size of the apical protrusions from the anterior to the posterior midgut regions. There is an increase in the amount of PAS-positive (Periodic Acid-Schiff Reaction) granules detected in the cytoplasm of both the columnar and regenerative cells, from the anterior to the posterior region. The goblet cell apical surface is narrow in the anterior region, and enlarged in the posterior midgut; the chamber's cytoplasm extrusion are small and thin at the apical cavity surface, being thicker, longer and more numerous at the basal portion of the cavity. Our results suggest that the sugarcane borer midgut has two morphologically different regions, the anterior and the posterior; the middle region is a transitional region.     

Intercellular junctions of antennal gland epithelial cells in the crayfish,Orconectes virilis

Summary Labyrinth and nephridial canal cells of the crayfish (Orconectes virilis) antennal gland possess two types of intercellular junctions revealed by freeze-fracture studies. Apical margins of the cells are connected by long septate junctions. In replicas, these junctions consist of many parallel rows of 80–140 Å intramembrane particles situated on the PF membrane face (EF and PF fracture faces of Branton et al., 1975). Rows of pits are found on the EF fracture face and are deemed complementary to the rows of particles. Moreover, lateral margins of basal regions of the epithelial cells are attached by many intercellular junctions. These contacts are characterized in thin plastic sections by a narrow dense cytoplasmic plaque located subjacent to the plasma membrane at sites of adjoined cells, and 5 to 12 fine strands of dense material that extend across the intercellular gap between adjoined cells. In freeze-fracture replicas, EF intramembrane faces basal to the region of the plasma membrane containing septate junctions exhibit numerous discoid clusters of particles. The particle aggregates, assumed to represent freeze-cleave images of adhering junctions, range from 900 to 3,700 Å in diameter, with individual particles about 185 Å in diameter. These junctions appear to connect epithelial cell processes formed by basal infoldings of the plasma-lemma, and occur between adjacent cells as well as adjacent processes of a single cell. The discrete aggregates of particles resemble replicated desmosomes (Shienvold and Kelly, 1974) and hemi-desmosomes (Shivers, 1976); therefore, they probably do not constitute a basis for electrical coupling between antennal gland epithelial cells.Supported by the National Research Council of Canada     

Structure of the nephridium in Ophryotrocha puerilis (Polychaeta,Dorvilleidae)

Summary The nephridia of Ophryotrocha puerilis are segmental organs. The nephrostome opens at the posterior margin of a setigerous segment into the coelomic cavity of this segment. The nephridial canal is made up of about 15 cells. These cells form an S-shaped tubule which extends into the following segment. The lumen of the nephridial canal ranges from 2 to 7 m in diameter. The nephropore opens laterally on the ventral surface of the body wall.In cross sections, one, two, or three cells are seen forming the canal. The inner surfaces of the canal cells are of different appearances along the canal. Since no regular pattern of cell distribution was found along the canals of different nephridia it is assumed that changes in cell structure along the canal are due to functional states or properties rather than to anatomically fixed regional differences. The canal cells either show smooth contours or they form brush borders of microvilli or sponge-like inner surfaces with a system of vacuolar canals running through the cytoplasm. Most of the canal cells are filled with various kinds of vesicles. Usually two or three cells contain larger vesicles up to 2.5 m in diameter with more or less electron-dense contents. Some of these vesicles resemble lysosomes. There are at least three bundles of cilia in each canal. In young specimens the number of cilia in one bundle is smaller (10–15) than in adult specimens (60–70). The nephridia do not show sex specific differences. The female nephridia do not function as genital ducts. As judged from the sizes of sperm and nephridia it appears to be possible that sperm are shed via male nephridia.     

The fine structure of the nephronic tubule of the mudskipper Periophthalmus koelreuteri (Pallas)

Ultrastructural examination of the head kidney of Periophthalmus koelreuteri (Pallas) (Teleostei, Gobiidae) revealed that the nephronic tubule cells are bound by tight junctions and desmosomes with little intercellular space. The first proximal segment (PI) consists of low columnar cells with well developed brush borders, indented nuclei, and numerous apical endocytic vesicles and lysosomes. A second cell type possessing clusters of apical cilia and lacking brush border and lysosomes is occasionally found between PI cells. The second proximal segment (PII) is formed of high columnar cells with brush border, regular spherical nuclei and numerous mitochondria located between well developed infoldings of the basal membrane. Single ciliary structures protrude into the lumen from PI and PII cells. The distal segment is lined by low columnar epithelium with few microvilli, regular spherical nuclei, numerous scattered mitochondria, and microbodies. The collecting tubule cells are cuboidal with few euchromatic nuclei, some mitochondria, and secondary lysosomes.     

Microscopic Anatomy and Ultrastructure of Nephridium in the Sipunculan Thysanocardia nigra Ikeda, 1904 from the Sea of Japan

The microscopic anatomy and ultrastructure of nephridium have been studied in the sipunculan Thysanocardia nigra Ikeda, 1904 (Sipuncula, Sipunculidea) from the Sea of Japan using histological and electron microscopic techniques (SEM and TEM). This paper describes ultrastructural features of nephridial epithelium, muscle grid, and coelomic epithelium on the surface of the nephridium, the area of the ciliary funnel, and the tongue. Several types of cells were distinguished in the excretory tube of the nephridium: (1) a columnar epithelium of the excretory bunches; (2) a cubical or flattened epithelium of flask-shaped infoldings; and (3) granulocytes that migrate from the coelom to the extracellular matrix of the nephridial wall. The system of podocytes and multiciliary cells were described in the nephridial coelothelium. Two types of secretion of nephridial epithelium have been discovered: a merocrine secretion of columnar cells and an apocrine secretion of cells of the flask-shaped infoldings. Using ultrastructural data, two zones of filtration through the wall of excretory tube have been found, namely (1) the tips of flask-shaped infoldings (via the extracellular matrix and microvillary canals between the epithelial cells) and (2) areas between the flask-shaped infoldings (via the contacts of podocytes, extracellular matrix, and the basal labyrinth of the columnar cells). Unlike previously studied representatives of the genus Phascolosoma, no coelomic epithelium is present on the tips of the flask-shaped infoldings in Th. nigra. This data on the anatomy and histology allow us to conclude that the funnel only works like a gonoduct.     

Regional differences in the morphology of the goat epididymis: a light microscopic and ultrastructural study

The goat epididymis, based on morphological differences, was divided into five regions; regions I and II, and the proximal part of region III constituted the head; the distal part of region III and region IV, the body; and region V, the tail. The epithelium of all regions contained principal and basal epithelial cells and intraepithelial lymphocytes and macrophages. In addition, regions II to IV also contained a few apical cells. Clear cells were absent. The epithelium varied in height from the tallest in region I (88 +/- 33 microns) to the shortest in region V (38 +/- 5 microns). Conversely, the luminal diameter, thickness of smooth muscle wall, and luminal sperm concentration were highest in region V. The irregular epithelial height of regions I and IV accounted for a stellate lumen in contrast to the oval lumen of the other regions. Whereas the lumen of region I contained only a few sperm, those of regions II, III, and IV were filled with sperm. Principal cells were the only cell type that showed striking cytological differences between regions. While they contained absorptive features (canaliculi, pinocytotic and coated vesicles, and subapical vacuoles) in all regions, the principal cells of region II were filled with large, heterogeneous vacuoles (up to 5 microns in diameter), suggesting that they may be preferentially involved in transporting and digesting particulate material. Besides absorptive features, principal cells of all regions contained morphological correlates of protein synthesis such as highly developed Golgi complexes in the supranuclear area and numerous cisternae of RER near the Golgi body and in the infranuclear cytoplasm. The cisternae of RER were more developed in region IV, and in some instances, they were distended with flocculent material resembling newly synthesized protein. Unlike the protein synthesizing organelles, principal cells of all regions lacked morphological correlates of steroid hormone synthesis. These results are compared with previously published data on the regional differences in the epididymis of other species, especially with those of the rat and the bull, in an effort to understand the significance of the epididymis in sperm maturation.     

Structure of the kidney in the crab-eating frog, Rana cancrivora

The structure of the nephron in the ranid frog, Rana cancrivora, was studied by light and electron microscopy. This frog is the only amphibian species to live in mangrove swamps of very high salinity. The nephron consists of the following parts: renal corpuscle, ciliated neck segment, proximal tubule, ciliated intermediate segment, distal tubule, connecting tubule, and collecting duct. The distal tubule is located in the ventromedial region of the kidney, and the other tubules are situated in the dorsolateral region. Renal corpuscles are found between the two regions. Some renal corpuscles have a wide Bowman's space because of the small glomerulus within them. The proximal tubules are composed of columnar cells with a dense luminal brush border of long microvilli and numerous apical vesicles and vacuoles. The initial part of the distal tubule consists of heavily interdigitated cells, characterized by a very regular palisade arrangement of mitochondria. In the terminal part of the distal tubule, shorter mitochondria of the infolding cells are situated irregularly around the nucleus. The connecting tubule consists of principal cells and canaliculus cells. The collecting duct consists of columnar or cuboidal cells; cytoplasmic organelles are relatively sparse. The canaliculus cells are intercalated between principal cells from the terminal distal tubule to the proximal part of the collecting duct. Our findings indicate that the kidney of R. cancrivora is structurally similar to kidneys of other amphibians. These findings are discussed with regard to probable correlations between ultrastructure and function in R. cancrivora.     

Histological and histochemical studies of the kidney of stickleback Gasterosteus aculeatus L. I. Morphological changes of the kidney epithelial cells during the spawning period]

1; The tubule of kidney of Gasterosteus aculeatus L. consists of four histologically different regions: Proximal tubule I and III, connection segment and collecting tubule. 2. All of tubule segments inclusively the urinary duct out of the proximal tubule I are showing synthesis of secretion. 3. There are producing two various secretion in two distinct species of cells. From the cells of proximal tubule II are secreted and extruded a granular secretion and from the cells of abducted urinary ducts (connection segment, collecting duct and urinary duct) a hyalo-mucous secretion. 4. During the breeding season the morphological variationes were divided into three stadiums, the stadium of differentiation, of producing of secretion and of reproduction. In second stadium were differenced three phases, in particular characterizing by rhythmical variationes of nucleus structure and synthesis of secretion as extrustion. 5. There are discussing the parallels to synthesis of secretion in glandular cells.     

Ultrastructure du rein labial céphalique deCampodea chardardi Condé (Diplura,Insecta)

Résumé L'ultrastructure du rein labial céphalique deCampodea chardardi Condé a été étudiée. Cette néphridie comprend trois parties: le saccule terminal, le labyrinthe et le canal excréteur.Les cellules du saccule sont des podocytes typiques, contenant de nombreuses vacuoles de pinocytose et des inclusions diverses. La lumière est envahie par des micro-organismes bacilliformes.Le labyrinthe possède des cellules à indentations basales profondes avec de nombreuses mitochondries, et des microvilli distaux.Le canal excréteur débouchant sur la face ventrale du labium est caractérisé par la présence d'une intima cuticulaire.Le rein labial des Diploures a été comparé avec des organes segmentaires néphridiens d'autres Arthropodes, et avec le néphron des Vertébrés.

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The fine structure of the labial cephalic kidney ofCampodea chardardi Condé (diplura, insecta)

Summary The ultrastructure of the cephalic labial kidney ofCampodea chardardi Condé has been studied. Each nephridium is subdivided into three segments: end-sac, coiled tubule and efferent-duct.The cells of the sacculus are typical podocytes, and contain numerous pinocytotic vesicles and various vacuoles. The lumen contains micro-organisms.The cells of the coiled tubule bear basal infoldings with numerous mitochondria and distal microvilli.The efferent duct terminates close to the ventral face of labium, and possesses characteristic cuticular intima.The labial kidney of Diplura is compared with published data on the nephridial organs of other Arthropods and Vertebrate nephron.

Nous tenons à remercier Monsieur le Professeur Noirot pour ses encouragements et conseils.