The spermatogenesis of Ephydatia fluviatilis (Porifera)

Summary Spermatogensis of the freshwater sponge Ephydatia fluviatilis begins with differential mitosis of choanocytes in the flagellated chambers. The spermatogonia thus produced aggregate in the mesenchyme by amoeboid movement. They are surrounded by dendritic cells which eventually form the walls of spermatocysts, within which spermatogenesis takes place. Notable features are the early formation of flagella in first order spermatocytes and the appearance of two flagella in the metaphase of the second maturation division.Spermatids and spermatozoa are arranged in characteristic ways. The spermatids have their heads near the spermatocyst wall, with the flagella pointing toward the center. Later the spermatozoan heads form a median band in the spermatocyst, and the flagella extend toward the periphery.Normally all stages of spermatogenesis can be found simultaneously in a given sponge, but development within a single spermatocyst proceeds in relative synchrony. Young spermatocysts can take up additional free spermatogonia; moreover, spermatocysts at about the same stage of development, up to a maximal diatmeter of 200 m, can fuse with one another.The E. fluviatilis studied here seem to be gonochorists.     

Oogenesis and larval development of Ephydatia fluviatilis (Porifera,Spongillidae)

Summary In Ephydatia fluviatilis young oocytes already appear in autumn. They pass the winter in the highly reduced sponge, but vitellogenesis and further development do not take place before following spring. The fact that the young oocytes appear before the normal period of reproduction makes E. fluviatilis different from all other local freshwater sponges, which reduce totally in autumn. E. fluviatilis seems to be a gonochorist. The oocytes originate from archaeocytes and during the first growth phase they reach a diameter of approximately 40 m. In the second growth phase the oocyte is enclosed in a single-layered follicle epithelium and grows to 170–180 m by phagocytosis of trophocytes. The fully developed egg cell finally shows a distinct layering of the incorporated yolk material. Cleavage is totally equal to unequal so that macro- and micromeres appear in some cleavage stages. Cleavage leads to a solid embryo consisting of uniform cells. At this stage of development the first scleroblasts appear. As the cells develop they are surrounded by companion cells, managing the transport of the scleroblasts. The further development to the larva is marked by the appearance of the larval cavity, typical for larvae of Spongillids, which finally occupies about half the volume of the larva at emergence. The periphery of the larva consists of a single-layered ciliated epithelium. After emergence the larva forms flagellated chambers, which are integrated into the primordia of the excurrent canal system. This system connects with the larval cavity and ensures that it becomes part of the excurrent canal system of the young sponge. Particularly in the region of the larval cavity the ciliated epithelium of the free larva is reduced. Here a new larval surface epithelium is formed by pinacocytes.     

Vergleichende rasterelektronenmikroskopische Darstellung der Gemmulaschalen von Ephydatia fluviatilis,E. muelleri und Spongilla fragilis (Porifera)

Zusammenfassung Die Gemmulaschalen der Süßwasserschwämme besitzen eine arttypische Oberflächenstruktur, die in der vorliegenden Arbeit bei drei Spongillidenarten rasterelektronenmikroskopisch dargestellt ist. Anhand angeschnittener, aus dem Einbettungsmittel herausgelöster Gemmulaschalen wird die Schaleninnenstruktur rasterelektronenmikroskopisch untersucht. Das mit dieser Methode (Weissenfels 1982a) gewonnene Bildmaterial liefert Informationen zur Architektur der Gemmulaschalen und zur Entstehung der sog. Kästchenschicht in den Gemmulaschalen von Spongilla fragilis.

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Comparative scanning-electron-microscope study of the gemmule shells of Ephydatia fluviatilis, Ephydatia muelleri and Spongilla fragilis (Porifera)

Summary The gemmule shells of fresh-water sponges have a species-specific surface structure, described here for three spongillid species by reference to scanning electron micrographs. The internal structure of the shell is revealed in scanning electron micrographs of sectioned shells released from the embedding medium. Pictures obtained by this method (Weissenfels 1982a) provide information about the architecture of the gemmule shells and the development of the so-called compartmented layer in the gemmule shells of Spongilla fragilis.

     

Die Entstehung der Gemmula-Schalen bei Spongilla fragilis Leidy (Porifera)

Zusammenfassung Die Dauerstadien des Süßwasserschwamms Spongilla fragilis bestehen aus mehreren, mit einer kompakten Innenschicht versehenen Einzelgemmulae, die durch zwei weitere Schalenschichten (Kästchen- und Außenschicht) miteinander verkittet sind.Die Einzelgemmulae werden in geringem zeitlichen Abstand dicht nebeneinander angelegt. Sie besitzen zunächst ein eigenes Spongioblasten-Epithel, das die Innenschicht der Schale sezerniert. Während die Kästchenschicht aufgelagert wird, nehmen die Spongioblasten benachbarter Gemmula-Anlagen Kontakt auf und bilden dann ein einheitliches Epithel an der Oberfläche der Gemmula-Gruppe. Jeder Spongioblast sezierniert eine Kästchenreihe; deren radiäre Wände entstehen jeweils zwischen zwei benachbarten Spongioblasten.Die Mikropylenmembran liegt am Grunde eines Porusrohres, dessen Wand eine Fortsetzung der Gemmula-Schale darstellt. Das Porusrohr ist an seinem distalen Ende durch eine weitere, dünne Membran verschlossen. Die proximal gelegene Mikropylenmembran wird von modifizierten Spongioblasten (Mikropylen-Spongioblasten) gebildet und stimmt in ihrem Bau mit der Mikropylenmembran von Ephydatia fluviatilis weitgehend überein.

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Development of the gemmule shells in Spongilla fragilis leidy (Porifera)

Summary The overwintering stages of the fresh-water sponge Spongilla fragilis consist of several single gemmules, each covered by a compact inner shell layer; the group is cemented together by two additional layers (the compartmented layer and the outer layer). The individual gemmules are formed in close proximity, within a short period of time. Initially each is enclosed in its own spongioblast epithelium, which secretes the inner layer of the shell. As the compartmented layer is being built up over this, the spongioblasts of adjacent gemmule primordia come into contact, eventually forming a continuous epithelium over the surface of the gemmule group. Each spongioblast secretes a row of compartments, the radial walls of which are produced between adjacent spongioblasts. The micropyle membrane is situated at the base of a pore tube, the wall of which is continuous with the gemmule shell. The pore tube is closed at its distal end by another, thin membrane. The more proximal micropyle mebrane is formed by modified spongioblasts (micropyle spongioblasts); its structure closely resembles that of the micropyle membrane of Ephydatia fluviatilis.

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Abkürzungen AC Archäocyte - äS äußere Schicht der Porusrohr-Membran - AS Außenschicht der Gemmula-Schale - bSP basale Sponginplatte - D Dotterkorn - EPC Exopinacocyten-Epithel - fAC flache Archäocyte - G Gemmula - GA Gemmula-Anlage - hS homogene Schicht - iS innere Schicht der Porusrohr-Membran - IS Innenschicht der Gemmula-Schale - K Zellkern - KF Kollagenfibrille - KS Kästchenschicht - MM Mikropylenmembran - MP Mikropyle - MSB Mikropylen-Spongioblast - N Nukleolus - Nd Nadel - oL osmiophile Lamelle - oS osmiophile Schicht - PD Pinacoderm - PR Porusrohr - PRM Porusrohr-Membran - PRW Porusrohr-Wand - rER rauhwandiges endoplasmatisches Reticulum - RKS Randzone der Kästchenschicht - SB Spongioblasten-Epithel - SR Subdermalraum - ÜS Übergangsschicht - VV Verdauungsvakuole Die Arbeit wurde durch Mittel der Deutschen Forschungsgemeinschaft gefördert. Herrn Professor Dr. N. Weissenfels danke ich für zahlreiche Hinweise und Ratschläge bei der Erstellung der Arbeit. Für technische Assistenz danke ich Frau M. Geis, Frau I. Nüssle, Frau U. Müller und Frau B. Zarbock     

Bau und Funktion des Süßwasserschwamms Ephydatia fluviatilis (Porifera)

Zusammenfassung Der Süßwasserschwamm Ephydatia fluviatilis führt rhythmische Kontraktionen durch. Die Kontraktionsfrequenz beträgt bei 15° bis 16° C vier bis sechs Stunden, der eigentliche Kontraktionsvorgang ein bis zwei Stunden. Die Erhöhung der Wassertemperatur von 15° auf 19° C bewirkt irreguläre, zusätzliche Schwammkontraktionen, die nach Senkung der Temperatur auf die ursprüngliche Höhe (15° C) wieder entfallen. Dieser Aussage liegt die objektschonende Infrarot-Reflexionsmessung zugrunde.

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Structure and function of the fresh water sponge Ephydatia fluviatilis (Porifera)

Summary The fresh water sponge Ephydatia fluviatilis contracts rhythmically. At 15° or 16° C the frequency of contraction varies between 4–6 h; the contraction itself takes about 1 or 2 h. Increasing water temperature from 15° to 19° C causes irregular additional contractions, which cease if the temperature is reduced to the initial level (15° C). The results are based upon a non-invasive technique using infrared reflexion.

     

Untersuchungen zur Ultrastruktur der Choanocyte von Ephydatia fluviatilis L.

Zusammenfassung Aufgrund elektronenmikroskopischer Befunde wird die Morphologie der Choanocyten des Süßwasserschwammes Ephydatia fluviatilis beschrieben. Die Choanocyte besteht aus Zelleib, Geißel und Kragen. Der Zelleib ist gekennzeichnet durch einzelne Zisternen des endoplasmatischen Reticulums, die der basalen und zum Teil der lateralen Zellmembran parallel anliegen. Die kontraktilen Vakuolen der Choanocyten entleeren ihren Inhalt in das Lumen der Geißelkammer. In einigen Choanocyten kann senkrecht zum Basalkörper ein Procentriol nachgewiesen werden. Die Geißel zeichnet sich durch Plasmaleisten und Fahnen aus. Die den Kragen aufbauenden etwa 35 Fibrillen werden als Mikrovilli gedeutet. Vereinzelt tritt an der Basis des Kragens ein Faltenmuster auf.

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Ultrastructure of choanocytes in Ephydatia fluviatilis L.

Summary The morphology of the choanocytes of the freshwater sponge, Ephydatia fluviatilis, is described on the basis of electron microscope studies. The cell body of the choanocytes bears a cilium and a collar. In the cell body characteristic single cisternae of the endoplasmic reticulum are found in juxtaposition with the basal and lateral plasmalemmata. The contractile vacuoles extrude their contents into the lumen surrounded by the collar chamber. In some choanocytes a procentriole is found in addition to the typical basal body. The cilium of the choanocytes is characterized by cytoplasmic crests and thread-like extensions. The collar is formed by approximately 35 microvilli which show a peculiar arrangement. Occasionally, the basis of the collar displays cytoplasmic folds.

Die Arbeit wurde teilweise mit Unterstützung durch die Deutsche Forschungsgemeinschaft durchgeführt.     

The metamorphosis of the parenchymula-larva of Ephydatia fluviatilis (Porifera,Spongillidae)

Summary The sexual development of Ephydatia fluviatilis involves a ciliated parenchymula-larva. The mature larva leaves the body of the mother sponge through the excurrent canal system and arrives eventually in the outside world by way of the osculum. At this stage the types of cells found in the adult sponge are already present in the larva. The released larva swims around for a while and then, after a period of between 3 and 48 hours, it attaches, usually with the anterior, larval cavity-bearing pole, onto the substratum. While it is attaching and spreading itself out, the larva undergoes a metamorphosis. The most notable stages of this metamorphosis are as follows: (a) disintegration of the ciliated epithelium from the anterior pole of the larva and its substitution by a pinacocyte epithelium, (b) splitting of the larval cavity and (c) integration of the remains into the developing canal system together with the creation and further development of the organic features of a functioning sponge.     

Ultrastructural investigation of spermatogenesis in Spongilla lacustris and Ephydatia fluviatilis (Porifera,Spongillidae)

Summary Spermatogenesis of the spongillids investigated here is similar in Spongilla lacustris and Ephydatia fluviatilis and proceeds, on the whole, as in other Eumetazoa. Sponges however lack true sex organs, the germ cells developing from somatic cells. The male germ cells originate in spongillids from choanocytes and the female ones from archaeocytes. In Spongilla lacustris single choanocytes leave the flagellated chambers and transform into spermatogonia; in Ephydatia fluviatilis they result from differential cell division. The spermatogonia gather in distinct mesenchyme regions and are surrounded by cyst-building cells. Thus spermatocysts are built in which spermatogenesis proceeds. The spermatogonia in the spermatocysts differentiate into flagellated spermatocytes of I. order. In this process, the early appearance of the flagellum and its mode of formation are uncommon. The following meiotic divisions generate spermatocytes of II. order in the first step and spermatids in the second. In both developmental stages the cells remain connected by cytoplasmic bridges. In the subsequent spermiocytogenesis the cytoplasm of the spermatids is reduced. The reduced parts of the cytoplasm appear as cell fragments in the lumen of the spermatocysts and are eventually ingested by the cystwall cells. The mature spermatozoa arrange in the spermatocysts in a characteristic pattern. Later the spermatocysts open into the excurrent canal system and the spermatozoa leave the sponge with the egestive water stream.     

Effects of calcium and salinity on the growth rate of Ephydatia fluviatilis (Porifera: Spongillidae)

The freshwater sponge, Ephydatia fluviatilis (Porifera: Spongillidae), was maintained in a continuous-flow laboratory culture system under several conditions of calcium ion (Ca⁺⁺) concentration and salinity. Experimental results suggest that sponge growth rate increases with increasing Ca⁺⁺ concentration, that sponge growth rate decreases with increasing salinity, and that the negative effect of higher salinity can be overcome by increasing Ca⁺⁺ concentration. The experimental results correlate well with field observations on the effects of salinity and Ca⁺⁺ on the distribution of E. fluviatilis.     

Structure and function of the fresh water spongeEphydatia fluviatilis L. (Porifera)

Zusammenfassung Ephydatia fluviatilis nimmt partikuläre und gelöste Nahrung auf. Diese gelangt durch die einführenden Kanäle in den offenen mesenchymatischen Raum. Nahrungspartikel, insbesondere Bakterien, werden von den Choanocyten der Kragengeißelkammern reusenartig zurückgehalten und an Ort und Stelle von Choanocyten und zugewanderten Amöbocyten phagocytiert. Die lysosomale Verdauungskapazität der Amöbocyten übersteigt die der anderen phagocytierenden Zellen. Chaonocyten und Amöbocyten können ihre Phagosomen an Nahrung suchende Zellen abgeben.Im Mesenchym des Schwammes anfallende Exkremente werden von Endopinacocyten der ausführenden Kanäle transcytotisch nach außen befördert. Gelöste Proteine werden an der inneren Kragenbasis pinocytiert und in Nahrungsvakuolen gesammelt. Letztere werden an der Choanocytenbasis exocytiert, von Amöbocyten erneut endocytiert und lysosomal verdaut. Lamellär strukturierende Nahrungsreste nehmen den üblichen Defäkationsweg.

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Structure and function of the fresh water spongeEphydatia fluviatilis L. (Porifera)III. Capture of food, digestion and defecation

Summary Ephydatia fluviatilis ingests paniculate and dissolved food substances through the incurrent canal system into the open mesenchymal space. Particulate food, especially bacteria, is caught by the choanocytes of the flagellated chamber which form a filter-like structure, and phagocytosed by choanocytes and amoebocytes. The capacity of lysosomal digestion in the amoebocytes exceeds that of other phagocytotic cells. Both choanocytes and amoebocytes are able to transfer their phagosomes to other food-searching cells.Excrements released into the mesenchymal space are transported through the endopinacocytes into the excurrent canal system.Dissolved proteins are pinocytosed by the choanocytes at the inner face of the collar base and accumulated in food vacuoles. These are exocytosed at the basal side of the choanocytes and in turn endocytosed and digested by amoebocytes. Residual bodies with contents of lamellate structure are defecated in the same way via the endopinacocytes of the excurrent canals.

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Abkürzungen A Atrium (Abb. 1) - A Amöbocyt - AK ausführender Kanal - B Bakterium - Ch Choanocyt - D Diktyosom - E Exo-Endocytose - EK einführender Kanal - ER endoplasmatisches Retikulum - exV exocytierte Vakuole - FP Filopodium - G Geißel - GK Kragengeißelkammer - K Kern - Kr Kragen - M Mesenchym - Mi Mitochondrium - MV Mikrovilli des Kragens - N Nadel - NV Nahrungsvakuole - OR Oskularrohr - P Pore im Pinacoderm - PC Pinacocyt - Pd Pinacoderm - Pn Pinocytosevesikel - PV pulsierende Vakuole - R Reaktionsprodukt der sauren Phosphatase - SR Subdermalraum - TV Transcytosevakuole Herrn Prof. Dr. R. Danneel zur Vollendung seines 75. Lebensjahres in Dankbarkeit gewidmet. — Die Arbeit wurde durch Mittel der Deutschen Forschungsgemeinschaft gefördert. — Für technische Assistenz danke ich Frau M. Geis und Frau B. Zarbock     

The effects of cadmium and mercury on gemmule formation and gemmosclere morphology in Ephydatia fluviatilis (Porifera : Spongillidae)

A laboratory study of the effects of cadmium and mercury on the freshwater sponge, Ephydatia fluviatilis, was conducted. Sponge cuttings were exposed to concentrations of cadmium or mercury which ranged from 1.000 to 0.001 ppm for one month. The responses exhibited by the specimens resulted in four groups characterized as follows: sponge colony survived and produced gemmules with normal gemmoscleres; sponge colony survived and produced gemmules with malformed gemmoscleres; sponge colony survived but did not gemmulate; sponge colony died. A direct discriminant functions analysis of the four sponge groups, metal concentrations and other chemical data established a highly significant correlation between increasing metal concentrations and amount of damage to the sponge.     

Ecomorphic variation in gemmoscleres of Ephydatia fluviatilis Linnaeus (Porifera: Spongillidae) with comments upon its systematics and ecology

An ecological and taxonomic investigation of Ephydatia fluviatilis was conducted. E. fluviatilis was found in alkaline fresh waters and slightly brackish waters. Extreme variation was found in the gemmoscleres of E. fluviatilis from different Louisiana habitats. The variation appeared to be ecomorphic and related to the chemical characteristics of the habitats. Laboratory investigations, based on the formation of gemmules by sponges maintained under different conditions were used to determine the nature and extent of this variation. The experimental studies demonstrated that gemmoscleres of different forms can develop in sponges from the same locality if exposed to different environmental conditions and that Ephydatia robusta (Potts, 1887) as revised by Penney & Racek (1968), is synonymous with Ephydatia fluviatilis. Results of these studies demonstrate the difficulty of using such characteristics for the recognition of species, subspecies and other evolutionary units.     

Zur Entstehung der Vogelarten

Ohne Zusammenfassung     

Zur Entstehung der Mimikry der Kuckuckseier

Ohne Zusammenfassung     

Die Entstehung der polyploiden Zellkerne des Antherentapetums bei Antirrhinum majus L.

Zusammenfassung Das Antherentapetum beiAntirrhinum majus L. ist ein Sekretionstapetum. Die Zellen des Tapeturns können bis zu vier Kernen enthalten. Die Differenzierung des Tapetums ist an karyologisclie Vorgänge gebunden, die ein Mehrkernigwerden der Zellen und eine Polyploidisierung der Kerne bewirken. Die karyologischen Veränderungen erfolgen durch gehemmte Zellteilungen, gehemmte Kernteilungen und innere Chromosomenteilung, die vorübergehend zur Polymerie der Chromosomen führt, sowie in geringem Grade auch durch Kernfusionen, wobei alle Prozesse weitgehende Variationen erfahren können.Auszug aus einer Dissertation der Mathematisch-Naturwissenschaftlichen Fakultät der Martin-Luther-Universität Halle. Als Vortrag am 19. 9. 51 gehalten in Berlin anläßlich der Jahresversammlung der Deutschen Botanischen Gesellschaft.