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  • 1
    Electronic Resource
    Electronic Resource
    Larvale Nierenorgane bei Lepidochiton cinereus (Polyplacophora) und Aeolidia papillosa (Gastropoda) (1989)
    Springer
    Zoomorphology 108 (1989), S. 297-307 
    Details
    ISSN: 1432-234X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung Larvale Protonephridien werden bei L. cinereus und A. papillosa auf ultrastruktureller Ebene beschrieben. Die Organe bestehen jeweils aus einer Terminalzelle, zwei (A. papillosa) oder mehreren (L. cinereus) Kanalzellen und einer Nephroporuszelle. Die Terminalzelle ist multiciliär, besitzt Mikrovilli und ein geschlitztes cytoplasmatisches Element, das bei L. cinereus lappenförmig, bei A. papillosa als Hohlzylinder ausgebildet ist. Dieses cytoplasmatische Element fungiert als Trägerstruktur der Filtrationsbarriere (ECM bzw. Diaphragmata) und ist durch Desmosomen mit der folgenden Kanalzelle verbunden. Aufgrund homologer Übereinstimmungen der hier beschriebenen Protonephridien mit entsprechenden Organen anderer Bilateria sind larvale Protonephridien im Grundmuster der Mollusken anzunehmen.
    Notes: Summary Protonephridia are described at the electron microscopical level in the larvae of L. cinereus and A. papillosa. These nephridial organs are composed of one terminal cell, two (A. papillosa) or several (L. cinereus) duct cells, and one nephridiopore cell. In each case, the perikaryon of the terminal cell bears cilia, microvilli and a slashed cytoplasmic element (like a lobe in L. cinereus; like a hollow cylinder in A. papillosa), which functions as the supporting structure of the filtration barrier (ECM or diaphragm) and is desmosomally connected to the adjacent duct cell. Developmental aspects of the organs are described for L. cinereus. The description of protonephridia in larvae of a polyplacophoran permits a reevaluation of the nephridial design in larvae of molluscs: because of homologous correspondences to the protonephridia of other members of the Bilateria, larval protonephridia are postulated for the ground pattern of molluscs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00312162
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  • 2
    Electronic Resource
    Electronic Resource
    Ultrastructure and development of the nephridia in Anaitides mucosa (Annelida, Polychaeta) (1989)
    Springer
    Zoomorphology 109 (1989), S. 15-32 
    Details
    ISSN: 1432-234X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Different developmental stages (trochophores, nectochaetae, non-mature and mature adults) of Anaitides mucosa were investigated ultrastructurally. A. mucosa has protonephridia throughout its life; during maturity a ciliated funnel is attached to these organs. The protonephridial duct cells are multiciliated, while the terminal cells are monociliated. The single cilium is surrounded by 14 microvilli which extend into the duct lumen without coming into any contact with the duct cells. Corresponding ultrastructure and development indicate that larval and adult protonephridia are identical in A. mucosa. Differences between various developmental stages can be observed only in the number of cells per protonephridium. A comparison between the funnel cells, the cells of the coelothel and the duct cells reveals that the ciliated funnel is a derivative of the duct. Due to the identical nature of the larval and postlarval protonephridia, such a funnel cannot be a secondary structure. In comparison with the mesodermally derived metanephridial funnel in phoronids it seems likely that the metanephridia of annelids and phoronids evolved convergently.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00312180
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  • 3
    Electronic Resource
    Electronic Resource
    Ultrastructure and relationship between protonephridia and metanephridia in Phoronis muelleri (Phoronida) (1989)
    Springer
    Zoomorphology 109 (1989), S. 113-122 
    Details
    ISSN: 1432-234X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The actinotrocha of Phoronis muelleri has one pair of ectodermally derived, monociliated protonephridia. The duct runs mainly between the epidermis and the lining of the hyposphere coelom, pierces the septum and extends into the blastocoel. The proximal part is branched and closed up by terminal complexes consisting of two morphologically different cells which both serve filtration. During metamorphosis, the terminal complexes and the branches of the duct are cast off. The cells degenerate, pass into the remaining duct and are endocytosed by the duct cells. After metamorphosis the remaining part of the protonephridial duct is U-shaped, blindly closed and borders on the prospective lophophoral vessel. In a later stage the duct receives a ciliated funnel, which consists of monociliated epithelio-muscle cells and is a derivative of the lining of the metacoel. Thus, a part of the protonephridial duct of the larva and the whole metanephridial duct of the adult are identical. Aspects of a possible homology between phoronid nephridia and such organs in other bilaterians are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00312317
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  • 4
    Electronic Resource
    Electronic Resource
    Structure and formation of the uncini in Pectinaria koreni, Pectinaria auricoma (Terebellida) and Spirorbis spirorbis (Sabellida): inplications for annelid phylogeny and the position of the Pogonophora (1995)
    Springer
    Zoomorphology 115 (1995), S. 161-177 
    Details
    ISSN: 1432-234X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Setation is an important taxonomic character of the Annelida. Within this taxon, Terebellida and Sabellida both have transverse rows of short, apically toothed setae which are situated inside the neuropodial rim. The apical spines are curved and their tips point anteriorly. These setae are termed uncini. In the terebellidans Pectinaria koreni, Pectinaria auricoma and in the sabellidan Spirorbis spirorbis, these setae arise from a follicle which consists of a chaetoblast and two follicle cells. The special structure of the uncini is a result of temporal modifications of the actin-filament system of the chaetoblast and changing spatial interactions between the chaetoblast and the follicle cells during the formation of these setae. Once the uncinus is formed, the microvilli are withdrawn and electron-dense material is deposited in the remaining canals. The microvilli are replaced by short processes of the chaetoblast, and the actin-filament system is replaced by a system of intermediate filaments which help to mechanically attach the uncinus to the follicle. Such uncini are also described in both pogonophoran groups, the Perviata and the Obturata (Vestimentifera). In several structural details they correspond to those of the species investigated in this paper, so that the hypothesis of a homology of the uncini seems to be justified. This hypothesis leads to the conclusion that uncini evolved in the common stem lineage of Pogonophora, Terebellida and Sabellida, implying a monophyletic origin of these three taxa. The uncini are compared to the hooked setae of the Arenicolida, Maldanida and Psammodrilida, which are also aligned in transverse rows inside the neurophodial rim. Hooked setae and uncini are hypothesized to be homologous. It, therefore, can be concluded that Arenicolida, Maldanida and Psammodrilida are closely related to the monophylum consisting of Terebellida, Sabellida and Pogonophora, and that these six taxa share a common ancestor, which evolved transverse rows of setae with apically curved spines and a formative site lateral to the edge of the neuropodial rim. According to the phylogenetic relationships proposed here, the Pogonophora are a subordinate taxon within the Annelida.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00403171
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  • 5
    Electronic Resource
    Electronic Resource
    Structure, function and development of segmental organs in Annelida (1999)
    Springer
    Hydrobiologia 402 (1999), S. 21-37 
    Details
    ISSN: 1573-5117
    Keywords: evolution ; Annelida ; nephridia ; ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In Annelida, nearly each segment contains a pair of ducts that either are protonephridia or metanephridia. These segmental organs function as excretory organs and, after having been modified, they may also act as gonoducts during maturity. In certain polychaetous annelids and especially in clitellates this function has been adopted by additional gonoducts which generally are formed at the begining of maturity. At the end of the last century the gonocoel theory tried to explain the relation between gonads, coelomic cavities and nephridia. Using the gonocoel theory axiomatically, Goodrich (1945) assumed that in annelids a pair of protonephridia and a pair of gonoducts represent the primary condition. Evolution of metanephridia on the one hand and the fusion of gonoducts and nephridia on the other hand occurred within the Annelida. Based on recent ultrastructural investigations into the development of different segmental organs, this paper re-evaluates Goodrich′s hypothesis. According to these data the segmental organs differentiate from a single anlage. Each consists of three or four cells which line a small lumen filled with microvilli. The duct becomes ciliated and the most proximal cells are separated when the coelom extends by fluid accumulation between the lining cells. During enlargement of the coelomic cavity the proximal part of the anlage is passively opened, so that the cilia face the coelom, to form the funnel. If separation of the proximal duct cells is suppressed, the anlage differentiates into a protonephridium, which secondarily may acquire a funnel during maturity by proliferation of proximal duct cells. Thus, different pathways in nephridial development lead to completely different segmental organs in the fertile adult. Additional gonoducts evolve in different lineages within the annelids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003780223216
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  • 6
    Electronic Resource
    Electronic Resource
    No direct contact between the excretory system and the circulatory system in Prostomatella arenicola Friedrich (Hoplonemertini) (1988)
    Springer
    Hydrobiologia 156 (1988), S. 175-181 
    Details
    ISSN: 1573-5117
    Keywords: Nemertini ; ultrastructure ; protonephridia ; circulatory system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Excretory and circulatory systems in Prostomatella arenicola are examined at the ultrastructural level. Interdigitating cells, which rest on a thin fibrillar basal lamina, line the lumina of the lateral vessels. A layer of muscle cells and an underlying sheath of fibrillar extracellular material surround each vessel. The excretory system consists of one pair of laterally situated branched protonephridia. Each protonephridium is composed of several terminal cells, an efferent duct and a nephridiopore. The terminal parts of the protonephridia are not restricted to the vicinity of the circulatory system; they can also be found dorsally or laterally to the nerve cords between muscle cells. The presumed filtration area arises as a hollow cylinder from the terminal cell. This cylinder is perforated by numerous clefts which are never bridged by a filter diaphragm. Instead, each terminal cell cylinder is surrounded by an extracellular matrix. The terminal cells neither extend into the lumen of the lateral vessel nor contact the vessel lining cells. Phylogenetic implications of the results are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00027991
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  • 7
    Electronic Resource
    Electronic Resource
    Protonephridien: neue Erkenntnisse über Funktion und Evolution (1995)
    Weinheim : Wiley-Blackwell
    Biologie in unserer Zeit 25 (1995), S. 107-114 
    Details
    ISSN: 0045-205X
    Keywords: Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Bei wirbellosen Tieren treten verschiedene Exkretions- und Osmoregulationsorgane auf. Von diesen besitzen die Nephridialorgane eine besondere strukturelle Vielfalt; sie bestehen aus einer Filtrationsstruktur und einem ableitenden Kanalsystem. Das Filtrationselement erzeugt ein Ultrafiltrat, den Primärharn, der im Kanal modifiziert wird (Abbildung 1a, b.) In diesen Eigenschaften zeigen sie ein Funktionsprinzip, das auch vom Säugernephron bekannt ist. Bei den Nephridialorganen werden traditionell Protonephridien und metanephridiale Systeme unterschieden.Protonephridien sind zur Leibeshöhle hin blind geschlossen (Abbildung 1c.) Sie bilden eine räumliche Einheit von Filtration (durch eine extrazelluläre Matrix im Bereich der proximalen Zellen, der Terminalzellen) und Resorption (durch die nachgeschalteten Kanalzellen). Bei metanephridialen Systemen sind Filtrationsstruktur und Kanalsystem räumlich voneinander getrennt [1,2]. Die Filtration erfolgt durch eine das Blutgefäßsystem auskleidende, extrazelluläre Matrix in das Coelom, die Resorption im Verlauf eines Kanals, der mit einem Wimpertrichter in das Coelom öffnet (Abbildung 1d). Bei dem ableitenden und rückresorbierenden Kanal sprechen wir von einem Metanephridium; das gesamte Exkretionssystem bezeichnet man als metanephridiales System. Das Coelom stellt damit funktionell einen „Speicher“ für den Primärharn dar.Protonephridien sind erst in der Stammlinie der Bilateria entwickelt worden. Während einige Gruppen in allen Entwicklungsstadien Protonephridien als einzige Exkretionsorgane besitzen (Plathelminthes, Aschelminthes, Nemertini), treten sie in anderen Gruppen ausschließlich in den Larven auf (Mollusca, viele Annelida, Echiura, Tentaculata). In einigen Teilgruppen der Anneliden findet man Protonephridien allerdings auch in den postlarvalen Stadien (2,3).Die vorliegende Arbeit stellt aktuelle Überlegungen und Interpretationen zur Entwicklung und Funktion der Protonephridien vor.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/biuz.19950250211
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  • 8
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    No direct contact between the excretory system and the circulatory system in Prostomatella arenicola Friedrich (Hoplonemertini) (1988)
    Springer
    Details
    Publication Date: 1988-01-01
    Print ISSN: 0018-8158
    Electronic ISSN: 1573-5117
    Topics: Biology
    Published by Springer
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  • 9
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    Polychaete phylogeny based on morphological data – a comparison of current attempts (2005)
    Springer
    Details
    Publication Date: 2005-03-01
    Print ISSN: 0018-8158
    Electronic ISSN: 1573-5117
    Topics: Biology
    Published by Springer
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  • 10
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    Structure and development of nephridia in Annelida and related taxa (2005)
    Springer
    Details
    Publication Date: 2005-03-01
    Print ISSN: 0018-8158
    Electronic ISSN: 1573-5117
    Topics: Biology
    Published by Springer
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