Beate Ehlers

Monociliary receptors in interstitial Proseriata and Neorhabdocoela (Turbellaria Neoophora)

SummaryThe ultrastructure of monociliary receptors in 10 species of the Proseriata and Neorhabdocoela is described, with particular reference to the epidermal dendritic part.Sensory cells with a single kinocilium situated at the level of the distal epidermis membrane are considered as mechano- or chemoreceptors.There exist sensory cells with a dendrite penetrating one epidermis cell and bearing an embedded kinocilium and a collar of 8 stereocilia or ridges with a fribrillose substructure. These collared receptors probably function as mechanoreceptors.In comparison with collared sensory cells in species of other turbellarian orders, the embedded receptors in the Proseriata and Neorhabdocoela are more advanced and possess synapomorphous characteristics. With the embedded receptors a new evidence is given for the close phylogenetic relationship between the Proseriata and Neorhabdocoela.The distribution of collared cells in the animal system and their phylogenetic implication for a choanoflagellate origin of the Metazoa are briefly discussed.

Fine-structural characteristics of female and male germ cells in Proseriata Otoplanidae (Platyhelminthes)

Fine-structural features of female germ cells differentiating within the germaria of Otoplanella baltica and Notocaryoplanella glandulosa are documented and compared with those of other free-living platyhelminths having ectolecithal eggs.In these species, encompassed in the taxon Proseriata Lithophora, insemination of the germocytes occurs within the germaria. A sperm cell, that has penetrated a germocyte differs in special features from mature male germ cells found in the testes, in parts of the male genital system, or even in other regions of the organism. The hypothesis that dense bodies correspond to acrosomal material is supported.

Paddle cilia and discocilia — Genuine structures?

SummaryKinocilia of epidermal sensory cells in fixed marine Turbellaria often terminate as flattened biconcave discs. The distal part of the ciliary axoneme curves back upon itself forming a 360° loop which is enveloped by the plasmalemma. In living animals this structure can be induced by the addition of sodium cacodylate, monobasic sodium phosphate, dibasic sodium phosphate, sucrose, calcium chloride, or formaldehyde to the sea water. Specimens treated with sodium chloride, glutaraldehyde, or osmium tetroxide do not show modified cilia. In animals prepared for EM at low temperature and with a buffered hypotonic fixative less kinocilia are modified than in animals treated with a buffered iso- or hypertonic fixative and at a higher temperature. It is assumed that the unusually shaped cilia, described as “paddle cilia” or “discocilia” in other invertebrates, do not represent a genuine but an artificial structure.

Die Feinstruktur eines ciliären Lamellarkörpers beiParotoplanina geminoducta Ax (Turbellaria, Proseriata)

SummaryThe fine structure of a lamellate body in the head region ofParotoplanina geminoducta Ax, 1956 is described. It is constructed by some modified cilia, which protrude into an intracellular cavity. The plasmalemma of these cilia are prolonged and rolled up, thus forming a whorl. The lamellate body is supposed to have a photoreceptive function.ZusammenfassungAus der Kopfregion vonParotoplanina geminoducta Ax, 1956 wird die Feinstruktur eines Lamellarkörpers beschrieben. Er besteht aus mehreren modifizierten Cilien, die in ein intracelluläres Lumen hineinragen und deren verlängertes Plasmalemm spiralig aufgerollt ist. Dem Lamellarkörper wird eine vermutlich photoreceptorische Funktion zugeschrieben.

Struktur und Differenzierung penialer Hartgebilde vonCarenscoilia bidentata Sopott (Turbellaria, Proseriata)

SummaryThe stylet apparatus ofCarenscoilia bidentata Sopott consists of five hard elements. These are differentiated in a matrix syncytium. During the ontogeny at first microfibrils with a periodic cross-banding arise; then the microfibrils become enveloped by homogenous electron opaque materials. The wall of the developed intracellular hard elements consists of a central layer with microfibrils and outer layers of electron opaque materials. Hard differentiations with a comparable fine structure are only known from other proseriate turbellarians, but not from other platyhelminthes.ZusammenfassungDie Stilettapparatur vonCarenscoilia bidentata Sopott besteht aus mehreren verfestigten Elementen. Diese werden in einem mehrkernigen Matrixsyncytium ausdifferenziert; während der Ontogenese entstehen zuerst periodisch quergestreifte Mikrofibrillen, an die sich elektronendichtes homogenes Material anlagert. Die Wandung der fertig ausgebildeten intracellulären Hartstrukturen besteht aus einer zentralen Lage von Mikrofibrillen, der außen elektronendichte Schichten aufliegen. Hartgebilde mit einer vergleichbaren Feinstruktur sind bisher nur von weiteren proseriaten Turbellarien, nicht jedoch von anderen Plathelminthen bekannt.

Ultrastruktur pericerebraler Cilienaggregate beiDicoelandropora atriopapillata Ax undNotocaryoplanella glandulosa Ax (Turbellaria, Proseriata)

SummaryThe ultrastructure of pericerebrally located ciliary aggregations inDicoelandropora atriopapillata Ax, 1956, andNotocaryoplanella glandulosa (Ax, 1951) is described. The intracellular aggregations consist of some 100 cilia, which are arranged in an alternating position without gaps. The distal parts of the cilia are interweaved. The aggregations are interpreted as photoreceptors.ZusammenfassungDie Ultrastruktur pericerebral gelegener Cilienaggregate vonDicoelandropora atriopapillata Ax, 1956, undNotocaryoplanella glandulosa (Ax, 1951) wird beschrieben. Die intracellulÄren Aggregate setzen sich jeweils aus mehreren 100 Cilien zusammen, die lückenlos alternierend angeordnet und distal miteinander verflochten sind. Für die Cilienaggregate wird eine photoreceptorische Funktion wahrscheinlich gemacht.

Zur Morphologie sublitoraler Otoplanidae (Turbellaria, Proseriata) von Helgoland und Neapel

SummaryThe unknown morphology of the speciesOrthoplana filum (Meixner) andO. foliacea (Meixner) is treated. The investigations are based on two different populations from the North Sea and the Mediterranean, respectively.O. filum belongs to the genusMonostichoplana Ax. ForO. foliacea the new genusPseudorthoplana is established.Further species from the Gulf of Naples reveal new morphological characteristics with regard to the construction of the genital organs and the photoreceptors. These species belong to the new generaXenotoplana nov. gen. (2 taxa) andNapoliplana nov. gen. (1 taxon).ZusammenfassungDie unbekannte Morphologie der ArtenOrthoplana filum (Meixner) undO. foliacea (Meixner) wird an Populationen der Nordsee und des Mittelmeeres bearbeitet.O. filum gehört in die GattungMonostichoplana Ax. FürO. foliacea wird die neue GattungPseudorthoplana errichtet. Weitere Arten aus dem Golf von Neapel liefern neue morphologische Merkmale im Aufbau des Genitalapparates und der Lichtsinnesorgane. Für diese Otoplaniden werden die GattungenXenotoplana nov. gen. (2 Arten) undNapoliplana nov. gen. (1 Art) aufgestellt.