Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Polychaeta”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMed1978

Anatomical and ultrastructural study of the pharyngeal bulb in Protodrilus (Polychaeta, Archiannelida). I. Muscles and myo-epithelial junctions.

The pharyngeal bulb of Protodrilus is both a muscular and an epithelial organ whose function is the drawing up of food particles. The muscular system of the bulb is formed of tightly connected antagonistic muscles: the bulbus muscle and the sagittal and "grating plate" muscles. All of them are composed of obliquely striated fibers whose ultrastructural characteristics are similar to those of Hirudina and even more to those of epitokous forms of Nereidae and Syllinadae. Myo-epithelial cells do not exist in the pharyngeal bulb of Protodrilus contrary to what was previously thought; the muscles and the stomodeal epithelium are united by junction areas on both sides of the basal lamina. These myo-epithelial junctions may be compared of the myoepidermic junctions known in several Arthropods. A comparison of the ultrastructural features of the bulbus muscle fibers of Protodrillus (Protodrilidae) and Trilobodrilus (Dinophilidae) shows that the Protodrilus fiber clearly belongs to the obliquely striated type classically found in Polychaeta, while the Trilobodrilus fiber is a very peculiar type of obliquely striated fiber. These differences do not agree with Jägerstens hypothesis on the unity of the Archiannelida established on the basis of a structural similarity of the bulbus muscles.

Animals↗
PubMedDate not supplied

[2 new species of gregarines parasites of annelides: Pleurocystis eiseniellae of Eiseniella tetraedra Sav.)Oligochaeta), Pterospora petaloprocti of Petaloproctus terricola Quatr. (Polychaeta)].

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.

Animals↗
PubMed1975

Acrosome formation and the centriolar complex in the spermatozoa of Sabella penicillum (Polychaeta): an electron microscopical study.

The acrosomal vesicle of Sabella penicillum spermatids consists of an electrondense core and a more transparent surrounding zone. During subsequent differentiation the vesicle membrane forms several invaginations in the juxtanuclear area. These invaginations later establish contact with the core. In the mature spermatozoon the spaces between the invaginations appear as electron-dense "tubules"; this is probably due to a shift of material from core to periphery. The ultrastructure of the centriolar complex is described in detail.

Acrosome↗
PubMed1978

Discocilia--a new type of kinocilia in the larvae of Lanice conchilega (polychaeta, terebellomorpha).

A modified type of kinocilia has been found in the Aulophora-Iarva of the sedentarian polychaete Lanice conchilega. For this newly described cilium type the term "discocilium" is proposed. The only structural difference from usual locomotory cilia is the tip, which possesses a discoidal head. The head is formed from the terminal part of the cilium shaft, which is bent to give rise to a loop-like ring covered by the ciliary membrane. Three types of discocilia can be distinguished: a) discocilia having swollen, bulblike heads with a central straight axoneme; b) discocilia having heads with a curved lateral axoneme and c) discocilia in which the axoneme forms a loop. The internal structure shows the usual 9 + 2 arrangement of the filaments. The head shows no sign of secretion; it appears structureless in electron microscopical examination. There are two kinds of discocilia arrangements: 1) isolated bunches of cilia especially at the tentacles and in the frontal region, and 2) segmental dorsal rows of cilia. The possible formation of discocilia is described.

Animals↗
PubMed1979

Unusual granules in the ejaculatory duct of a Microphthalmus species (Polychaeta, Annelida).

The paired prominent ejaculatory ducts of the hermaphroditic polychaete Microphthalmus cf. listensis are surrounded by gland cells the processes of which penetrate the ducts themselves. These cells produce, in separate regions, two different types of spherical granules. Type I is composed of an electron dense and an electron lucent part. Type II granules contain a tubular filament that forms a single or double spiral in the periphery of a more or less unstructured electron dense material. Golgi vesicles give rise to this granule type. During the passage of sperm, these granules are obviously discharged into the lumen of the duct. Here they change form and probably dissolve. Their function is as yet unknown; capacitation of sperm is assumed.

Animals↗
PubMed1979

Autoradiographic detection of indolamine and catecholamine neurons in the nervous system of Owenia fusiformis (Polychaeta, Annelida).

Light- and electron-microscopic autoradiographic studies were carried out on Owenia to detect selectively catecholaminergic and indolaminergic neurons at two appropriate body levels according to the regenerative properties of this annelid, i.e. in the 1st and the 4th abdominal segments. Autoradiographically, intense 3H-5-hydroxytryptamine accumulation is seen in the 1st abdominal segment, and a less intense autoradiographic reaction in the 4th segment. Roughly, a similar difference in the distribution of the label is seen at both levels following 3H-noradrenaline administration. These observations, confirmed by a quantitative uptake analysis, suggest the presence of catecholaminergic and indolaminergic neurons in Owenia.

Animals↗
PubMed1992

Cellular immunity in an annelid (Nereis diversicolor, Polychaeta): production of melanin by a subpopulation of granulocytes.

We attempted to identify the nature and origin of the pigment produced by the marine worm Nereis diversicolor in order to isolate, in inert brown capsules, foreign objects introduced into its body cavity. This brown pigment, characterized by cytochemical techniques, could be a melanin. The activity of the enzyme phenoloxidase responsible for melanin biosynthesis was detected by enzyme cytochemistry techniques in vacuoles and the Golgi apparatus of coelomocytes activated by the presence of foreign bodies. Morphological techniques combined with a monoclonal immunological probe enabled us to establish that the "G2" granulocytes contain both the precursor of the pigment in dense bodies and the capacity for phenoloxidase synthesis when activated to encapsulate foreign bodies. The "G2" granulocyte may therefore be compared to a melanocyte in which melanin is not stored as in mammals, but immediately extruded following synthesis in the form of a thick fluid.

Animals↗
PubMed1978

Petroleum hydrocarbon resistance in the marine worm Neanthes arenaceodentata (polychaeta: annelida), induced by chronic exposure to No. 2 fuel oil.

1. Three successive generations of the marine polychaetous annelid Neanthes arenaceodentata taken from a laboratory population, were continuously exposed to one of three sublethal concentrations of No. 2 Fuel Oil water-soluble-fraction (WSFs). During each generation larvae, juvenile, and immature adult polychaetes were challenged with acute (96 hr) doses of No. 2 Fuel Oil or south Louisiana crude oil WSF to test their sensitivity to petroleum hydrocarbons (PHCs). 2. Larvae from all 3 generations, at all exposure concentrations, were no different from control (susceptible) larvae in their sensitivity to the two test oils. F1, F2, and F3 adults exhibited equally increased PHC resistance (X2) compared to control adults. 3. The only evidence of increased resistance beyond that observed in F1 animals was seen in results of bioassays with juvenile worms, wherein PHC resistance increased from slightly below control levels in F1 juveniles to slightly above control tolerance among F3 juveniles. 4. With the exception of F1 worms, removal from chronic exposure 7 or 14 days prior to challenge did not result in termination or reduction of resistance, implicating a genetic mechanism behind PHC resistance in N. arenaceodentata. 5. F3 resistant and unexposed control polychaetes accumulated, metabolized, and excreted a key diaromatic PHC (naphthalene-14C) in quantitatively identical fashion. Mechanisms responsible for resistance appeared unrelated to external permeability and/or excretion rates.

Animals↗
PubMed1978

Comparative ultrastructure of juvenile and adult nuchal organs of an annelid (Polychaeta: Opheliidae).

Opheliid nuchal organs are composed of ciliated cells, retractor muscles, and sensory cells. The perikarya of sensory cells are located in the posterior portion of the brain, and their distal processes extend along the body wall, as the nuchal nerve, and terminate just anterior to the ciliated region. The nuchal nerve of the juvenile is composed of 30-35 dendrites; the adult nuchal nerve has 35-40 dendrites. The ends of the sensory dendrites form sensory bulbs which are clustered around the olfactory chamber, and each bulb bears a modified cilium. Sensory cilia lose their axonemes and extend as microvillous-like structures into the olfactory chamber. Supportive cells delineate approximately the posterior and dorsal portions of the chamber with sensory bulbs forming the remaining ventral and anterior portions. On the lateral aspect of the chamber, cuticular matrix. The adult nuchal organ is larger than that of the juvenile, and the sensory portion of the olfactory chamber wall is expanded. Expansion of the sensory area is apparently the result of size increase in sensory bulbs and by intrusion of supportive cells between sensory bulbs.

Animals↗
PubMed1978

Anatomical and ultrastructural study of the pharyngeal bulb in Protodrilus (Polychaeta, Archiannelida) II. The stomodeal and its cuticle.

The epidermal and stomodeal cuticles of Protodrilus are described then compared. The thin epidermal cuticle, the thickness of which is about the same over all the body, is characterized both by the absence of fibrils in its deepest part and by the extension of epidermal microvilli above the cuticle. The stomodeal cuticle, the thickness of which is as variable as that of the epithelium, presents two layers of fibrils comparable to the collagen fibrils described in the cuticle of other Annelida, as well as a relatively diversified supramicrovillous coating. The anterior cuticular thickening or grating plate, is characterized by the length of the epithelial microvilli, the thickness of the cuticular matrix and the superficial cuticular zone with supramicrovillous denticles supported by an axis of fibrous bundles. In the stomodeal cuticle, the fibrillar material seems to give to the cuticle best resistance to deformation during the pharyngeal bulb contraction, while an especially elaborated supramicrovillous coating is found in regions most exposed to friction. These features contrast with the relative simplicity of the epidermal cuticle.

Animals↗
PubMed1979

Ultrastructural evidence for both autosynthetic and heterosynthetic yolk formation in the oocytes of an annelid (Phragmatopoma lapidosa: Polychaeta).

The ovaries of the reef-building polychaete Phragmatopoma lapidosa are attached to the genital blood vessels on the caudal surface of the intersegmental septa of the abdominal segments. Oogenesis is not synchronized and vitellogenesis occurs before the oocytes are released from the ovary into the coelomic cavity. A portion of each developing oocyte rests on the basal lamina of the genital blood vessel while the remaining surface of the oocyte is covered by follicle cells. Two morphologically distinct types of yolk are formed during vitellogenesis: Type I, which may be formed autosynthetically by the conjoined efforts of the rough ER and Golgi systems; and Type II, which is presumably formed heterosynthetically from endocytosis of yolk precursors from the genital blood vessel. Heterosynthetic production of yolk in an annelid has not been reported previously.

Animals↗