摘要:

AbstractFor the first time, the phenomenon of regeneration is reported for the phylum Gastrotricha. Adult specimens ofTurbanellasp. were transected transversely and events of regeneration were observed on the light microscopical level. In both anterior and posterior fragments the wound closure was completed I day after the operation, and in 3 days the epidermis was restored entirely. The dorsal commissure of the Y‐organ was rebuilt soon after wound closure. In anterior fragments cut at any level of the intestine, caudal adhesive tubes were formed anew, following the species‐specific pattern. In posterior fragments, and in both fragments if transected at a pharynx level, regeneration resulted in a complete wound healing, with no new adhesive tubes being obser

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1995.tb00975.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe 5‐HT (serotonin) distribution in the nervous system of the macrodasyoid gastrotrichTurbanella cornutawas studied using immunocytochemical methods. Positive immunoreaction was found in two pairs of neurons. The neurons of one pair had processes which extended peripherally to the surface of the body. Central processes of both pairs entered the brain commissure and proceeded into the longitudinal cords. Unlike other acoelomate worms studied so far, the Platyhelminthes and the Nematoda, in this gastrotrich no 5‐HT positive perikarya or processes were present in the pharynx innervation, and no positive neurons sent processes directly to the nerve c

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1995.tb00976.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe existence of collar cells lining the stomach gastrodermis in free‐livingPolypodium hydriformeand their ultrastructure are described. The collar cells are provided with a collar consisting of 9–10 microvilli which encircles a central flagellum and forms a flagellar pit. At the bottom of the pit around the basal part of the flagellum there is fine crystalline material which extends also in the spaces between the microvilli and keeps them straight. The flagellum has a typical axoneme (9+2), its basal body is located below the apical surface of the collar cell and continues into a striated rootlet. An accessory centriole is situated close to the upper part of the rootlet. The cell nucleus is located in the basal part of the cell. Prominent mitochondria with tubular cristae, Golgi cisternae and fragments of rough endoplasmic reticulum are situated mostly in the basal part of the cytoplasm. Discoidal vesicles are abundant in the apical cytoplasm. The collar cells are connected to each other by septate junctions and interdigitations. The ultrastructure of collar cells described here is discussed in comparison to that of other Cnidarians and in connection with the problem ofPolypodium'ssystematic posit

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1995.tb00977.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe spermatozoa of the yellow‐rumped elephantshrew Rhynchocyon chrysopygushave a spatulate head, tapering to a rounded proximal end with a marked narrowing at the equatorial segment. There is a short pointed subacrosome and about 24 gyres of mitochondria were found in the midpiece. The coarse fibres surrounding the axonome show enlargement of numbers 1, 5, 6 and 9. The spermatozoa of all genera of elephant shrews have now been described allowing comparisons among them.R. chrysopygushas the shortest spermatozoon and the fewest number of gyres. The pointed subacrosome is considered an ancestral feature and is shared withMacroscelides. The enlargement of coarse fibres 1, 5, 6 and 9 is found in several groups including members of the archonta and paenungulates, both postulated as being related to elephant shrew

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1995.tb00978.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractLight microscopy and scanning electron microscopy of three specimens ofCyathidium meteorensis(order Cyrtocrinida) revealed some special morphological features. The brachial articulation is provided with a long tendon at the aboral side; the entire articulation surface, including the areas where ligaments attach is built up by labyrinthic stereom. The calycinal ossicle lacks any internal vestiges of a pentameric composition; vertical planes with changing stereom direction lie irrespectively of radial or interradial planes. Gut, ovary and testis are histologically inconspicuous, and the location of the gonads inside the calyx is quite unusual. Both sexes develop outer gonoducts which probably are functionally adapted madreporic canals. The coelomic system differs from that of other crinoids in that a chambered organ is completely lacking. Simultaneously, the aboral nervous subsystem has no aboral nerve centre and simply terminates aborally in the ring‐shaped commissure. A glandular axial organ is absent, as are typical sacculi. The data are in accordance with two proposals made previously forHolopus rangii, viz., that the animals can feed raptorially, and that cyrtocrinids probably have evolved by loss of aboral calycinal ossicles of ancestors. In part, our observations differ from those inCyathidium foresti, so we have chosen to use the species namemeteorensiswhich has been considered a synonym offorest

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1995.tb00979.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractDuring development of the encapsulatedKronborgia isopodicolalarva, nuclei of the body tissues and differentiating eyes undergo a continuous condensation, the progression of which is described. The brain is composed of a central neuropil and an outer layer of nerve cell perikarya. Neurosecretory cells are located at the sides of the brain. Some neurosecretory cell extensions are interposed between the cerebral neuropil and nerve cell perikarya; others overlie the photoreceptor cell processes of the eyes. The advanced encapsulated larva possesses a frontal complex, consisting of modified epidermis, secretory cells, gland ducts and nerve cell processes. The advanced larva is transparent and diminished in size, advantages possibly due in part to the extraordinary process of comprehensive nuclear condensation during ontogeny. The larva has a uniform epidermal ciliation and, while sharing certain features with trochophore larvae, is not of the trochophore type.

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1995.tb00980.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe spermatozoa of the Japanese quail conform, in their general ‘sauropsid’ plan, to that of other non‐passerine birds. They are notable, however, in that the flagellum is very elongated (208 μm) and carries approximately 2,500 mitochondria in an extensive midpiece. Ultrastructurally, the acrosome and acrosome‐nucleus junction is exactly as reported for other galliform birds. The neck region contains two centrioles arranged almost in‐line; this unusual layout apparently occurs also in guinea fowl sperm. At the tip of the axoneme, beyond the termination of the central pair microtubules, is a structure—the tip granule—previously recognized in sperm of the domestic fowl. Trypsin digestion splits the axonemal cylinder, and the doublets then spiralize. This response has been reported before, in the sperm tails of other

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1995.tb00981.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractAscidians are known to have the unique ability to accumulate vanadium in their blood cells. Classification of the various types of blood is, however, the subject of some controversy. In the present study we found that the various types of blood cell can be classified on the basis of their autonomous fluorescence upon excitation with blue‐violet light. This method was of particular practical value in the classification of the vacuolated cells that account for about 80% of the total population of cells and are distinguished by their ability to accumulate vanadiu

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1995.tb00982.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe utility of sperm morphology in the systematics of polychaetes has been questioned in the past. This doubt stems from a problem with methodology, not with sperm morphology. It is argued that sperm characters used in combination with other morphological features have utility at various hierarchical levels. As a test of this proposition males in species from each of the following 10 fabriciin genera:Augeneriella, Fabricia, Fabriciola, Fahricinuda, Manayunkia, Novafabricia, Parafabricia, Pseudofabricia, Pseudofabriciolaand an undescribed new Genus A (Fitzhughet al., in preparation), were examined in order to provide new characters for phylogenetic systematic studies. All species were found to have a dorsal sperm duct running beneath the faecal groove of the thoracic region. No sabellin sabellids or serpulids have this duct. The above Fabriciinae have spermatids developing in large clusters of several hundred cells. Serpulids and sabellins nearly always have sperm developing in tetrads or small groups. Fabriciins studied also have a sperm structure distinct from the Sabellinae and the Serpulidae. Proposed synapomorphies for the members of the Fabriciinae, based on sperm structure, include (1) a thick glycocalyx over the plasma membrane; (2) a distinctive nuclear projection, with an anterior thickening of the nuclear membrane; (3) a thickened. spiraling ridge of nuclear membrane; (4) an extra‐axonemal sheath and (5) a unique sheath of mitochondrial material in the midpiece. Within the sub‐family there were differences among species in sperm structure. This variability involves acrosome morphology; the structure of the sperm nucleus and nuclear projection; the spiral of thickened nuclear membrane; the structure of the extra‐axonemal sheath; the mitochondrial sheath. The monophyly of the Fabriciinae (sensuFitzhugh, 1991, 1993) is well supported by this analysis. The status ofCaobangiais still unresolved and a close examination of this genus is warr

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1995.tb00983.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe visceral musculature of Chaetognaths was studied with special attention given to the digestive apparatus muscle. In the head the digestive apparatus muscle is relatively thick; individual muscles are difficult to distinguish at the anatomical level; in the anterior part of the oesophagus discontinuous bundles and layers of cross‐striated fibers are found. As a group however, the oesophageal musculature completely covers the oesophageal epithelium. The prominent muscle layers around the oesophagus probably help to force food into the intestine against the turgor pressure of the trunk cavity which tends to collapse the intestine. Around the intestine the musculature is largely circular and smooth. The intestinal epithelium is ciliated despite its muscular covering. Muscle fibers are not individually innervated. They form myoepithelial structures with various intercellular junction types. In the intestinal muscle the fibers show myoendothelial‐like junctions. Sphincters composed of myoepidermal cells surround the anus and the female gonopores. The somatic side of the general cavity is lined with a polymorphic squamous epithelium. Sometimes myoepithelial cells are found, with the occasional presence of extracellular matrix basal to the layer of the squamous epithelium. The ontogenetic relations between the polymorphic epithelium and the composite ‘mesenteries’ remain to be established. We have now some idea about the architecture of the body of Chaetognaths in relation to contractile str

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1995.tb00984.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY