摘要:

AbstractEach pigment‐cup eye ofMesostoma ehrenbergiconsists of two photoreceptor cells, the anterior cell being bilobate. the posterior almost linear, and of a multicellular pigment cup. The nuclei of the photoreceptor cells are located inside the medial region of the brain. Thin cytoplasmic photoreceptor projections provided with neurosecretory‐like granules are interposed between the inner surface of the eye cup and the distal extremity of the microvilli.The breakdown and renewal of microvillar membranes was analysed. Membrane turnover is a continuous process. At dusk and during the night abscission of photoreceptive membranes occurs. At dawn the membrane fragments are degraded to granular material, which is then endocytosed into the submicrovillar cytoplasm as coated vesicles. These vesicles form multivesicular bodies. The degradation of multivesicular body content occurs during the following light hours. The dark period is correlated with membrane synthesis for elongation of reticular membranes, which are converted into ellipsoid bodies. The formation of new microvillar membranes occurs at the base of the microvillar border, and involves the fusion with the old microvillar membranes of small vesicles detached from the tubular endoplasmic membranes and from the flattened concentric cisternae of ellipsoid bodies. The correlations with daily cycles of other invertebrates are discus

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1990.tb01188.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe neural gland complex ofAscidia interruptaconsists of three parts: dorsal tubercle, ciliated duct, and neural gland. The dorsal tubercle protrudes above the pharyngeal lining and bears a ciliated funnel. The funnel opens into a ciliated duct which opens into the neural gland, a blind sac in a blood sinus below the brain. Funnel and duct cells are joined by adhaerens junctions and, apically, by putative tight junctions. The neural gland wall is a loose, irregular, non‐ciliated epithelium of phagocytes. Adhaerens, but not tight, junctions join the cells. Secretory cells were not observed. Tracers delivered onto the dorsal tubercle and dissolved in seawater around undissected animals are transported unidirectionally inward into the neural gland. The continuous ciliary incurrent moves the tracers across the wall of the neural gland and into the pharyngeal blood vessels. Small particulates and large macromolecules, however, are removed from the water stream by endocytosis on neural gland cells. Large particulates delivered onto the dorsal tubercle do not enter the system but rather are rejected by cilia on the surface of the tubercle. The neural gland complex is interpreted as an organ of blood volume regulation that consists of a pump (cilia) and coarse (tubercle) and fine (gland) filters. Analogous and homologous systems are discusse

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1990.tb01189.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractIn normal ascidian development, cuticular fins begin to form at the late tailbud stage and are fully formed at hatching. When one or several neurulae were manually demembranated (follicle cells, vitelline coat and test cells removed) and cultured in seawater they failed to form caudal fins. Fins were normal when the follicle cells alone were removed. The shape of the fins was normal when demembranation was delayed to the late tailbud stage. Does demembranation cause the loss of an essential factor produced by the embryos themselves or do the test cells provide a factor for fin morphogenesis? Demembranated neurulae ofAscidia callosawere cultured in groups ranging in size from 2 to 80 in 1 ml volumes of seawater.The mean lengths of the caudal fins increased with group size. In larger groups, some embryos developed fins that were normal in shape and as long as undemembranated controls. Results were similar withCorella inflata. These experiments suggest that a diffusible substance from the embryos facilitates fin morphogenesis and that test cells are not required. Test cells deposit ‘ornaments’ on the tunic in some species. In other species no ornaments are produced. Ten families are compared. It is proposed that the test cells make the tunic hydrophi

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1990.tb01190.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe body ofHirudo medicinalisconsists of 32 segments. The quinquannulate midbody segments 3–18 bear 14 sensilla on the central (neural) annulus. Elsewhere segments are represented by fewer than five annuli but sensilla are retained on the neural annulus. From neural sensilla protrude S hairs (cilia from uniciliate cells) which are thought to detect water currents. Two categories of multiciliate cell, of unknown function, are also present within neural sensilla; (i) grouped cilia extending beyond the cuticle (G hairs), and (ii) cilia which radiate out beneath the cuticle. Studies of the entire external surface of leech body wall with a scanning electron microscope revealed the presence of large numbers of sensilla on every annulus including the neural annuli. These sensilla lack S hairs. Our results show: (i) annular sensilla have a significantly smaller surface area than neural sensilla (p<0.001 Mann‐Whitney test, 2 tailed), (ii) The position and number of the small sensilla varies from annulus to annulus, segment to segment and individual to individual, (iii) Significantly higher numbers of small sensilla were found where non‐neural annuli remain single and have not undergone a further division during development as happens in the quinquannulate segments. The data suggest that small sensilla continue to be added during the adult life of the

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1990.tb01191.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractIn the females ofDendrolimus pinithe pheromone‐producing epithelium is present ventrally between the 8th and 9th abdominal segments. The epithelium is about 40 μm thick. The cells possess extensive microvillar borders, both apically towards the cuticle and laterally, towards the adjoining cells. In the spaces between the cells in the upper half of the epithelium there are loosely arranged cuticular lamellae adjacent to the microvillous borders. The epithelial cells have large, basally situated nuclei, whereas the apical parts have extensive arrangements of tightly packed and orderly arranged smooth endoplasmic reticulum. Clear vesicles and microbod–ies are present in the cytoplasm. The gland has a structural potential for high pheromone‐producing capacity (the well‐developed endoplasmic reticulum) as well as an effective emission apparatus (the microvillous borders/cuticular lamellae). These two elements could facilitate a pulsed pheromone emission that is effective in arousing the sensory system

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1990.tb01192.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractA new rhizocephalan parasite which infests the barnaclesChthamalus challengeriandBalanus amphitrite amphitriteis described. It is known only from the type locality, Aburatsubo, Kanagawa Prefecture, Japan. Its position in the family Chthamalophilidae is assured by the cyprids lacking a thorax, by the position of the mesenteric canal opposite to the stalk, and by its host being a balanomorph barnacle. Among the three previously described species of the Chthamalophilidae, the new species most closely resemblesBoschmaella balani, but it differs in details of the internal root system and in the externa being found both on the host body and on the inner mantle. About two‐thirds of the infested hosts carry more than one extern

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1990.tb01193.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractBoschmaella japonicainfests the barnaclesChthamalus challengeriandBalanus amphitrite amphitrite. Its morphology is very similar to the previously known members of the family Chthamalophilidae (Rhizocephala, Akentrogonida). LikeBoschmaella balaniandBocquelia roseait has an internal root system within the host. Transmission electron microscopy revealed that the ‘incubatory cavity’ in previous descriptions of the Chthamalophilidae is lined by a thin cuticle, and it is therefore homologous to the mantle cavity found in other Rhizocephala. The development of the male structure resembled events inChthamalophilus delagei. It is evaginated from the mantle into the mantle cavity as a free‐floating, epithelium‐lined capsule, ‘the spermatogenic island’, which later fragments into numerous secondary spermatogenic islands, where spermatogenesis takes place. Based on new morphological evidence and a comparison with other rhizocephalans, it is suggested that all species of the Chthamalophilidae are gonochorists, in which male cyprids implant spermatogonia directly into the mantle of female externae. The larvae ofBoschmaella japonicahatch as cyprids which, like those of other chthamalophilids, lack a thorax and thoracic cirri. This larval feature is thought to be an important factor limiting dispersal of these species. The incidence of multiple‐infested hosts is very high inBoschma

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1990.tb01194.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractCharacteristics of reptilian muscle fibres were investigated in the biceps brachii of the African chameleon,Chamaeleo senegalensis. Fibres were classified as slow and fast. These types of fibre were distinguished on the basis of histochemical staining for myofibrillar ATPase (mATPase). Fast fibres stained dark for mATPase while slow fibres stained light.The patterns of innervation of slow and fast fibres were investigated by staining nerve endings for acetylcholinesterase activity. Slow fibres have a pattern of multiple innervation, whereas fast fibres are associated with individual endplates. The organization of the myofibrils and the sarcoplasmic reticulum in slow muscle fibres from the chameleon biceps brachii was compared with that in fast fibres. Slow fibres lacked an M‐line and the Z‐lines were uneven. They had fibrils that were not clearly separated from each other and the sarcoplasmic reticulum was poorly developed. These features are in sharp contrast to those of fast fibres which had straight Z‐lines, clear M‐lines and well‐developed sarcoplasmic

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1990.tb01195.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY