摘要:

AbstractHair cell orientations of all inner ear sensory epithelia in glass eel, yellow eel and silver eel are presented. The patterns of hair cell orientation do not change with age. All sensory epithelia increase in area during growth of the eel. Examination of the hair cell population in macula utriculi show constant hair cell densities and increased hair cell population during development. Further, regional differences in hair cell densities and hair cell types are observed. The hair cells/axons ratio increases 3‐fold from glass eel to silver eel stadium. Nerve stainings in silver eel reveal complex innervation patterns with large stubby fibres confined to restricted regions. Histograms of nerve fiber diameters show marked differences from glass eel to silver eel. Growth of sensory epithelia is discusse

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1984.tb01041.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractThis paper describes some features of the chaetognath nervous system from ultrastructural observations and observations on material stained with specific techniques for nervous tissue, and from records of the activity of the locomotor muscles and ventral ganglion. Sensory cells grouped on the ventral surface of the head bear ciliary processes (some with multiple tubules), and are probably in connexion with the central nervous system by their own axons, unlike the sensory cells of the hair fan vibration receptors of head and body. The ventral ganglion is motor to the locomotor muscles of the body, and controls the rhythmic locomotor activity of the animal. Electrical events associated with contraction of these muscles are compound non‐overshooting spike‐like potentials. The ventral ganglion contains several large nerve fibres constant in position and connexions in different individuals. Some of these arise from cells in the ganglia of the head, and pass to the ventral ganglion, others from cells within the ventral ganglion, and probably supply the ciliary hair fan receptors of the body, whilst the motor axons issuing from the ventral ganglion are smaller in diameter. The ganglion is arranged on a ladder‐like plan, and axons of the lateral cell bodies cross the central neuropil transversely before they contribute to the longitudinal tracts or pass out in the radial nerves. Synapses in the neuropil contain 30–40 nm electron lucent vesicles; the transmitter is unknown, but is unlikely to be either acetylcholine orl‐glutamate. Occasional larger electron dense vesicles up to 70 nm in diameter are also found within nerve fibres of the neuropil. It is concluded that the arrangement of the peripheral nervous system is unlike that of several groups which have been suggested as related to cha

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1984.tb01042.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractThe vascular supply of red, intermediate and white fibres in the axial muscle of axolotl (Ambystoma mexicanumShaw) was visualized with Indian ink‐injections and quantified with morphometrical methods on semithin sections.Red fibres were surrounded by 1.4 ± 0.6 capillaries (mean + SD), the intermediate fibres by 1.2 ± 0.9 capillaries and white fibres by 0.3 ± 0.6 capillaries. The mean vascularized surface area per unit volume of fibre was 0.0159, and 0.0068 and 0.0007 (μm2/μm3) for red, intermediate and white fibres, respectively. A unit volume of mitochondria within each type of fibre was supplied by 0.15, 0.17 and 0.08 μm2vascularized surface for red, intermediate and white fibres, respectively. This indicates that there exist a good balance between oxygen demand represented by mitochondrial content and oxygen supply represented by the vascularized

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1984.tb01043.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractThe larval morphology and settlement of the vesicularioid ctenostome bryozoanBowerbankia gracilishas been investigated by light and electron microscopy in an attempt to elucidate the mechanism of attachment to the substratum at the onset of metamorphosis. The oral epithelium in the free‐swimming larva is infolded to form a glandular internal sac at the oral pole. The internal sac is not specialized into distinct regions, but consists of a uniform, simple columnar epithelium filled with secretory granules. The hemispherical internal sac is underlain by a cup‐shaped layer of undifferentiated cells that constitutes the polypide rudiment. The cupiform layer of undifferentiated cells is in turn embraced by a network of muscle fibers called the rete muscularis. At the onset of metamorphosis, the larva constricts oro‐laterally and the internal sac is everted against the substratum. As the sac everts, the glandular cells secrete an adhesive that is wafted up over the metamorphosing larva by the reversed beating of the coronal cilia. At the same time, the cupiform layer of undifferentiated cells flattens in the plane of the oro‐lateral constriction and doubles in thickness. The cells of the cupiform layer undergo a corresponding transformation from short columnar cells to flask‐shaped cells that bulge into the glandular cells of the internal sac. The narrow ends of the flask‐shaped cells abut the strongly contracted muscle fibers of the rete muscularis. It is hypothesized that the contraction of the muscle fibers of the rete muscularis is responsible for the change in shape of the undifferentiated cells and, consequently, for the eversion of the internal sac. On the basis of this study and a review of the literature, it is concluded that attachment to the substratum at the onset of metamorphosis typically is effected by the eversion of an internal sac in larvae of the ctenostome superfamily Vesi

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1984.tb01044.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractAdult female frogs were exposed to artificial hibernation in a refrigerator, at about 1–3°C, 1–2 months earlier than in nature, isolated or together with males. Ovarian functional state at the beginning of hibernation was assessed from ovarian biopsies taken in mid‐September. All frogs ovulated during hibernation which was interrupted in mid‐May, but in seven out of 19 frogs ovulation was incomplete. The number of non‐ovulated oocytes varied from a minor fraction to about two thirds of the complement of vitellogenic oocytes, indicating that the follicle size reached at the time of induced hibernation was at the critical level for successful maturation. This critical size was about half the normal oocyte volume at the onset of natural hibernation. There was no vitellogenic growth during hibernation, which presumably constitutes the period of follicle maturation. In five of the frogs, oogenesissensu strictohad occurred during the period of hibernation, some oogenic events being completely finished at autopsy in mid‐May and others still

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1984.tb01045.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1984.tb01046.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY