摘要:

AbstractThe otoplanid nervous system investigated inOtoplana truncaspinaLanfranchi, 1969 andParotoplanella heterorhabditicaLanfranchi, 1969 consits of: (a) an ellipsoidal cerebral ganglion located between the gut and the cephalic intestine and invested by a fibrillar collagen‐like capsule 0.3 μm thick; (b) anterior extracapsular ganglion cell clusters; (c) a peripheral nerve plexus locally thickened at the level of the epithelial sensory and glandular areas, with extensive synaptic connections. At least two neuron types can be identified within the ganglion: (a) an inner layer close to the central neuropile of the 1st type of neurons, showing a vesicular cytoplasm rich in RER and Golgi complexes processing both round, clear, 25–45 nm in diameter, and dense cored vesicles, 50–80 nm in diameter; (b) an outer layer of the 2nd type of neurons, adjoining the capsule and filled with uniformly dense vesicles, 60–90 nm in diameter. Synaptic endings in the neuropile are provided with clear vesicles and dense cored vesicles or uniformly dense vesicles. The presynaptic side has paramembranous projections channelling the vesicles to the active zone; omega‐like profiles are also observed. Thin banded muscle fibres run within the brain. A comparison is drawn with the other turbellarian neuron types described in the literature, to suggest their possible function. The functional implications of the synaptic ultrastructure are

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1985.tb00825.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractThe statocyst architecture in the three otoplanid speciesNotocaryoturbella bigermariaLanfranchi, 1969,Otoplana truncaspinaLanfranchi, 1969 andParotoplanella heterorhabditicaLanfranchi, 1969 is compared. Common features are: (a) a fibrillar collagen‐like, 0.2 μm thick, investing capsule continuous with the brain capsule; (b) an inner wall made up of six or more flattened and overlapping parietal cells; (c) a statolith forming cell hanging from the dorsal side down in the lumen, with a large statolith containing vacuole; (d) a bilateral pair of spindle shaped accessory cell groups, adjoining the statolith cell and sending projections to the wall—nerve projections run through the capsule; (e) one accessory cell enveloping the other cells of the group has a filament containing cytoplasm, the filaments coverging into a hemidesmosome making contact with a projection coming from a parietal cell; (f) muscles from the longitudinal body musculature inserting onto the capsule externally. The lack of ciliary structures differentiates the turbellarian statocyst from the majority of invertebrate statocysts. The developmental origin, the phylogenetical meaning and the functional and adaptive value of the statocyst in Turbellaria are here commente

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1985.tb00826.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractThis study deals with geographical variations in brain‐body weight relationships in the alpine newt,Triturus alpestris alpestris.According to the canonical axis, C.A., the mean allometry in this species is 0.473±0.03; an allometry value of 0.5 is considered to be characteristic ofCaudata.No significant difference was observed between the four reduced major axes (R.M.A.) of lowland animal samples (mean value of the pooled samples, C.A. = 0.469±0.210). In contrast, between the mountain samples a significant difference exists, the R.M.A. in the sample from l'Alpe d'Huez (Isère, France) being 0.331±0.57 as compared to 0.72±0.18 in the sample from Durmitor (Montenegro, Yugoslavia). In spite of this difference, their encephalisation index (Ie) did not differ significantly, having on average a value of 118.18±8.5, against Īe = 93.8±8.0 for lowland samples. A significant difference in encephalisation index between mountain and lowland alpine newts thus exists. This is probably the first observation in vertebrates of an encephalisation index increase with altitude. A biological hypothesis is proposed to explain this peculiar ob

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1985.tb00827.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractThe paired balancers of larvalPleurodeles waltl, a urodelan species of the Amphibia, were investigated throughout their life span until final degeneration, using electron microscopy. The evidence from cellular ultrastructure illustrates the mucus‐secreting function of these organs, and the outer epithelial cells actively synthesize muco‐proteinaceous substance. An extensive granular endoplasmic reticulum and well developed Golgi complexes participate in the mucus manufacture. The balancer epidermis is also extensively innervated throughout by non‐myelinated neurites, most of them without Schwann cells, a feature which argues strongly in favour of the organ also having a sensory function, whose nature has yet to be deter

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1985.tb00828.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractIn sharks bioluminescence is only known from the family Squalidae. It evolved independently in two out of six squalid subfamilies, Dalatiinae and Etmopterinae. The distribution of photophores was mapped in several species. It is suggested that in the Dalatiinae, which do not school, but migrate vertically, luminescence serves as ventral countershading. The Etmopterinae school and feed close to the bottom. Their luminescence is an aid in schooling. Four different placoid scale patterns are found in luminescent sharks and they allow to accommodation the photophores in the skin.

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1985.tb00829.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractStructural and ultrastructural studies on the gut of a freshwater Cyclopoida,Macrocyclops albidus(Crustacea, Copepoda) during its post‐naupliar development show constant morphological and cytological characteristics. The alimentary canal is composed of three parts: oesophagus, gut and rectum. Three zones are described from the gut, which forms the major part of the alimentary canal. The median part, or midgut, is the more interesting, characterized by its vacuolar cells. All cells of the gut have constant features. An hypothesis on the digestive function is given in relation to behavioral observations and histological and biochemical dat

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1985.tb00830.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY