摘要:

AbstractThe spermatogenesis and mature spermatozoon ofParavortex cardiiwere studied by transmission electron microscopy. Meiotic divisions occur without cytokinesis and the spermatid nuclei appear embedded in a common cytoplasmic mass. The mature spermatozoon is filiform, very regular in contour and circular in cross‐section. A tubular lining of microtubules lying close to the plasma membrane is found along the spermatozoon. Rows of spherical glycogen particles with helical arrangement lay internal to the cortical microtubules. The spermatozoon ofP. cardiimay be divided into two regions, nuclear and cytoplasmic regions. The nuclear region contains an elongated nucleus with a densely packed nuclear material. The mitochondria are distributed throughout the cytoplasmic region; they pack tightly together and often fuse to form one large one. This spermatozoon lacks both acrosome and the so‐called dense bodies. A ciliary or centriolar apparatus was not observed. Accordingly, the spermatozoon ofP. cardiiis considered to be aflagellate in type. Spermatozoa are compared among flatworms, and some considerations on the significance of their ultrastructure for phylogeny in the Platyhelminthes are tentatively gi

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1988.tb00916.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractThe fine structure of the spermatozoa of two spionids is described. The spermatozoon ofPrionospiocf.queenslandicais typical of an animal utilizing external fertilization, in having a subspheroidal nucleus, a midpiece composed of unmodified rounded mitochondria surrounding two centrioles and a free flagellum. The acrosome is unusual in showing bilateral symmetry. The spermatozoon ofTripolydorasp. resembles that of spionids utilizing spermatophores, in possessing an extremely elongate nucleus and midpiece. The nucleus is penetrated by the 9+2 axoneme for its entire length, linking with a single centriole at the anterior end. Platelets surround the nucleus and intermingle with the mitochondria of the midpiece, which terminates with an annulus. The acrosome shows some internal vesiculation and substructuring. Sperm structure in relation to reproductive methods is discussed and the view of external fertilization as primitive is questioned.

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1988.tb00917.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractThe luminal surface of the coronet cells of the dogfish saccus vasculosus has been studied by scanning and transmission electron microscopy. Most of these cells have a mulberrylike structure composed of 25–35 closely arranged globules originated from ciliary stalks. In adult dogfish some coronet cells have globules either shedding or in different phases of formation from cilia. We report here the description of dogfish coronet cells and the discussion on a putative globule formation cycle. Cerebrospinal fluid (CSF) contacting neurons of the dogfish saccus vasculosus were also describe

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1988.tb00918.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractThe labelling index (TLI) of the digestive mucosa of some fish species was determined following a pulse labelling with tritiated thymidine ([3H]TdR) and light microscopic autoradiography. In the oesophageal epithelium, proliferation was observed to occur in non mucus‐secreting cells. In the intestine, both undifferentiated and absorptive cells incorporated [3H)TdR within 1 h after injection. Statistically significant differences in [3H]TdR incorporation were observed between the upper intestine region and both the middle and lower parts on the one hand, and between the middle and lower parts on the other hand. Mucus‐secreting cells seemed unable to proliferate. In the stomach, significantly fewer labelled nuclei were counted; they were located in the isthmus epithelium. No significant difference was observed between the TLI of these regions in the different spec

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1988.tb00919.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractThe highly complex epidermis ofXenoturbella bockihas been studied, mainly employing transmission electron microscopical and histochemical methods. The epidermal organization is described to best advantage in terms of the various cell types present, their intricate interrelationships and their interaction with the highly developed subepidermal membrane complex (SMC). The epidermis is composed mainly of ciliated epidermal supporting cells, at least two types of gland cells (one dominant mucous type with basophilic, alcian blue‐positive granules; another possessing acidophilic, PAS‐positive granules), several types of nerve cells present in the intraepidermal nerve layer and, finally, some peculiar basally arranged ‘pillow cells’. Junctional structures are sparsely developed. The epidermal supporting cell is provided with a distinct cell web, but diagnostic for this cell type is the presence of a very prominent single supporting fibre (SF) composed of supporting filaments. Distally some of these filaments may terminate on the tapering proximal ends of ciliary rootlets, a highly unusual phenomenon. Basally the SF is attached to the SMC in a complex arrangement. The possible relationship of the supporting filaments to cytoskeletal intermediate filaments is discussed. The SF is compared to other cytoplasmic filament systems in mammals and various invertebrates. The ultrastructural organization ofXenoturbellais now fairly well understood, nevertheless, our conclusion must be that it is still not possible to assign an appropriate place for this animal in the systematic‐phylogenet

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1988.tb00920.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractThe putatively luminous villous tissue in an abdominal pouch of a male specimen of the oceanic midwater sharkEuprotomicroides zantedeschiais described. The epithelium within the pouch is probably stratified. The most conspicuous cell type is tall columnar cells, typically containing small cytoplasmic granules and a large inclusion. Cells with similar cytoplasmic characteristics, thought to be photogenic cells, are present in the epidermal skin photophores in other selachians which are known to be luminous.

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1988.tb00921.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractThe external form of the follicles was mostly spherical or oval and the large oval follicles reached more than 300 times 180 μm in size. Cytoplasmic inclusions of various sizes were observed in the follicular epithelium. Follicles were composed of hexagonal epithelial cells, and on the apical surface of the cells many microvilli were found (380–500 microvilli per cell) with globular or amorphic cytoplasmic protrusions. In a few cells a central cilium was also observed. From these results a relationship between thyroid structure and function in the hagfish is discuss

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1988.tb00922.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY