摘要:

AbstractThe abdominal fat body of the cockroachBlattella germanicacontains three characteristic cell types—trophocytes, bacteriocytes and urate cells—which have been investigated by electron microscopy. The trophocytes are rich in lipid droplets of different sizes; glycogen, rough endoplasmic reticulum and mitochondria are also abundant. In females immediately after eclosion, the trophocytes contain a greater number of lipid droplets, some of which have different electron density; glycogen and cytoplasmic organelles are clearly reduced. The bacteriocytes hold rod‐like and spherical bacteroids, which are encapsulated by a vacuolar membrane; they show a thin cytoplasmic membrane and an evident cell wall surrounded by a membrane‐like outer envelope. The bacteroids appear to be dividing either by transverse partition or by budding. The urate cells, adjacent to the bacteriocytes, are characterized by complex urate vacuoles delimited by a double layer‐

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1986.tb00850.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThe morphology of the olfactory organs in two sharks, the spiny dogfish and the small‐spotted catshark, was studied by light microscopy and electron microscopy (TEM and SEM). The olfactory epithelium is arranged on olfactory lamellae which are provided with secondary folds. The epithelium mainly consists of microvillous receptor cells, multiciliated supporting cells and basal cells. The find of only one type of receptor cells, the microvillous type, is discussed and the condition considered a derived (apomorphic) character. The route of the water current through the olfactory organ and the different driving forces of the ventilation process are subject to discussion. In both the pelagic dogfish and the bottom‐dwelling catshark the pressure difference between the incurrent and excurrent nostrils achieved by active swimming appears to be the driving force, whereas the role of the beating of the non‐sensory cilia is not evident. In the bottom‐dwelling catshark the ventilation of the olfactory organ is also supported by the respiratory a

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1986.tb00851.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThe U‐shaped alimentary tract ofCephalodiscusis of exclusively epithelial structure; on the basis of fine structural criteria the entire tract can be divided into two large subdivisions: an anterior one with mouth, mouth cavity, pharynx and oesophagus, and a posterior one with stomach and intestine. The anterior subdivision is built up of a relatively uniform, innervated, pseudostratified, ciliated epithelium with mucus cells which are concentrated in the initial parts of the mouth cavity. Cilia and mucus presumably constitute a mechanism transporting food particles into the stomach. In the area of the gill slits specific vacuolated cells occur which may lend rigidity to the walls of the slits. The gastric epithelium consists of prismatic cells characterized by, among others, large inclusion bodies, which may represent digestive vacuoles, small dense rod‐shaped granules and an elaborate system of microridges, at the base of which abundant endocytotic vesicles occur. The dorsal gastric pouch contains cells rich in rough ER and secretory granules, probably containing digestive enzymes. Thus morphological evidence points both to intra‐ and extracellular digestion. The intestinal epithelium resembles that of the stomach, however, it is lower, its organelles are fewer and it bears, beside cilia, mainly microridges, which towards its distal end become sparse. Both in the gastric and intestinal epithelium small granulated cells have been found, which presumably represent endocrine

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1986.tb00852.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractUltrastructural observations are presented for some of the stages occurring during fertilization inDionchus remorae(a gill parasite ofEcheneis naucrates) and are believed to be the first published concerning a monogenean. Fertilized female germ cells were found in the ovary. Several loops of the spermatozoon were present within the oocyte cytoplasm; the sperm nucleus became electron lucent and the parallel peripheral doublets of the axonemes became increasingly divergent. The cortical granules in the oocyte were not released immediately after penetration by the spermatozoon. The homogeneity apparently found in the oocyte ultrastructure and process of fertilization in the monogeneans and digeneans contrasts with the variety that exists in their sperm ultrastructure.

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1986.tb00853.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractFine structural observations on the extracellular matrix (ECM) and connective tissue system of the enigmatic vermiform animalXenoturbella bockihave demonstrated a complex and interesting organization of the ECM. Most conspicuous is the subepidermal membrane complex (SMC), and the major part of the ECM is present in this structure, which consists of a limiting basal lamina on each side of a central thick filamentous layer, probably of a collagenous nature. Distinct anchoring filaments are found as part of the SMC. A basal lamina is also observed in connection with the gastrodermal cells. The mesoderm is represented by a loose, ill‐defined parenchyma, without filaments. The SMC is discussed in relation to subepidermal basal matrices occurring in turbellarians and enteropneusts, the two groups to which a relationship toXenoturbellapreviously has been suggested. Comparisons between the ECM inXenoturbellaand in turbellarians do not support the notion of a relationship between these groups. Conversely, the present study strengthens previous indications of distinct similarities between certain characteristics of the epidermis and the SMC present in both enteropneusts and inXenoturbell

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1986.tb00854.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThe electrocardiogram ofMyxine glutinosais described and its events related to systole in the sinus venosus, atrium and ventricle. Intraatrial, ventricular, ventral aortic and dorsal aortic pressures are presented. Ventricular systolic pressure was 10.3 ± 2.0 cm H2O; average dorsal aortic pressure was 7.0 ± 1.7 cm H2O. The resistance of the gill vessels caused a loss of 28% of the ventral aortic pressure. The conclusion is drawn that the basic mechanism of the heart ofMyxineis like that of fish and higher vertebrates, and that the low pressure it develops is to be ascribed to structural and functional features of the myocardiu

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1986.tb00855.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1986.tb00856.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY