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  • Wiley-Blackwell  (3)
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  • 1
    Electronic Resource
    Electronic Resource
    Structure of the ovotestis and evidence for heterosynthetic incorporation of yolk precursors in the oocytes of the nudibranch mollusc, Spurilla neapolitana (1989)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 201 (1989), S. 105-118 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The ovotestis of Spurilla neapolitana consists of a series of spherical lobes, each of which is composed of radially arranged, sac-like acini or follicles. The male and female portions of each acinus are separated by ovarian follicle cells and testicular accessory cells. A thick basal lamina serves as a barrier between adjacent acini. The surface of each ovotestis lobe is covered by several layers of myoepithelial cells resting on a connective tissue layer. Developing oocytes are intimately associated with follicle cells except in the last stages of vitellogenesis. Follicle cells are characterized by the presence of extensive arrays of rough endoplasmic reticulum (RER) and Golgi complexes and may play a role in vitellogenesis. An ultrastructural analysis of vitellogenesis suggests that oocytes utilize both auto- and heterosynthetic mechanisms of yolk formation. Autosynthetsis is suggested by the activity of the Golgi complex and RER, while heterosynthesis is indicated by high levels of endocytotic activity by the oocyte. Follicle cell development and high endocytotic activity in the oocytes may be a reproductive adaptation to accelerate yolk synthesis, resulting in more rapid egg production.
    Additional Material: 28 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1052010202
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  • 2
    Electronic Resource
    Electronic Resource
    The ultrastructure of oogenesis and yolk formation in Labidocera aestiva (Copepoda: Calanoida) (1984)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 179 (1984), S. 33-46 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Yolk formation in the oocytes of the free-living, marine copepod, Labidocera aestiva (order Calanoida) involves both autosynthetic and heterosynthetic processes. Three morphologically distinct forms of endogenous yolk are produced in the early vitellogenic stages. Type 1 yolk spheres are formed by the accumulation and fusion of dense granules within vesicular and lamellar cisternae of endoplasmic reticulum. A granular form of type 1 yolk, in which the dense granules within the cisternae of endoplasmic reticulum do not fuse, appears to be synthesized by the combined activity of endoplasmic reticulum and Golgi complexes. Type 2 yolk bodies subsequently appear in the ooplasm but their formation could not be attributed to any particular oocytic organelle.In the advanced stages of vitellogenesis, a single narrow layer of follicle cells becomes more developed and forms extensive interdigitations with the oocytes. Extra-oocytic yolk precursors appear to pass from the hemolymph into the follicle cells and subsequently into the oocytes via micropinocytosis. Pinocytotic vesicles fuse in the cortical ooplasm to form heterosynthetically derived type 3 yolk bodies.
    Additional Material: 25 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1051790105
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  • 3
    Electronic Resource
    Electronic Resource
    Ultrastructure of the “pigment knob” of Pleuromamma spp. (Copepoda: Calanoida) (1988)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 197 (1988), S. 315-326 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The calanoid copepod genus Pleuromamma is easily distinguished from all other copepods by the presence of a rounded, dark-red cuticular structure ( = pigment knob) that protrudes from the left or right side of the second thoracic segment in both sexes. The present study of the pigment knob reveals a complex ultrastructure consisting of various cell types within three distinct areas that are bathed by hemolymph from the lateral sinus. The knob is covered by a greatly expanded cuticle through which a pore passes. The pore appears to connect with a centrally positioned pigment cell containing a large mass of darkly staining granules. This suggests that the knob may have a secretory function. Observations of live animals and dissected pigment knobs, however, indicates that the knob does not secrete a luminescent material nor does it luminesce internally.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1051970306
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