ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    ISSN: 1432-0878
    Keywords: Gametogenesis polychaete ; Oogenesis ; Peritoneum ; Nurse cell ; Vitellogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Oogenesis in Typosyllis pulchra begins with a short proliferative gonial phase. Gonial clusters, consisting of six to eight syncytial sibling cells, are surrounded by gonial peritoneum and are eventually liberated into the coelom. At about the same time as the onset of the coelomic phase, one gonial cell in each cluster differentiates, begins to accumulate yolk and increases in size, eventually to become a mature oocyte. Yolk is composed of lipid droplets and membranebound protein granules. The protein component appears to be at least partially synthesized by the oocyte although there are some signs of endocytosis. Nurse cells and peritoneal cells are apparently able to manufacture some protein that may also be utilized by the oocyte. The nurse cells maintain cytoplasmic continuity with the oocyte, and mitochondria and ribosomes are often seen within the intercellular bridges between oocyte and nurse cell. Immediately prior to spawning, oocytes undergo prematuration and cytoplasmic reorganization. Ultrastructural changes which occur during oocyte growth and maturation are described.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 1432-0878
    Keywords: Gametogenesis polychaete ; Stolonization ; Gonad ; Gonial cell ; Spermiogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Typosyllis pulchra reproduces by the production of three to four gamete-bearing stolons (schizogamy) during consecutive 30-day periods. Although gonads are found in a large number of segments, only those in the posterior-most segments produce gametes and become incorporated into the developing stolon. The more anterior gonads remain undifferentiated and probably sexually undetermined until they are needed in future stolonizations. Gonial cells, which will eventually become either male or female, are ultrastructurally identical at the onset of each stolonization period. Spermatogenesis is marked by a short proliferative period followed by differentiation and spermiogenesis. The first ultrastructural signs of spermatogenesis were found in coelomic spermatogonia on day 10 of stolon formation. Spermatogonia are joined by intercellular bridges, which are maintained until the early spermatid stage. Synaptonemal complexes mark the onset of meiosis, which is apparently synchronized in the syncytial clusters of primary spermatocytes. Spermiogenesis occurs during the final 10 days of stolonization and a variety of stages is present within a single animal. All sperm mature by the time the stolon detaches. Acrosome formation and nuclear condensation are described in addition to the ultrastructure of mature sperm.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...