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Gametogenesis and fertilization in Dirofilaria immitis (Nematoda: Filarioidea)

  • C. J. Delves (a1), R. E. Howells (a1) and R. J. Post (a1)
Abstract
SUMMARY

Gametogenesis in Dirofilaria immitis has been studied principally by means of the aceto-orcein chromosomal squash technique, but with additional ultrastructural observations. A terminal germinative zone, in which a continuous and rapid division of germ cells occurs, has been identified in the gonoduct of both male and female worms. Approximately 20% of cells within these germinative zones were in arrested mitotic division following the incubation in vitro of excised gonads in 0·01% colchicine for 4 h. All primary spermatocytes within a 1–2 cm length of the testis proximal to the germinative zone were at the prophase of the 1st meiotic division. In the corresponding region of the ovary, the primary oocytes were similarly at the prophase of the 1st meiotic division in 75% of female worms examined but in the remaining 25% all primary oocytes possessed markedly less condensed, probably interphase nuclei. A possible hormonal control of the cyclical development of primary oocytes, but not primary spermatocytes in D. immitis is suggested. In most of the remaining length of the gonoducts beyond this region of cells at meiotic prophase, the chromatin material of both primary spermatocytes and oocytes is decondensed. Recondensation of chromosomes in the spermatocytes is observed just prior to entry into the seminal vesicle, where meiosis I is completed and meiosis II takes place. In the primary oocyte, completion of meiosis only occurs after fertilization within the seminal receptacle by an entire male gamete. Following the 2 meiotic divisions in the oocyte and subsequent extrusion of the 2 polar bodies, the haploid chromosome complement of the female unites with that of the male, re-establishing the diploid number of the zygote (2n = 10). Male chromosomes within the oocyte remain visible throughout late oogenesis and fusion occurs without the formation of pronuclei.

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K. Awadzi , H. Schulz-Key , R. E. Howells , D. R. W. Haddock & H. M. Gilles (1982). The chemotherapy of onchocerciasis, VIII. Levamisole and its combination with the benzimidazoles. Annals of Tropical Medicine and Parasitology 76, 459–73.

H. W. Beams & S. S. Sekhon (1972). Cytodifferentiation during spermiogenesis in Rhabditis pellio. Journal of Ultrastructure Research 38, 511–27.

W. E. Foor (1968). Zygote formation in Ascaris lumbricoides. Journal of Cell Biology 39, 119–34.

H. Hirai , Y. Sakaguchi & I. Tada (1985). Chromosomes of Onchocerca volvulus and O. gutturosa. Zeitschrift für Parasitenkunde 71, 135–9.

D. Hirsch , D. Oppenheim & M. Klass (1975). Development of the reproductive system of Caenorhabditis elegans. Developmental Biology 49, 200–19.

J. E. Kimble & J. G. White (1981). On the control of germ cell development in Caenorhabditis elegans. Developmental Biology 81, 208–19.

C. C. Lee (1975). Dirofilaria immitis: ultrastructural aspects of oocyte development and zygote formation. Experimental Parasitology 37, 449–68.

J. J. Prestage (1960). The fine structure of the growth region of the ovary in Ascaris lumbricoides var. suum with special reference to the rachis. Journal of Parasitology 46, 6978.

A. Terry , R. Terry & M. J. Worms (1961). Dipetalonema witei, filarial parasite of the jird, Meriones libycus. The reproductive system, gametogenesis and development of the microfilaria. Journal of Parasitology, 47, 703–11.

A. C. Triantaphylloy & H. Hirschmann (1966). Gametogenesis and reproduction in wheat nematode Anguina tritici. Nematologica 12, 437–43.

A. C. Walton (1924). Studies on nematode gametogenesis. Zeitschrift für Zellen-und Gewebelehre 1, 167239.

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Parasitology
  • ISSN: 0031-1820
  • EISSN: 1469-8161
  • URL: /core/journals/parasitology
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