The role of oocyte maturation in the ontogeny of the fertilization site in the hydrozoan Hydractinia echinata
- 76 Downloads
In hydrozoans the sperm will fuse with the egg only at the site of polar body formation. The primary oocyte and maturing oocytes which have produced the first polar body cannot be fertilized even though maturing oocytes which have produced the first polar body attract sperm. These eggs do not acquire the ability to be fertilized until after second polar body formation. If either first or second polar body formation is inhibited or if first and second polar body formation do not take place in close proximity to each other, the fertilization site is not set up. Under normal circumstances the site of polar body formation takes place at the region on the maturing oocyte surface nearest the site where the germinal vesicle resided in the primary oocyte. When maturing oocytes are centrifuged prior to polar body formation, the site of polar body formation is frequently shifted so that it does not correspond to the site where it would be given off under normal circumstances. Under these conditions the shifted site of polar body formation is the only site where the egg can be fertilized, indicating that the fertilization site is selected during oocyte maturation.
Oocyte maturation in these hydrozoans is mediated by a hormone released by the somatic cells of gonophores as a consequence of bringing dark adapted gonophores into the light. The hormone acts directly on the oocyte to induce maturation. The oocyte only has to be exposed to the hormone for the first few minutes of the maturation process in order to complete the process of maturation.
Key wordsHydrozoan Fertilization site formation Role of polar bodies
Unable to display preview. Download preview PDF.
- Austin C (1965) Fertilization. Prentice Hall, Englewood Cliffs, New JerseyGoogle Scholar
- Ballard W (1942) The mechanism for synchronous spawning in Hydractinia and Pennaria. Biol Bull 82:329–339Google Scholar
- Beckwith C (1914) The genesis of the plasma-structure in the egg of Hydractinia echinata. J Morphol 25:189–251Google Scholar
- Carré D, Sardet C (1981) Sperm chemotaxis in siphonophores. Biol Cell 40:119–128Google Scholar
- Conklin E (1917) Effects of centrifugal force on the structure and development of the eggs of Crepidula. J Exp Zool 22:311–419Google Scholar
- Freeman G (1982) The ontogeny of the fertilization site in Hydractinia echinata (Hydrozoa). Biol Bull 163:372–373Google Scholar
- Guerrier P (1968) Origine et stabilité de la polarité animale-végetative chez quelques spiralia. Ann Embryol Morphol 1:119–139Google Scholar
- Honegger T (1981) Light and scanning electron microscopic observations of sexual reproduction in Hydra cornea. Int J Inv Reprod 3:245–255Google Scholar
- Honegger T (1983) Ultrastructural and experimental investigations of sperm-egg interactions in fertilization in Hydra cornea. Wilhelm Roux's Arch 192:13–20Google Scholar
- Ikegami S, Honji N, Yoshida M (1978) Light-controlled production of spawning-inducing substance in jellyfish ovary. Nature (Lond) 272:611–612Google Scholar
- Miller R (1974) Sperm behavior close to Hydractinia and Ciona eggs. Am Zool 14:1250Google Scholar
- Miller R (1981) Sperm-egg interactions in hydromedusae. In: Adams T, Clark W (eds) Recent Advances in Invertebrate Reproduction. Elsevier/North Holland, Amsterdam, pp 287–317Google Scholar
- Noda K, Kanai C (1981) Light and electron microscopic studies on fertilization of Pelmatohydra robusta. I. Sperm entry to specialized region of the egg. Dev Growth Differ 23:401–413Google Scholar
- Novikoff A (1938) Embryonic determination in the annelid Sabellaria vulgaris. II. Transplantation of polar lobes and blastomeres as a test of their inducing capacity. Biol Bull 74:211–234Google Scholar
- Shimizu T (1980) Cortical differentiation of the animal pole during maturation division in fertilized eggs of Tubifex (Annelida, Oligochaeta). Dev Biol 85:65–76Google Scholar
- Shirai H, Kanatani H (1980) Effect of local application of l-methy-ladenine on the site of polar body formation in starfish oocyte. Dev Growth Differ 22:555–560Google Scholar