. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. Release of Gonad Stimulating Factor AMP -»cAMP adenylate cyclase Pedicle. Release of Oocyle Maturing Factor Follicle cell •Germinal vesicle Oocyte in Ovary Figure 5. (Left) Diagram of the anterior region ofGloititlia with one of its valves removed, showing the relative positions of the lophophore and ovary. They are in communication via the animal's coelomic space. (Upper right) Enlarged diagram of lophophore tentacle showing the release of gonad-stimulating factor. In this diagram, the factor is shown being released from a
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. Release of Gonad Stimulating Factor AMP -»cAMP adenylate cyclase Pedicle. Release of Oocyle Maturing Factor Follicle cell •Germinal vesicle Oocyte in Ovary Figure 5. (Left) Diagram of the anterior region ofGloititlia with one of its valves removed, showing the relative positions of the lophophore and ovary. They are in communication via the animal's coelomic space. (Upper right) Enlarged diagram of lophophore tentacle showing the release of gonad-stimulating factor. In this diagram, the factor is shown being released from a nerve cell process. (Lower right) Enlarged view of oocyte in ovary. The gonad-stimulating factor from the lophophore is shown stimulating cAMP synthesis in follicle cells. These cells then produce an oocyte-maturing factor that acts on oocytes, causing germinal vesicle breakdown. that normal spawning is triggered when a cell type in the lophophore secretes a hormone with oocyte-maturing ac- tivity into the body cavity. Storch and Welsch (1976) de- scribe the ultrastructure of the lophophore and tentacles of the related genus Lingula, and Hay-Schmidt (1992) describes the larval lophophore, with special reference to the nervous system, in Lingula and Glottidia. At present, it is not clear what cell types in the lophophore produce the oocyte-maturing activity. The lophophore is well in- nervated, and a neurosecretory product is certainly a pos- sibility. In polychaetes and asteroids nerve cells produce hormones that play a role in oocyte maturation. The lo- phophore hormone then acts on a somatic cell in the ovary, presumably the follicle cell, perhaps increasing its cAMP levels. This leads to the release of another hormone that acts over a much smaller distance on large oocytes to trigger their maturation. Figure 5 outlines this hypo- thetical endocrine pathway. The oocyte-maturing hor- mone from the lophophore may also act on the follicle cells, causing them to retract, there
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
