. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 266 G. FREEMAN sperm are added to these oocytes, the germinal vesicle does not break down and development is not initiated. However, studies of fixed oocytes, stained with DAPI fol- lowing exposure to sperm, indicate that sperm-egg fusion does occur in some cases. The lophophore contains a factor that induces oocyte maturation In a number of invertebrate and vertebrate animals, oocyte maturation in the ovary is controlled by hormones secreted by other organs (, Meijer, 1979a, b, for poly- chaetes and Shirai and Walker, 1
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 266 G. FREEMAN sperm are added to these oocytes, the germinal vesicle does not break down and development is not initiated. However, studies of fixed oocytes, stained with DAPI fol- lowing exposure to sperm, indicate that sperm-egg fusion does occur in some cases. The lophophore contains a factor that induces oocyte maturation In a number of invertebrate and vertebrate animals, oocyte maturation in the ovary is controlled by hormones secreted by other organs (, Meijer, 1979a, b, for poly- chaetes and Shirai and Walker, 1988, for asteroids). Organ extracts from sexually mature Glottidia were tested for their capacity to induce oocyte maturation. Organ extracts were prepared from gut, liver, lophophore (including the mouth and the first part of esophagus), mantle, ovary, and testis (see Hyman, 1959, for a description of these organs). A piece of ovary was incubated in extract for up to 3 h and examined during this period for germinal ves- icle breakdown of its oocytes. At the end of the incubation period, the piece of ovary was treated with calcium-free seawater to obtain free oocytes, and individual full-grown oocytes were examined for germinal vesicle breakdown by compressing them slightly under a coverslip and ex- amining them with a compound microscope. At least three experiments were done for each organ, testing extracts of that organ from three animals. In the case of the gut, liver, lophophore, and mantle, extracts from both sexes were tested. The only organ exhibiting oocyte-maturing activity was the lophophore. After 70-90 min of incubation in lo- phophore extract, the follicle cells around the oocyte re- tracted and the ovary dissociated into a pile of mature, full-grown oocytes and a residue composed of growing oocytes and follicle cells (Fig. 3). The germinal vesicles of these shed oocytes had broken down. DAPI staining of fixed oocytes showed that the chromosomes were con- densed at
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
