zona

The early vitellogenic oocyte was partially surrounded by follicle cells, which maintained intimate contact with the smooth oolemma of the oocyte.

A number of lipid droplets and the mitochondria appeared near the oolemma (Fig.

The insemination cones of both control and MT-inhibited trials were morphologically similar, and the sperm head and mitochondria passed through the oolemma and entered the egg cytoplasm within 4 min of binding (Fig.

Once the bulk of the axoneme passed through the oolemma, the sperm head frequently moved rapidly through the egg cytoplasm.

In addition, projections of the follicle cells also can attach to the oolemma of the oocyte by means of gap junctions that allow small molecules to pass between the follicle cells and the prophase-arrested oocyte (Anderson and Albertini, 1976; Patino and Purkiss, 1993; York et al., 1993).

The results suggest that (i) follicles need to be detached from the ovaries for ovulation and GVBD to occur and (ii) within 30-40 min after follicular detachment from the ovaries, oocyte maturation is triggered by a maturation-inducing substance that is transferred from the follicle cells to the oocyte via junctional complexes connecting follicle cells to the oolemma. The results of this investigation are compared to previously published data on brachiopods, and the events observed during in vitro maturation are discussed with respect to how oocyte maturation may be accomplished during normal development in the field.

Criteria for normal elevation were the continued separation of the HE from the oolemma, as viewed by light microscopy, and the presence of the bilayered structure indicative of normal HE assembly, as described by Pillai and Clark (1988).

In TEM preparations of eggs treated with polyoxin D, the HE was abnormal and collapsed to the oolemma surface [ILLUSTRATION FOR FIGURE 3B OMITTED].

ingentis eggs spawned into ASW, a distinct PVS was visible at 75 min postspawn [ILLUSTRATION FOR FIGURE 1 OMITTED], separating the oolemma from the elevated HE.

At 75 min postspawn, inhibitor-treated eggs had envelopes that were more refractile and less birefringent than the control eggs, and the envelopes often collapsed to the oolemma [ILLUSTRATION FOR FIGURE 4 OMITTED].