The effects of obstructing the madreporite on [Delta]WI, BWI, and GWI of test and control animals were evaluated with the Mann-Whitney U test, using the z statistic to estimate significance.
Substantial numbers were also found within the water vascular system, especially in the madreporite and stone canal [ILLUSTRATION FOR FIGURES 1-12 OMITTED].
Table I Levels of FID (percentage of medium concentration) in the PCF of madreporite obstructed (Test) and unaltered (Control) Strongylocentrotus pallidus after incubation in FID seawater Days in medium Weight (g) 1 2 3 4 5 Test 87.5 0 0 0 0 0 112.4 0 155.3 0 Control 80.7 0 0 0 0 0 94.7 0 116.1 0 Uptake of FID
These experiments with fluorescent microbeads and soluble tracer (FID) show that in contrast to previous work in asteroids (Ferguson 1989, 1990b) entry of seawater into the madreporite of echinoids is very limited.
Is there any consistent flow of seawater at all into the sea urchin madreporite? Recent work by Tamori et al.
In working with the starfish Pisaster ochraceus, the transmadreporite seawater influx was estimated from the rate of weight loss in animals with an obstructed madreporite (Ferguson, 1992).
Does such a low rate of madreporite seawater entry have any functional significance?
That was the case, as notable radioactivity was found in the lining cells of the madreporite ampulla [ILLUSTRATION FOR FIGURES 19, 20 OMITTED].
It was found that surgical obliteration of the madreporite, ampulla, and lower stone canal had very little effect on tube foot function for at least a week.
This study has shown that Ophioderma has a complex water vascular system, but one in which the passages from the exterior (the madreporite pores) appear to be of minor importance compared to provisions for internal recirculation of fluid via the axial sinus and its extensions.
[Net negative coelomic pressures have recently been described in sea urchins by Ellers and Telford (1992), but these are produced by a different mechanism.] It appears, then, that Ophioderma has little need to take up seawater through its madreporite either to support its tube feet or to maintain its perivisceral coelomic fluid, and it has a limited ability to do so.
Cytology and function of the madreporite systems of the starfish Henricia sanguinolenta and Asterias vulgaris.