madreporite


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madreporite

the porous opening to the hydrocoel in ECHINODERMS.
References in periodicals archive ?
In addition, an understanding of the arrangement of the primary skeletal structures during the early post-metamorphic stages of Asteroidea allows identification of the true homologies and ontogenetic patterns inferred from evolutionary models (the Ocular Plate Rule and the Madreporite Mode Appearance) (Mooi and David, 2000; Gale, 2011).
Formation of the madreporite is observed in juveniles at 88 days after fertilization (Fig.
The uniqueness of the madreporite creates an asymmetry within the
Initial orientation was standardized relative to the madreporite to minimize potential directionality bias (Polls and Gonor, 1975).
The relation of the madreporite to the physiological anterior end in the twenty-rayed starfish, Pycnopodia helianthoides (Stimpson).
During each 25-min trial, the position of the sea star (determined using the madreporite as a reference) was recorded by eye every 30 s.
Observers often assume that seawater is drawn in through the madreporite by the stone canal cilia to hydraulically extend the tube feet.
But in addition to this osmotic uptake, studies with fluorescent microbeads demonstrate that seawater does flow into the madreporite pores of asteroids (Ferguson, 1990b) and, to a lesser extent, of ophiuroids (Ferguson, 1995), and that it is distributed to peripheral parts of the water vascular system.
In addition, the madreporite may contribute water to the water vascular system and perivisceral coelom (Ferguson, 1989, 1990b).
One month later (mid-June), the young starfish possessed a well-developed buccal cavity, stomach, and pyloric caeca, which were easily observed across the transparent body wall on the oral surface [ILLUSTRATION FOR FIGURE 9L OMITTED] with the madreporite and anus on the aboral surface.
It is generally assumed, for example, that the madreporite admits seawater into the system, and that ciliary pumping by the stone canal connected to it forces the seawater taken in to flow out to the tube feet where it replenishes fluid losses due to their activity.
More recently, my own work with fluorescent molecular tracers and microbeads, and other methods, has shown that seawater does routinely enter the madreporite of all starfishes tested; but this uptake is not specifically directed at tube foot inflation.