rhopalium


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rhopalium

[rō′pāl·ē·əm]
(invertebrate zoology)
A sense organ found on the margin of a discomedusan.
References in periodicals archive ?
[T.sub.4], [T.sub.6], [T.sub.8], [T.sub.10], [T.sub.12], and [T.sub.14], with [T.sub.0] being the initial time of the amputation of the rhopalium and the subscripts representing the number of days since amputation.
At [T.sub.4], the development of the rhopalium had begun, and it was visible at the tip of the stalk as an increase in cell density.
In the period between [T.sub.2] and [T.sub.4], the first RF-LIR cells started to appear in the rhopalium near the base of the stalk (Fig.
For probing specific areas of a rhopalium, a 0.5-mm-diameter optic fiber was held in a micromanipulator close to the tissue being stimulated.
On- and off-responses were recorded with suction electrodes attached to the aboral surface of a rhopalium, near the attachment of the rhopalial stalk--the location of swim pacemakers (Fig.
First, in the region adjacent to a rhopalium, the neurites had a preferred orientation leading from the rhopalium (Fig.
Tubulin-IR staining of the rhopalia was hard to evaluate since the entire rhopalium tended to label.
In the region of the rhopalium, some neurons turned radially to extend into a compressed network within the smooth muscle band.
Signals from one rhopalium could easily travel from one bell quadrant to the next through the nerve ring and through the nerve net.
Each rhopalium is attached to the bell by a stalk and resides within a small exumbrellar indentation in the bell, referred to as a niche.
What little is known about the neural circuitry of the rhopalium comes from the work of Berger (1898), Yamasu and Yoshida (1976), Laska and Huendgen (1984), Parkefelt et al.
From a functional point of view, this muscle organization would curl the rhopalium inward, away from the opening of the rhopalial niche, and hide it behind the small loop of exumbrellar tissue (hood) that partially covers the opening.