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 ?
Light-off impulses, recorded from the nerve ring, were up to 25 mV in amplitude and occurred 1:1 with the impulses of the stimulated rhopalium and rhopalial stalk (Figs.
Attachment of the same electrode to an adjacent area of the rhopalium yielded no such activity (Fig.
On-responses were not recorded in the nerve ring; however, their amplitude was small in the illuminated rhopalium, so they may have escaped detection.
Tubulin-IR staining of the rhopalia was hard to evaluate since the entire rhopalium tended to label.
The terminal end of each rhopalium contains a statolith, but it is covered with a tightly adhering epithelium.
Signals from one rhopalium could easily travel from one bell quadrant to the next through the nerve ring and through the nerve net.
The frenulum was thought to serve a structural role (buttress) in stabilizing the velarium during a swim contraction (Gladfelter, 1973), yet its position at the perradius just opposite the rhopalial niche is well suited to receive direct motor commands from the adjacent rhopalium.
Brightly stained FMRFamide-IR cells can be found in the pacemaker region of each rhopalium and at the base of each pedalium.
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.
2006) and the bilateral neural organization of the rhopalium (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.