Additional components of the swim system include the velarium, which narrows the bell opening during swim contractions, and the perradial frenula, which buttress the velarium but also actively contract with each swim pulsation (Gladfelter, 1973).
Preliminary evidence suggests that the threshold for activation of the tentacles is similar when the stimulating electrode is placed in the center of a subumbrellar quadrant or on a perradial muscle strip (radial muscle with condensed nervous components; Eichinger and Satterlie, 2014), suggest ing the primary conducting path is indeed diffuse.
Gonads on perradial canals, stretching margin to subportion gastric peduncle, well developed on medial section of each perradial canal, and undifferentiated on first portion of gastric peduncle.
Las gonadas se ubican en los canales perradiales y se extienden desde cerca del margen umbrelar hasta la porcion subterminal del pedunculo gastrico; estan muy desarrolladas en la region media de cada uno de los canales perradiales, y en la primera porcion del pedunculo gastrico son indiferenciadas y delgadas.
The motor nerve net of the perradial frenula is also notable in that neuronal density appears greater than that of the velarium or subumbrella (based on qualitative assessments; Satterlie et al., 2005).
The perradial frenula are three-dimensional muscle sheets, oriented perpendicular to the 2-dimensional subumbrella and velarium.
Four perradial and four interradial rhopalia in deep pits in subumbrella 1.7 cm (33% of marginal bell radius [=5.15 cm] from the bell margin.
Four perradial and four interradial rhopalia in deep pits, surrounded by two thickened lips in subumbrella, [approximately equal to]27% of marginal bell radius (= 8.19 cm) from bell margin; rhopaliar pit depth [approximately equal to]1 mm, rhopaliar pit width [approximately equal to] 4.2 mm, rhopaliar pit length [approximately equal to] 6.9 mm; rhopalium has simple statocyst without obvious ocellus (Fig.
The lips are longer in the perradial
plane, giving the mouth a scalloped appearance.
However, both Lucernaria and Lucernariopsis lack perradial
anchors and have a single-chambered peduncle, whereas Haliclystus has anchors and a four-chambered peduncle.
Manubrium fleshy, rigid; rectangular, pyramidal, or rounded in side view; variably ruffled at 4 corners; width approximately 1/3 of bell diameter; with stiffened, whorled, perradial
Rhopalia interradial and perradial
, and set into cones approximately 1 cm from margin of bell.