During a previous study of lithocyte transport on balancers (8), I noticed that free lithocytes, dissociated from the statolith, are often whirled or spun about by water currents under the dome (Tamm, unpubl.
Lithocytes are transported along the ciliary surface to build the statolith of ctenophores.
Each lithocyte is filled with a membrane-bound calcareous concretion surrounded by a rim of cytoplasm and nucleus (Samassa, 1892; Krisch, 1973; Aronova, 1974; Tamm, 1982, 2014a, c; Noda and Tamm, 2014).
1) (Tamm, 2014c); and the addition of new lithocytes only at the two ends of the statolith by transport along the ciliary surfaces of the balancers (Noda and Tamm, 2014).
The beads somewhat resembled the aggregated lithocytes of living statoliths, but were much smaller relative to statolith size.
These stages of lithocyte development are found in the epithelial floor of all Mnemiopsis specimens examined, from early cydippid larvae to the largest adults (see below).
During this transport the attached lithocyte jiggles at the frequency of beating of the balancer it is riding on (Figs.
The function of dome ciliary motility may be related to the newly discovered process of statolith formation by lithocyte transport up the balancers (see Discussion).
In both ctenophores, this route of lithocyte delivery results in four clefts at the corners of the statolith for the supporting balancers.
Which member of a balancer pair is used to transport a newly released lithocyte could depend on a chance encounter with the closest balancer base, but evidence is lacking.
Comparing the kinetics of lithocyte formation (Fig.
The relation between lithocyte supply and demand is complicated by the absence of time or age data to correlate with our morphological measurements.