Is the righting response a useful indicator of functional well-being in the green sea urchin, Strongylocentrotus droehachiensis?

The righting coefficient of individual Strongylocentrotus droebachiensis varied unpredictably from day to day, and in successive trials on the same day. In another set of trials, on samples obtained by either dredging or SCUBA diving, there was no statistically significant (P > 0.05) relationship between the activity coefficient and infection by the endoparasitic nematode Echinomermella matsi. A weak (R² = 0.2), but statistically significant (P < 0.01), negative linear relationship between righting coefficient and body size (wet weight or test diameter) or gonad size (wet weight) was limited to non-infected sea urchins obtained by SCUBA diving. The righting coefficient was not correlated with the gonad index or parasite abundance of the sea urchins. These results are contrary to claims in the recent literature.