Superoxide dismutase, thermal respiratory acclimation, and growth in an earthworm, Eisenia foetida.

The superoxide dismutase activity units/mg protein were determined for earthworms (Eisenia foetida) acclimated at 15°, 22.5° and 30°C. Worms acclimated at 15° gave a value of SOD units significantly lower than those acclimated at 30°. Those at 22.5° gave an intermediate value. SOD activity units of the anterior, mid and posterior regions showed no indication of the classical U-shaped axial gradient of respiration. SOD levels increased as O2uptake increased, though to a lesser extent, indicating that SOD levels are somehow tied to metabolic rate even if not in a one to one relationship. The increased ratio of SOD/specific metabolic rate of 15° compared to 30° acclimates implies that at 15° worms have more protection against the superoxide radical and thus would be expected to survive longer.

On the non-hormonal control of the termination of regeneration.

Simultaneous amputation at three different anterior and three posterior levels in the earthworm Eisenia foetida did not produce any measurable effect on the number of segments regenerated posteriorly compared to controls with intact heads. In every group, the number of segments formed depended only on the level of the posterior cut, declining by ten every time the level of the posterior cut was moved ten segments further from the head end. Repeated anterior amputation to prevent regeneration of the brain and subpharyngeal ganglia was without effect. No consistent differences were observed in the anterior neurosecretory cells either at the start or the end of regeneration. These results are discussed in relation to the "progress zone theory," the limited clonal cell life theory, and the theory of "sequential cumulative inhibition." It is concluded that the information determining the number of segments regenerated posteriorly resides in the tissues adjacent to the cut surface.