Stress and changes in the blood of newts,Notophthalmus viridescens,during early regeneration

Summary During the summers of 1984 and 1985, adult red-spotted newts,Notophthalmus viridescens, were maintained in the laboratory at 23°±0.5°C under natural photoperiods. From each of the experimental animals, the right forelimb was amputated just proximal to the elbow. Control newts were not manipulated surgically. Eight, 15, and 22 days after the time of amputation, equal numbers of regenerating and control animals were sacrificed, and blood smears of each individual were prepared with Wright's stain.Mean differential counts of leukocytes of the two groups of newts indicated that the relative number of neutrophils increased and the relative number of lymphocytes decreased in the regenerating animals as compared to their controls (Fig. 1 and Fig. 2). Earlier studies had shown that lymphopenia and neutrophilia occur in red-spotted newts treated with hydrocortisone or with ACTH or subjected to environmental stress (Bennett and Daigle 1983). Consequently, it is suggested that amputation and/or early regeneration may stimulate the increased production of hormones associated with stress in vertebrates, which may, in turn, influence regeneration, itself, and that the detailed study of the distribution of leukocytes inNotophthalmus viridescens may provide an assay with which to study the regulation of regeneration in this species.