Changes In Migration Research Articles

Migratory disorders and muscular changes in infancy

Migratory disorders and muscular changes in infancy

Response to experimental photoperiods by a migratory bunting, Emberiza melanocephala

Little is known about the effects of photoperiod on avian migrants that visit southeast Asia. In this paper, we report experiments performed on an emberizid finch, the Black‐headed Bunting Emberiza melanocephala, to investigate its photoperiodic responses under artificial photoperiods, and continuous light and darkness.Two series of experiments were performed with the photosensitive male birds. In the first series, different groups were exposed to seven different artificial photoperiods: 3L/21D, 6L/18D, 8L./16D, 11L/13D, 12L/12D, 15L/9D and 20L/4D, for 30 days. They were weighed and laparotomized at the beginning and end of the experiments. The birds responded to 12L/12D, 15L/9D and 20L/4D, but not to 3L/21D, 6L/18D, 8L/16D and 11L/13D. In the second series, photosensitive birds were placed under continuous light (LL) and dark (DD) conditions for 130 and 90 days. Periodic observations indicated that testicular growth and fattening followed by involution and fat‐depletion had resulted in birds under LL, indicating the onset of photorefractoriness, while DD had no effect either on gonads or fattening in the buntings.Our results demonstrate that light stimulation is a prerequisite to reproductive and metabolic activities (pre‐migratory and migratory changes, fattening and weight gain) in the Black‐headed Bunting, which has a photoperiodic threshold to these events at between 11 and 12 h daily photoperiods.

Changes in spleen histology in response to antigenic stimulation in the snapping turtle, Chelydra serpentine

Proliferative and migratory changes of lymphoid cells in the spleen were observed in turtles stimulated with KLH and maintained at 30 degrees C. Small foci of pyroninophilic lymphoblasts were first seen in the white pulp at about day 5. Progressive enlargement of these centers continued and peaked by days 8-12. By days 15-20 the white pulp returned to a normal (unimmunized) state, while the number of pyroninophilic cells, primarily plasma cells, increased markedly in the red pulp. At days 22-25, the number of plasma cells returned to normal levels and the spleen appeared normal for the remainder of the 60 day observation period. These events suggest that at 30 degrees C, the turtle is capable of a strong and prompt proliferative response in the white pulp sheaths, followed by migration and differentiation of lymphoblasts into plasma cells, in the red pulp. Observations of pyroninophilic cells in sinuses, venules and veins of the spleen and a concomitant depletion of cells in red pulp, further suggest a migration from the spleen to other sites. Following a second antigenic challenge, at day 60, no significant histological changes were observed at 30 degrees C. Nor were any changes observed following primary or secondary antigenic challenge, in animals maintained at 10 degrees C. These findings are discussed with regard to immunological memory and low temperature immunosuppression in ectothermic vertebrates.