LIFE-HISTORY AND POPULATION-DYNAMICS OF KINBERGONUPHIS-SIMONI (POLYCHAETA, ONUPHIDAE)

The relationship between life-history characteristics and population dynamics were investigated in the onuphid polychaete Kinbergonuphis simoni (Santos, Day and Rice) between 1982 and 1987. The studied population is located in Upper Tampa Bay, Florida, USA. This worm attains sexual maturity at 5 to 10 mo of age, depending on temperature. Several consecutive broods are produced during a female's life time, with 7 to 26 young per brood. Adults die in June-July after the breeding season. Generations of breeding individuals do not overlap and the replacement of generations occurs in July-August. Only one extended breeding season is experienced per life time. Life span does not exceed 2 yr. Field population density in 1982 was high in fall and spring (2000 to 9000 individuals/m2), low in summer (1600 individuals/m2), and slightly depressed in winter (2500 to 4000 individuals/m2). Changes in population density may be explained by seasonal, temperature-controlled changes in instantaneous birth and death rates. Birth rates are high in fall and spring, while death rates are high in early summer. Death of juveniles contributes to the winter density decrease.