A life table study on three genetic strains ofOphryotrocha diadema(Polychaeta, Dorvilleidae)

Abstract

A life-table study was performed on three strains of Ophryotrocha diadema. The wild type strain, YY (yellow eggs), was compared with a recessive mutant strain, ww (white eggs), and the F1, hybrid, Yw. The viability of the YY strain was greater than that of the ww strain. The hybrids were intermediate. Expectation of life. e., of zygotes were: YY 27.9, Yw 19.1, and ww 15.1 wk, respectively. The total outcome of reproduction followed the same pattern; the net reproductive rates, R 0, were related as 1:0.62:0.47 for YY: Yw: ww. Reproduction began in the fourth week. A maximum reproductive output during the next 4 wk was followed by a fast decline. The intrinsic rate of natural increase, r, was 0.880 per week for the YY strain, 0.903 for the Yw strain and 0.872 for the ww strain. For all strains, the first 7 wk of reproduction contributed more than 99% of the Lotka equation σ e −rx l x m x = l, i.e., l x m x values at older ages would not substantially affect population growth. In this 7–wk period (and the pr...