To determine the effect of asexual reproduction by transverse fission on the
population structure of holothurians, ensities and individual weights of
Holothuria atra (JÄÄger,1833)and
Stichopus chloronotus (Brandt, 1835)were measured over a
26-month period on near-shore reefs of the Great Barrier Reef. Densities of
H.atra (0.01—0.69 individuals m
–2 )and S. chloronotus
(0.11—1.67) did not increase during periods of intense asexual
reproduction, and the density on each reef remained relatively stable.The
effect of fission was clearly visible in the weight —frequency
distributions of both species. The average individual wet weight in each
population declined (H. atra from 105/134 g to
64/94 g in two respective populations;S. chloronotus
from 128/302 g to 82/190 g in two respective populations) with the
onset of fission in early winter, and more individuals in the weight range of
fission products were found. The biomass followed the seasonal trend of the
average weights for both species, with minimum values in winter. A conceptual
model based on these and previous findings identified five possible factors
(mortality, habitat stability, optimum individual size, food availability,
larval supply) involved in promoting or repressing transverse fission, and the
model indicated the consequences for the population.
Papers from the Echinoderm Conference. 4. Sexual and asexual reproduction of Holothuria atra Jaeger at Heron Island Reef, Great Barrier Reef