ReeferAl
05/05/2004, 02:19 PM
It looked like a paragraph from a prior article found its way into the current one:
These worms have separate sexes, but they lack permanent gonads. The eggs and sperm form from the lining of the body cavity in the bottom part of the worm. When they are gravid, sperm and eggs are collected by the kidneys until the appropriate environmental cues are received. They broadcast their gametes into the surrounding water, where fertilization occurs. They undergo a development that is quite similar to some of the primitive mollusks. Those developmental patterns are what link the sipunculans to the mollusks in the discussions of animal evolution. At some time in the far distant past, some small worm probably had a minor mutation of some sort, and gave rise to two slightly different types of offspring. Both types were viable; one group was the ancestor to all mollusks, the other to all sipunculans. Asexual reproduction by fission also occurs in sipunculans, particularly in the tropical forms that are likely to be found aquaria.
Allen
These worms have separate sexes, but they lack permanent gonads. The eggs and sperm form from the lining of the body cavity in the bottom part of the worm. When they are gravid, sperm and eggs are collected by the kidneys until the appropriate environmental cues are received. They broadcast their gametes into the surrounding water, where fertilization occurs. They undergo a development that is quite similar to some of the primitive mollusks. Those developmental patterns are what link the sipunculans to the mollusks in the discussions of animal evolution. At some time in the far distant past, some small worm probably had a minor mutation of some sort, and gave rise to two slightly different types of offspring. Both types were viable; one group was the ancestor to all mollusks, the other to all sipunculans. Asexual reproduction by fission also occurs in sipunculans, particularly in the tropical forms that are likely to be found aquaria.
Allen