Description:-
Large, sac-shaped organisms; transparent.
Asplanchna brightwelli exhibits polymorphism. Tocopheral (vitamin E) in body tissue is required to reproduce sexually. When tocopheral is not present in diet, all females are saccate (sac-shaped) and reproduce by diploid, parthenogenesis (amictic). After consuming tocopheral in prey items, the saccate females produce female offspring that are larger and have outgrowths. These outgrowths protect the females from cannibalism. These outgrowths are extended by hydraulic pressure when the rotifer draws-in its corona. This feature increases the animal's size and difficulty in handling when attacked by predator.
Females can reproduce sexually for brief periods but usually reproduce parthenogenetically. During the sexual reproduction phase, mictic females produce eggs having two polar bodies upon maturity. If these eggs are unfertilized (haploid and parthenogenitically produced) they develop into males. If fertilized the eggs (diploid) develop into thick-walled resting eggs. These resting eggs hatch into amictic females. Asplanchna brightwelli can be either “long-lived” or “short-lived”, depending on both their genotype and the temperature of their environment. Long-lived Asplanchna brightwelli have a low rate of reproduction over a longer period. Short-lived individuals produce many offspring over a shorter period. While the short-lived Asplanchna brightwelli reproduce at a higher rate the long-lived individuals produce more offspring over time. It is energetically costly to reproduce many offspring over a short period but there is a high risk of mortality when older females reproduce.
References:-
Gopakumar, G and Jayaprakas, V (2003) Community structure and succession of brackishwater rotifers in relation to ecological parameters Journal of the Marine Biological Association of India The Marine Biological Association of India, Cochin 45(1) 20-30 Available at - NIO, Goa
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