Responses in Growth Mortality, and Reproduction to Variable Food Levels by the Rotifer, Asplanchna Girodi

• Published in: Ecology (Durham) Vol. 62; no. 6; pp. 1585 - 1596
• Main Authors: Robertson, J. Roy, Salt, George W.
• Format: Journal Article
• Language: English
• Published: Brooklyn, N.Y., etc Ecological Society of America 01-12-1981; Duke University Press; Brooklyn Botanic Garden, etc
• Subjects: Asplanchna; Ecological competition; Fecundity; Food; Food availability; Food security; Freshwater; Longevity; Mortality; Population density; Population ecology; Zoology
• ISSN: 0012-9658; 1939-9170
• DOI: 10.2307/1941514

We have determined the changes in fecundity, mortality, and growth of the ploimate rotifer, Asplanchna girodi, in response to variations in food density. Rotifers were raised from birth on either fixed allotments of Paramecium tetraurelia or on allotments that varied temporally. Fecundity, growth rates, and size of the rotifer at the time of birth of the first offspring varied directly with food level. Longevity and age at the birth of the first young varied inversely with food level. The size of offspring remained constant regardless of parental food intake. Individuals switched from low to high food rations produced more offspring than those given a high ration from birth. The per capita death rate was insensitive to food level, but the birth rate varied directly with food level. Young individuals were better able to resist starvation than adults. These responses of A. girodi to varying resource densities are interpreted as being adaptive in environments with temporally varying food resources. When food levels are high, many young are produced and act to buffer the population against a decline in numbers when the food levels are reduced. The restoration of higher food levels causes the starved individuals to respond with high fecundities, which act to restore population densities to previous levels. In all resource environments, individual fecundity is adjusted to produce young with high changes of survival and reproduction.