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The Population Dynamics of the Planarian, Dugesia Tigrina
Author(s) -
Armstrong Joseph T.
Publication year - 1964
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.2307/1933849
Subject(s) - cannibalism , biology , planarian , ecology , population , reproduction , population density , zoology , density dependence , food shortage , hibernation (computing) , allee effect , predation , regeneration (biology) , demography , algorithm , sociology , computer science , microbiology and biotechnology , state (computer science)
Populations of asexual D. tigrina, a planarian, begun with 35 animals and maintained in finger bowls on constant food rations, increase to an equilibrium size which is then maintained without loss or replacement of individuals. The decline is natality leading to equilibrium is a consequence of increasing food scarcity and not of increasing animal density per se. Experimentally increasing reproductive efficiency merely accelerates population growth and raises equilibrium size. Mortality occurs almost exclusively as the cannibalism of newborn tails by mature worms. The rate of this mortality depends on a number of factors including animal density per se, but if fails to contribute to the progressive slowing of population growth. A morphological variant of D. tigrina was isolated which showed a high rate of cannibalism and a low rate of reproduction.