Population Growth in Planaria
نویسنده
چکیده
Planaria reproduce by transverse fission. Isolated worms increase in number exponentially, while social animals at the same density are inhibited in terms of numerical increase, but over a 25 day period undergo a larger increase in mass. Isolated posterior fission products reproduce faster than isolated anterior fission products. Regulation of population growth is independent of density over a 16-fold range and regulatory factors cannot be demonstrated in the medium. Regulation of population growth depends on direct contact between animals. Fission period varies from individual to individual and from period to period for a given individual. Doubling time is related to the absolute number of individuals comprising the population as follows: PN = (PM.N)/(K + N), where PN is the doubling period of a population of N individuals, PM is the doubling time of an infinitely large population, N is the number of individuals in the population, and K is the number of individuals in a population the period of which is one-half PM. At 220 -240 C PM is estimated to be 43.3 days and K is 1.87 individuals. A model system assumes that inhibitor flows through the population from animal to animal from the slowest to the fastest animal in the population thus acting to synchronize population increase as well as to determine the rate of population growth. A possible source of the inhibitor is discussed.
منابع مشابه
Population Growth in Planaria Dugesia tigrina (Gerard)
Planaria reproduce by transverse fission. Isolated worms increase in number exponentially, while social animals at the same density are inhibited in terms of numerical increase, but over a 25 day period undergo a larger increase in mass. Isolated posterior fission products reproduce faster than isolated anterior fission products. Regulation of population growth is independent of density over a ...
متن کاملPlanaria: Memory Transfer through Cannibalism Reexamined.
Planaria which have cannibalized untrained planaria exposed to photic stimuli only, handling only, or previous conditioning, all require significantly fewer trials in a conditioning situation than naive planaria.
متن کاملPhysiological controls of large‐scale patterning in planarian regeneration: a molecular and computational perspective on growth and form
Planaria are complex metazoans that repair damage to their bodies and cease remodeling when a correct anatomy has been achieved. This model system offers a unique opportunity to understand how large-scale anatomical homeostasis emerges from the activities of individual cells. Much progress has been made on the molecular genetics of stem cell activity in planaria. However, recent data also indic...
متن کاملNucleotides and Amino Acids in Planaria
Neither intact nor regenerating planaria incorporated any signiiicant amount of tritiated thymidine, tritiated L-leucine, or C14-Lleucine from free solution even over long periods of exposure. Tritiated thymidine was incorporated into regenerating rat liver and fed to planaria, but tritium hydrogen exchange rendered this method useless. A large incorporation of C14-uracil and C14-Lleucine into ...
متن کامل