Polyploidy as a chromosomal component of stochastic noise: variable scalar multiples of the diploid chromosome complement in the invertebrate species Girardia schubarti from Brazil / Poliploidia como componente cromossômico de ruído estocástico: variações escalares múltiplas do componente cromossômico diploide do invertebrado Girardia schubarti ocorrente no Brasil

Abstract Chromosome stoichiometry, a form of genetic plasticity, specifically refers to variation in the standard diploid genomic composition of an individual or species. In the present work, freshwater planarians (Girardia schubarti) were analyzed to recognize variations in chromosomal stoichiometry especially of complete ploidal change between specimens, within specimens and between cells within specimens and any relations they might have with selected components of phenotypic plasticity. Homoploid polyploids for the group reached rational scalar multiples (e.g. tetraploids) or irrational scalar multiples (e.g. triploids). Karyotypic mosaics emerged where individual cells presented polyploid multiples in arithmetic and geometric progressions. Ploidal multiplicity, a chromosomal component of stochastic noise, had positive phenotypic effects (increased dimensions) on morphologic criteria of body length, body width and dorsal surface reflecting a significant genotypic plasticity (GP) and robust phenotypic plasticity (PP). Variable but significant association of genotypic plasticity with robust phenotypic variance suggests kinetics of phenotypic homeostasis that is species-specific permitting phenotypic adaptability to environmental variables by means of GP. That association is diminished, deactivated or lost in more advanced and more complex organisms.

Resumo A estequiometria cromossômica, uma forma de plasticidade genotípica, representa variações na composição genômica diploide de um indivíduo ou espécie. Planárias límnicas (Girardia schubarti) foram analisadas para verificar a estequiometria cromossômica, especialmente alterações na ploidia entre espécimes, em cada espécime e entre células do mesmo espécime, além de relações dessas alterações com a plasticidade fenotípica. Espécimes poliploides homoploides apresentaram múltiplos escalares racionais ou irracionais, tais como triploides. Mosaicos cariotípicos ocorreram quando células apresentaram poliploides múltiplos em progressões aritméticas e geométricas. Nas planárias estudadas, a multiplicidade ploidal, um componente cromossômico de ruído estocástico, apresentou efeitos fenotípicos positivos, causando aumento das dimensões dos indivíduos, tais como comprimento corporal, largura do corpo e superfície dorsal, indicando plasticidade genotípica (GP) significativa e plasticidade fenotípica (PP) robusta. Associações significativas da plasticidade genotípica com variâncias fenotípicas robustas, embora variáveis, sugerem que a homeostase fenotípica, a qual é espécie-específica, possibilita adaptações a variáveis ambientais através da GP. Tal associação apresenta-se reduzida, desativada ou perdida em organismos mais complexos.

Polyploidy as a chromosomal component of stochastic noise: variable scalar multiples of the diploid chromosome complement in the invertebrate species Girardia schubarti from Brazil.

Chromosome stoichiometry, a form of genetic plasticity, specifically refers to variation in the standard diploid genomic composition of an individual or species. In the present work, freshwater planarians (Girardia schubarti) were analyzed to recognize variations in chromosomal stoichiometry especially of complete ploidal change between specimens, within specimens and between cells within specimens and any relations they might have with selected components of phenotypic plasticity. Homoploid polyploids for the group reached rational scalar multiples (e.g. tetraploids) or irrational scalar multiples (e.g. triploids). Karyotypic mosaics emerged where individual cells presented polyploid multiples in arithmetic and geometric progressions. Ploidal multiplicity, a chromosomal component of stochastic noise, had positive phenotypic effects (increased dimensions) on morphologic criteria of body length, body width and dorsal surface reflecting a significant genotypic plasticity (GP) and robust phenotypic plasticity (PP). Variable but significant association of genotypic plasticity with robust phenotypic variance suggests kinetics of phenotypic homeostasis that is species-specific permitting phenotypic adaptability to environmental variables by means of GP. That association is diminished, deactivated or lost in more advanced and more complex organisms.