Critical thermal maxima and minima of the platyfish Xiphophorus maculatus Günther (Poecillidae, Cyprinodontiformes): a tropical species of ornamental freshwater fish

• Autor(a) principal: Prodocimo,Viviane
• Data de Publicação: 2001
• Outros Autores: Freire,Carolina Arruda
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Revista Brasileira de Zoologia (Online)
• Texto Completo: http://old.scielo.br/scielo.php?script=sci_arttext&pid=S0101-81752001000500007
• topic: Xiphophorus maculatus; temperature; critical thermal maxima and minima; acclimation; platyfish

Temperature as an environmental factor has been a frequent subject of study, since it affects either directly or indirectly all living organisms. The determination of thermal limits (critical thermal minima - CTmin and maxima - CTmax) for the tropical ornamental freshwater teleost Xiphophorus maculatus Günther, 1866 (platyfish) was performed after their acclimation to the following temperatures: 15, 20, 25, and 30ºC, for seven days. After this period, the water temperature was elevated or reduced at a rate of 0.125ºC/min until CTmax and CTmin could be determined as the temperature at which 50% of the animals had lost equilibrium. Mean values for CTmax and CTmin for the acclimation temperatures of 15, 20, 25, and 30ºC were respectively: 39.8,39.8,40.4,41.5ºC (CTmax), and 9.6, 12.8, 13.1, 16.0ºC (CTmin). CTmax and CTmin for X. maculatus were thus affected by acclimation temperature. This tropical species is more heat- than cold- tolerant and would not resist the typical low winter temperatures of southern Brazil. Platyfish can adapt to natural environments in regions of mean annual temperatures around 20-25ºC or be kept in aquaria with other ornamental species that accordingly prefer this temperature range.