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

Abstract

ABSTRACT. Temperature as an enviromnental factor has been a frequent subject of study, since il arfects eilher directly or indirectly allliving organisms. The detelmination ofthelmallimits (criti caI thennal minima -CT min and maxima -CT max) for the tropical ornamental freshwater teleost Xiphophorus maculatus Günther, 1866 (platytish) was performed after their acc\imation to the following temperatures: 1 S, 20, 25, and 30°C, for seven days. After this period, the water temperature was elevated or reduced at a rale ofO. 12SoC/min unlil CTmax and CTmin could be delelmined as lhe temperature at which SO% ofthe animaIs had lost equilibrium. Mean values for CT max and CTmin for the acc\imation temperatures of 1 S, 20, 25, and 30°C were respectively: 39.8,39.8,40.4, 4l.S°C (CTmax), and 9.6,12.8,13.1, 16.0°C (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 ofsouthern Brazil. Platytish can adapt to natural environments in regions ofmean annual temperatures around 20-25°C or be kept in aq uaria with other ornamental species that accordingly prefer lhis lemperature range. KEY WORDS. Xiphophorus maculatus, temperature, criticaI thermal maxima and mini ma, acc\imation, platytish .The relevance of the temperature as an environmental parameter has been thoroughly evidenced in the literature. It is one of the most studied ecological factors, not only because it is relatively easy to measure, but also because it is a limiting factor for the chemical reactions on which vital functions are based (EVANS 1993; POUG H et aI. 1996; SCHMIDT-NIELSEN 1997). The effects oftemperature can be observed on animal movement, feeding, growth, and reproduction , among other functions (FERNANDES & RANTIN 1986a; BENFEY et aI. 1997).Fish are certainly no exception to the rule and their physiology is strongly affected by the temperature . In nature, fish occur along a re latively wide range of temperatures, from seawater freezing point (-1.8°C) until 37°C or even higher temperatures, such as 40°C or 41°C (HUTCHISON 1961; SCHMlDT -NIELSEN 1997), although obviously their occurrence in both extremes is relative ly low (DOUDOROFF 1942), and most species live under intermediate thermal regimes. The range of temperatures in the natural environment of animais living in different geographical areas obviously lead to differences in the temperatures they can tolerate experimentally (BRETT 1956), not only for fish but also for other ectothermic organisms.

Critical thermal limits of Poecilia caucana (Steindachner, 1880) (Cyprinodontiformes: Poeciliidae)

“…As with most studies reporting critical thermal limits Dalvi et al, 2009;Barrionuevo & Fernandes, 1995;Currie et al, 1998;Prodocimo & Freire, 2001), we focused on a single population of P. caucana. Because populations might be locally adapted or show long-term effects of diet and other environmental factors (Feminella & Mattheus, 1984;Atwood et al, 2003;Narum et al, 2013), the conclusions that follow regarding vulnerability to climate change are preliminary and subject to revision once more populations of this species are assessed.…”

“…Three species (N, Ns, and P) having data for only one acclimation temperature are represented by vertical lines. Pf = Prochilodus scrofa (currently Prochilodus lineatus), fry, and Ps = P. scrofa, adults (Barrionuevo & Fernandes, 1995); Ca = Carassius auratus (Ford & Beitinger, 2005); Cc = Catla catla and Cm = Cirrhinus mrigala ; Cp = Cyprinus carpio ; Danio rerio, transgenic breed, and D. rerio, wild (Cortemeglia & Beitinger, 2005); Sb = Siphateles bicolor (McClanhan et al, 1986); Lr = Labeo rohita Das et al, 2004); N = Notropis chrysocephalus, Ns = N. spilopterus, P = Pimephales notatus (Hockett & Mundahl, 1989); Ro = Rhinichthys osculus (Kaya et al, 1992); Hb = Horabagrus_brachysoma (Dalvi et al, 2009); Ip = Ictalurus punctatus (Currie et al, 1998); Pp = Pangasius pangasius (Debnath et al, 2006); Om = Oncorhynchus mykiss (Currie et al, 1998); Cv = Cyprinodon variegatus (Bennett & Beitinger, 1997); Pc = Poecilia caucana (this study); Xm = Xiphophorus maculatus (Prodocimo & Freire, 2001); Ms = Micropterus salmoides (Currie et al, 1998).…”

“…In addition, we estimated the thermal tolerance polygon for P. caucana and compared it to existing data on other tropical fish species. Although the available data are still too limited to reach any definitive conclusions about patterns of variation in thermal tolerance among tropical fishes, our work is one the first efforts to synthetize the existing information (Prodocimo & Freire, 2001). …”

Thermal Tolerance and Survival of Nile Tilapia and Blue Tilapia under Rapid and Natural Temperature Declination Rates

“…Historically, most research on thermal minima of tilapias and other fishes has used rapid declines in temperature, ranging from a fraction of 1°C per minute (e.g., Currie et al. ; Prodocimo and Freire ) to 1°C per hour (e.g., Cameron et al. ), and up to 0.5°C per day (Wilson et al.…”

“…Varying methodology in investigating thermal minima of fish species makes it challenging for managers to understand the possible invasion risk or further spread of some alien species. Historically, most research on thermal minima of tilapias and other fishes has used rapid declines in temperature, ranging from a fraction of 1°C per minute (e.g., Currie et al 1998;Prodocimo and Freire 2001) to 1°C per hour (e.g., Cameron et al 2012), and up to 0.5°C per day or 1°C per day (e.g., Bennett et al 1997;Charo-Karisa et al 2005;Green et al 2012). The slowest temperature declination rate applied to Blue Tilapia was 1°C per 3 d (Zale 1984), and the slowest rates applied to Nile Tilapia were 0.5°C per d Wilson et al 2009) and 1°C per 2 d .…”