Oxygen consumption of Astyanax fasciatus (Characidae, Pisces): a comparison of epigean and hypogean populations
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The standard and routine oxygen consumptions of Astyanax fasciatus from one surface population (Rio Teapao) and three cave populations (Chica, Micos and Pachon caves: ‘sAnoptichthys jordani’, the ‘Micosfish’ and ‘Anoptichthys antrobius’) were determined individually over 24 hours by the use of a flow-through respirometer and polarographic oxygen electrodes. The phylogenetically oldest Pachon fish had a significantly lower standard metabolic rate (0.230 ± 0.036 mg O2 g-1 h-1) than the epigean Teapao fish, the hybrid Chica fish and the phylogenetically younger Micos fish (0.314 ± 0.081 mg O2g--1h-1, 0.284 ± 0.048 mg O2g-1h-1, 0.277 ± 0.063 mg O2g-1h-1). No significant differences could be determined among the latter three populations. A significant difference in routine metabolic rate existed only between the Pachon fish (0.309 ± 0.0.56 mg O2g-1h-1) and the Teapao fish (0.415 ± 0.071 mg O2g-1h-1). The Chica fish (0.356 ± 0.084 mg O2g-1h-1) and the Micos fish (0.355 ± 0.080 mg O2 g-1h-1) could not be separated from either the Teapao or the Pachon fish, but a decreasing trend from the surface population through the Chica and the Micos to the Pachon population was obvious. During a starvation period of 29 days the metabolic rate of epigean Teapao and hypogean Pachon fish decreased significantly by 32.5% and 34.8% (standard oxygen consumption rate) and 27.5% and 28.2% (routine oxygen consumption rate), respectively. Body mass loss during the starvation period was 16.3% for the Teapao fish and 9.5% for the Pachon fish.
KeywordsMetabolic rate Cavernicolous species Cave adaptation Evolution Starvation Mexico
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