Thermal Preference in Sympatric Bichirs: Senegal Bichir Polypterus senegalus and Saddled Bichir P. endlicherii (Polypteridae)

For the first time for Cladistia it is shown that Senegal bichir Polypterus senegalus and saddled bichir P. endlicherii exhibit thermopreferential behavior, the features of which differ between the two species. In the temperature-gradient field, the Senegal bichir in comparison to the saddled bichir is characterized by the lower motor activity, narrower range of the preferred temperatures, shifted toward the higher values (32–35 vs. 22–34°C), as well as relatively high mean preferred temperature (33.9 vs. 29.1°C), weighted for the time of occupancy of different temperature zones by the fishes. The differences of thermopreferential behavior we found could be caused by preference for different biotopes of the studied species, the distribution ranges of which overlap significantly.