Annual variation of the thermal parameters of the guitarist beetle Megelenophorus americanus (Coleoptera: Tenebrionidae) in the Monte desert

ARAGÓN Y TRAVERSO, JUAN HÉCTOR; PIÑEIRO GOMEZ, MAURICIO DANIEL; OLIVARES TOSELI, JUAN PABLO SEGUNDO; SANABRIA, EDUARDO ALFREDO

Mendoza

Simposio; Fourth International Tenebrionoidea Symposium; 2015

Investigation of thermal physiology gives us information about how species are influenced by the climate. Our aim was to study the thermal variation of Critical thermal maximum (CTMax), volunteer escape (VE), and fluid release (FR) to determine if Megelenophorus americanus shows acclimatization along the year in the Monte desert of San Juan, Argentina. Individuals were collected the last week of every month, during their activity period (at night). The inactivity period of this species is from March to October. We measured the operative temperatures (Te) from nulls models put in three different microhabitats. The average value was considered as Te. The field body temperature (Tb) was recorder with the infrared digital thermometer. In the laboratory the individuals were incubated 48hs at 20°C with a 12:12 light:night hour photoperiod. Beetles were exposed at an increment of temperature of 1°C/min. Three types of behaviors were registered during the heating experiment: the VE, FR and CTMax. Our results show significant correlations between Te and Tb, FR and CTMax (Spearman: R=0.97, p=0.001; R=0.40, p=0.001:R=0.40, p=0.002 respectively). VE showed significant deferens between months (ANCOVA: F(5,50) =6.06, p=0.0001), as well as FR (ANCOVA: F(5,50) =2.9592, p=0.02) and CTMax (ANCOVA: F(5,50) =4.47, p=0.001). The variation of Te shows its highest values in January and its lowest values in March. Also the correlation between CTMax and Te is an indicator of thermal acclimatization mechanism that may help individuals to survive in environments with extremely high temperatures. On the other hand, the behavior of spitting fluids on its head could be a mechanism to make brain´s temperature decrease for keeping neuronal activities working. This should be tested in further studies. We observed in December values atypically low for the thermal parameters and environmental temperatures, regarding November and January. We assume that is a consequence of the unusually rainy and cold summer that was experimented that year.