Annual variation of the thermal parameters of the guitarist beetle megelenophorus americanus (coleoptera: tenebrionidae) in the monte desert

ARAGÓN Y TRAVERSO JUAN HECTOR; PIÑEIRO M; OLIVARES J; SANABRIA E

Mendoza

Simposio; Fourth international tenebrionidae symposium; 2015

Sociedad entomológica argentina

investigatio of thermal physiology gives us information about how species are influenced by climate. Our aim is to study the thermal variation of Critical Thermal Maximum (CTMax), volunteer scape (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 specie is from March to October. We measured the operative temperatures (Te) from null models put in three different microhabitats. The average value was considered as Te. the field body temperature (Tb) was recorded with the infrared digital thermometer. In the Laboratory the individuals were incubated 48hs at 20ºC with 12:12 light:night hour photoperiod. Beetles were exposed at an increment of temperature of 1ºC/min. Three types of behavior were registered during the heating experiment: the VE, FR and CTMax. Our results show signifiante 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 diferences 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 the Te shows its highest values in January and its lowest values in March. Also the correlation between CTMax and Te is an indicatorof 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 makes breain´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 assume that is a consequence of the unusually rainy and cold summer that was experienced that year