The life cycle of the giant water bug of northwestern Patagonian wetlands: the effect of hydroperiod and temperature regime

JARA, F.; PEROTTI MG

INVERTEBRATE BIOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2018 vol. 137 p. 105 - 115

1077-8306

We analyzed the effect of hydroperiod and water temperature in the life cycle of the giant water bug Belostoma bifoveolatum in wetlands of northwestern Patagonia. Individual abundance (nymphs and adults) in each wetland was estimated using the dip-net technique. Water depth and temperature were monitored throughout the study period. We calculated the accumulated day-degrees for egg hatching and complete development. B. bifoveolatum was found to colonize the temporary wetlands during late September or early October, when daylight lasts ∼12 h. The giant water bug produced one or two generations per year (univoltine or bi-voltine) and presented a relatively constant breeding season, starting in late September or early October. Nevertheless, breeding period duration varied with hydroperiod length. Males bearing eggs (35 to 144 egg ind-1) appeared in October. Hatching success was high, with ∼80 % of eggs hatching when cumulative temperature reached between 250 and 300 day-degrees, which represents three or four weeks in the natural conditions of these wetlands. Complete development of the water bug was found to occur between 800 and 1200 day-degrees (∼7-8 weeks). Belostoma was more abundant in shallow and sunny patches of the wetlands, where temperature was comparatively higher, than in deeper or shaded sites. The results shown here indicate that hydroperiod duration and temperature are the main factors regulating the voltinism and development of B. bifoveolatum, also driving the population structure of this giant water bug in the studied wetlands. Nevertheless, the inter-annual variability observed in nymph development could also be influenced by food availability (prey abundance) and the impact of cannibalism.