UV radiation effect on survival and growth, and quantification of free-radicals in protozoeal stages of the Argentine red shrimp

M. ALEJANDRA MARCOVAL; JERONIMO PAN; A. CRISTINA DÍAZ; SUSANA VELURTAS; JORGE L. FENUCCI

Mar del Plata

Congreso; The Changing Coastal and Estuarine Environment: A Comparative Approach; 2012

The aim of this study was to determine the effect of ultraviolet radiation (UVR) on survival, development, growth and bioaccumulation of UV-absorbing compounds, and to determine free radical scavenging properties in protozoeal stages of the Argentine red shrimp, Pleoticus muelleri. P. muelleri is a commercially-important coastal species, distributed from Southern Brazil to Patagonia (23-50 ºS). Shrimp nauplii were incubated at 200 L-1 densities in 5-L parabolic tanks under controlled conditions of temperature, pH and salinity. Nauplii were exposed by triplicate to three radiation treatments, namely: a) PAB treatment: in which uncovered experimental tanks received the total radiation spectrum (UVR 280-400 nm + PAR 400-700 nm); b) PAR treatment: in which containers were covered with Ultraphan film (opaque to UVR, Digefra, 50% transmission at 395 nm) to receive only PAR; and c) controls: in which containers were placed in semidarkness. Q-Pannel UVA-340 lamps generated UVR, and Philips fluorescent bulbs provided PAR. Experimental diets consisted of combinations of the diatom Chaetoceros sp. and the nanoflagellate, Isochrysis galbana, known to produce UV-absorbing compounds. Experiments lasted until larvae reached the mysis I stage. Antioxidant activity was quantified measuring the free-radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) by electron paramagnetic resonance (EPR). The PAR and PAB treatments respectively yielded 85 and 62 % protozoea survival; 325 and 275 % increase in size; and larvae took 9 and 13 days respectively to reach the mysis I stage. The synthesis of UVR protective compounds was not detected spectrophotometrically for any treatment. Conversely, all samples presented DPPH activity, evidencing a protective response. The DPPH signal decayed drastically within 20 min and after 1 h the DPPH remnant was about 50%. We conclude that UVR affects the development and survival of protozoeal stages of P. muelleri, when fed the microalgal species used in this study.