Temperature effects on aerobic and anaerobic metabolic of decapod crustaceans in South America.

AVALOS, CECILIA; HEILMEYER, OLAF; GUSTAVO ALEJANDRO LOVRICH; SVEN THATJE,

Concepción, Chile

Simposio; CENSOR Midterm Symposium; 2006

Universidad de Concepción, Alfred Wegener Institut

In nature, organisms must respond to a wide array of environmental conditions in order to survive.Temperature is a crucial environmental factor setting limits for life, influencing the activity oforganisms including the rates of growth and reproduction (Lannig et al. 2003) and producingchanges in rates of biochemical and physiological processes and in the stability of bio-molecules(reviewed by Somero 2004).Recent studies have revealed that environmental temperature influences total metabolic rates inaquatic ectotherms and can also significantly affect metabolic regulation, eliciting transition toanaerobiosis even in fully oxygenated waters (reviewed by Pörtner 2001). The temperaturesassociated with a transition to an anaerobic mode of mitochondrial metabolism has been definedas critical temperatures (Tc, Pörtner 2001). Critical temperatures differ between species andpopulations depending on latitude or seasonal temperature acclimation and therefore they arerelated to geographical distribution (Pörtner 2001). Metabolic adjustments in response totemperature change are especially crucial for aquatic ectotherms, whose body temperaturefluctuates over the full range of their habitat temperatures.The aim of this study is to understand the distribution limits of the decapod species, and possiblegeographical shifts due to changes in temperature. As part of the investigation, temperature effectsat different hierarchical levels are studied: 1- organism: through respiration experiments: basalmetabolism, active metabolism, SDA (specific dynamic action of food) and 2- cellular: throughenzymatic analysis: Aerobic and anaerobic enzymes activity and succinate accumulation. Inparticular, this study is addressed to two infraorders among decapods:1) Anomura: Comparison between two Galatheidae species with similar ecological roles andfishery importance (Munida gregaria and Pleuroncodes monodon), in a latitudinal gradient2) Brachyura: Comparison between populations of Cancer setosus in a latitudinal gradient.Here I present the first results, from Munida gregaria:(1) Organism level: Respiration data from Puerto Montt, Chile(2) Cellular Level: Aerobic and anaerobic enzymes data from Beagle Channel, Argentina.1) Animals were caught off Puerto Montt (47ºS), Chile, with an underwater vacuum at ~10 m depth.Oxygen consumption of animals (n=6 per treatment; mean carapace length=13,5 mm ± 1 mm)acclimated to 6º, 12º and 18º was measured in a closed system. Oxygen content was determined with microoptodes connected to a single channel MICROX TX3 array. After standard metabolism(defined as oxygen consumption of unfed, unstressed animals) was measured, animals wereforced to move and be active. Oxygen consumption was measured to obtain active metabolism.2) Animals (20 mm CL ± 3 mm) were sampled with an epibenthic trawl in the Beagle Channel andtransported alive to the aquaria of the CADIC (Ushuaia, Argentina). After an initial one-weekacclimation period to reduce sampling stress, animals were split into groups and acclimated to 4º,8º, 12° and 16º. Animals were kept in individual aquaria at the desired temperature for 30 days andafterwards were dissected. Hepatopancreas, gills and muscle were taken from each animal andsnap frozen in cryovials. Samples were kept at -40º for enzymatic and metabolite analyses andtaken to the Alfred Wegener Institute (AWI) for analysis.1) Results show that standard metabolism of M. gregaria was significantly positive affected bytemperature (6º= 0,105 mgO2.h-1.g-1; 12º= 0,161 mgO2.h-1.g-1; 18º= 0,232 mgO2.h-1.g-1).Active metabolism, however, could only be measured in few animals. In the cases theanimals showed high levels of activity, a significant non-temperature dependent 2 to 3 foldincreases in their oxygen consumption was measured.2) The protocols to measure citrate synthase (CS), pyruvate kinase (PK), cytochrome Coxidase (COX) activity and succinate accumulation were modified or adjusted for Munidasamples. Sample from animals acclimated at 4º (morpho subrugosa) and 8º (morphosgregaria and subrugosa) were analysed. COX could not be determined in any of thetissues, possible due to the enzyme sensibility. CS activity could be measured in muscleand gills, while PK was only detected in muscle. Succinate concentration was below thedetermination-threshold of the method.c