Metabolic rates of the antarctic amphipod Gondogeneia antarctica at different temperatures and salinities

Abstract

A B S T R A C TChanges in environmental factors may deeply affect the energy budget of Antarctic organisms as many of them are stenothermal and/or stenohaline ectotherms. In this context, the aim of this study is to contribute to knowledge on variations in the energy demand of the Antarctic amphipod, Gondogeneia antarctica as a function of temperature and salinity. Experiments were held at the Brazilian Antarctic Station "Comandante Ferraz", under controlled conditions. Animals collected at Admiralty Bay were acclimated to temperatures of 0°C; 2.5°C and 5°C and to salinities of 35, 30 and 25. Thirty measurements were made for each of the nine combinations of the three temperatures and three salinities, totalling 270 measurements. Metabolic rates were assessed by oxygen consumption and total nitrogenous ammonia excretion, in sealed respirometers. When acclimated to salinities 30 or 35, metabolic rates at 0°C and 2.5°C were very similar indicating a possible mechanism of metabolic compensation for temperature. At 5.0°C, however, metabolic rates were always higher. Lower salinities enhanced the effects of temperature on metabolism and ammonia excretion rates. The physiological adaptations of individuals of G. antarctica suggest adaptive mechanisms for energy saving, adjusted to an environment with stable conditions of temperature and salinity. Little is known about the joint effects of salinity and temperature and this study is an important contribution to the understanding of the mechanism of polar organisms in their adaptation to both factors. R E S U M OAlterações ambientais podem modificar a alocação de energia dos organismos, principalmente dos ectotermos estenotérmicos e/ou estenohalinos. Nesse contexto, este trabalho contribui com o conhecimento da demanda de energia do anfípode antártico Gondogeneia antarctica em função da temperatura e da salinidade. Experimentos foram realizados na Estação Antártica Brasileira "Comandante Ferraz", em condições laboratoriais controladas. Animais coletados na Baía do Almirantado foram aclimatados a temperaturas de 0°C; 2.5°C e 5°C e salinidades de 35, 30 and 25. Foram realizadas trinta medições para cada uma das nove combinações das três temperaturas com as três salinidades, totalizando 270 medições. As taxas metabólicas foram estimadas por meio do consumo de oxigênio e excreção de amônia, em câmaras respirométricas seladas. Quando aclimatados a salinidades 30 ou 35, as taxas metabólicas a 0°C e 2.5°C foram semelhantes indicando possível mecanismo de compensação térmica, nessa faixa de variação dos fatores. A 5.0°C, no entanto, as taxas metabólicas foram sempre mais elevadas. Baixas salinidades potencializaram os efeitos da temperatura no consumo de oxigênio e na excreção de produtos nitrogenados. Os resultados estão relacionados a mecanismos adaptativos para economia de energia em indivíduos G. antarctica, ajustados a um ambiente que tem condições estáveis de temperatura e de salinidade. Pouco se sabe sobre os efeitos conjugados da salinidade e temperatura nos organismos e...

OXYGEN CONSUMPTION AND AMMONIA EXCRETION OF THE ANTARCTIC AMPHIPOD Bovallia gigantea PFEFFER, 1888, AT DIFFERENT TEMPERATURES AND SALINITIES

“…At lower salinities, the higher energy demand may cause a partial shift on the part of the metabolic substrate from almost pure protein to a mixture of proteins and lipids, reducing nitrogen excretion. Similar features were also found for individuals of the Antarctic amphipods Gondogeneia antarctica (GOMES et al, 2013). They were even more sensitive to salinity variations, probably by virtue of their reduced body mass.…”

“…Nevertheless, the highly stable temperature conditions of Antarctic waters and habitat similarities directed their metabolic adaptations to the same range of resistance. The metabolic rates of B. gigantea and G. antarctica (GOMES et al, 2013), both of which live in well illuminated shallow waters, are relatively higher than the same rates for other amphipods such as Waldeckia obesa, a scavenger of dark, deep waters (CHAPELLE; PECK, 1995;GOMES et al, 1995). At salinity 35 and 0°C, correcting for the effects of body mass using the method described by STEFFENSEN et al (1994), the mean oxygen consumption rate of B. gigantea was 56 µlO 2 /g/h, whereas the mean oxygen consumption rate of G. antarctica is 65 µlO 2 /g/h and that of W. obesa is only 16 µlO 2 /g/h.…”

“…Depending on the size of the animal, sealed respirometric chambers of 150 to 200ml were used for the measurements, as described by GOMES et al (2013). In summary, each acclimated amphipod was placed inside one chamber for 3 hours with running water to reduce the effects of handling.…”

Oceanography and Marine Biology

“…These include: amphipods (e.g. Opalinski & Jazdzewski 1978, Rakusa-Suszczewski 1982, Chapelle et al 1994, Chapelle & Peck 1995, Doyle et al 2012, Gomes et al 2013; isopods (e.g. Belman 1975, Luxmoore 1984, Robertson et al 2001; the nemertean Parborlasia corrugatus (Clarke & Prothero-Thomas 1997, Obermüller et al 2010; bivalves (Ralph & Maxwell 1977, Davenport 1988, Ahn & Shim 1998, Kowalke 1998, Peck & Conway 2000, Brockington 2001a, Heilmayer & Brey 2003, Heilmayer et al 2004, Morley et al 2007, Cummings et al 2011; gastropods (Ralph & Maxwell, 1977, Houlihan & Allan 1982, Peck 1989, Peck & Veal 2001, Fraser et al 2002, Harper & Peck 2003, Obermüller et al 2010, Morley et al 2012a, Watson et al 2013, Peck et al 2015b, Suda et al 2015; cephalopods (Daly & Peck 2000, Oellermann et al 2012; bryozoans ; brachiopods (Peck et al 1986a,b,c, 1987a, 1997a,b, Peck 1989; ascidians (Kowalke 1998, Torre et al 2012; sponges…”

“…There have been many studies of physiological capacities to respond to temperature stress in Antarctic marine species over recent decades on a very wide range of different taxa, including fish (e.g. Macdonald & Montgomery 1982, Hardewig et al 1999b, Hofmann et al 2000, Wilson et al 2001, Podrabsky & Somero 2006, Franklin et al 2007, Robinson & Davison 2008, Bilyk & DeVries 2011, Strobel et al 2012, Todgham et al 2017, molluscs (Peck 1989, Urban & Silva 1998, Clark et al 2008a,b, Morley et al 2010,b,c, Reed et al 2012, Reed & Thatje 2015, echinoderms (Stanwell-Smith & Peck 1998, Clark et al 2008b, Morley et al 2012b, amphipods (Young et al 2006a,b, Clark et al 2008b, Doyle et al 2012, Gomes et al 2013, Schram et al 2015b, isopods (Whiteley et al 1996, Robertson et al 2001, Young et al 2006a,b, Janecki et al 2010, brachiopods (Peck 1989, Peck et al 1997a, sponges (Fillinger et al 2013), and macroalgae or phytoplankton (Montes-Hugo et al 2009, Schloss et al 2012. There have also been many assessments of the effects of elevated temperature using a larger-scale approach, both experimentally and using field observations identifying multispecies response or evaluating community, ecosystem or overall biodiversity level responses (e.g.…”