Fish Physiol Biochem (2016) 42:869–882 DOI 10.1007/s10695-015-0181-3 Aerobic and anaerobic enzymatic activity of orange roughy (Hoplostethus atlanticus) and alfonsino (Beryx splendens) from the Juan Fernandez seamounts area L. M. Saavedra . R. A. Quin˜ones . R. R. Gonzalez-Saldı´a . E. J. Niklitschek Received: 8 September 2015 / Accepted: 10 December 2015 / Published online: 19 December 2015 Ó Springer Science+Business Media Dordrecht 2015 Abstract The aerobic and anaerobic enzymatic with species that migrate through OMZs. This poten- activity of two important commercial bathypelagic tial and the higher muscle citrate synthase and electron species living in the Juan Ferna´ndez seamounts was transport system activities indicate that alfonsino has analyzed: alfonsino (Beryx splendens) and orange greater swimming activity level than orange roughy. roughy (Hoplostethus atlanticus). These seamounts This species has also a high MDH/LDH ratio in its are influenced by the presence of an oxygen minimum heart, brain and liver, revealing a potential capacity to zone (OMZ) located between 160 and 250 m depth. conduct aerobic metabolism in these organs under Both species have vertical segregation; alfonsino is prolonged periods of environmental low oxygen able to stay in the OMZ, while orange roughy remains conditions, preventing lactic acid accumulation. With at greater depths. In this study, we compare the aerobic these metabolic characteristics, alfonsino may have and anaerobic capacity of these species, measuring the increased swimming activity to migrate and also could activity of key metabolic enzymes in different body stay for a period of time in the OMZ. The observed tissues (muscle, heart, brain and liver). Alfonsino has differences between alfonsino and orange roughy with higher anaerobic potential in its white muscle due to respect to their aerobic and anaerobic enzymatic greater lactate dehydrogenase (LDH) activity activity are consistent with their characteristic vertical (190.2 lmol NADH min-1 gww-1), which is related distributions and feeding behaviors. to its smaller body size, but it is also a feature shared L. M. Saavedra (&) R. R. Gonzalez-Saldı´a Center for the Study of Multiple-Drivers on Marine Socio- Unidad de Biotecnologı´a Marina, Facultad de Ciencias Ecological Systems (MUSELS), Universidad de Naturales y Oceanogra´ficas, Universidad de Concepcio´n, Concepcio´n, Barrio Universitario S/N, Concepcio´n, Chile Casilla 160C, Concepcio´n, Chile e-mail: [email protected] E. J. Niklitschek R. A. Quin˜ones Centro i*mar, Universidad de Los Lagos, Camino a Interdisciplinary Center for Aquaculture Research Chinquihue Km 6, Casilla 557, Puerto Montt, ChileX (INCAR), Universidad de Concepcio´n, O’Higgins 1695, Regio´n Concepcio´n, Chile R. A. Quin˜ones Departamento de Oceanografı´a, Facultad de Ciencias Naturales y Oceanogra´ficas, Universidad de Concepcio´n, Casilla 160C, Concepcio´n, Chile 123 870 Fish Physiol Biochem (2016) 42:869–882 Keywords Seamounts Á Enzymatic activity Á roughy is bathypelagic and lives below the OMZ at Oxygen minimum zone Á Beryx splendens Á preferred depths of 500–1000 m, whereas alfonsino Hoplostethus atlanticus uses shallower habitats, with greater presence around 400 m (Niklitschek et al. 2007; Guerrero and Arana 2009) and daily migrations into more superficial waters (Vinnichenko 1997), entering and crossing Introduction the OMZ on a daily basis (Fig. 1). This vertical segregation between the habitats used Seamounts are highly productive ecosystems in which by the species should be reflected in important the upwelling of nutrient-rich water and the trapping of differences in their metabolic properties (Siebenaller diurnally migrating plankton (Rogers 1994) provide a and Somero 1989). For instance, interspecific com- unique deep-sea environment for fishes and invertebrates parisons of enzymatic activity have shown a general (Koslow 1997). In spite of the large number of seamounts pattern of decreasing metabolic activity with increas- in the global ocean, especially in the Pacific, relatively ing depth (Siebenaller and Somero 1989; Childress few studies have been carried out on the biology and and Thuesen 1992). Moreover, vertically migratory ecology of seamount biota (Clark et al. 2014). fishes such as alfonsino are expected to have metabolic A stable and persistent feature of seamounts located adaptations that allow them to cross and remain in the in the eastern Pacific is the presence of a permanent OMZ (Childress and Seibel 1998), as this zone is oxygen minimum zone (OMZ) (Rabalais et al. 2010). known to be an important barrier for the distribution of Therefore fish inhabiting or crossing this layer as part marine organisms (White 1987; Eissler and Quin˜ones of their daily routine are expected to exhibit metabolic 1999; Gonza´lez and Quin˜ones 2002). Adaptations to and physiological adaptations, which are still poorly low oxygen availability in biota dwelling permanently understood (Martı´nez et al. 2011). This understanding or semipermanently in OMZ may be achieved using has become more relevant today when the increment several strategies, such as (1) more effective oxygen in hypoxic zones in the ocean worldwide has become a incorporation, (2) less metabolic demand and (3) global issue (Zhang et al. 2010; Diaz and Rosenberg conducting anaerobic metabolism (Childress and 2008; Rabalais et al. 2010), which due to global Seibel 1998). It has also been suggested that some warming could become more acute in the future (Justic vertically migrating species can alternate between et al. 1996; Diaz and Rosenberg 2008; Hansen and anaerobic metabolism while in the OMZ and aerobic Bendtsen 2009; Falkowski et al. 2011). metabolism when they encounter more oxygenated An important group of Eastern Pacific seamounts waters (Childress 1977). An important enzymatic corresponds to the Juan Fernandez Ridge, located on adaptation to hypoxia is the change in affinity of the Nazca Plate off the coast of Chile between enzymes involved in glycolysis and other pathways of 32–34°S and 73–82°W (Pilger 1981). Here the OMZ carbohydrate metabolism (Panepucci et al. 2000;Wu is composed of equatorial subsurface waters (Ahu- 2002; Pollock et al. 2007). mada and Chuecas 1979), ranges between 150 and Analysis of enzyme activities can be used as an 350 m depth and presents dissolved oxygen values approach to assess reliance on anaerobic metabolism -1 between 0.3 and 2.0 mL O2 L (Fig. 1a) (Nikl- in OMZ species (Childress and Seibel 1998; Yang itschek et al. 2007). Below this depth, oxygen levels et al. 1992), as well as to determine metabolic increase to a maximum of approximately 4 mL O2 - differences between fish that have different patterns L-1 around 600 m and decrease again to about of vertical distribution (Childress and Somero 1979; -1 2mLO2 L at a depth of approximately 950 m Siebenaller et al. 1982; Vetter et al. 1994; Childress (Chiang and Quin˜ones 2007; Niklitschek et al. 2007). 1995; Vetter and Lynn 1997). For, instance, citrate Two commercially important bathypelagic species synthase (CS), associated with oxidative phosphory- are exploited in this ridge, orange roughy [Ho- lation, is used as an indicator of aerobic metabolism, plostethus atlanticus (Collet)] and alfonsino [Beryx and lactate dehydrogenase (LDH) is indicative of splendens (Lowe)], which exhibit clear vertical seg- anaerobic metabolism (Childress 1995; Farwell et al. regation with only a slight overlap between 550 and 2007; Martı´nez et al. 2011). Malate dehydrogenase 650 m (Niklitschek et al. 2007, Fig. 1b, c). Orange (MDH) plays a role in both aerobic and anaerobic 123 Fish Physiol Biochem (2016) 42:869–882 871 Fig. 1 a Dissolved oxygen profile from a zonal transect (75°W to 78.8°W) of Juan Fernandez seamounts; b vertical distribution of alfonsino and c orange roughy in these seamounts (extracted from Niklitschek et al. 2007) pathways (Vetter et al. 1994), because the mitochon- respiration potential (Ikeda et al. 2006). Thus we drial isozyme (m-MDH) is a component of the Krebs characterize metabolic differences between species cycle and also passes reduced equivalents between the and explore hypotheses about the value of such mitochondria and the cytoplasm. The cytoplasmic differences as adaptive mechanisms making possible isozyme (s-MDH) shares the mentioned function with fairly distinct habitat use patterns under such strong m-MDH and in certain species can be important for gradients in hypoxic conditions. maintaining the cytoplasmatic redox balance during intense anaerobiosis (Hochachka and Somero 1984). In this paper, we analyze and compare the activity Materials and methods of different metabolic enzymes in several tissues of H. Atlanticus and B. Splendens collected at the Juan Collection and preservation of study animals Fernandez Ridge. We also estimate and compare metabolic rates through the activity of the electron Fish samples were obtained from deep-bottom trawls transport system (ETS), which is a measure of deployed between July 30 and August 7, 2005, by the 123 872 Fish Physiol Biochem (2016) 42:869–882 Fig. 2 Map showing the sampling sites. The three seamounts (JF2, JF3 and JF4) belong to the Juan Fernandez Archipelago. Coordinates correspond to UTM zone 18S factory vessel ‘‘Betanzos,’’ as part of the 2005 annual samples were collected between 350 and 450 m from orange roughy–alfonsino hydroacoustic survey (Nik- JF2 (Table 1; Fig. 2). These sampling depth ranges litschek et al. 2006). The sampling area included three represented frequent catch strata