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Home , Erythrinus erythrinus, Hypoxia in fish, Mylossoma duriventre, Tambaqui

S. Afr. J Zoo I. 1998, 33(2) 107-114

Hypoxia adaptation in of the Amazon: a never-ending task

A.L. Val*, M.N.P. Silva and V.M.F. Almeida-Val National Institute for Research in the Amazon, Alameda Cosme Ferreira, 1756,69083-000 , Amazonas, Brazil E-mail: [email protected]

Received 27 1Vovember /997; accepted J6April1998

In addition to seasonal long-term changes in dissolved oxygen and carbon dioxide, water bodies of the Amazon present periodic short-term episodes of and even anoxia. To preselVe and acid base bal­ ance, fish of the Amazon have developed multiple adaptive solutions which occur at all biological levels. These solutions are thought to represent adaptive convergence rather than phylogenetic relatedness. Fish of the Ama­ zon exposed to different experimental conditions adjust, for example, several parameters to improve oxygen transfer from the gas-exchange site to the tissues. These parameters include morphological changes such as the development of the lower lip in C%ssoma, changes in ventilation rates, changes in Circulatory parameters, increased Circulating red blood cells, decreased levels of intraerythrocytic phosphates, and adjustments of intraerythrocytic pH (pHi). These adjustments that allow fish to sUlVive both short- and long-term hypoxia occur in different degrees in different fish species and mayor may not occur simultaneously. In addition, these adjust­ ments in oxygen transfer affect many other parameters, particularly acid-base status. We suggest that these adjustments are initiated as soon as the detects the environmental change in oxygen availability and are mediated by a single factor, possibly one of the . In this paper we aim to show that adaptation to hypoxia is a never-ending task for the fish of the Amazon.

* To whom correspondence should be addressed

Introduction The amount of dissolved oxygen in waters of the Amazon The story of hypoxia adaptation in fish of the Amazon is also basin is determined by complex interactions of physical, a story of changing environments. To understand why chemical and biological processes. Such processes include hypoxia adaptation in fish of the Amazon is a never-ending photosynthesis, respiration, light penetration, organic decom­

. position, molecular oxygen , wind, water body depth ) task, a general view of the is fundamental. 9 and shape, temperature, etc. Since all these parameters are 0 During the Cretaceous, Gondwanaland broke up in the south­ 0

2 affected by the regular river water level oscillation, a seasonal

ern hemisphere and two continents appeared: d change in dissolved oxygen in a given place and time, related e and AfTica. The Andes mountains then appeared in the west­ t to the flood pulse, is observed. These changes are called long­ a ern part of the Amazon at the end of the Miocene and induced d

( term changes in dissolved oxygen. Indeed, mixed patterns of

stupendous changes in the Amazon basin. The Pacific drain­ r e age of upper tributaries of the was cut and the dissolved oxygen occur simultaneously. For example. during h s high water levels extremes of oxygen may occur in different i whole Amazon basin became Atlantic oriented. As a conse­ l b quence a complete new set of habitats was made available parts of the same lake as a consequence of water plant cover. u

P During the low water season anoxic conditions are observed

and seasonal river water level oscillations became the main e in such places owing to the decomposition of the water plants.

h driving force of the Amazon basin (reviewed by Val & Al­ t meida-Val Such anoxic conditions occur together with high levels of dis­

y 1995). b Junk, Bayley & Sparks (1989) refer to the river water level solved hydrogen sulphide and methane (reviewed by Val & d e oscillation as flood pulses. In fact, a crest of m, occasion­ Almeida-Val 1995). t 10 n ally more, occurs every year on the main river channel in Because water of varying characteristics occurs in the a r

g front of Manaus. S iDee the Amazon basin is a flat land, 80o/a many aquatic formations of the Amazon, not surprisingly

e extremes of dissolved oxygen are observed at a given c of the whole region is under the 30 m contour line, which n moment. So, while low levels of dissolved oxygen are e means that a significant part of the basin is flooded every year c i l making new habitats in the flooded forest (igap6) and in the observed in varzea lakes and igap6s for example, normal or

r even over-saturated levels are observed in open areas such as e floodplain areas (wirzea) available to fish. In addition, the d river water level oscillation causes the appearance and disap­ in the flowing river. Since these systems are interconnected n u

pearance of many other aquatic formations of the Amazon during high water levels, fish have the choice of staying in the y a such as paranas (channels), /garapes (small slTeams), varzea lakes where food is available or leaving such places in w search of better oxygen conditions. e beaches, etc. During high water levels the water bodies t a (lakes, paranas, igarapes, etc) are all interconnected. In the In parallel to these long-term changes in oxygen, extreme G varzea and igapos only the upper part of the trees remains variations in dissolved oxygen tend to occur in a very short t e above the water. During low water levels, the receding water period of time. In the lakes of the Marchantaria Island, for n i b leaves behind small water bodies. Chemical, physical, and example, oxygen levels may drop to zero at night and reach a

S biological parameters of the water change accordingly. Thus, over-saturated levels at noon the very next day (Junk, Soares y virtually all living organisms of the Amazon are affected by & Carvalho 1983; Val 1986; Val & Almeida-Val 1995). b

d such a predictable annual flood pulse. Short-term changes in dissolved oxygen force rapid respira- e c u d o r p e R 108 S. Afr. J. Zool. 1998,33(2)

tory adjustments in aquatic , particularly (Val tions after the uplift of the Andes mountains. Complex organ­ 1996). ism---environment interactions set the distribution of fishes Another remarkable characteristic of the Amazon water is across the myriad of habitats of the Amazon (Almeida-Val, the microstratification of dissolved oxygen. It has been specu­ Val & Hochachka 1993; Almeida-Val & Farias 1996). lated that the top millimetres of the water column contain as This adaptive radiation of fish of the Amazon has occurred much as 90% of all water-dissolved oxygen. The oxygen dis­ and is still occurring in an ever-changing environment. Etho­ solved in the first 10 cm of the water column of many aquatic logical, morphological, anatomical, physiological and bio­ habitats of the Amazon represents the sole source of oxygen chemical adjustments are improved to maintain the essential for several aquatic animals during the regular episodes of during the regular natural environmental hypoxia/anoxia (reviewed by Val 1996). So, aquatic habitats changes. These adjustments occur in different degrees in dif­ of the Amazon can be seen as an ever-changing environment ferent groups of fishes, enabling them to survive extreme regarding oxygen availability. environmental conditions such as acidic and ion-poor waters (Gonzalez, Wood, Wilson, Patrick, Bergman, Narahara & Val Adaptations to chronic of the 1998; Wood, Wilson, Gonzalez, Patrick, Bergman, Narahara Amazon & Val 1998), high hydrogen sulphide and methane levels The Amazon basin encompasses the richest fish fauna in the (Brauner, Ballantyne, Randall & Val 1995; Val, Marcon, Costa, Barcellos, Maco-Garcia & Almeida-Val 1998) and world. The current number of fish species is estimated to deep hypoxia or even anoxia (Val 1993; Val & Almeida-Val range from 1300 to 2500, including representatives of almost all freshwater groups of fishes (Roberts 1972; Bohlke, Weitz­ 1995; Val el al. 1998). They are thought to represent adaptive convergence rather than phylogenetic relatedness (Almeida­ man & Menezes 1978; Rapp-Py-Daniel & Leao 1991). Rep­ Val el al. 1993). resentatives of primitive orders such as Lepidosirenifonnes and Laminiformes coexist with advanced , the Pleu­ According to Randall, Burggren, Farrell & Haswell (1981), ronectiformes and Tetraodontiformes. The dominant group is hypoxia and anoxia have been common events in the evolu­ the Ostariophysi which is by far the largest group of tionary history of waters since the Cambrian period and fish, fish currently living in the Amazon. Fink & Fink (1979) refer consequently, have evolved many different strategies to face to it as an example of explosive radiation from a small such environmental constraints, Air-breathing is one solution number of ancestors. is the richest order of tel­ and it was tried independently in many unrelated groups of eosts in the Amazon, including more than 1200 fish species, fish of the Amazon. Simultaneously, those fish species unable followed by the Siluriformes (catfishes) with 1000 fish spe­ to utilise air as a source of oxygen have developed many

. cies (Table I). Such richness has been explained by the modifications directed towards enhancing oxygen transfer to )

9 dynamics of the Amazon basin, the size and diversity ofhabi­ tissues, including behavioural, morphological, physiological, 0

0 tats, the open character of the basin, the species paucity in and biochemical adjustments. It is likely that such adaptive 2 adjustments and the mechanisms of detection of environmen­ d some parts of the basin, and the genetic and physiological e t plasticity of the animals which has been related to the ampli­ tal changes in oxygen availability and/or physiological needs a

d have evolved simultaneously as a way to increase survival

( fication of the genome in early vertebrates and has provided

r capacity (Arthur, Hogan, Bebout, Wagner & Hochachka

e them with the capacity to face the new environmental condi- h 1992; Almeida-Val & Farias 1996; Hochachka 1996; Val s i l 1996; Walker & Henderson 1996). b Table 1 Main orders of fish of the Amazon with an u P

indication of estimated number of species in the Ama­ e Behavioural adjustments h zon and in the World. Data originally reviewed by Val t

y & Almeida-Val (1995). Note that Gymnotiformes are Behavioural change is the most common adaptive response of b endemic to the Amazon .• not all of the Amazon to low oxygen. When fish face oxygen d e depletion in their environment the simplest way to avoid the t Order Species in the world Species in the Amazon n problem is to leave the environment, i.e. to escape. Junk el al. a Lepidosireniformes

r 5

g (1983) reported a significant decrease in species richness and

e Laminiformes

c abundance when oxygen levels were low in Camaleao Lake, a n Rajiformes 70' 12

e typical varzea lake of Marchantaria island. The authors c i l Osteoglossiformes 206 4 showed that only those fish species specialised in some way r e Clupeifonnes 331 17 to tolerate low levels of oxygen remain in the lake during d periods of oxygen shortage (Table 2). Most of the water­ n Characi formes \335 1200 u

breathing fish species are able to detect a current oxygen y Siluritbnnes 2211 1000 a depletion or even to anticipate it, leaving the place before

w Gymnotifonnes 54 54

e large drops occur. Lateral migrations, i.e. migrations that t a Batrachoidiformes 64 involve small distances normally between the river and flood­ G Cyprinodontiformes 845 30 plain areas, have been described for several fish species of the t e Amazon and they are related to oxygen availability in the n Synbranchiformes 15 i

b lakes among other environmental constraints (Cox-Fernandes Percitol;mes 7791 350 a

S 1989). In addition to these migrations, other fish species Pleuronectiformes 538 5 y change their natural habitat to explore alternative sources of b Tetraodontiformes 329 5 d oxygen. Sometimes, for example, several of these animals are e c u d o r p e R S. Afr. 1. Zool. 1998, 33(2) 109

Table 2 Families of fish occurring at Camaleao Lake during low dissolved oxygen with an indication of their main adaptation to hypoxia. After Junk et a/. (1983), Val & Almeida-Val (1995) Fami Iies/SubfamiJies Species Main adaptation Type Anostomidae Schizodonjascialum Unknown UnknO\1;n Lepor;nus fascia/us Rhylhiodus microlepis Bryconinae Brycon melanopterus Aquatic surface respiration Lip expansion associated with physiological adjustments Callichthyidae Hoplosternum liltorale Air breathing Stomach and intestine Callichthys calJichlhys Hopioslemum thoracalum Cichlidae Cichlasoma spp Metabolic depression Metabolic depression and gene regulation As/rona/us ocel/a/us Prerophylium seafare Curimatidae Curimata latior Unknown Unknown Curimata la/;eeps Curimata !meri Curimatella meyer; Electrophoridae Electrophorus elec/ricus Air breathing Pharingeal, branchial. and mouth diverticula Hop/erylhrinus unitaeniatus Air breathing Modified swimbladder erythrinus Lcpidosirenidae Lepidosiren paradoxa Air breathing Lung Loricariidae Liposarcus pardalis Air breathing Stomach and intestine Plecostomus sp Myleinae Colossoma macropomum Aquatic surface respiration Lip expansion associated with physiologic and metabolic brachypomum adjustments duriventre . )

9 Mylossoma aureum 0

0 Osteoglossidae gigas Air breathing Aquatic surface respiration 2

d Osreogiossum bicirrhosum e t a Prochilodontidae Prochilodus nigricans Physiological Adjustments of Hb:NTP ratios d (

Semaprochilodus taemuros r e

h Semaprochilodus msignis s i l Synbrachidae Synbranchus marmoratus Air breathing Pharingeal, branchial, and mouth diverticula b u P e h seen ex"loring the water-air interface or gUlping air when dis­ expanded lip is not vascularized and has no gas exchange t

y solved oxygen is low. Species of Pterygoplichthys and function. It serves to funnel the surface layer of water, which b Hoplosternum surface rhythmically to gulp air when exposed d is richer in oxygen as mentioned above, across the . Inter­ e t to hypoxia, using their vascularized stomach and intestine as estingly, the lip is expanded to different extents and at differ­ n a an accessory air-breathing organ (Kramer & McClure 1981; ent oxygen thresholds in many non-related fish species such r g

Val 1995). According to Jensen, Nikinmaa & Weber (1993) as species of the genera Colossoma, Brycon, Triportheus, and e c this is a 'sophisticated version of the escape response'. Val Mylossoma (see Val & Almeida-Val 1995). In Co/ossoma n e (1995) has shown that the air-breathing organ contributes as c exposed to deep hypoxia (Pwo, ~ 30 mmHg) the lower lip i l much as 70% of the total oxygen transferred to the tissues in expands in 2 h and retracts in about the same time when oxy­ r e specimens of Loricariidae exposed to deep hypoxia. Interest­ gen returns to nonnal levels. Because of the contribution of d n ingly, as we shall see later, these behavioural adjustments the expanded lip to oxygen uptake, no significant difference u may be improved simultaneously with physiological and bio­ y in the blood oxygen content is observed between specimens a chemical adjustments, possibly mediated by a single factor.

w of Colossoma exposed to nonnoxia and those exposed to e t Indeed, as the animal reaches a place where oxygen is availa­ hypoxia with access to the water surface. However, in ani­ a ble again, the oxygen transfer system and the metabolic

G mals denied access to the water surface a significant decrease

t machinery are reorganised accordingly. e of 35% in blood oxygenation is estimated during hypoxia n i (Almeida-Val et al. 1993; Val 1996). b a Morphological adjustments The lip expansion in Colossoma results in a stabilisation of S

y Several fish species of the Amazon are able to expand the plasma lactate levels as described by Almeida-Val et al. b lower lip to skim the oxygen-rich water surface. The (1993). In a recent series of experiments we have in addition d e c u d o r p e R 110 S. Afr. J. Zool. 1998, 33(2)

shown that the level of organic phosphates in the erythrocytes again these parameters return to normal levels. It has been of this fish species is also restored to levels similar to those suggested that these mechanisms are modulated by a single observed in animals kept under normoxia and well above factor, possibly one of the catecholamines. those in animals denied access to the water surface (unpub­ Moura (1994) has shown that the increase in circulating red lished data). This is a clear indication that lip expansion in blood cells in occurs simultaneously with a Colossoma helps the animal to extract almost normoxic decrease in spleen weight and haemoglobin content. She water, and thus the haemoglobin oxygen affinity can be showed also that this mechanism in tambaqui is adrenergi­ reduced towards normoxic values. Consequently, the partial cally stimulated as has been described for several other fish pressure gradient between blood and tissue can be species (see Randall & Perry 1992). In addition to alpha increased. adrenergic stimulation, beta adrenergic stimulation has been In the facultative air-breathers Plerygoplichlhys and described for fish of the Amazon. Val, Menezes & Wood Hoploslernum exposed to deep hypoxia, the use of the acces­ (1998), for example, have shown that a beta adrenergic sory air-breathing organ is followed by a significant reduction response was clearly present in two (Colossoma and Sema~ of perfusion. This is needed to prevent oxygen leaking to prochilodus) out of six species analysed when surveying the the hypoxic environment. Again, as these adjustments are erythrocytes of Amazonian teleosts of the for the made the levels of organic phosphates are restored to normal presence of adrenergically mediated Na'/H' exchangers. levels to maintain oxygen transfer to tissues. In addition to The major organic phosphates modulating haemoglobin these adjustments, morpho-functional adaptations of gills oxygen affinity in fish are A TP and GTP (see Val 1996; including changes in the number and length of gill filaments, Weber 1996). In addition to these two compounds, inositol and size and frequency of the secondary lamellae, have been pentaphosphate (lPP) and 2,3-diphosphoglycerate (2,3 DPG) described for several species (Fernandes 1996). are encountered in the erythrocytes of Arapaima and Hoplos­ ternum, two fish species endemic to the Amazon basin, PhYSiological and biochemical adjustments respectively (Bartlett 1978; Val, Affonso, Souza, Almeida­ In addition to behavioural and morphological adjustments, Val & Moura 1992; Val 1993). In all fish species so far ana­ fish may respond to low oxygen by adjusting several physio­ lysed, exposure to hypoxia results in a significant decrease in logical and biochemical parameters, such as: (i) increasing the levels of ATP and GTP within the erythrocytes. This ventilatory frequency, ventilatory volume and heart rate; (ii) decrease correlates with an increase in haemoglobin oxygen increasing the number of circulating erythrocytes, haemo­ affinity which improves oxygen uptake at the gills during globin concentration and hematocrit value; (iii) increasing environmental hypoxia. In general, the qualitative and quanti·

. haemoglobin-oxygen affinity by changing intracellular levels tative differences between species generally correlate with )

9 of allosteric modifiers, specially decreasing Hb:NTP ratios; differences in the structural properties of the haemoglobins 0

0 (iv) using with different functional properties; that are species-specific (Weber 1996). However, whereas 2 NTP predominates in the erythrocytes of juveniles of Ara­ d (v) changing gene expression to adjust metabolic pathways; e t and (vi) depressing . paima that are water breathers, IPP predominates in adults a

d without any apparent change in haemoglobin structure (Val

( Increasing gill ventilation by increasing tidal volume and! r or respiratory frequency is a strategy used by many fish spe­ 1986; Weber 1996). e h The mechanism related to the adjustment of intraerythro­ s cies to maintain arterial P02 during hypoxia exposure i l cytic levels of A TP and GTP is unknown. Greaney & Powers b (reviewed by Milson 1993). Rantin & Kalinin (1996) have u shown that Colossoma macropomum hyperventilated (2.2- (1978) suggested that the decrease in NTP levels would be a P

e fold higher), increased intrabuccal pressure four times, but direct consequence of low oxygen supply to oxidative phos­ h t

presented no significant change in cardiac frequency when phorylation, an explanation that has not been accepted y

b exposed to deep hypoxia (20 mmHg). Kalinin el al. (1996) (Nikinmaa 1990). Dalessio, DiMichele & Powers (1991)

d have also shown several adjustments in the ventilatory flow, have reported a significant decrease (44%) in ATP and GTP e t levels in Fundulus helerociilus erythrocytes incubated with n intra buccal and intraopercu lar volume of Hop/ias malabari­ a r cus and H. lacerdae. In general the responses are instantane­ adrenaline. This explanation can not be generalised either g (Nikinmaa 1992; Randall & Perry 1992; Val el al. 1998). In e ous and are related to stimulation of oxygen c fish of the Amazon, a significant change in NTP levels is n (Milson 1996). e c observed before catecholamines are released (Val 1993). In i Hematocrit, circulating red blood cells and haemoglobin l

r concentration are significantly increased in animals exposed addition, the erythrocytes of several species are not sensitive e d to both natural and experimentally induced hypoxia (see to adrenaline (Val el al. 1998). n

u Rowley, Hunt Page & Maiwaring 1988; Val 1993; Val & Adjustments of NTP levels are improved as soon as the

y Almeida-Val 1995). However, there is a limitation in increas­ animal is exposed to a new condition either physiologically or a

w ing circulating red blood cells which is the extra heart work environmentally induced. Piaraclus brachypomum, for exam­ e t needed to pump a more viscous blood. In fact, oxygen trans­ ple, exhibits a cyclic change in Hb:NTP ratio that correlates a

G port capacity decreases as the hematocrit diverges from the with diurnal changes in oxygen availability in their natural t e optimum (see Val 1995). Air-breathers, however, do present environment (Val 1996). In Colossoma, the intraerythrocytic n i higher values for haemoglobin and hematocrit than water­ levels of A TP and GTP are partially recovered as soon as the b a breathers. Interestingly, the water-air breathing transition is lip is extended and the animal has access to the water surface. S

y followed by a significant increase in circulating haemoglobin In Plerygoplichlhys, a facultative air-breather, a similar situa­ b and hematocrit values. Clearly, when oxygen is available tion is observed. These examples suggest that these fish spe- d e c u d o r p e R S. Afc J. Zool. 1998, 33(2) III

cies continuously adjust their intraerythrocytic microenviron­ Phenotypic adjustments ment. The occurrence of phenotypic adjustments in fish of the Ama­ Multiple haemoglobins appear to be present in most fISh zon was reperted in water-breathing fish 10 years ago (Alme­ species. Haemoglobin multiplicity has been considered an ida-Val 1986). Adjustments in gene expression are known to adaptation to unstable environments because there is a clear occur according to environmental changes. These adjust­ association between structural and functional heterogeneity ments are referred to as phenotype plasticity by several for several species such as: the catfish Hoplosternum littorale authors (reviewed by Almeida-Val 1998). (Perez 1980); the catfish Plerygoplichlhys pardalis (Brunori, During the last fifteen years the concept of phenotype plas­ Bonaventura, Focesi, Galdames-Portus & Wilson 1979), the ticity has emerged in the literature including a new idea about prochilodontid Semaprochilodus laeniurus (Val 1983); the diversity (West-Eberhard 1989). According to Walker (1998) catfish Callichlhys callichlhys (Wilhelm & Weber 1983); the the interest in phenotypic plasticity as a relevant evolutionary anostomid Leporinus /riderici (Peterson, Schwantes, De Luca factor was resuscitated by the idea that gene regulation & Schwantes 1989), among others. This observation has been orchestrates the time order of ontogenesis and metabolism, strengthened since some fish species present cyclic changes and establishes the direct biomechanical connection between in the concentrations of specific haemoglobin components environmental stimuli and specific genetic loci via percep­ during the thermoacclimatory process (reviewed by Perez, tion, and regulatory proteins. Fish have sophisti­ Rylander & Nirchio 1995). Cyclic changes in the concentra­ cated systems to detect environmental changes in order to tion of specific haemoglobin fractions related to other envi­ modulate their and biochemistry accordingly. ronmental factors, presumably oxygen availability, have also Catecholamines, cortisol, oxygen itself, HIF (hypoxia been described for Colossoma in the Amazon (Val 1986). induced factor), among others, play an important role in such However, it should be stated that no clear relationship exists modulation (Randall & Perry 1992; Hochachka 1996). These between haemoglobin heterogeneity and environmental char­ aspects are poorly described in fish of the Amazon. acteristics when data from marine, freshwater, and estuarine In fact, in addition to the above described cyclic adjust­ fishes are pooled (Perez el at. 1995; Val & Almeida-Val ments of haemoglobin phenotypes, we have shown for the 1995). enzyme (LDH; E.e. I. I. I .27) that the One of the most common mechanisms for surviving adjustments of metabolic profiles are possible through the hypoxia in nature is the depression of oxidative metabolism regulation of enzyme levels (coarse adjustments) and through and the subsequent activation of the anaerobic metabolism adjustments of isozyme levels and their distribution among (Nilsson 1995). Suppressing energy demands is common dur­ tissues (fine adjustments). Many Amazon fish species present

. LDH adjustments according to environmental conditions. We ) ing hypoxia exposure when the temperature is low (Van 9 have described heart LDH isozyme changes in Colossoma 0 Waversheld, Addink & van den Thillart 1989). Some temper­ 0 macropomum that could be related to oxygen availability in 2

ate fish present modified metabolic pathways to cope with

d its environment (Almeida-Val el al. 1990). In this case, LDH e oxygen depletion; the and the crucian , for t kinetics were adjusted accordingly (Almeida-Val & Val a example, produce ethanol and carbon dioxide as end products d

( 1990). Another interesting example comes from cichlids, a

to avoid accumulation of acidic products in their body during r highly 'plastic' group of animals. Species of cichlids so far e long term hypoxia exposure (Shoubridge & Hochachka h

s analysed present two patterns of LDH tissue distribution i 1983). Tropical fish can not rely on temperature drops to l

b which are related to the oxygen availability in their natural decrease their metabolic rates and avoid high energy u habitats (Almeida-Val el al. 1995). Among these animals, P

demands. However, to deal with such situations, some fishes e some species are even considered anoxia tolerant like the h of the Amazon do depress their metabolism when exposed to t

Oscar, ASlrono/Us ocellalus (Muusze el at. 1998), and may y hypoxia to decrease energy demands and to avoid end pro­ b present two patterns for LDH, as described in Cichlasoma duct accumulation. Cichlasoma amazanarum (Almeida-Val d amazonarum, Astrono/us ocel/atus, and Cichla monoculus e t & Farias 1996) and As/ronotus ocelfatus (Muusze, Marcon, n (Almeida-Val et al. 1995). The species Cichla.>Oma amazon­ a van den Thillart & Almeida-Val 1998) show metabolic r arum is one of the best examples of phenotype plasticity g

depression after 24 h of hypoxia exposure. Catecholamines e regarding LDH tissue distribution. When exposed to long­ c increased in Astrana/us acel/a/us and Serrasalmus nattereri n term (50 days) severe hypoxia (36 mmllg), this fish species e exposed to hypoxia, resulting in the activation of anaerobic c exhibits a modification of LDH distribution, particularly in i l and in metabolite level changes. Additionally, r heart, liver, and brain. Activation of isozyme A4 was e many fish of the Amazon present phenotype adjustments d observed in heart and brain while isozyme 8 4 was deactivated n which consist in down-regulating enzyme levels and up-regu­

u in skeletal muscle and activated in liver. These changes were

y lating glycolytic capacity (Almeida-Val el at. 1993; Almeida­ followed by changes in LDH absolute activities and pyruvate a Val & Hochachlca 1995; Val & Almeida-Val 1995). More­ w inhibition (Figure I). Such plasticity allows the animals to e t over, some adjustments in isozyme tissue distribution, mainly regulate their anaerobic metabolism in order to avoid accu­ a

G in LDH (lactate dehydrogenase, E.e. 1.1. I .27), occur in many mulation of end products. While these data relate to oxygen t

e fish species of the Amazon (Almeida-Val, Schwantes & Val depletion, increase in oxygen content may also induce LDH n i 1990; Almeida-Val, Farias, Silva, Duncan & Val 1995). LDH gene regulation. In fact, exposure of Serrasalmus rhombeus b a is the key enzyme of the anaerobic end of glycolysis and its (the black ) to hypoxia and hyperoxia (6 h) results in S lS y isozyme system is tissue regulated according to metabolic tissue isozyme adjustments, i.e., LDH-A4 (muscle type) b requirements. activated in heart and liver (Figure 2). d e c u d o r p e R 112 S. Afr. J. Zool. 1998,33(2)

5000 ,------,------" not avoid the presence of oxyradicals (Marcon 1997). Anti­ _ nonno x:ia _ hypoxia oxidant defences against hyperoxia include an up-regulation ~ of antioxidant enzymes among others. Hypoxia exposure can 'c 4000 also induce antioxidant defences in some Amazon fish, and E o this is so because the animal is preventing the risk of cell ~ 3000 mus.::l. liver bn,n damage when oxygen is available again (Marcon 1997). 2 1;: :E 2000 Concluding remarks :;;., ~ In fish exposed to hypoxia (natural or experimental, short or ~ 1000 long term), behavioural, physiological and biochemical .1! :x: adjustments are made to preserve the oxygen supply to o • metabolising tissues. Many of these adjustments are prompt ...J o whereas others are on a long-term basis. Behavioural (lateral muscle heart liver brain migrations and aquatic surface respiration, for example) and Figure 1 Changes in tissue LDH levels from Cichlasoma amazon­ morphological (lip extension, stomach/intestine vasculariza­ arum exposed to deep hypoxia for 50 days (after Almeida-Val et 01. tion) adjustments result in changes in oxygen availability and 1995). oxygen transfer mechanisms are readjusted accordingly. Long-term adjustments in the concentrations of specific hae­ moglobin components or LDH profiles are equally important regarding this aspect. So, adjustments of oxygen transfer in fish of the Amazon which experience a diversity of habitats and long and short-tenn changes in their environmental con­ ditions are a never-ending task. o - ______------Acknowledgements MHLMHL Hyperoxia This paper is based on work supported by INPA, CNPq, and SUDAM. ALV and VMFA V are recipients of a research fel­ lowship from the Brazilian National Research Council (CNPq). . ) 9

0 References 0 2

ALMEIDA-VAL, V.M.F. 1986. Lactato desidrogenase de duas d e 0 ______especies de peixes da Amazonia, Myiossoma durivenrris e t a Colossoma macropomum (Characifonnes): Aspectos adaptativos. d MHLMHL (

Ph .D. Dissertation . INPA, Manaus . r e Normoxia ALMEIDA-VAL, V.M .F. 1998. Phenotypic plasticity in Amazon h s fishes: water versus air-breathing. In: Water/Air Transitions in i l

b Biology, (ed.) A.K. Mittal, F.B. Eddy & 1.S. Datta Munshi. u Oxford & IBH Publishing Co ., New Delhi, in press. P

e ALMEIDA-VAL, V.M .F. & FARIAS, J.P. 1996. Respiration in fish h t of the Amazon: Metabolic adjustments to chronic hypoxia. In:

y Physiology and Biochemistry of the fishes of the Amazon, (eds) b

d AL. Val , V.M.F. Almeida-Val & OJ. Randall. INPA, Manaus. e t ----- ALMEIDA-VAL, V.M.F. , FARIAS, J.P. , SILVA, M.N.P., n 0------_MHLMHL a DUNCAN & VAL, A.L. 1995. Biochemical adjustments to r g J. Hypoxia hypoxia by Amazon cichlids. Braz. Med. Bioi. Res. 28: e

c 1257-1265. n

e ALMEIDA-VAL, V.M.F. & HOCHACHKA, P.W. 1995. Air­ c i

l breathing fishes : Metabolic biochemistry afthe first diving

Figure 2 Changes in tissue di stribution ofLDH isozyme in Serrasal­ r vertebrates. In: Biochemistry and molecular biology of fishes, e mus rhombeus exposed to hyperoxia, normoxia and hypoxia (6 h). d (ed.) P. W. Hochachka & T Mommsen. Elsevier, Amslerdam. n M - muscle; H - heart; L -liver. u ALMEIDA-VAL, V.M.F., SCHWANTES, M.L.B. & VAL, A.L.

y 1990. LDH isozymes in Amazon fish . I. Electrophoretic studies a

w on two species from family: Mylossoma duriventris e t Indeed, there is the 'other side of the coin' regarding oxy­ and Colossoma macropomum. Comp. Biochem. Physiol. 9SA: a 77- 84. G gen availability in an ever-changing envirorunent that we t ALMEIDA-VAL, V.M.F. & VAL, A.L. 1990. Adapta~ao e should address at this point. Each time the animal copes with n bioquimica em peixes da AmazOnia. Ciencia Hoje . II : 62-67. i hypoxia it has to cope with recovery from the hypoxic state b ALMEIDA-VAL, V.M.F., VAL, A.L. & HOCHACHKA, P.W. a when the oxygen becomes available again. The re-perfusion S

1993. Hypoxia tolerance in Amazon fishes : Status of an under­ y of some organs such as heart, brain and liver with an oxygen

b explored biological 'goldmine '. In: Surviving Hypoxia:

d rich blood may cause irreversible damage as the animal can Mechanisms of Control and Adaptation, (ed.) P.W. Hochachka, e c u d o r p e R S. Afc. J. Zoo I. 1998, 33(2) 113

P.L. Lutz, T. Sick, M. Rosenthal & G. Van den Thillart. CRC respiration in the catfish Corydoras aeneus (Callichthyidae). Press, Boca Raton. Physiol. Zool. 54 18')...194. ARTHUR, P.G., HOGAN, M.e., BEBOUT, D.E., WAGNER, P.D. MARCON,l.L. 1997. Estresse oxidativo em duas especies de & HOCHACHKA, P.W. 1992. Modelling the effects of hypoxia tele6steos amazonicos, Astronotus ocellatus e Colossoma on ATP turnover in exercising muscle. 1. App!. Physiol. 73: macropomum, expostos a diferentes tensoes de oxigenio: Uma 737-742. abordagem comparativa. Ph.D. Dissertation. rNPA, Manaus. BARTLETT, G.R. 1978. Phosphates in red cells of two South 139 p. American osteoglossids; Arapaima gigas and Osteoglossum MILSON, W.K. 1993. Afferent inputs regulating ventilation in bicirrhosum. Can. 1. ZaoL 56: 878-881. vertebrates. In: The vertebrate gas transport cascade: Adaptations BOHLKE, I.E., WEITZMAN, S.H. & MENEZES, N.A. 1978. to environment and mode of life, (ed.) J.E.P.W. Bicudo. CRC Estado atual da sistematica dos peixes de agua dace da America Press, Boca Raton. do SuI. Acta Amazonica. 8: 657-677. MILSON, W.K. 1996. Control of breathing in fish: Role of BRAUNER, C.l., BALLANTYNE, e.L., RANDALL, D.l. & VAL, chemoreceptors. In: Physiology and Biochemistry of the Fishes of A.L. 1995. Air breathing in the armoured catfish (Hoplosternum the Amazon, (ed.) AL. Val, V.M.F. Almeida-Val & D.l. Randall. littorale) as an adaptation to hypoxic, acid, and hydrogen sulphide INPA, Manaus. rich waters. Can. 1. Zoof. 73: 739--744. MOURA., M.A.F. 1994. Efeito da anem ia, do exercicio fisico e da BRUNORI, M., BONAVENTURA, I., FOCESI IR., A, adrenal ina sabre 0 ba90 e eritr6citos de Colossoma macropomum GALDAMES-PORTUS, M.1. & WILSON, MT. 1979. Separation (Pisces). M.Sc. Thesis. PPG INPA/FUA and characterization of the components of MUUSZE, B., MARCON, I., VAN DEN THILLART, G. & Pterygopiichthys pardalis, the acaribodo. Camp. Biochem. ALMEIDA-VAL, V.M.F. 1998. Hypoxia tolerance of Amazon Physiol. 62A: 173-177. fish: respiratory and energy metabolism of the cichlid Astronotus COX-FERNANDES, e. 1989. Estudo das migrac5es laterais de ocellatus. Compo Biochem. Physiol. in press. peixes do sistema lago do Rei (liha do Careiro), AM. Brasil. MSc NIKINMAA, M. 1990. Vertebrate Red Blood Cells. Adaptations of Thesis. PPG INPAlFUA. Manaus. function to respiratory requirements. Springer-Verlag, Heidelberg. DALESSIO, P.M., DIMICHELE, L. & POWERS, D.A. 1991. 262 pp. Adrenergic regulation of erythrocyte oxygen affinity, pH, and NIKINMAA, M. 1992. Membrane transport and control of nucleotide triphosphatelhemoglobin ratio in the , hemoglobin-oxygen affinity in nucleated erythrocytes. Physiol. Fundulus heteroclitus. Physiol. Zool., 64: 1391-1406. Rev. 72(2): 301-321. FERNANDES, M.N. 1996. Morpho-functional adaptations of gills NILSSON, G.E. 1995. Oxygen availability: brain defence in tropical fish. In: Physiology and Biochemistry of the fishes of mechanisms. In: Biochemistry and Molecular Biology of Fishes. the Amazon, (ed.) A.L. Val, V.M.F. Almeida-Val & D.I. Randall. Environmental and Ecological Biochemistry, (ed.) P.W. INPA, Manaus. Hochachka & T.P. Mommsen. Elsevier Science, Amsterdan.

. FINK, W.L. & FINK, S.V. 1979. Central Amazonia and its fishes. PEREZ, lE. 1980. Respiracion aerea y acuatica en peces de la )

9 Compo Biochem. Physiol. 62A: 13-29. especie Hoplosternum littorale II. Afinidad de sus hemoglobinas 0

0 GONZALEZ, R.I., WOOD, e.M., WILSON, R.W., PATRICK, por el oxigeno. Acta Gent. Venez. 31: 449-455. 2 M.L.. BERGMAN, H.L., NARAHARA, A & VAL, A.L. 1998. PEREZ, I., RYLANDER, K & NIRCHIO, M. 1995. The evolution d e Effects of water pH and Ca2+ concentration on ion balance in fish of multiple hemoglobins in fishes. Rev. Fish BioI. Fish. 5: t a of the Rio Negro. Physiol. Zool. 71(1): 15-22. 304-319. d (

GREANEY, G.S. & POWERS, D.A. 1978. Allosteric modiflers of PETERSON, e.G., SCHWANTES, AR., DE LUCA, P.H. & r e fish hemoglobins: in vitro and in vivo studies of the effect of SCHWANTES, M.L. 1989. Functional properties of the two h s J. major haemoglobin components from Leporinusfriderici (Pisces). i ambient oxygen and. pH on erythrocyte A TP concentrations. l

b Exp. Zool. 203: 339-350. Comp Biochem. Physiol. 948 823-827. u HOCHACHKA, P.W. 1996. Oxygen sensing and metabolic RANDALL, D.I., BURGGREN, W.W., FARRELL, A.P. & P

e regulation: Short, intermediate and long term roles. In: Physiology HASWELL, M.S. 1981. The evolution of air-breathing h t vertebrates. Cambridge University Press, Cambridge. 133 pp

and Biochemistry of the fishes of the Amazon, (ed.) A.L. Val, y V.M.F. Almeida-Val & D.I. Randall. INPA, Manaus. RANDALL, D.I. & PERRY, S.F. 1992. Catecholamines. In: Fish b

d IENSEN, F.B., NIKINMAA, M. & WEllER, R.E. 1993. Physiology, (ed.) W.S. Hoar, D.l. Randall & AP. Farrell, volume e t Environmental perturbations of oxygen transport in teleost fishes: XIIB. Academic Press, New York. n

a causes, consequences and compensations. In: Fish Ecophysiology, RANTIN, F.T. & KALININ, A.L. 1996. Cardiorespiratory function r g (ed.) I.e. Rankin & F.B. lensen. Chapman & Hail, London. and aquatic surface respiration in Colossoma macropomum e

c IUNK, W.l., LlAYLEY, P.B. & SPARKS, R.E. 1989. The flood exposed to graded and acute hypoxia. In: Physiology and n

e pulse concept in River-Floodplain Systems. In: Proceedings of the Biochemistry of the Fishes ofthe Amazon, (ed.) AL. Val, V.M.F. c i International Large River Symposium, (ed.) D.P. Dodge. Can. Almeida-Val & OJ. Randall. INPA, Manaus. l

r Spec. Publ. Fish. Aquat. Sci., Canada. RAPP-PY-DANIEL, L.H. & LEAO, E.L.M. 1989. A cole,30 de e d IUNK, W.l., SOARES, M.G. & CARVALHO, F.M. 1983. peixes do INPA Base do conhecimento cientifico sobre a n

u Distribution of fish species in a lake of the Amazon river ictiofauna amazonica gerado pelo Instituto Nacional de Pesquisas

y floodplain near Manaus Clago Camale~o), with special reference to da Amazonia. In: Bases cienttficas para estrategias de preserva9ao a extreme oxygen conditions. Amazoniana 7: 397-431. e desenvolvimento da Amazonia: Fatos e perspectivas, (ed.) A.L. w e t KALiNIN, A.L., RANTIN, FT., FERNANDES, M.N. & GLASS, Val, E. Feldberg & R Figliuolo. INPA, Manaus. a M.L. 1996. Ventilatory flow relative to intrabuccal and ROBERTS, T.R. 1972. Ecology of the flshes in the Amazon and G

t intraopercular volumes in two ecologically distinct erythrinids Congo basins. Bull. Mus. Compo Zool. 143: 117-147. e

n (Hoplias malabaricus and Hoplias lacerdae) exposed to normoxia ROWLEY, AF., HUNT, T.e., PAGE, M. & MAIWARIl'G, G. i b and graded hypoxia. In: Physiology and Biochemistry of the 1988. Fish. In: Vertebrate red blood cells, (ed.) A.F. Rowley & a

S Fishes of the Amazon, (ed.) AI.. Val, V.M.F. Almeida-Val & D.I. N.A. Ratcliffe. Cambridge University Press, Cambridge.

y Randall. INPA, Manaus. SHOUBRlDGE, EA & HOCHACHKA, P. W. 1983. The b KRAMER, D.L. & MCCLURE, M. 1981. The transit cost of aerial integration and control of metabolism in the anoxic goldfish. d e c u d o r p e R 114 S. Afr. J. ZooL 1998,33(2)

Molec. Physiol. 4: 165-195. Biological aspects of Amazonian fishes. VI. Hemoglobins and VAL, A.L. 1986. Hemoglobinas de Colossoma macropomum whole blood properties of Semaprochilodus species Cuvier, 1818 (Characoidei, Pisces): Aspectos adaptativos (Ilha da (Prochilodontidae) at two phases of migration. Compo Biochem. Marchantaria, Manaus, AM). Ph.D. Dissertation. Instituto Physiol. 83B: 65'Hi67. Nacional de Pesquisas da Amazonia e Universidade do VAN WAVERSVELD, J., ADDINK, A.D.F. & VAN DEN Amazonas, Manaus, AM. THILLART, G. 1989. Simultaneous direct and indirect VAL, A.L. 1993. Adaptations of fishes to extreme conditions in calorimetry on norrnoxic and anoxic goldfish. J. expo Bioi. 142: fresh waters. In: The vertebrate gas transport cascade. Adaptations 325-335. to environment and mode of life, (ed.) J.E.P.W. Bicudo. eRe WALKER, I. 1998. Prediction of evolution? Somatic plasticity as a Press, Boca Raton. basic, physiological condition for the viability of genetic VAL, A.L. 1995. Oxygen transfer in fish: morphological and mutations. Acta Biotheoretica, in press. molecular adjustments. Braz. J. Med. BioI. Res. 28: 1119-1127. WALKER, I. & HENDERSON, PA 1996. Ecophysiological VAL, A.L 1996. Surviving low oxygen levels: Lessons from fishes aspects of Amazonian blackwater litterbank fish communities. In: of the Amazon. In: Physiology and Biochemistry of the fishes of Physiology and Biochemistry of the Fishes of the Amazon, (ed.) the Amazon, (ed.) A.L Val, V.M.F. Almeida-Val & DJ. Randall. A.L. Val, V.M,F. Almeida-Val & DJ. Randall. INPA, Manaus. INPA, Manaus. WEBER, R.E. 1996. Hemoglobin adaptations in Amazonian and VAL, A.L, AFFONSO, E.O., SOUZA, R.H.S., ALMEIDA-VAL, temperate fish with special reference to hypoxia, allosteric V.M.F. & MOURA, MAF. 1992. Inositol pentaphosphate in effectors and functional heterogeneity. In: Physiology and erythrocytes of an Amazonian fish, the pirarucu (Arapaima Biochemistry of the fishes of the Amazon, (ed.) A.L. Val, V.M.F. g,gas). Coo J Zool. 70: 852-855. Almeida-Val & DJ. Randall. rNPA, Manaus. VAL, A.L. & ALMEIDA-VAL, V.M.F. 1995. Fishes of the Amazon WEST-EBERHARD, M.1. 1989. Phenotypic plasticity and Ihe and their environments. Physiological and biochemical features. origins of diversity. Ann. Rey. Ecol. Syst. 20: 249-278. Springer-Verlag, Heidelberg. WILHELM, D. & WEBER, R.E. 1983. Functional characterization VAL, A.L, MARCON, J.L, COSTA, O.T.F., BARCELLOS, of haemoglobins from South Brazilian freshwater teleosts. I. l.F.M .. MACO GARCIA, J.T. & ALMEIDA-VAL, V.M.F. 1998. Multiple haemoglobins from the gutJgiIl breather, Callichthys Fishes of the Amazon: Surviving environmental changes. In: callichlhys. Camp. Biachem. Physiol. 75A: 475-482. Advances in , (ed.) A. Kapoor. New Dehli. In press. WOOD, c'M., WILSON, R.W., GONZALEZ, R.I., PATRICK, VAL, A.L, MENEZES, G.C & WOOD, CM. 1998. Red blood cell M.L., BERGMAN, H.L., NARAHARA, A. & VAL, A.L 1998. adrenergic responses in Amazonian teleosts. J. Fish BioI. 52: Responses of an Amazonian teleost, the tambaqui (Colossoma 83-93. macropomum) to low pH in extremely soft water. Physiol. Zool. in VAL, AL SCHWANTES, AK & ALMEIDA-VAL, V.M.F, 1986. press. . ) 9 0 0 2 d e t a d ( r e h s i l b u P e h t y b d e t n a r g e c n e c i l r e d n u y a w e t a G t e n i b a S y b d e c u d o r p e R