Oxygen Affinity Of Hemocyanin Research Articles

The evolution of hemocyanin genes in Tectipleura: a multitude of conserved introns in highly diverse gastropods

BackgroundHemocyanin is the oxygen transporter of most molluscs. Since the oxygen affinity of hemocyanin is strongly temperature-dependent, this essential protein needs to be well-adapted to the environment. In Tectipleura, a very diverse group of gastropods with > 27,000 species living in all kinds of habitats, several hemocyanin genes have already been analyzed. Multiple independent duplications of this gene have been identified and may represent potential adaptations to different environments and lifestyles. The aim of this study is to further explore the evolution of these genes by analyzing their exon–intron architectures.ResultsWe have reconstructed the gene architectures of ten hemocyanin genes from four Tectipleura species: Aplysia californica, Lymnaea stagnalis, Cornu aspersum and Helix pomatia. Their hemocyanin genes each contain 53 introns, significantly more than in the hemocyanin genes of Cephalopoda (9–11), Vetigastropoda (15) and Caenogastropoda (28–33). The gene structures of Tectipleura hemocyanins are identical in terms of intron number and location, with the exception of one out of two hemocyanin genes of L. stagnalis that comprises one additional intron. We found that gene structures that differ between molluscan lineages most probably evolved more recently through independent intron gains.ConclusionsThe strict conservation of the large number of introns in Tectipleura hemocyanin genes over 200 million years suggests the influence of a selective pressure on this gene structure. While we could not identify conserved sequence motifs within these introns, it may be simply the great number of introns that offers increased possibilities of gene regulation relative to hemocyanin genes with less introns and thus may have facilitated habitat shifts and speciation events. This hypothesis is supported by the relatively high number of introns within the hemocyanin genes of Pomacea canaliculata that has evolved independently of the Tectipleura. Pomacea canaliculata belongs to the Caenogastropoda, the sister group of Heterobranchia (that encompass Tectipleura) which is also very diverse and comprises species living in different habitats. Our findings provide a hint to some of the molecular mechanisms that may have supported the spectacular radiation of one of Metazoa’s most species rich groups.

The effects of hypercapnia on the West Coast rock lobster (Jasus lalandii) through acute exposure to decreased seawater pH — Physiological and biochemical responses

The cold water palinurid Jasus lalandii (“West Coast rock lobster”) is a commercially important crustacean in South Africa and Namibia and inhabits the Benguela Current Eastern Boundary System. This habitat is characterised by strong upwelling events in summer and algal blooms with their subsequent decay in autumn. Upwelling can lead to acute hypercapnia whereas the algal decay is associated with acute hypercapnic hypoxia. Both types of hypercapnic events could become more frequent and severe in the future due to ongoing climate change. The aim of the present study was, however, to study the capability and mechanisms of response in J. lalandii to hypercapnia exclusively. Accordingly, the following research questions were formulated: 1) To what extent is haemocyanin oxygen-binding affinity of adult J. lalandii pH-sensitive? 2) Can adult male J. lalandii respond swiftly to drastic changes in pH? 3) What physiological mechanisms facilitate a potential response to a drastically declining pH, i.e. acute hypercapnia? These questions were answered by analysing 1) the pH sensitivity of the haemocyanin's oxygen binding properties and 2) in vivo changes in the acid–base balance of adult J. lalandii during acute exposure to hypercapnia (pH7.4). Results showed the following: 1) Haemocyanin displays a strong Bohr shift (whole haemolymph: ΔlogP50/ΔpH=−1.17; dialysed haemolymph: ΔlogP50/ΔpH=−0.84) in response to lowering of pH. 2) Acute hypercapnia leads to a decline in extracellular pH within the initial 1.5h of exposure. 3) Thereafter, active compensation becomes apparent as the bicarbonate levels start to increase, with complete compensation reached after 5h of exposure (+2.3mmoll−1; +48%). 3) This bicarbonate increase is reversed when returning lobsters to normocapnia (pH7.9). 4) Levels of molecular modulators of haemocyanin oxygen affinity (Ca2+, Mg2+ and l-lactate) do not change during acute exposure to hypercapnia.Our results show the capability of adult J. lalandii to rapidly and fully compensate the experienced extracellular acidosis, protecting oxygen carrying capacity of haemocyanin and ensuring an outward gradient of CO2. The West Coast rock lobster is therefore well equipped for its habitat where these hypercapnic events are known to occur frequently.

The fundamental niche of blood oxygen binding in the pelagic ocean

Marine species ranging in size from microscopic zooplankton to large predatory fish move vertically in the ocean water column to forage for food and avoid predators. Oxygen and temperature decrease, often rapidly, from shallow to deeper depths, restricting the ability of species to use the vertical habitat. One physiological trait that determines the tolerance of organisms to low oxygen is the oxygen affinity of oxygen carrier proteins, hemoglobin and hemocyanin, in the blood. To quantify the range of oxygen affinities for marine organisms, we surveyed the literature for measurements of oxygen binding to blood at multiple temperatures to account for its temperature sensitivity. Oxygen affinity is mapped within the ocean environment using the depth at which oxygen pressure decreases to the point at which the blood is 50% oxygenated (P50depth) as organisms move from the surface to depth in the ocean water column. We find that vertical gradients in both temperature and oxygen impact the vertical position and areal extent of P50depths. Shifts in P50due to temperature cause physiological types with the same P50in the surface ocean to have different P50depths and physiological types with different P50's in the surface ocean to have the same P50depth. The vertical distances between P50depths are spatially variable, which may determine the frequency of ecological interactions, such as competition and predation. In summary, P50depth, which represents a key physiological transition point between dexoxygenated and oxygenated blood, provides mechanistic insight into organism function within the water column of the global ocean.

Respiratory Properties of Hemocyanin From Wild and Aquacultured Penaeid Shrimp and the Effects of Chronic Exposure to Hypoxia.

Properties of hemocyanins vary greatly among crustaceans due to environmental conditions, lifestyle, and genetic variation. These properties can also be modified to maintain aerobic respiration in response to ambient hypoxia, as experienced by both aquacultured and wild populations of penaeid shrimp. Under normoxic conditions, hemocyanin concentrations were significantly higher (P < 0.001) in aquacultured Pacific whiteleg shrimp, Litopenaeus vannamei (10.3 g/100 ml ± 0.23 SEM, n = 49), compared to those in individuals of wild-caught L. vannamei (7.0 g/100 ml ± 0.52 SEM, n = 10), wild Farfantepenaeus aztecus (7.10 g/100 ml ± 0.48 SEM, n = 28), and wild Litopenaeus setiferus (8.0 g/100 ml ± 0.22 SEM, n = 37). Oxygen affinity of hemocyanin at 25 °C in both populations of L. vannamei was higher (Kruskal-Wallis ANOVA on ranks, P < 0.001) (aquacultured P50 = 1.47 kPa ± 0.03 SEM; wild P50 = 1.72 kPa ± 0.01 SEM at pH 7.4) than that of both Atlantic species (F. aztecus P50 = 3.94 kPa ± 0.06 SEM, L. setiferus P50 = 3.98 kPa ± 0.04 SEM at pH 7.4). The effect of l-lactate on oxygen affinity was similar among all wild groups, but significantly smaller in the aquacultured L. vannamei. Total hemocyanin concentration and oxygen binding properties were measured after exposure to 12 days and 25-31 days of hypoxia (30% air saturation). Aquacultured L. vannamei showed no change in hemocyanin concentration for up to 31 days, but both wild F. aztecus and wild L. setiferus displayed a significant increase over the same time period. No discernible change in oxygen affinity of hemocyanin was detected in any of the three species. Hypoxia tolerance appears to differ among these species of penaeid shrimp, due to either an inherent difference among the species, domestication by aquaculture, or a combination of both.

Molluscan mega-hemocyanin: an ancient oxygen carrier tuned by a ~550 kDa polypeptide

BackgroundThe allosteric respiratory protein hemocyanin occurs in gastropods as tubular di-, tri- and multimers of a 35 × 18 nm, ring-like decamer with a collar complex at one opening. The decamer comprises five subunit dimers. The subunit, a 400 kDa polypeptide, is a concatenation of eight paralogous functional units. Their exact topology within the quaternary structure has recently been solved by 3D electron microscopy, providing a molecular model of an entire didecamer (two conjoined decamers). Here we study keyhole limpet hemocyanin (KLH2) tridecamers to unravel the exact association mode of the third decamer. Moreover, we introduce and describe a more complex type of hemocyanin tridecamer discovered in fresh/brackish-water cerithioid snails (Leptoxis, Melanoides, Terebralia).ResultsThe "typical" KLH2 tridecamer is partially hollow, whereas the cerithioid tridecamer is almost completely filled with material; it was therefore termed "mega-hemocyanin". In both types, the staggering angle between adjoining decamers is 36°. The cerithioid tridecamer comprises two typical decamers based on the canonical 400 kDa subunit, flanking a central "mega-decamer" composed of ten unique ~550 kDa subunits. The additional ~150 kDa per subunit substantially enlarge the internal collar complex. Preliminary oxygen binding measurements indicate a moderate hemocyanin oxygen affinity in Leptoxis (p50 ~9 mmHg), and a very high affinity in Melanoides (~3 mmHg) and Terebralia (~2 mmHg). Species-specific and individual variation in the proportions of the two subunit types was also observed, leading to differences in the oligomeric states found in the hemolymph.ConclusionsIn cerithioid hemocyanin tridecamers ("mega-hemocyanin") the collar complex of the central decamer is substantially enlarged and modified. The preliminary O2 binding curves indicate that there are species-specific functional differences in the cerithioid mega-hemocyanins which might reflect different physiological tolerances of these gill-breathing animals. The observed differential expression of the two subunit types of mega-hemocyanin might allow individual respiratory acclimatization. We hypothesize that mega-hemocyanin is a key character supporting the adaptive radiation and invasive capacity of cerithioid snails.

The Effect of Temperature on the pH, d-Lactate and Haemocyanin Oxygen Affinity ofOpistophthalmus latimanus(Koch) (Scorpionidae) Haemolymph

The pH and d-lactate of the haemolymph from the scorpion, Opistophthalmus latimanus, were measured at different ambient temperatures. The oxygen affinity and molecular cooperativities of haemocyanin in its native and dialysed form were determined when exposed to different ambient temperatures. D-lactate concentration in native haemolymph increased significantly from 0.31 mmol/l at 7 °C to 1.93 mmol/l when haemolymph was exposed to 25 °C for 6 hours but decreases to 0.32 mmol/l at 37 °C The extinction coefficients of O. latimanus haemocyanin at 240 nm and 278 nm were 2.41 and 11.26, respectively, and correspond well with similar data on the crustacean Limulus polyphemus. The subunit cooperativity (n50) of the native haemocyanin molecule increased linearly from n = 3.00 to n = 5.34 at 37 °C. A d-lactate effect on n50 between pH 7.40 and 7.87 could be demonstrated while the heat of oxygenation (ΔH) was -127.64 kJ/mol between 17 °C and 25 °C Like other scorpions investigated, haemocyanin of O. latimanus exposed to wide temperature regimes show a strong temperature dependence of oxygen affinity (as P50) and cooperativity (as n50).

Unusual oxygen binding behavior of a 24-meric crustacean hemocyanin

Hemocyanins from Crustacea usually are found as 1x6 or 2x6-meric assemblies. An exception is the hemocyanin isolated from thalassinidean shrimps where the main component is a 24-meric structure. Our analysis of oxygen binding data of the thalassinidean shrimp Upogebia pusilla based on a three-state MWC-model revealed that despite the 24-meric structure the functional properties can be described very well based on the hexamer as allosteric unit. In contrast to the hemocyanins from other thalassinidean shrimps the oxygen affinity of hemocyanin from U. pusilla is increased upon addition of l-lactate. A particular feature of this hemocyanin seems to be that l-lactate already enhances oxygen affinity under resting conditions which possibly compensates the rather low intrinsic affinity observed in absence of l-lactate. The fast rate of oxygen dissociation might indicate that in this hemocyanin a higher cooperativity is less important than a fast response of saturation level to changes in oxygen concentration.

The Role of Circulating Metal Ions During Shell Fights in the Hermit Crab Pagurus bernhardus

AbstractFighting animals must make a series of decisions, and understanding the proximate causes behind these decisions can give insight into how they are made. For example, fights have been analysed with respect to energetic costs and endocrine changes associated with engaging. However, another mechanism for the control of demanding activity, such as fighting, is the modulation of aerobic capacity by divalent metal ions. Here we examine post‐fight haemolymph concentrations of magnesium (Mg2+) and calcium (Ca2+) ions in the common European hermit crab Pagurus bernhardus. Hermit crabs fight over the ownership of gastropod shells, where they adopt two very different roles during the encounter: attacker and defender. Despite the two roles performing different activities, we found that Mg2+ and Ca2+ affected them similarly, with concentrations of these ions being highest in successful individuals. Haemolymph concentrations of Mg2+ and Ca2+ were also found to increase as a result of fighting, and these elevated levels will, via allosteric interactions, increase the oxygen affinity of the respiratory pigment haemocyanin, enhancing respiratory capacity and therefore fighting ability. Furthermore, the present study revealed that seasonal changes in circulating levels, along with the ability of competitors to respond to them, may ultimately influence an individual’s success in aggressive interactions.

The oxygen-binding modulation of hemocyanin from the Southern spiny lobster Palinurus gilchristi

Arthropod hemocyanins transport and store oxygen and are composed of six subunits, or multiples thereof depending on the species. Palinurus gilchristi hemocyanin is found only as 1 x 6-mers, as normally occurs in spiny lobsters. An alkaline pH and removal of calcium ions induce a wholly reversible dissociation into monomers. The oxygen-binding properties of 1 x 6-meric hemocyanin from P. gilchristi were investigated with respect to pH and modulating effect exerted by calcium, lactate and urate. The oxygen affinity was highly affected by pH in the presence of calcium ions, while in its absence the Bohr coefficient became 60% lower. The protein is insensitive to lactate, but affected by urate which markedly increased hemocyanin-oxygen affinity, acting as the physiological major positive effector. Calcium ions decrease oxygen affinity at low concentration range (0-1 mM), while as concentration becomes higher than 100 mM, the oxygen affinity increases, indicating the presence of two independent types of calcium-binding sites with high and low affinity, respectively. The previous hypothesis, that the presence of high-affinity binding sites in addition to low affinity ones could be a characteristic feature of Palinuran hemocyanins, has been tested by analyzing, with respect to calcium-hemocyanin interaction, three other species belonging to Palinura.

Respiratory physiology of the Oniscidea: Aerobic capacity and the significance of pleopodal lungs

The radiation of the terrestrial isopods (sub-order Oniscidea) has been accompanied by evolution of pleopodal lungs in the sections Tylida and Crinocheta. To understand the significance of such lungs for aerobic respiration, comparative studies were conducted using 6 species. Ligia occidentalis, lacking lungs, behaved as a metabolic conformer in reduced PO 2, and showed decreased V̇O 2 in low humidity and following dehydration. In species possessing lungs, metabolism was insensitive to dehydration. However, lung development did not show a clear relationship to metabolic regulation: Porcellio dilatatus was a metabolic conformer while Tylos punctatus and Armadillidium vulgare were efficient regulators. The metabolic conformers did not accumulate lactate during moderate hypoxia (10% O 2), indicating that reduced V̇O 2 is not compensated with anaerobic glycolysis. In contrast, Alloniscus perconvexus, a littoral species with limited metabolic regulation, showed the largest lactate accumulation during hypoxia and also possessed the highest tissue LDH activity. It is hypothesized that these are adaptations to periodic hypoxia in sand burrows and the high metabolic cost of burrowing. Differences in lactate accumulation during immersion were curious, with the largest increases occurring in L. occidentalis and A. perconvexus that tolerate prolonged immersion in seawater. Possible functions of this lactate accumulation may include modulation of hemocyanin oxygen affinity.

Allosteric Models for Multimeric Proteins: Oxygen-Linked Effector Binding in Hemocyanin

In many crustaceans, changing concentrations of several low molecular weight compounds modulates hemocyanin oxygen binding, resulting in lower or higher oxygen affinities of the pigment. The nonphysiological effector caffeine and the physiological modulator urate, the latter accumulating in the hemolymph of the lobster Homarus vulgaris during hypoxia, increase hemocyanin oxygen affinity and decrease cooperativity of oxygen binding. To derive a model that describes the mechanism of allosteric interaction between hemocyanin and oxygen in the presence of urate or caffeine, studies of oxygen, urate, and caffeine binding to hemocyanin were performed. Exposure of lobster hemocyanin to various pH values between 7.25 and 8.15 resulted in a decrease of p50. In this pH interval, p50 decreases from 95 to 11 Torr without effectors and from 49 to 6 Torr and from 34 to 5 Torr in the presence of 1 mM urate or caffeine, respectively. Thus, the allosteric effects induced by protons and urate or caffeine are coupled. In contrast, isothermal titration calorimetry did not reveal any differences in binding enthalpy (DeltaH degrees ) for urate or caffeine under either normoxic or hypoxic conditions at different pH values. Despite these apparently conflicting results, they can be explained by the nested MWC model if two different types of modulator binding sites are assumed, an allosteric and a nonallosteric type of site. Simulations of in vivo conditions with this model indicate that the naturally occurring modulator urate is physiologically relevant in H. vulgaris only during hypoxic conditions, i.e., either during environmental oxygen limitation or extensive exercise.

Calcium, Copper Protein And Oxygen Affinity In Haemocyanins Of Aestivating And Nonaestivating Snails (&lt;i&gt;Achatina achatina&lt;/i&gt;)

Under dry conditions, land snails withdraw into their shells closing the entrance with a calcified mucous membrane called epiphragm and become dormant (aestivate). In this state, the partial pressure of oxygen gradually falls to low levels whereas the partial pressure of carbon dioxide rises. We have investigated the effect of aestivation on the haemolymph inorganic ions, the oxygen affinity of haemocyanin in the giant African snail, Achatina achatina. After four months of aestivation, they were 46.35%, 4.19%, 44.60% decreases in haemolymph protein, pH and body weight respectively and significant increases in haemolymph Cu2+ and Ca2++, i.e is 161.16% and 75.09% respectively. The increases in divalent ions which may have resulted from the need to buffer the decrease in extracellular pH during aestivation is likely responsible for the high oxygen affinity of haemocyanin (43.0% increase) from aestivating snails through co-operative oxygen binding. Key Words: Aestivation, snail, Achatina achatina, inorganic ions, haemocyanin, absorption spectra, oxygen affinity. Bio-Research Vol.2(1) 2004: 115-123

Effects of emersion and elevated haemolymph ammonia on haemocyanin-oxygen affinity of Cancer pagurus

The subtidal crab Cancer pagurus (L.) experiences involuntary periods of emersion associated with practices used in their marketing and distribution. During 24 h emersion, impaired gill function caused an increase of circulating total ammonia (TA=NH3+NH4 +) of 0.35 mmol TA l–1 (167%). The oxygen-binding characteristics of the haemocyanin of C. pagurus were examined at 10°C in the presence of total ammonia (0.2–1.0 mmol TA l–1). The haemocyanin–oxygen affinity was decreased in the presence of TA (ΔlogP 50/Δlog[TA]=0.16). Emersion induced significant acidosis and elevated circulating levels of haemolymph TA, lactate and urate, but all had returned to normal levels within 24 h of re-immersion. The accumulation of haemocyanin-modulating substances during 24 h emersion compensated partially (40%) for the effect of the acidosis, but the net effect of the emersion period was a significant decrease in oxygen affinity, corresponding to an increase of P 50 (10°C ) from 1.24 kPa (immersed) to 1.96 kPa (24 h emersion). The implications of the findings are considered in terms of the effects and adaptations to emersion.

Study on the oxyhemocyanin, deoxyhemocyanin, oxygen affinity and acid–base balance of Marsupenaeus japonicus following exposure to combined elevated nitrite and nitrate

Marsupenaeus japonicus (11.47±0.71 g) exposed individually to six different nitrite and nitrate regimes {(0.002 (control), 0.359 and 1.456 mM nitrite combined with 0.005 (control) and 7.458 mM nitrate)} in salinity of 30 ppt (parts per thousand) were examined for hemocyanin oxygen affinity, the fractionation of oxyhemocyanin and deoxyhemocyanin, and the acid–base balance after 24 h. Ambient nitrite at concentration of 0.359 mM caused reduction of oxyhemocyanin and protein by 27 and 11%, respectively, whereas ambient nitrate as high as 7.458 mM caused reduction of oxyhemocyanin and protein by 10 and 7%. Ambient nitrite at concentration of 1.456 mM caused increases of P 50 (indicating reduced oxygen affinity) and pO 2, but caused reduction in hemolymph pCO 2, pH, HCO 3 − and TCO 2. Following exposure to combined solutions of 1.456 mM nitrite and 7.458 mM nitrate there were no further changes in oxyhemocyanin, protein, hemolymph P 50, pO 2, pCO 2, HCO 3 − and TCO 2, but there was a significant reduction of pH.

Modulation of haemocyanin oxygen affinity: properties and physiological implications in a changing world.

Crustacean haemocyanin oxygen affinity may be modified through changes in concentration of various inorganic and organic allosteric modulators. These may act in both positive and negative directions, increasing or decreasing haemocyanin oxygen affinity, and assist both in oxygen loading at the gills and oxygen release in the tissues. Inorganic ions, except for Mg(2+), do not normally influence cooperativity or the Bohr effect, whereas most of the organic modulators decrease cooperativity without affecting the Bohr coefficient. Several new findings on the influence of sulphide and thiosulphate are reviewed together with evidence for unidentified factors that decrease haemocyanin oxygen affinity. The physiological implications of all these findings are discussed in the context of maintaining a flexible response to a changing environment.

Temperature effects on hemocyanin oxygen binding in an antarctic cephalopod.

The functional relevance of oxygen transport by hemocyanin of the Antarctic octopod Megaleledone senoi and of the eurythermal cuttlefish Sepia officinalis was analyzed by continuous and simultaneous recordings of changes in pH and hemocyanin oxygen saturation in whole blood at various temperatures. These data were compared to literature data on other temperate and cold-water cephalopods (octopods and giant squid). In S. officinalis, the oxygen affinity of hemocyanin changed at deltaP50/degrees C = 0.12 kPa (pH 7.4) with increasing temperatures; this is similar to observations in temperate octopods. In M. senoi, thermal sensitivity was much smaller (<0.01 kPa, pH 7.2). Furthermore, M. senoi hemocyanin displayed one of the highest levels of oxygen affinity (P50 < 1 kPa, pH 7.6, 0 degrees C) found so far in cephalopods and a rather low cooperativity (n50 = 1.4 at 0 degrees C). The pH sensitivity of oxygen binding (delta log P50/delta pH) increased with increasing temperature in both the cuttlefish and the Antarctic octopod. At low PO2 (1.0 kPa) and pH (7.2), the presence of a large venous oxygen reserve (43% saturation) insensitive to pH reflects reduced pH sensitivity and high oxygen affinity in M. senoi hemocyanin at 0 degrees C. In S. officinalis, this reserve was 19% at pH 7.4, 20 degrees C, and 1.7 kPa O2, a level still higher than in squid. These findings suggest that the lower metabolic rate of octopods and cuttlefish compared to squid is reflected in less pH-dependent oxygen transport. Results of the hemocyanin analysis for the Antarctic octopod were similar to those reported for Vampyroteuthis--an extremely high oxygen affinity supporting a very low metabolic rate. In contrast to findings in cold-adapted giant squid, the minimized thermal sensitivity of oxygen transport in Antarctic octopods will reduce metabolic scope and thereby contribute to their stenothermality.

Effects of thiosulphate on haemocyanin oxygen affinity in the isopod Saduria entomon (L.) and the brown shrimp Crangon crangon (L.)

The sulphide-tolerant brackish water isopod Saduria entomon has haemocyanin with a high affinity for oxygen. Sulphide is oxidized in the hepatopancreas to thiosulphate. Oxygen needed for this oxidation is transported bound to haemocyanin. Thiosulphate was found to improve haemocyanin oxygen affinity in S. entomon. The modulating effect was time and concentration dependent. The effect was greater at higher pH, i.e. the Bohr effect was greater (−1.82) compared to that seen without thiosulphate (−1.36). S. entomon exposed to simultaneous severe hypoxia and sulphide had a low haemolymph pH and the partial pressure of oxygen required to reach 50% saturation was even lower than that measured in vitro. This is ascribed to the combined effects of thiosulphate and lactate as well as unknown co-factors. Thiosulphate had no effect at all in the sulphide and hypoxia non-tolerant natantian Crangon crangon. It is suggested that thiosulphate can be important as a haemocyanin modulator for crustaceans digging in sulphide-rich sediments or constantly exposed to sulphide.

Hemocyanin oxygen affinity, and the fractionation of oxyhemocyanin and deoxyhemocyanin for Penaeus monodon exposed to elevated nitrite

Hemocyanin oxygen affinity and the fractionation of oxyhemocyanin and deoxyhemocyanin in the hemolymph of Penaeus monodon were studied for individual shrimps exposed to 0.001 (control), 0.07, 0.36, 0.72 and 1.44 mmol l −1 nitrite for 3 h up to 48 h in a salinity of 30 ppt at 25°C. The hemolymph P 50 increased (indicating reduced affinity) and the hemolymph pO 2 increased directly with ambient nitrite and exposure time. Hemolymph pH, oxyhemocyanin and hemolymph protein were inversely related to ambient nitrite and exposure time. P. monodon, following 6 h exposure to ambient nitrite at 0.36 mmol l −1, decreased significantly the fraction of oxyhemocyanin and increased that of deoxyhemocyanin. The increase of P 50 and the increased fraction of deoxyhemocyanin suggests that hemocyanin oxygen binding decreases with a concomitant decrease of hemolymph pH, when P. monodon is subjected to nitrite.

Oxygen transport by the hemocyanin of the protobranch mollusc Solemya reidi

Oxygen transport by the hemocyanin of the protobranch mollusc Solemya reidi Bernard was studied in native hemolymph samples. Clams were collected from two different reducing environments, beneath log booms in Alberni Inlet, British Columbia, Canada, and from the sewage effulent in Santa Monica Bay, California, USA. The hemocyanin concentration in a pooled hemolymph sample (n = 10 individuals) was 33.5 mg ml−1. The mean hemolymph pH of five Alberni clams maintained for 3 wk in mud was 7.96 ± 0.06. No significant variation in hemocyanin oxygen-affinity or cooperativity was found for hemocyanin in whole hemolymph samples from these five individually studied clams. There was a significant difference only at 15 °C in the oxygen affinity of hemocyanin in pooled whole-hemolymph samples from S. reidi collected from Alberni Inlet compared with clams collected from Santa Monica Bay. Little effect of temperature on hemocyanin oxygen-affinity was found for temperatures below 20 °C; above 20 °C, the oxygen affinity was reduced for clams from both sites. Temperature and pH had no apparent affect on hemocyanin cooperativity. Moderate Bohr shifts were found at all temperatures examined. The presence of physiologically relevant concentrations of thiosulphate in hemocyanin samples resulted in a decrease in hemocyanin oxygen-affinity, opposite to the effect on hemocyanin found for the hydrothermal vent crab Byth-ograea thermydron, but thiosulphate had no effect on hemocyanin cooperativity.

Effects of short-term hypoxia on metabolism and haemocyanin oxygen transport in the prawns Palaemon adspersus and Palaemonetes varians

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 167:177-183 (1998) - doi:10.3354/meps167177 Effects of short-term hypoxia on metabolism and haemocyanin oxygen transport in the prawns Palaemon adspersus and Palaemonetes varians Annemette Nielsen, Lars Hagerman* Marine Biological Laboratory, Copenhagen University, Strandpromenaden 5, DK-3000 Helsingør, Denmark *Addressee for correspondence. E-mail: mbllh@inet.uni2.dk In summer, high temperatures are combined with severe nocturnal hypoxia in the shallow water of Danish fjords. Under these conditions, the prawns Palaemonetes varians (Leach) and Palaemon adspersus (Rathke) are spatially separated, with the former occupying the areas of highest temperature and lowest oxygen tension. If kept together, P. adspersus shows aggressive behaviour towards P. varians. Aerobic/anaerobic respiration and haemocyanin characteristics were measured in laboratory experiments (24°C, 14 ppt). Although the 2 species have similar metabolic rates, P. varians survives severe hypoxia better and has a lower Pc (critical oxygen tension, below which respiration is partly or fully anaerobic) than P. adspersus. Both species accumulate high levels of lactate during anaerobiosis and remove it at similar rates. The haemocyanin concentration and total oxygen carrying capacity (0.78 ± 0.25 mmol l-1 and 2.25 ± 0.56 vol%) of P. varians was higher than P. adspersus (0.28 ± 0.07 mmol l-1 and 1.14 ± 0.15 vol%). Haemocyanin oxygen affinity was always higher in P. varians regardless of pH, but the Bohr factor (-1.44 and -1.46) and cooperativity (n50: 2.61 ± 0.20 and 2.82 ± 0.49) were similar for P. varians and P. adspersus, respectively. P. varians is thus better adapted to severe hypoxia than P. adspersus. Aerobic/anaerobic metabolism · Lactate · Oxygen affinity Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 167. Publication date: June 18, 1998 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1998 Inter-Research.