Haliotis Iris Research Articles

Differential effects of suspended sediments on larval survival and settlement of New Zealand urchins Evechinus chloroticus and abalone Haliotis iris

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 314:149-158 (2006) - doi:10.3354/meps314149 Differential effects of suspended sediments on larval survival and settlement of New Zealand urchins Evechinus chloroticus and abalone Haliotis iris Nicole E. Phillips*, Jeffrey S. Shima School of Biological Sciences, PO Box 600, Victoria University of Wellington, Wellington 6001, New Zealand *Email: nicole.phillips@vuw.ac.nz ABSTRACT: Larvae of marine organisms play an important role in the dynamics of populations, are generally sensitive to environmental stressors, and vary dramatically among species in life history traits. We examined the effects of suspended sediments from terrestrial runoff on larval development, survival, and settlement of New Zealand sea urchins Evechinus chloroticus and abalone Haliotis iris. Larval urchins and abalone were reared under 5 suspended sediment regimes (variable concentrations and timing of exposure, benchmarked against nearby field conditions), and in the absence of sediments. Stage specific per capita mortality rates of urchin larvae increased with concentrations of suspended sediments, and generally, these rates (and the sensitivity of urchin larvae to sediments) decreased with age. Mortality rates of abalone similarly increased in response to sediment concentrations, although older larvae continued to incur high losses when exposed to sediments. Mortality rates of both abalone and urchins increased in response to acute exposure to sediments early in development. For urchins, this effect was immediate and coincident only with exposure to sediments, whereas elevated mortality rates persisted well after the removal of sediments for abalone. Cumulative survival to competency was similar among species and generally decreased with exposure time and/or concentration of sediments. Urchins were twice as likely to settle and metamorphose as abalone but patterns were not related to larval sediment regime for either species. The strong species specific responses to suspended sediments we observe may greatly alter patterns of larval connectivity in marine meta-communities. KEY WORDS: Suspended sediment · Runoff · Larval mortality · Recruitment · Settlement · Abalone · Urchins Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 314. Online publication date: May 22, 2006 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2006 Inter-Research.

The effects of tactile stimulants on feeding, growth, behaviour, and meat quality of cultured Blackfoot abalone, Haliotis iris

The New Zealand Blackfoot abalone or paua, Haliotis iris uses both tactile and chemosensory cues to detect and feed on drifting seaweed in its natural habitat. In aquaculture situations, abalone are usually provided with static artificial food pellets, effectively removing the tactile stimulus. This study investigated the effects of tactile stimuli from suspended particles on pellet ingestion, growth, behaviour and meat quality of juvenile paua (length 40–45 mm). Over eleven months, individuals were offered a commercial pellet diet (AbFeed™) and small quantities of one of four particulate materials: macerated seaweed (Gracilaria spp. and Macrocystis pyrifera) and 2 sizes of synthetic PVC fragments. There was seasonal variation in the ingestion rate of abalone from all treatments and the control (no stimulants) with lowest rates during winter (June to September) and highest rates in summer (December to February).The specific growth rate (% body weight gain per day) and shell length increase varied seasonally. Of the four treatments, the only effective stimulant was Gracilaria spp. which resulted in summer shell growth of 110.6±3.2 μm d−1 compared with 86.9±4.0 μm d−1 for control abalone. Behavioural observations showed that when Gracilaria particles were present, abalone spent >80% of their time engaged in feeding-related activity. Control abalone, without the algal stimulant, spent most of their time in a sedentary position. None of the particulate stimulants tested had any significant effect on food conversion ratio, water content, protein, lipid and glycogen levels or meat tenderness. These parameters were, however, significantly affected by season. A preliminary trial of the Gracilaria particle treatment in a commercial system over 90 days enhanced the growth of cultured H. iris (45±5 mm shell length) by 15.3%. The main commercial implication of this research is that the addition of algal stimulants is suggested as a cost-effective means of improving abalone performance using pre-existing culture systems and food types.

Heterogeneous perfusion of the paired gills of the abaloneHaliotis irisMartyn 1784: an unusual mechanism for respiratory control

The abalone Haliotis iris retains the ancestral gastropod arrangement of a pair of bipectinate gills (ctenidia). The gills share a single branchial chamber, are supplied from a common haemolymph sinus and effectively support the whole of oxygen uptake by the animal. Using chronic indwelling cannulae and pulsed Doppler probes, post-branchial haemolymph oxygen partial pressures (PaO2) and haemolymph flow rates were measured in the left and right efferent ctenidial veins. During periods of internal hypoxia following emersion and handling, total branchial haemolymph flow (24.4+/-3.6 ml kg-1 min-1) was partitioned nearly equally between the left and right gills (13.3+/-2.6 and 10.8+/-1.4 ml kg-1 min-1, respectively) and their PaO2 values were similar (81.9+/-6.1 and 87.3+/-4.7 mmHg, respectively). In animals settled for >24 h, branchial haemolymph flow decreased to 9.1+/-2.1 ml kg-1 min-1, primarily resulting from a virtual shutdown of the left gill flow to only 4.6% of total flow (left, 0.41+/-0.34 ml kg-1 min-1; right, 8.6+/-2.0 ml kg-1 min-1). At rest, right gill PaO2 (85.5+/-6.8 mmHg) was essentially unchanged while PaO2 of the slowly perfused left gill rose to 105.3+/-10.2 mmHg, close to the PO2 of the exhalant seawater (104.5+/-3.1 mmHg). The aerobic metabolic scope of H. iris therefore appears to be met primarily by circulatory adjustments at the left gill, which at rest is highly perfusion limited (left Ldiff, 0.14+/-0.07; right Ldiff, 0.44+/-0.08).

Oxygen uptake, diffusion limitation, and diffusing capacity of the bipectinate gills of the abalone, Haliotis iris (Mollusca: Prosobranchia)

Extant abalone retain an ancestral system of gas exchange consisting of paired bipectinate gills. This paper examines the hypothesis that fundamental inefficiencies of this arrangement led to the extensive radiation observed in prosobranch gas exchange organs. Oxygen uptake at 15 °C was examined in the right gill of resting adult blackfoot abalone, Haliotis iris Martyn 1784. Pre- and post-branchial haemolymph and water were sampled and oxygen content, partial pressure ( Po 2), pH, and haemocyanin content measured; in vivo haemolymph flow rate was determined by an acoustic pulsed-Doppler flowmeter. During a single pass across the gills, mean seawater Po 2 fell from 138.7 Torr to 83.4 Torr, while haemolymph Po 2 rose from 37.2 Torr to 77.0 Torr raising total O 2 content from 0.226 to 0.346 mmol L − 1 . Haemolymph flowed through the right gill at a mean rate of 9.6 mL min − 1 and carried 0.151 to 0.355 mmol L − 1 of haemocyanin (mean body mass 421 g). Only 34.7% of the oxygen carried in the arterial haemolymph was taken up by the tissues and less than half of this was contributed by haemocyanin. A diffusion limitation index ( L diff) of 0.47–0.52, a well-matched ventilation–perfusion ratio (1.2–1.4) and a diffusing capacity ( D) of 0.174 μmol O 2 kg − 1 Torr − 1 indicate that the gills operate efficiently and are able to meet the oxygen requirements of the resting abalone.

Isolation, Characterization, and Expression Analysis of Three Actin Genes in the New Zealand Black-Footed Abalone, Haliotis iris

Three actin genes -- H. irisA1, H. irisA2, and H. irisA3 -- from the mollusc Haliotis iris (New Zealand black-footed abalone) were isolated by polymerase chain reaction (PCR). The genes were similar to molluscan (84.1% to 94.9%) and vertebrate (84.5% to 86.6%) actins. The sequence similarity between the genes ranged from 88.5% to 93.2%. The greatest disparity, 32.3%, was found over a 99-nt region located at nt 808-906 of H. irisA1, corresponding to amino acids 212-244 of the three actins. The H. iris actin gene family contains at least eight members. Reverse transcription (RT)-PCR analysis of the three genes showed H. irisA1 and H. irisA2 were expressed at low levels in fertilized eggs and blastula stages and at high levels in trochophore and veliger larvae. H. irisA3 was detected in fertilized eggs; it was not detected in the blastula stages and at high levels in the trochophore and veliger larvae. The structure and expression of the three actin genes are discussed.

Modelling transport of larval New Zealand abalone (Haliotis iris) along an open coast

The dispersal and transport of larval New Zealand abalone Haliotis iris was simulated using coupled two-dimensional hydrodynamic and Lagrangian particle-trajectory models. The aim was to estimate pelagic larval dispersal potential along the open coast, as a starting point from which basic management questions can be made for this recreationally and commercially important species. Larval dispersal was simulated from representative spawning sites under a range of representative hydrodynamic conditions, including wave-induced circulation cells. Larval presence over near-shore reef habitat declined as the energy of the flow field and corresponding larval dispersal and transport increased. Thus, spawning during high-energy conditions will promote dispersal and transport but reduce successful recruitment on near-shore reefs. This indicates that seeding of the adjacent coast is likely to be sporadic, with existing populations necessarily being somewhat self-recruiting. Results suggest that an ideal management system would ensure that adult populations were maintained at intervals of 10–30 km along the coast to maintain larval supply to areas in between. Dispersal characteristics were specific to the release site, and the simulations suggest that marine reserves can be positioned to accordingly achieve desired functions: for example, optimal choices can be made for seeding areas, recruitment or self-maintaining areas.

Demographic variation in the New Zealand abalone Haliotis iris

Growth data for the New Zealand abalone Haliotis iris were collected from 30 sites around the New Zealand coast by tag–recapture methods. Most data were collected to provide input into abalone stock assessments within discrete management areas, but had not been examined to determine the nature or extent of any large-scale patterns that might be useful to fishery managers. Sites spanned more than 10° of latitude and were subject to a large range of wave energies and temperatures. Mean monthly sea surface temperature (SST) and wave energy were estimated for each site and a generalised linear regression model was used to examine the relationship between variables. Size-at-maturity was also examined at ten sites. Initial length of abalone explained 35% of the variation in incremental growth, and a further 19% was explained by maximum SST, which also explained 60% of the variation in asymptotic length. Fastest growth was generally in areas with lower mean monthly maximum SST, and sites with the slowest growth had the highest mean monthly maximum SST. Size-at-maturity decreased with increasing temperature. The implications of these broad patterns upon abalone fisheries management strategies are discussed.

The role of body surfaces and ventilation in gas exchange of the abalone, Haliotis iris

The role of body surfaces and ventilation in gas exchange of the abalone, Haliotis iris

The mineralogical microstructure of shells: PART 2. The iridescence colors of abalone shells

The iridescence colors of abalone shell arise from Bragg diffraction of light from the layers of the nacre. The thickness of the aragonite nacre tiles is locally regular but varies during the growth cycles of the shell and this can give rise to complex color play. In Paua shell (Haliotis iris) and in H. fulgens (particularly the muscle scar shell) the thickness of the nacre tiles varies from 0.25(3) to 0.39(3) μm, but locally the thickness is constant within domains of hundreds of tiles. Other species such as H. laevigata and H. rufescens are similar, but their tile thicknesses range from 0.35(4) to 0.52(4) μm. In all species, the color displayed changes with observation angle and is due to layer diffraction. In H. iris and H. fulgens, the colors displayed encompass the complete visible spectrum; color hues are pure and are well-defined first-order diffraction colors. Shells of the other species display red and green, but not blue colors. The colors are rendered most vividly where dark organic growth layers are formed. These absorb or scatter light and enhance the iridescence colors. The origin and nature of the diffraction colors are compared with those observed in labradorite and opal. The degree of regularity in tile thickness needed to allow diffraction colors to be generated is modeled using pearl (sheet nacre) and abalone shell (columnar nacre) as examples. The wavelength dispersion is proportional to the product of the squares of the refractive indices of the material, the normalized standard deviation of the thickness, and the order of the diffraction color. For this reason, only first-order diffraction color is seen from shells.

The role of body surfaces and ventilation in gas exchange of the abalone, Haliotis iris

The archaeogastropod Haliotis iris possesses paired bipectinate gills and normally four to six shell holes. In still water, endogenous water flow entered the branchial chamber anteriorly to the left of the head and was exhaled primarily from the three most posterior holes. The first or second anterior aperture was occasionally weakly inhalant. Cardiac interaction superimposed an oscillatory component upon ciliary ventilation but did not augment mean flow. At normal endogenous flow rates 49% of oxygen was extracted from the branchial flow, increasing to 71% at lower flows. In still water, normoxic M(O(2)) was 0.47 micromol g(-1) h(-1). Oxyregulation occurred down to P(O(2)) approximately 80 Torr, with partial oxyregulation down to 45 Torr (P (crit)), and oxyconformity below this. The oxyregulatory plateau was absent in artificially ventilated animals but normoxic M(O(2)) was higher (0.65 micromol g(-1) h(-1)). Endogenous ventilation was unaffected by hypoxia to 15 Torr. Heart rate decreased by approximately 20% at 26 Torr before falling more steeply. Oxygen uptake from the branchial ventilation stream fully accounted for normoxic M(O(2)). In hypoxia (<30 Torr), no uptake occurred from the head or foot despite extensive eversion of the epipodium. Blood oxygen measurements excluded the right mantle as a significant gas exchange organ. Changes in oxygen uptake caused by changes in the velocity of external water currents support the concept of induced ventilation and suggest that in still water aerobic respiration was ventilation-limited. Although ciliary ventilation appears adequate to support resting aerobic metabolism, induced ventilation may provide increased aerobic scope for activity and repayment of oxygen debt.

Extracellular fluid volume, urine filtration rate and haemolymph mixing time in the abalone, Haliotis iris Martyn: a comparison of 51Cr-EDTA and 14C-inulin as extracellular markers

Measurement of extracellular fluid volume (ECFV, haemolymph or blood volume) of abalone is important for understanding respiratory and circulatory functions and for investigation of factors affecting meat recovery in the fishery. The compounds 14C-inulin and 51Cr-ethylenediaminetetraacetic acid (EDTA) were evaluated as markers for the determination of ECFV and primary urine formation (filtration) in New Zealand blackfoot abalone or paua, Haliotis iris. The volume of distribution of either marker reliably estimated ECFV after correction for clearance (56.6 ± 3.5 mL 100 g–1 soft tissue). 51Cr-EDTA was cleared from the haemolymph three to five times faster than 14C-inulin and was sequestered in the kidneys, digestive gland and mucous gland. 51Cr-EDTA was therefore unsuitable as a filtration marker. Urine filtration rate was best estimated from the appearance of inulin in the seawater (16.2 ± 2.1 mL 100 g–1 soft tissue day–1). The ECFV (inulin space) of isolated tissues ranged from 12–17 mL 100 g–1 tissue in the digestive gland, foot and adductor muscle to 60–70 mL 100 g–1 tissue in the kidneys, right ctenidium and epipodium. Equalisation of both markers between the efferent ctenidial vein and haemolymph lacunae of the shell adductor muscle occurred extremely slowly (t1/2 ~2 h, t0.95 ~8 h), confirming the poor perfusion of this anaerobic muscle.

An efficient water conditioning system for land-based abalone aquaculture

Data collected from a single grow-out tank in an abalone farm in southern New Zealand has highlighted hygiene maintenance problems in the use of semi-closed water conditioning systems for the aquaculture of New Zealand black foot abalone Haliotis iris. The data shows that semi-closed systems can have high concentrations of un-ionized ammonia, which is harmful to the animals. In this paper an alternative open flow-through system is suggested where energy demand is limited by heat recovery at the grow-out tank outlet. Using temperature data collected over 1 year, and a previously obtained expression for standing losses, a simple energy model is presented for an open system with heat recovery. To compliment the energy model, a function has been established for abalone production with respect to the concentration of un-ionized ammonia and water temperature. The energy model and production function are combined to determine the impact of plant design and tank conditions on the economics of the operation for the southern New Zealand climate. It is demonstrated that temperature control is financially preferable to an open system with no temperature control, and estimates of optimum operating conditions are given. Copyright © 2004 John Wiley & Sons, Ltd.

Mineralogical Variation in Shells of the Blackfoot Abalone, Haliotis iris (Mollusca: Gastropoda: Haliotidae), in Southern New Zealand

The New Zealand blackfoot abalone, Haliotis iris Gmelin, is among the few gastropods that precipitate both calcite and aragonite in their shells. The location, composition, and thickness of these mineral layers may affect color, luster, and strength of the shell, which is locally important in jewelry manufacture. Skeletal mineralogy and shell structure of H. iris from three southern New Zealand locations were determined using X-ray diffractometry, scanning electron micrography, and mineral staining. In H. iris an outer calcitic layer is separated from an inner aragonitic surface by both calcified and noncalcified organic layers running longitudinally through the shell. Skeletal mineralogy within individual shells varies from 29 to 98% aragonite, with older shell having significantly higher aragonite content than young sections. Variation within populations ranges from 40 to 98% aragonite, and among three populations from 34 to 98% aragonite. Shell thickness, too, varies within individual shells from 0.2 to 4.2 mm, with a significant positive relationship with age. Withinpopulation variation in shell thickness ranges from 2.1 to 5.4 mm, with no significant difference in shell thickness variation among populations. The high degree of variability within and among individual shells suggests that it is essential to test replicate samples from individual mollusk shells, especially when they have complex bimineral structure.

Thermal constraints on glycolytic metabolism in the New Zealand abalone, Haliotis iris: the role of tauropine dehydrogenase

Black‐foot abalone, Haliotis iris, were sampled from two populations in warm northern waters, and from two in colder southern waters. Abalone muscle is characterised by high activity of the glycolytic pyruvate reductase enzyme, tauropine dehydrogenase (TDH). Adductor muscle TDH was profiled for thermostability and activity to test the hypothesis that the enzyme may show adaptation in titre or kinetic characteristics reflecting thermal habitat. Temperature dependency of the apparent Michaelis‐Menten constant of TDH for pyruvate (appKmpyr) suggested eurythermal enzyme behaviour below 20°C, and compromised function at the higher temperatures of northern populations occurring in the summer months. Thermostability profiles and enzyme activities suggest TDH expression does not differ significantly among populations (P > 0.05), indicating that this locus shows no compensation for temperature. The optimal temperature for efficient TDH function, estimated from Vmax./appKmpyr, is close to 20°C. The possible thermal constraints on glycolytic metabolism in H. iris are discussed.

Flow cytometric evaluation of mitochondrial function and membrane integrity of marine invertebrate sperm

Summary A method was developed to evaluate the mitochondrial function and membrane integrity of marine invertebrate sperm using flow cytometry in combination with rhodamine 123 (R123) and propidium iodide (PI) staining. The method was evaluated with sperm of sea urchins (Evechinus chloroticus), mussels (Perna canaliculus) and abalone (Haliotis iris). Using R123 and PI simultaneously, it was possible to distinguish live sperm with functioning mitochondria and intact membranes from dying or dead sperm. The mitochondrial inhibitor rotenone was used to confirm that R123 was only accumulated by sperm with functioning mitochondria. The stain combination was further validated using known ratios of fresh to killed sperm. Among individual males evaluated, the percentage of sperm identified as live varied considerably, irrespective of the species studied. Among samples from the same male, however, the percentage of sperm identified as live was similar. The method developed has application for assessing the quality of sperm used in cryopreservation and bioassays.

Molecular analysis of a haplosporidian parasite from cultured New Zealand abalone Haliotis iris.

In the Austral summer and autumn of 2000 and 2001, mortalities of black-footed abalone Haliotis iris (Martyn, 1784) occurred in a commercial facility in New Zealand. Histological analyses suggested that infection by a haplosporidian parasite was responsible. To confirm identification as a haplosporidian and to help determine if this parasite represented a new, undescribed species, DNA was extracted from infected host tissues scored as positive for infection by histological examination. Small-subunit rRNA (SSU rRNA) gene sequences from both the host abalone and a parasitic organism were amplified by PCR and characterized. Although the sequence for this parasite was novel, not matching any known SSU rRNA gene sequences, phylogenetic analyses strongly supported grouping this parasite with the haplosporidians. Parsimony analyses placed the parasite at the base of the phylum Haplosporidia, ancestral to Urosporidium crescens and the Haplosporidium, Bonamia, and Minchinia species. Sequencing of multiple parasite DNA clones revealed a single polymorphic site in the haplosporidian SSU rRNA gene sequence.

A length-based Bayesian stock assessment model for the New Zealand abalone Haliotis iris

We describe a length-based Bayesian model for stock assessment of the New Zealand abalone Haliotis iris (paua). We fitted the model to five data sets: catch-per-unit-effort (CPUE) and a fishery-independent survey index, proportions-at-length from both commercial catch sampling and population surveys, and tag–recapture data. We estimated a common component of error and used iterative re-weighting of the data sets to balance the residuals, removing the arbitrary data set weightings used in previous assessments. Estimates at the mode of the joint posterior distribution were used to explore sensitivity of the results to model assumptions and input data; the assessment itself was based on marginal posterior distributions estimated from Markov chain–Monte Carlo simulation. Assessments are presented for two stocks in the south of New Zealand. One may be recovering after recent catch reductions; the other is over-exploited and likely to decline further. Assessment for the first stock was robust; assessment for the second stock was sensitive to the CPUE data and may be too optimistic. We discuss future directions and potential problems with this approach.

Selective capture of blue cod Parapercis colias by potting: behavioural observations and effects of capture method on peri-mortem fatigue

Selective fishing is the successful capture of target species and size classes in a way that minimises bycatch, minimises damage to flesh, and maximises post-mortem (PM) value. We studied selective harvesting of blue cod Parapercis colias (Pinguipedidae) in central New Zealand, where it is captured mainly by commercial pot-fishing and recreational line-fishing. Potting with paua Haliotis iris (=abalone) guts selectively targeted large blue cod from localities that had six or more fish species and many small blue cod. Video observations of pot entries indicated that blue cod entered and left the pot throughout 30 min sets. Blue cod were observed by video to commence swimming when pot-hauling started. Observations of line-hooked fish indicated a characteristic spinning behaviour while hauling. Fatigue during harvesting is a major factor in reducing the PM quality and shelf-life of fish muscle. Despite the relatively benign nature of capture via pot, it appears that burst exercise during hauling and a brief flurry of flapping as the pot leaves the water is sufficient to compromise flesh quality. Fish that were fatigued during harvesting had a poorer peri-mortem ‘ATP potential’ than fish that had been tank-rested for a year and then harvested using rested harvesting techniques. Modifying the potting method by providing a reservoir of water reduced peri-mortem fatigue during capture but by an insufficient amount to significantly improve PM flesh quality. Blue cod flesh is compromised by pot capture, which is widely perceived as a benign harvesting method. In order to maximise value of blue cod, low-stress harvesting methods which take advantage of the behaviour of the fish are required.

Sodium pentobarbitone-induced relaxation in the abalone Haliotis iris (Gastropoda): effects of animal size and exposure time

Different-sized Haliotis iris (20–160 mm shell length (SL)) were subjected to the anaesthetic sodium pentobarbitone and the time taken for animals to release from aquaria walls and recover from the anaesthetic recorded. In a second experiment, animals remained in the anaesthetic bath for 0, 30 or 60 min after release from aquaria walls and were then allowed to recover. In both experiments, heart rate was used as an indicator of animal health and measured using ultrasonography, a non-destructive method not previously reported for this purpose in abalone. Heart rate was measured before, at release, during recovery, and 8 days after relaxation in the first experiment and before, at release, and during recovery in the second experiment. No deaths attributable to sodium pentobarbitone were recorded in either experiment. Larger animals took longer on average to release from aquarium walls and longer to recover than did smaller animals. Heart rate of the small abalone (<70 mm SL) could not be detected by ultrasonography, but larger abalone had higher “base” heart rates than medium animals (>70 mm SL). Heart rate of medium to large abalone was depressed during relaxation to about half (13±5 beats per minute (bpm)) that recorded prior to relaxation (26±6 bpm). Some treated animals (17%) exhibited arrhythmia immediately after relaxation or during recovery in both experiments. Animals did not feed until 1–2 days after recovery. In the second experiment, longer immersion time resulted in further depression of heart rate and longer recovery time.

The archaeogastropod molluscHaliotis iris: tissue and blood metabolites and allosteric regulation of haemocyanin function

We investigated divalent cation and anaerobic end-product concentrations and the interactive effects of these substances and pH on haemocyanin oxygen-binding (Hc-O(2)) in the New Zealand abalone Haliotis iris. During 24 h of environmental hypoxia (emersion), D-lactate and tauropine accumulated in the foot and shell adductor muscles and in the haemolymph of the aorta, the pedal sinus and adductor muscle lacunae, whereas L-lactate was not detected. Intramuscular and haemolymph D-lactate concentrations were similar, but tauropine accumulated to much higher levels in muscle tissues. Repeated disturbance and short-term exposure to air over 3 h induced no accumulation of D- or L-lactate and no change in [Ca(2+)], [Mg(2+)], pH and O(2)-binding properties of the native haemolymph. The haemolymph showed a low Hc-O(2) affinity, a large reverse Bohr effect and marked cooperativity. Dialysis increased Hc-O(2) affinity, obliterated cooperativity and decreased the pH-sensitivity of O(2) binding. Replacing Mg(2+) and Ca(2+) restored the native O(2)-binding properties and the reverse Bohr shift. L- and D-lactate exerted minor modulatory effects on O(2)-affinity. At in vivo concentrations of Mg(2+) and Ca(2+), the cooperativity is dependent largely on Mg(2+), which modulates the O(2) association equilibrium constants of both the high-affinity (K(R)) and the low-affinity (K(T)) states (increasing and decreasing, respectively). This allosteric mechanism contrasts with that encountered in other haemocyanins and haemoglobins. The functional properties of H. iris haemocyanin suggest that high rates of O(2) delivery to the tissues are not a priority but are consistent with the provision of a large O(2) reserve for facultatively anaerobic tissues during internal hypoxia associated with clamping to the substratum.