Brendon J. Dunphy

Oxygen consumption and enzyme activity of the subtidal flat oyster (Ostrea chilensis) and intertidal Pacific oyster (Crassostrea gigas): responses to temperature and starvation

Abstract Intertidal Pacific oysters (Crassostrea gigas) and subtidal flat oysters (Ostrea chilensis) were held at 10, 15, or 20°C without food for 16 weeks. Rates of oxygen consumption in the subtidal oyster were more sensitive to temperature than those of the intertidal oyster, but temperature sensitivity decreased in starved Pacific oysters. Metabolic fuel reserves of glycogen in the adductor muscle were markedly higher in C. gigas, and decreased with starvation. Higher activities of the key metabolic enzymes, strombine dehydrogenase, alanopine dehydrogenase, and citrate synthase were found in C. gigas than in O. chilensis, indicating greater scope for energy production. These observations were consistent with the greater aerobic scope and glycolytic potential of C. gigas in the thermally variable intertidal environment, and in the face of severe nutritional challenge. Ostrea chilensis was metabolically challenged by warm temperatures and food deprivation, factors that need to be considered in the development of aquaculture methods for this species.

Potential impact of metabolic acidosis on the fixed-acid Bohr effect in snapper (Pagrus auratus) following angling stress.

Oxygen equilibrium data were obtained for intact erythrocytes from Pagrus auratus and the pH-dependence of the fixed-acid Bohr and Root effects described. Indicators of aerobic-anaerobic poise were then measured following a period of strenuous exercise induced by angling capture. Haematological indices and plasma metabolites were evaluated with respect to their potential impact on the blood oxygen transport mechanism. An increase in post-capture haemoglobin content, blood lactate, and glucose were observed. The fall in caudal venous pH from 7.53 to 7.41, reflecting the acid-base status of blood draining the working tail musculature, remained within the operational zone of the maximal fixed-acid Bohr effect (Phi(7.4-7.8)=-0.95), but above the critical pH at which the Root effect suppresses oxygen transport capacity. These stress-induced changes reflect a strategy of optimal O(2) unloading to tissues with the Root effect unlikely to be expressed in the swimming vasculature.

Endobiont infestation, shell strength and condition index in wild populations of New Zealand abalone, Haliotis iris

Anecdotal suggestions that abalone in northern New Zealand are more heavily infested with endobiont sponges and polychaetes than those in the south led to a comparison of populations in the two regions. Shells from wild populations of Haliotis iris were examined by X-ray analysis to evaluate the degree of infestation and penetration. The mechanical strength of shells and condition index of the abalone were measured and compared with the degree of endobiont infestation. There were no significant differences in measured characteristics in abalone from the northeastern region of New Zealand (36°16′–36°22′S) compared with those from the South Island (40°44′–41°11′S) nor among populations within these regions. Shell strength, previously unknown for abalone, was considerably weakened by bifacial porosis and was correlated with condition index.

Identification of the Optimal Fluorochrome for Marking Larvae of the Pulmonate Limpet Siphonaria australis

ABSTRACT This study identified the most suitable fluorochrome to mark prodissoeonch of larval Siphonaria australis, a common pulmonate gastropod commonly found on rocky shores throughout New Zealand. The pulmonate habit of laying attached larval egg masses makes them an excellent candidate for studies of larval connectivity using chemical staining methods. Larval S. australis egg masses were immersed in 200 mg/L of either alizarin red S (ARS), calcein, or Oxytetracycline (OTC) for 24 h before viewing under ultraviolet light to allow quantification of mark brightness using image analysis software. Counts of pre- and postimmersion mortality were also made to identify any fluorochrome toxicity to S. australis larvae. Calcein was found to be the most suitable fluorochrome to use when fluorescently marking larval S. australis, because average brightness was significantly greater than either ARS or OTC, with negligible mortality levels recorded for calcein. The results show that fluorochromes can penetrate the gelatinous egg matrix and the larval capsules, thus providing an opportunity for staining large numbers of these species for alongshore connectivity studies.

Identifying Thermally-Stressed Adult Green-Lipped Mussels (Perna canaliculus Gmelin, 1791) via Metabolomic Profiling*

Abstract: The green-lipped mussel (Perna canaliculus Gmelin, 1791) is an economically and ecologically important marine species within New Zealand, yet the ability of adult mussels to cope with acute temperature change remains unknown. To address this, we sought to characterize the thermotolerance capacity of P. canaliculus adults and, using metabolomics, identify any metabolic biomarkers of thermal stress in this species. To achieve this, mussels were exposed to a 3 h acute temperature challenge using temperatures of 20 °C (Ambient), 25 °C, 29 °C, 31 °C, 33 °C, and 35 °C. No mortality was observed in mussels exposed to 31 °C or less, even after 30 days recovery. However, mussels exposed to 33 and 35 °C exhibited 100% mortality within 48 h of the challenge. Gill tissues were harvested from mussels for metabolomic analysis of thermal stress biomarkers via Gas Chromatography-Mass Spectrometry (GC-MS). Discriminant Function Analysis (DFA) of 52 metabolites identified eight key biomarkers indicative of thermal stress in this species (i.e., cis-11-Eicosenoic acid, Palmitic acid, Proline, GABA, Aspartic acid, Fumaric acid, beta-Alanine and Asparagine). These metabolites were entirely consistent in their ability to classify the exposure temperature that mussels experienced, indicating that the discriminatory capacity of these biomarkers was strong. Therefore, our results reveal that mortality in thermally-stressed adult P. canaliculus seems assured once temperatures reach 33 °C. Additionally, metabolite biomarkers can discriminate those mussels exhibiting varying levels of thermal stress; thus, metabolomics offers a new tool for physiologists seeking to gain greater mechanistic understanding of the effects of acute thermal stresses on invertebrate species.

MatlabHTK: a simple interface for bioacoustic analyses using Hidden Markov Models

Summary 1.Passive bioacoustic recording devices are now widely available and able to continuously record remotely located sites for extended periods, offering great potential for wildlife monitoring and management. Analysis of the huge datasets generated, in particular for specific biotic sound recognition, remains a critical bottleneck for widespread adoption of these technologies as current methods are labour intensive. 2.Several methods borrowed from speech processing frameworks, such as hidden Markov models, have been successful in analysing bioacoustic data but the software implementations can be expensive and difficult to use for non-specialists involved in wildlife conservation. To remedy this, we present a software interface to a popular speech recognition system making it possible for non-experts to implement hidden Markov models for bioacoustic signal processing. Octave/Matlab functions are used to simplify the set up and the definition of a bioacoustic signal recogniser as well as the analysis of the results. 3.We present the different functions as a workflow. To demonstrate how the package can be used we give the results of an analysis of a bioacoustic monitoring dataset to detect the nocturnal presence and behaviour of a cryptic seabird species, the common diving petrel Pelecanoides urinatrix urinatrix, from Northern New Zealand. 4.We show that the package matlabHTK can be used efficiently to reconstruct the daily patterns of colony activity in the common diving petrel. This article is protected by copyright. All rights reserved.

Optimising translocation efforts of Mottled Petrels (Pterodroma inexpectata): growth, provisioning, meal size and the efficacy of an artificial diet for chicks

Abstract In an effort to promote population recovery, translocations of the endemic Mottled Petrel (Pterodroma inexpectata) from remote offshore islands to the mainland are planned within New Zealand. To optimise these efforts we studied chick growth, adult provisioning and meal size for this species and report the results of a simulated translocation undertaken to assess how translocated chicks, fed an artificial diet, performed in comparison with handled and non-handled controls that were provisioned by their parents. Our results found that wing-chord length and chick mass did not differ between translocated and control chicks, with all chicks fledging at approximately the same mass and wing size ranges. There was no difference in the timing of emergence from burrows before fledging between control and translocated chicks. The probability of a chick receiving a meal each night declined as chicks approached fledging and average meal size did not change as chicks approached fledging. From these data we now have the basis with which to make recommendations to increase the success of future translocation efforts for Mottled Petrels. It is important to share any knowledge of the biology and ecology of gadfly petrels, and any successes or failures in translocation practices in order to promote the best possible chance of future conservation of these species.

A non-invasive anaesthetic method for accessing the brood chamber of the Chilean flat oyster (Ostrea chilensis)

A cost effective method to discern brooding from non-brooding specimens of the Chilean flat oyster (Ostrea chilensis Phillipi, 1844) is needed to optimise current hatchery practices for this species. Accordingly, we investigated the efficacy of two treatments, AQUI-S® and MgCl2, in anaesthetising individuals of this species and then mapped any subsequent mortality of anaesthetised oysters. Oysters immersed for 3 h in solutions of 20, 40, 80 and 100 µL L−1 of AQUI-S® exhibited no signs of anaesthesia and also recorded low levels of mortality (i.e. 8% or less). Conversely, oysters immersed in 30, 40 and 50 g L−1 MgCl2 showed between 96%–100% anaesthesia after 3 h whereas only 70% of oysters immersed in 60 g L−1 MgCl2 were anaesthetised over this time period. Time taken for 50% of oyster shells to open (SO50) was compared among MgCl2 treatments with oysters immersed in 60 g L−1 taking significantly longer than (103 min) those immersed in 30–50 g L−1 (SO50 values of 43, 54 and 37 min respectively). Furthermore, treating oysters with MgCl2 resulted in low levels of mortality (i.e. 13% or less) and was not related to MgCl2 concentration. Thus, our results show that immersing O. chilensis in MgCl2 to be an efficient and cost effective method to access the brood chamber of this species. We recommend the use of 30 g L−1 for routine anaesthesia and recommend that future work investigates the efficacy of cheaper MgCl2 sources and what effects MgCl2 anaesthetisation has on developing larvae.

Seasonal activity and unpredicted polar front migration of northern New Zealand Common Diving Petrels (Pelecanoides urinatrix)

ABSTRACT The Common Diving Petrel (Pelecanoides urinatrix) is an abundant seabird species within New Zealand waters. Breeding in this species occurs from late July through to December and adults are thought to remain in New Zealand waters during non-breeding months. Yet no studies of the spatial ecology of the species within New Zealand have been undertaken to confirm this. We used geolocation loggers with seawater immersion probes to characterise the year-round distribution and activity of P. urinatrix from two colonies (Kauwahaia Island and Burgess Island) in northern New Zealand. Adult birds exhibited extended pre-laying occupation of breeding sites (~95 days) and throughout breeding remained within 300 km of their colony. Burgess Island birds returned near nightly to their burrows throughout the breeding season. During non-breeding birds made a rapid and unpredicted migration south-east to the Antarctic polar front (covering 3000–5000 km in 3–13 days) and exhibited a dramatic shift in behaviour by spending 95% of their time on (and under) the water surface. Given its already high wing loading, it appears that the primary moult reduced flight efficiency during this time. But by targeting highly productive oceanic regions, and the improved foraging opportunities therein, P. urinatrix may offset this reduced flight capacity.

Effect of tidal regime on the thermal tolerance of the marine gastropod Lunella smaragda (Gmelin 1791).

The tidal cycle around New Zealand results in spring low tides consistently occurring during the hottest part of the day (mid-afternoon) in north-eastern New Zealand, and during the cooler dawn/dusk periods in the north-west of the country. We hypothesised that due to mid-afternoon spring low tides, intertidal populations residing at north-eastern sites would show greater thermotolerance than their north-west conspecifics. To test this we used the marine gastropod, Lunella smaragda, which were collected from sites on both the East and West coasts of the Auckland region and exposed to an acute heat shock. Thermotolerance was measured as survivorship (LT50), drop down time (time to heat coma) and thermal stability of the anaerobic energy producing enzyme Tauropine dehydrogenase. Furthermore, temperature loggers were deployed at each site so as to record and compare thermal regimes among sites. A strong temperature spike associated with spring low tide was found at all sites, and maximal temperatures of all East coast sites were higher than West coast sites (in some case by up to 10°C). In terms of thermotolerance, mortality of L. smaragda occurred at 42°C leading to 100% mortality at 45°C. However, comparison of LT50 showed snails were equally thermotolerant regardless of site of collection. Similar results were found in TDH thermal stability with animals from all sites showing an approximately 80% decrease in enzyme activity after 10min exposure to 42°C. Whilst drop down times were different among sites these were correlated with animal size as opposed to site of collection. Thus, East coast populations of L. smaragda appear no more thermotolerant than their West coast counterparts. Such a result is concerning as maximal temperatures at East coast sites already exceed the LT50 values of L. smaragda recorded in the lab suggesting these populations have less of a thermal safety margin.