Norman L.C. Ragg

In situ infrared spectroscopic investigation of Perna canaliculus mussel larvae primary settlement

The adhesion of Perna canaliculus mussel larvae on a germanium (Ge) prism in filtered seawater at 16°C has been investigated by in situ attenuated total reflection infrared (ATR-IR) spectroscopy. The adhesive from the mussel larvae was spectrally monitored over 2 h and the IR spectrum showed its glycoproteinaceous nature with sulphated and carboxylated moieties. The adhesive from the mussel larvae differs from that of the adults, resembling the mucus secretion found in other benthic marine species at a larval stage. To date, this appears to be the first work describing the main chemical features of secreted adhesive associated with the primary settlement of mussel larvae. The acquired knowledge on the larval adhesive features may lead to enhanced settling methods in aquaculture or to antibiofouling strategies. The ATR-IR approach under temperature control is potentially useful for such studies on other small benthic organisms in both marine and freshwater environments.

Energetics of Byssus Attachment and Feeding in the Green-Lipped Mussel Perna canaliculus

In most animals, significant increases in metabolic rate are due to activity and to feeding (known as apparent specific dynamic action). We determined the energetic costs of activity and feeding in adult green-lipped mussels (Perna canaliculus). Maximal metabolic rate was determined, using closed-chamber respirometry, during byssus re-attachment, during specific dynamic action after 16 h of feeding with Isochrysis galbana, and for the two activities combined, in 23 mussels. Metabolic rate was significantly elevated above rest by about 1.9-fold during byssus attachment (17.1 ± 1.53 μg O2 h–1 g–1 whole mussel wet weight at rest, increased to 27.9 ± 0.91 μg O2 h−1 g−1), and by 2.2-fold after feeding (31.4 ± 1.20 μg O2 h−1 g−1). Combined feeding and byssus attachment led to a still higher metabolic rate (34.0 ± 1.23 μg O2 h−1 g−1). Behavior was also significantly altered, with mussels being almost continuously open during attachment and after feeding (90%–99% of the time); however, the time spent open during the day decreased, reaching a minimum of 52% ± 9% 3 days after feeding, and remained low (67%–82%) for the following 45-day starvation period. Significant diurnal differences were observed, with mussels continuously (92%–100%) open at night. The key findings from this study are that green-lipped musssels (1) have an aerobic scope of approximately 2-fold; (2) reach a higher metabolic rate during feeding than during activity, and the two combined can raise the metabolic rate higher still; (3) display a marked diurnal behavior.

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.

Ocean acidification in New Zealand waters: trends and impacts

ABSTRACT The threat posed by ocean acidification (OA) to the diversity and productivity of New Zealand marine ecosystems is assessed in a synthesis of published trends and impacts. A 20-year time series in Subantarctic water, and a national coastal monitoring programme, provide insight into pH variability, and context for experimental design, modelling and projections. A review of the potential impact of changes in the carbonate system on the major phyla in New Zealand waters confirms international observations that calcifying organisms, and particularly their early life-history stages, are vulnerable. The synthesis considers ecosystem and socio-economic impacts, and identifies current knowledge gaps and future research directions, including mechanistic studies of OA sensitivity. Advanced ecosystem models of OA, that incorporate the indirect effects of OA and interactions with other climate stressors, are required for robust projection of the future status of New Zealand marine ecosystems.

Physiological Indicators of Stress and Morbidity in Commercially Handled Abalone Haliotis iris

ABSTRACT Abalone are enigmatic, displaying subtle responses to stress, including a delayed onset of morbidity, and death after severe stress. The present study therefore sought to further elucidate the nature of stress responses in the blackfoot abalone Haliotis iris and develop practical indices to quantify stress and forecast survival. Abalone were challenged with air exposure (16°C, 4–120 h). Physiological responses were assessed at three organizational levels: whole organism (heart rate), extracellular (hemolymph metal concentrations), and intracellular (hemocyte lysosome stability). Hemolymph sodium:potassium ratio showed a strong negative correlation with emersion time (R2 = 0.82) and a reasonable capacity to predict subsequent survival (R2 = 0.50); a [Na]:[K] of 23 was representative of an undisturbed abalone, whereas values less than 15 typically indicated morbidity. Hemocytes tended to lyse before lysosome destabilization could be quantified by neutral red loss; the stability assay therefore failed to yield meaningful data. Resting heart rate declined from 19.4 min-1 (undisturbed) to a minimum of 1 min-1 recorded after 48 h emersion; however, the correlation between heart rate and emersion time or subsequent survival was weak. Hemolymph sodium:potassium ratio warrants further investigation as a practical and sensitive forensic tool to quantify stress, but will require complementary approaches to robustly determine the survival tipping point.

Practical Fertilization Procedure and Embryonic Development of the New Zealand Geoduck Clam (Panopea Zelandica)

Cultivation of the geoduck Panopea zelandica (Quoy & Gaimard, 1835) requires knowledge on embryonic development to produce spat in hatcheries. This study investigated the development of P. zelandica embryos at 15°C and 35 ppt and the optimal sperm:egg ratios for fertilization under hatchery conditions. Panopea zelandica broodstock were induced to spawn by serotonin injection. Sperm and eggs were collected and fertilization was conducted at sperm:egg ratios of: 50:1, 100:1, 500:1, 1000:1 and 10,000:1 over 40 min. The optimal sperm:egg ratio was Panopea zelandica eggs (~80 μm diameter) developed the first and second polar bodies within 15–20 and 50–55 min post-fertilization, respectively. The blastula appeared at ~8 hpf, including the X R and X L cells and the presumptive shell field depression. Gastrulation occurred at 12–18 hpf with organic material apparent at the shell field depression. The mid-stage trochophore, which appeared at around 35 hpf had an apical plate with an apical tuft. The shell field spread to form the periostracum, which expanded and folded into right and left segments covering the late trochophore. The early D-stage veliger appeared at 45 hpf with the soft body being enclosed by two valves and the appearance of the velum. These observations will serve as the basis for future analyses of P. zelandica embryogenesis and for optimization of commercial production of D-veliger larvae.

Complete mitochondrial genome of the green-lipped mussel, Perna canaliculus (Mollusca: Mytiloidea), from long nanopore sequencing reads

Abstract We describe here the first complete genome assembly of the New Zealand green-lipped mussel, Perna canaliculus, mitochondrion. The assembly was performed de novo from a mix of long nanopore sequencing reads and short sequencing reads. The genome is 16,005 bp long. Comparison to other Mytiloidea mitochondrial genomes indicates important gene rearrangements in this family.