Description: Dynamic in vivo 31P-NMR spectroscopy in combination with Magnetic Resonance Imaging (MRI) was used to study muscle bioenergetics of boreal and Arctic scallops (Pecten maximus and Chlamys islandica) to test the hypothesis that future Ocean Warming and Acidification (OWA) will impair the performance of marine invertebrates.

Description: Object：Dynamic in vivo 31P-NMR spectroscopy in combination with Magnetic Resonance Imaging (MRI) was used to study muscle bioenergetics of boreal and Arctic scallops (Pecten maximus and Chlamys islandica) to test the hypothesis that future Ocean Warming and Acidification (OWA) will impair the performance of marine invertebrates. Materials & methods： Experiments were conducted following the recommendations for studies of muscle bioenergetics in vertebrates. Animals were long-term incubated under different environmental conditions: controls at 0 °C for C. islandica and 15 °C for P. maximus under ambient PCO2 of 0.039 kPa, a warm exposure with +5 °C (5 °C and 20 °C, respectively) under ambient PCO2 (OW group), and a combined exposure to warmed acidified conditions (5 °C and 20 °C, 0.112 kPa PCO2, OWA group). Scallops were placed in a 4.7 T MR animal scanner and the energetic status of the adductor muscle was determined under resting conditions using in vivo 31P-NMR spectroscopy. The surplus oxidative flux (Qmax) was quantified by recording the recovery of arginine phosphate (PLA) directly after moderate swimming exercise of the scallops. Results：Measurements led to reproducible results within each experimental group. Under projected future conditions resting PLA levels (PLArest) were reduced, indicating reduced energy reserves in warming exposed scallops per se. In comparison to vertebrate muscle tissue surplus Qmax of scallop muscle was about one order of magnitude lower. This can be explained by lower mitochondrial contents and capacities in invertebrate than vertebrate muscle tissue. Warm exposed scallops showed a slower recovery rate of PLA levels (kPLA) and a reduced surplus Qmax. Elevated PCO2 did not affected PLA recovery further.

Description: Object: Dynamic in vivo 31P-NMR spectroscopy in combination with Magnetic Resonance Imaging (MRI) was used to study muscle bioenergetics of boreal and Arctic scallops (Pecten maximus and Chlamys islandica) to test the hypothesis that future Ocean Warming and Acidification (OWA) will impair the performance of marine invertebrates. Materials & methods: Experiments were conducted following the recommendations for studies of muscle bioenergetics in vertebrates. Animals were long-term incubated under different environmental conditions: controls at 0 °C for C. islandica and 15 °C for P. maximus under ambient PCO2 of 0.039 kPa, a warm exposure with +5 °C (5 °C and 20 °C, respectively) under ambient PCO2 (OW group), and a combined exposure to warmed acidified conditions (5 °C and 20 °C, 0.112 kPa PCO2, OWA group). Scallops were placed in a 4.7 T MR animal scanner and the energetic status of the adductor muscle was determined under resting conditions using in vivo 31P-NMR spectroscopy. The surplus oxidative flux (Qmax) was quantified by recording the recovery of arginine phosphate (PLA) directly after moderate swimming exercise of the scallops. Results: Measurements led to reproducible results within each experimental group. Under projected future conditions resting PLA levels (PLArest) were reduced, indicating reduced energy reserves in warming exposed scallops per se. In comparison to vertebrate muscle tissue surplus Qmax of scallop muscle was about one order of magnitude lower. This can be explained by lower mitochondrial contents and capacities in invertebrate than vertebrate muscle tissue. Warm exposed scallops showed a slower recovery rate of PLA levels (kPLA) and a reduced surplus Qmax. Elevated PCO2 did not affected PLA recovery further. Conclusion: Dynamic in vivo 31P-NMR spectroscopy revealed constrained residual aerobic power budgets in boreal and Arctic scallops under projected ocean warming and acidification indicating that scallops are susceptible to future climate change. The observed reduction in muscular PLArest of scallops coping with a warmer and acidified ocean may be linked to an enhanced energy demand and reduced oxygen partial pressures (PO2) in their body fluids. Delayed recovery from moderate swimming at elevated temperature is a result of reduced PLArest concentrations associated with a warm-induced reduction of a residual aerobic power budget.

Description: We examined the RNA and DNA concentration of field-caught scallops Chlamys islandica, maintained in suspended cultures at 15 and 30 m depth, and scallops from a wild population at 50 to 60 m in Kobbefjord, southwest Greenland. General relations between RNA and DNA concentrations and individual shell height were established, and we found that the RNA:DNA ratio (RD) worked well as a standardisation of the RNA concentration independent of size and sex. During an experimental period of 14 mo, we observed a pronounced seasonal pattern in RD and mass growth, and differences between depths. Even though the period with high levels of RD reflected the growth season relatively well, RD was a poor predictor of individual mass growth rates of C. islandica. However, we found a non-linear response in RD to increased food concentrations resulting in RD being up- and down-regulated at the beginning and end of the productive summer season, respectively. These results indicate that short-term dynamics in the actual mass growth rate might be controlled through regulation of ribosome activity rather than ribosome number (RNA concentration). This adaption would allow scallops to up-regulate protein synthesis more rapidly, thereby ensuring efficient utilisation of the intense peaks in food availability in coastal areas in the Arctic. Therefore, we suggest that RD in C. islandica reflects the growth potential rather than the actual growth rate. Still, the amount of unexplained variance in RD is considerable and not independent over time, suggesting the existence of unresolved mechanisms or relationships.

Description: Gonatus fabricii (Lichtenstein, 1818) is an ecologically important squid that spends its entire life cycle within the Arctic where it is the most abundant cephalopod. Due to the rarity of mature and reproducing females, it is unknown how many eggs females spawn (actual fecundity). Among 47,000 specimens studied between 2005 and 2019 one spent, degenerated and gelatinous female with a mantle length of 230 mm was caught in West Greenland in 2019. Examination allowed the first detailed description of fecundity and spawning pattern in the species. Oocyte development shows that the most considerable maturation of mid-vitellogenic oocytes to late vitellogenic and then to ripe stages occurs immediately after the first ripe oocytes appear in the ovary. There were no ripe oocytes in the ovary or oviducts. The ovary contained an estimated 6561 oocytes and 2551 post-ovulatory follicles and hence the total fecundity was 9112. This specimen of G. fabricii realised 28.0% of its potential fecundity which is comparable to Berryteuthis magister, which also belongs to Gonatidae, and lower than in the majority of studied deep-sea squids (including other gonatids). Spent females may provide clues as to where the major spawning areas of this abundant but poorly known squid are located.

Description: We report two Arctic species of incirrate octopods new to science. One is formally described here as Muusoctopus aegir Golikov, Gudmundsson & Sabirov sp. nov. while the other, Muusoctopus sp. 1, is not formally described due to a limited number of samples (all are immature individuals). These two species differ from each other, and from other Muusoctopus, especially in: 1) absence of stylets (in M. aegir sp. nov.); 2) proportions of mantle and head; 3) funnel organ morphology (W-shaped with medial and marginal limbs of equal length in M. aegir sp. nov., or medial are slightly longer; V V-shaped with medial limbs slightly longer and broader than marginal in Muusoctopus sp. 1); 4) sucker and gill lamellae counts; 5) relative arm length and sucker diameter; and 6) male reproductive system relative size and morphology. Species of Muusoctopus now comprise four of 12 known Arctic cephalopods. Additionally, this study provides: a) new data on the morphology and reproductive biology of M. johnsonianus and M. sibiricus, and a diagnosis of M. sibiricus; b) the equations to estimate mantle length and body mass from beak measurements of M. aegir sp. nov. and M. johnsonianus; c) a cytochrome c oxidase subunit I gene barcode for M. sibiricus; d) new data on the ecology and distribution of all studied species; and e) a data table for the identification of northern North Atlantic and Arctic species of Muusoctopus.

Description: Cephalopods are important in Arctic marine ecosystems as predators and prey, but knowledge of their life cycles is poor. Consequently, they are under-represented in the Arctic ecosystems assessment models. One important parameter is the change in ecological role (habitat and diet) associated with individual ontogenies. Here, the life history of Gonatus fabricii, the most abundant Arctic cephalopod, is reconstructed by the analysis of individual ontogenetic trajectories of stable isotopes (δ13C and δ15N) in archival hard body structures. This approach allows the prediction of the exact mantle length (ML) and mass when the species changes its ecological role. Our results show that the life history of G. fabricii is divided into four stages, each having a distinct ecology: (1) epipelagic squid (ML 〈 20 mm), preying mostly on copepods; (2) epi- and occasionally mesopelagic squid (ML 20–50 mm), preying on larger crustaceans, fish, and cephalopods; (3) meso- and bathypelagic squid (ML 〉 50 mm), preying mainly on fish and cephalopods; and (4) non-feeding bathypelagic gelatinous females (ML 〉 200 mm). Existing Arctic ecosystem models do not reflect the different ecological roles of G. fabricii correctly, and the novel data provided here are a necessary baseline for Arctic ecosystem modelling and forecasting.