Recruitment mechanisms of Atlantic cod ( Gadus morhua ) living in an extreme low-salinity environment

Spawning areas of eastern Baltic cod revisited: Using hydrodynamic modelling to reveal spawning habitat suitability, egg survival probability, and connectivity patterns

The adaptation and diversity of animals to the extreme environments of the Qinghai-Tibet Plateau (QTP) are typical materials to study adaptive evolution. The recently discovered Jinchuan yak population has many individuals with multiple ribs. However, little is known about this yak's origin, evolution, and the genetic mechanisms that formed its unique multirib trait. Here, we report a valuable population genome resource of the Jinchuan yak by resequencing the whole genome of 150 individuals. Population genetic polymorphism and structure analysis reveal that Jinchuan yak can be differentiated as a unique and original yak population among the domestic yak. Combined with geological change, the Jinchuan yak's evolutionary origin is speculated to be about 6290 years ago, which may be related to the unique geographical environment of the eastern edge of the QTP during this period. Compared with other domestic yaks, this new population has 280 positively selected genes. The genes related to skeletal function hold a considerable and remarkable proportion, suggesting that the specific skeletal characteristics have been enhanced in the adaptive evolution of Jinchuan yak in the extreme plateau environment. The genome-wide association study has revealed that TUBA8 and TUBA4A, the genes that regulate the cytoskeleton, are potential genes associated with the multirib trait. Our findings provide a basis to further understand the generation mechanism of the adaptive evolution of this new population in high-altitude extreme environments and the multivertebrate trait of domestic animals.

A hydrodynamic model coupled with a Lagrangian particle tracking technique was utilized to simulate spatially and temporally resolved long-term environmentally related (i) size of habitat suitable for reproduction, (ii) egg/yolk-sac larval survival, (iii) separation of causes of mortality, and (iv) connectivity between spawning areas of Baltic flounder with pelagic eggs. Information on reproduction habitat requirements and mortality sources were obtained from field or laboratory studies. In our modelling study we only quantified physical processes generating heterogeneity in spatial distribution of eggs and yolk-sac larvae, as e.g. predation is not accounted for. The spatial extent of eggs and larvae represented as modelled particles is primarily determined by oxygen and salinity conditions. The reproduction habitat most suitable was determined for the Gdansk Deep, followed by the Bornholm Basin. Relatively low habitat suitability was obtained for the Arkona Basin and the Gotland Basin. The model runs also showed yolk-sac larval survival to be to a large extent affected by sedimentation. Eggs initially released in the Arkona Basin and Bornholm Basin are strongly affected by sedimentation compared with those released in the Gdansk Deep and Gotland Basin. Highest relative survival of eggs occurred in the Gdansk Deep and in the Bornholm Basin. Relatively low survival rates in the Gotland Basin were attributable to oxygen-dependent mortality. Oxygen content had almost no impact on survival in the Arkona Basin. For all spawning areas mortality caused by lethally low temperatures was only evident after severe winters. Buoyancy of eggs and yolk-sac larvae in relation to topographic features appear as a barrier for the transport of eggs and yolk-sac larvae and potentially limits the connectivity of early life stages between the different spawning areas.

BackgroundAtlantic cod (Gadus morhua L.) has formed the basis of many economically significant fisheries in the North Atlantic, and is one of the best studied marine fishes, but a legacy of overexploitation has depleted populations and collapsed fisheries in several regions. Previous studies have identified considerable population genetic structure for Atlantic cod. However, within Norway, which is the country with the largest remaining catch in the Atlantic, the population genetic structure of coastal cod (NCC) along the entire coastline has not yet been investigated. We sampled > 4000 cod from 55 spawning sites. All fish were genotyped with 6 microsatellite markers and Pan I (Dataset 1). A sub-set of the samples (1295 fish from 17 locations) were also genotyped with an additional 9 microsatellites (Dataset 2). Otoliths were read in order to exclude North East Arctic Cod (NEAC) from the analyses, as and where appropriate.ResultsWe found no difference in genetic diversity, measured as number of alleles, allelic richness, heterozygosity nor effective population sizes, in the north-south gradient. In both data sets, weak but significant population genetic structure was revealed (Dataset 1: global FST = 0.008, P < 0.0001. Dataset 2: global FST = 0.004, P < 0.0001). While no clear genetic groups were identified, genetic differentiation increased among geographically-distinct samples. Although the locus Gmo132 was identified as a candidate for positive selection, possibly through linkage with a genomic region under selection, overall trends remained when this locus was excluded from the analyses. The most common allele in loci Gmo132 and Gmo34 showed a marked frequency change in the north-south gradient, increasing towards the frequency observed in NEAC in the north.ConclusionWe conclude that Norwegian coastal cod displays significant population genetic structure throughout its entire range, that follows a trend of isolation by distance. Furthermore, we suggest that a gradient of genetic introgression between NEAC and NCC contributes to the observed population genetic structure. The current management regime for coastal cod in Norway, dividing it into two stocks at 62°N, represents a simplification of the level of genetic connectivity among coastal cod in Norway, and needs revision.

Effects of salinity and temperature conditions on the reproductive success of turbot ( Scophthalmus maximus) in the Baltic Sea

As the climate changes, we must understand the biology of our fish stocks to better support the conservation of our global fisheries. Gadus Morhau, commonly known as Atlantic Cod, differs from other tetrameric hemoglobin species in that one of the key packing contacts, Phenylalanine 122, is replaced by Leucine, changing the interaction between the key packing contacts and thus the overall structure of the hemoglobin. Additionally, due to a hemoglobin polymorphism, Atlantic Cod has multiple subpopulations, the most common of which are the homozygous genotypes Hbl‐1 and Hbl‐2. Hbl‐1 and Hbl‐2 genotypes differ due to a mutation in amino acid sequence on the β1 chain, in the Hbl‐1 genotype, at Methionine 55, Lysine 62, and Leucine 122 (as mentioned above). However, on the Hbl‐2 genotype, the amino acids in the corresponding locations are Valine 55, Alanine 62, and Methionine 122. These mutations result in a significant divergence in structure that completely changes the optimal living conditions for the fish. tThe ideal environmental temperatures for different types of Atlantic Cod, the Hbl‐2 allele has a frequency of 99% in northern regions, whereas the Hbl‐1 allele is more common in warmer areas, suggesting that the Hbl‐2 allele helps the fish adapt to colder temperatures. Furthermore, temperature seems to impact the oxygen affinity of the two genotypes. Due to its structure, Hbl‐2 has higher oxygen bonding affinity at temperatures 10 degrees Celsius and lower, whereas the Hbl‐1 allele functions more efficiently at temperatures 14 degrees Celsius or higher. Using JMol modeling software, we compared the structures of the Hbl‐1 to Hbl‐2 Atlantic Cod hemoglobins paying close attention to the relationship between substitutional packing contacts Leucine 122 in Hbl‐1 and Methionine 122 in Hbl‐2, and the commonality of contact amino acid, Arginine B12, which is located on the α1 chain of the hemoglobin. We used JMol to analyze how amino acid substitutions in the β1 chain of the Atlantic Cod cause significant structural differences that leads to variation in optimal living conditions; we infer those adaptations may prove advantageous to their survival in their extreme environments. The Mahtomedi MSOE Center for BioMolecular Modeling MAPS Team used 3‐D modeling and printing technology to examine the structure‐function relationships of the Atlantic Cod hemoglobin polymorphisms. The visual model will be a valuable tool in developing our story.

The Arabian Gulf is one of the most thermally extreme marine environments on earth, representing a unique ‘natural laboratory’ in which to develop an understanding of how reef fishes may respond to future climate change. Recent research comparing fish in the southern Arabian Gulf with those on reefs in the more benign Gulf of Oman and Arabian Sea has provided insights into how reef fish communities, populations and individuals may respond to increasingly extreme temperatures in other regions. Reef fish communities in the southern Arabian Gulf were shown to be low in species diversity, abundance, and biomass compared with those on reefs in less extreme environments. Arabian Gulf reef fish communities were also functionally distinct, with coral-dependent fishes and important functional groups such as parrotfish being relatively rare. Demographic studies of several species have shown that the extreme thermal environment of the southern Gulf is associated with faster growth rates than conspecifics outside of the Gulf, but that these fish mature at significantly smaller sizes, which may have implications for reproduction and population replenishment. Such studies can provide insight into how populations and communities in other regions may respond as sea temperatures increase in the future. While Arabian Gulf reef fish represent a valuable asset for understanding biological responses to extreme temperatures, they are not immune to the growing pressure of climate change in the region itself. Recent experiments have shown that while Arabian Gulf reef fishes may have the capacity to survive higher temperatures than conspecifics in surrounding seas fish in the Gulf are living very near their physiological limits, suggesting that they are likely to be highly susceptible to even modest increases in seawater temperature. Climate change is also likely to have indirect effects on reef fishes in the Gulf through increased habitat loss, with all coral dependent fishes known for the Gulf already classified as vulnerable to extinction as a result of reef degradation in recent decades. There are also considerable gaps in knowledge of how ocean acidification may affect reef fishes, particularly the more vulnerable larval stages, and how this may synergize with thermal and other anthropogenic stressors.

Studies on human physical performance in extreme environments have effectively approached the investigation of adaptation mechanisms and their physiological limits. As scientific interest in the interplay between physiological and psychological aspects of performance is growing, we aimed to investigate cardiac autonomic control, by means of heart rate variability, and psychological correlates, in competitors of a subarctic ultramarathon, taking place over a 690 km course (temperatures between +5 and −47°C). At baseline (PRE), after 277 km (D1), 383 km (D2), and post-race (POST, 690 km), heart rate (HR) recordings (supine, 15 min), psychometric measurements (Profile of Mood States/POMS, Borg fatigue, and Karolinska Sleepiness Scale scores both upon arrival and departure) were obtained in 16 competitors (12 men, 4 women, 38.6 ± 9.5 years). As not all participants reached the finish line, comparison of finishers (FIN, n = 10) and non-finishers (NON, n = 6), allowed differential assessment of performance. Resting HR increased overall significantly at D1 (FIN +15.9; NON +14.0 bpm), due to a significant decrease in parasympathetic drive. This decrease was in FIN only partially recovered toward POST. In FIN only, baseline HR was negatively correlated with mean velocity [r −0.63 (P.04)] and parasympathetic drive [pNN50+: r −0.67 (P.03)], a lower HR and a higher vagal tone predicting a better performance. Moreover, in FIN, a persistent increase of the long-term self-similarity coefficient, assessed by detrended fluctuation analysis (DFAα2), was retrieved, possibly due to higher alertness. As for psychometrics, at D1, POMS Vigor decreased (FIN: −7.0; NON: −3.8), while Fatigue augmented (FIN: +6.9; NON: +5.0). Sleepiness increased only in NON, while Borg scales did not exhibit changes. Baseline comparison of mood states with normative data for athletes displayed significantly higher positive mood in our athletes. Results show that: the race conditions induced early decreases in parasympathetic drive; the extent of vagal withdrawal, associated to the timing of its recovery, is crucial for success; pre-competition lower resting HR predicts a better performance; psychological profile is reliably depicted by POMS, but not by Borg fatigue scales. Therefore, assessment of heart rate variability and psychological profile may monitor and partly predict performance in long-duration ultramarathon in extreme cold environment.

Dynamic expression profiles of virus-responsive and putative antimicrobial peptide-encoding transcripts during Atlantic cod (Gadus morhua) embryonic and early larval development

The spatial distribution of cod ( Gadus morhua L.) spawning grounds in the Kattegat, eastern North Sea

Discrimination between Icelandic cod ( Gadus morhua L.) populations from adjacent spawning areas based on otolith growth and shape

In plant ecology, extreme environments are those that pose physiological or other limitations to plant growth, especially for non-adapted taxa. In these environments, the severity of climate conditions and/or the limitations imposed by particular soil substrates represent major selective pressures for plants, leading to the evolution of a wide array of functional traits, specific strategies and adapted taxa. In this special issue, we present a collection of papers that focuses on plants in various extreme environments, including the Arctic and Antarctic, regions with serpentine and gypsum soils, high mountain areas and deserts. The papers include a broad array of methods to study the ecology and evolution of plants in extreme environments, such as field surveys, greenhouse and field experiments, molecular phylogenetic analyses and/or physiological measurements. Overall, this special issue showcases research on how plants thrive in extreme environments which, in turn, may provide pointers to how plant communities might respond to living in increasingly challenging environments resulting from unprecedented land-use changes and climate warming at the present time and in the future.

Running the gauntlet: Connectivity between spawning and nursery areas for arrowtooth flounder (Atheresthes stomias) in the Gulf of Alaska, as inferred from a biophysical individual-based model

The impact of crude oil pollution on early life stages (ELS) of fish, including larvae and embryos, has received considerable attention in recent years. Of the organic components present in crude oil, polycyclic aromatic hydrocarbons (PAHs) are considered the main class of compounds responsible for toxic effects in marine organisms. Although evidence suggests that they are more toxic, alkylated PAHs remain much less studied than their unsubstituted congeners. Recently, it was established that embryos of Atlantic haddock (Melanogrammus aeglefinus) are particularly sensitive to dispersed crude oil, and it was hypothesized that this was caused by direct interaction with crude oil droplets, which adhered to the chorion of exposed embryos. Such a phenomenon would increase the potential for uptake of less water-soluble compounds, including alkylated PAHs. In the current study, we compared the uptake of parent and alkylated PAHs in Atlantic cod (Gadus morhua) and haddock embryos exposed to dispersed crude oil at a range of environmentally relevant concentrations (10–600 μg oil/liter seawater). Although the species are biologically very similar, the cod chorion does not become fouled with oil droplets, even when the two species are exposed to dispersions of crude oil droplets under similar conditions. A close correlation between the degree of fouling and toxicological response (heart defects, craniofacial malformation) was observed. Oil droplet fouling in haddock led to both quantitative and qualitative differences in PAH uptake. Finally, kinetic data on a large suite of PAHs showed differential elimination, suggesting differential metabolism of unsubstituted versus alkylated compounds.

Spatiotemporal dynamics of predators and survival of marine fish early life stages: Atlantic cod (Gadus morhua) in the North Sea