Key Species Research Articles

Mitochondrial DNA of the Arabian Camel Camelus dromedarius.

The Camelidae family, ranging from southwest Asia to north Africa, South America, and Australia, includes key domesticated species adapted to diverse environments. Among these, the Arabian camel (Camelus dromedarius) is vital to the cultural and economic landscape of the Arabian Peninsula. This review explores the mitochondrial DNA of the dromedary camel, focusing on the D-loop region to understand its genetic diversity, maternal inheritance, and evolutionary history. We aim to investigate the unique characteristics of Arabian camel mtDNA, analyze the D-loop for genetic diversity and maternal lineage patterns, and explore the implications of mitochondrial genomic studies for camel domestication and adaptation. Key findings on mtDNA structure and variation highlight significant genetic differences and adaptive traits. The D-loop, essential for mtDNA replication and transcription, reveals extensive polymorphisms and haplotypes, providing insights into dromedary camel domestication and breeding history. Comparative analyses with other camelid species reveal unique genetic signatures in the Arabian camel, reflecting its evolutionary and adaptive pathways. Finally, this review integrates recent advancements in mitochondrial genomics, demonstrating camel genetic diversity and potential applications in conservation and breeding programs. Through comprehensive mitochondrial genome analysis, we aim to enhance the understanding of Camelidae genetics and contribute to the preservation and improvement of these vital animals.

Different halophytes orchestrate microbial diversity in the rhizosphere of salinity-impacted soils

Investigating rhizosphere communities in saline soils is crucial for identifying the taxonomic groups that play significant roles in halophyte adaptation. However, how the microbiome is structured under different saline conditions remains unclear. This study aimed to analyze bacterial communities in the rhizospheres of halophyte species in different saline environments. Five rhizospheres were analyzed using high-throughput sequencing of the 16S rRNA gene: S1, Salicornia fruticosa from a hypersaline tidal plain; S2, Sporobolus virginicus; S3, Cyperus ligularis from a hypersaline lagoon; S4, Salicornia fruticosa and S5, Blutaparon portulacoides from an abandoned salt pan. Bacterial communities in the S4 and S5 rhizospheres were influenced by P and K content, suggesting that specific nutrients can foster unique microbial structures, potentially assisting in adaptation to saline soils. The unique ASV (Amplicon Sequence Variant), richness, diversity, and microbial core of the S1 system, along with its similarities to S2 and S3, suggest common halophyte adaptation strategies across different saline environments, aiding targeted survival efforts. Identifying keystone species such as Thermoleophilia in S1, Alphaproteobacteria in S2 and S3, multiple species in S4, and the presence of Clostridia and Bacilli in S5 shed light on the roles these bacteria play in halophyte survival. Metagenomic prediction analysis demonstrated that chemoheterotrophy and aerobic chemoheterotrophy were the main prediction functions. In summary, this study revealed the intricate microbial structures in halophyte rhizospheres, enriching our understanding of saline ecosystems.

Impact of severe drought on biogenic volatile organic compounds emissions from Sphagnum mosses in boreal peatlands

Climate change and the associated increased frequency of extreme weather events are likely to alter the emissions of biogenic volatile organic compounds (BVOCs) from boreal peatlands. Hydrologically sensitive Sphagnum mosses are keystone species in boreal peatland ecosystems that are known to emit various BVOCs. However, it is not known how their emissions respond to seasonal droughts. In this study, we quantified the effect of severe drought, and subsequent recovery, on the BVOC emissions from Sphagnum mosses using mesocosms originating from wet open and naturally drier treed boreal fens and bogs. Here we report the emissions of 30 detected BVOCs, of which isoprene was the most abundant with an average flux rate of 5.6 μg m−2 h−1 (range 0–31.9 μg m−2 h−1). The experimental 43-day ecohydrological drought reduced total BVOC and isoprene emissions. In addition, in mesocosms originating from bogs, sesquiterpene emissions decreased with the drought, while the emissions of green leaf volatiles were induced. Sesquiterpene emissions remained low even six weeks after rewetting, indicating a long and limited recovery from the drought. Our results further imply that long-term exposure to deep water tables does not decrease sensitivity of Sphagnum to an extreme drought; we did not detect differences in the emission rates or drought responses between Sphagna originating from wet open and naturally drier treed habitats. Yet, the differences between fen and bog originating Sphagna indicate local variability in the BVOC quality changes following drought, potentially altering the climate feedback of boreal peatland BVOC emissions.

Urbanization reduces the stability of soil microbial community by reshaping the diversity and network complexity

Rapid urbanization considerably alters soil environment, biodiversity, and stability of terrestrial ecosystems. Soil microbial community, a key component of global biodiversity, plays a pivotal role in ecosystem stability and is highly vulnerable to urbanization. However, effects of urbanization on the diversity, stability, and network structure of soil microbial community remain poorly understood. Herein, we investigated the diversity and stability of soil microbial communities, including bacteria, fungi, and protists, across three regions with different levels of urbanization—urban, suburb, and ecoregion—using high-throughput sequencing techniques. Our results revealed that urbanization led to a notable decrease in the alpha diversity of soil microbial community, causing a significant reduction in soil stability, as assessed by the average variation degree (AVD). The loss of stability was linked to the diminished alpha diversity of the soil fungal and protistan communities, along with weakened interactions among bacteria, fungi, and protists. Notably, the majority of keystone species identified through network analysis were classified as bacteria (Proteobacteria) and displayed a strong positive correlation with the environmental factors influencing AVD. This highlights that the variability of bacteria and the immutability of fungi and protists are important to sustain soil microbial stability. Furthermore, structural equation models indicated that protistan diversity primarily drove soil microbial stability across all regions studied. In the suburban and ecoregion areas, soil microbial stability was directly influenced by the soil properties, bacterial diversity, and keystone species, as well as indirectly affected by heavy metals. These results underscore how urbanization can reduce the stability of soil microbial community via declined diversity and network complexity, whereas the establishment of ecoregions maybe contribute to preserve the diversity and stability of soil microbial community.

Vertical structure of Caribbean deep-reef fishes from the altiphotic to deep-sea boundary

While recent technical breakthroughs have enabled advances in the description of reefs down to 150 m, the structure and depth zonation of deep-reef communities below 150 m remains largely unknown. Here, we present results from over 10 years of deep-reef fish surveys using human-occupied submersibles at four locations across the Caribbean Sea, constituting one of the only continuous reef-fish surveys from 10 to 480 m (1 site) and 40 to 300 m (3 sites). We identify four vertically stratified deep-reef fish communities between 40 and 300 m bordered by an altiphotic (0–10 m) and a deep-sea (300–480 m) community. We found a strong faunal break around 150 m that separates mesophotic and rariphotic zones and secondary breaks at ~ 70 to 90 m and ~ 180 to 200 m subdividing these zones into upper and lower communities. From 300 to 480 m in Roatán, we found a single fish community dominated by deep-sea families, indicating that the lower boundary of the reef-fish realm occurs at 300 m. No differences were found between communities ranging from 20 to 60 m, suggesting that fishes from the lower altiphotic and upper mesophotic form an ecological continuum. While some variability was observed across sites, the overall depth zonation and key species characterizing depth zones were consistent. Most deep-reef species observed were depth specialists restricted to a single depth zone, but many shallow-reef species extended down to mesophotic depths. Depth segregation among species of a genus was found across ten reef-fish genera and likely constitutes one of the mechanisms driving community distinctiveness and thereby fish diversity across depths.

Darriwilian conodont biostratigraphy from the Rio Francia section, Central Precordillera, Argentina: A new insight into the Darriwilian conodont biozones

Darriwilian conodont data from the uppermost meters of the San Juan Formation in the Rio Francia section are documented. A detailed analysis of conodont biostratigraphy is conducted, recording early-middle Darriwilian interval zones based on first occurrence of the index species of genus Lenodus. Four conodont biozones were documented: Lenodus antivariabilis, L. variabilis, L. crassus and L. pseudoplanus. The overlapped range of the L. variabilis, L. crassus and L. pseudoplanus verified the lower part of L. pseudoplanus Zone for the first time in the Precordillera. The co-occurrence of the P. horridus middle form first and second stage with key species of the Lenodus support this record, providing an accurate regional correlation between several sections in the Central and Eastern Precordillera. Based on the conodont data presented herein, the early-middle Darriwilian conodont biozonation of the Precordillera can now be tied more robustly to global biostratigraphic frameworks.

Nematode-trapping fungus Arthrobotrys oligospora recruited rhizosphere microorganisms to cooperate in controlling root-knot nematodes in tomato.

The objective of this study was to elucidate the role and mechanism of changes in the rhizosphere microbiome following A. oligospora treatment in the biological control of root-knot nematodes and identify the key fungal and bacterial species that collaborate with A. oligospora to biocontrol root-knot nematodes. We conducted a pot experiment to investigate the impact of A. oligospora treatment on the biocontrol efficiency of A. oligospora against Meloidogyne incognita infecting tomato. We analyzed the rhizosphere bacteria and fungi communities of tomato by high-throughput sequencing of the 16S rRNA gene fragment and the internal transcribed spacer (ITS). The results indicated that the application of A. oligospora resulted in a 53.6% reduction in the disease index of M. incognita infecting tomato plants. The bacterial diversity of rhizosphere soil declined in the A. oligospora-treated group, while fungal diversity increased. The A. oligospora treatment enriched the tomato rhizosphere with Acidobacteriota, Firmicutes, Bradyrhizobium, Sphingomonadales, Glomeromycota and Purpureocillium. These organisms are involved in the utilization of rhizosphere organic matter, nitrogen, and glycerolipids, or play the role of ectomycorrhiza or directly kill nematodes. The networks of bacterial and fungal co-occurrence exhibited a greater degree of stability and complexity in the A. oligospora treatment group. This study demonstrated the key fungal and bacterial species that collaborate with the A. oligospora in controlling the root-knot nematode and elaborated the potential mechanisms involved. The findings offer valuable insights and inspiration for the advancement of bionematicide based on nematode-trapping fungus.

Collembola and ants: Influence of trails of red wood ants (Formica lugubris) on the community of soil springtails

Red wood ants are keystone species in forest ecosystems. Because ants are active polyphagous predators, they control the abundance of other arthropods. In addition to direct effects on other species, there are a number of indirect effects caused by ants. In our study, we investigated the influence of ants on springtails, which they rarely come into contact with. Springtails have been set as a model group to assess the state of soil animals, since they are one of the most numerous and widespread groups of soil microarthropods. They are characterized by high sensitivity to environmental changes. The basic characteristics (abundance, species richness, and species diversity) of the springtail community and the response of certain species to the presence of ant trails have been studied. The total abundance and species richness of springtails decreased along ant trails. Among occurred species Parisotoma ParIsotoma notabilis, Lepidacyrtus lignorum, Isotomiella minor, Desoria tigrina, and Pseudasinella alba are the most numerous species both along ant trails and in control samples. There are no significant changes in species diversity (assessed by the Shannon-Weaver index). Species structure of springtail communities along ant trails and in control is different. Two groups of common Collembola species are identified: (1) increasing their numbers in the presence of ants, (2) on the contrary, decreasing. The presence of ants in a forest ecosystem influences the soil springtail community, although ant-Collembola interactions are indirect.

Facile synthesis, morphological, optical, catalytic and photocatalytic properties of Ag nanoparticles decorated Ce doped ZnO hybrid plasmonic nanorods

Designing plasmonic metal–semiconductor hybrid nanostructures for photodecomposition of industrial textile effluent has been considered as a great way to boost the catalytic and photocatalytic capability by promoting effective separation of photoexcited charge carriers. Herein, fabrication of Ag nanoparticles decorated Ce doped ZnO nanostructures were demonstrated via facile wet chemical method. The morphology and structure of the fabricated photocatalysts were analysed using FESEM, XRD and Raman spectroscopy whereas PL, TRPL and UV–vis absorption spectroscopy were employed to examine their optical behaviour. Catalytic response of the synthesized catalysts was studied for 4-NP to 4-AP reduction and the results are more favourable for Ag loaded Ce doped ZnO catalysts and achieved 96.4 % reduction of 4-NP in only 4 min. Photocatalytic measurements showed that higher Ag NP loading onto Ce doped ZnO nanostructures led to superior photodegradation ability over other photocatalysts for the degradation of synthetic dyes and levofloxacin antibiotic. The sunlight driven photodecolorization of harmful synthetic dyes and levofloxacin were studied and efficacy of 97.5, 97.1, 85.1, and 70.9 % were achieved for MG, MB, RhB and MO dyes, respectively in 12 min and 97.2 % efficiency for degradation of levofloxacin was achieved in 20 min of sunlight exposure. Furthermore, the key reactive species was identified and tentative photodegradation process was explained. This work provides an excellent plasmonic-semiconductor catalyst and photocatalyst with good photostability and practical applicability indicating its enormous potential for application in environmental remediation.

New Variants in the Chloroplast Genome Sequence of Two Colombian Individuals of the Cedar Timber Species (Cedrela odorata L.), Using Long-Read Oxford Nanopore Technology

The plant species Cedrela odorata has been largely exploited in the timber industry due to the high demand for its wood. Therefore, C. odorata has been considered a vulnerable species since 1994, under the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). C. odorata is a key timber species included in the management and conservation plans for the Amazon and Central American rainforests. These plans include the development of genetic and genomic resources to study local populations of the species in Colombia. In this study, two novel chloroplast (cp) genomes were assembled and annotated using the MinION long-read sequencing technology. The new cp genomes were screened for sequence variants (SVs), and a total of 16 SNPs were identified, presumably unique to populations from the Amazon region in Colombia. Comparative genomics with other reported cp genomes from different populations of C. odorata support the hypothesis of intraspecific diversity associated with their place of origin. These cp genome sequences of C. odorata from Colombian individuals represent valuable genomic resources for the species, suitable for identifying novel DNA fingerprinting and barcoding applications.

A multi-decadal 1 km gridded database of continental-scale spring onset products

The timing of spring onset is a particularly sensitive climate change indicator that also allows the study of weather interannual variations and extremes. This indicator can be derived from a suite of phenological models called the Extended Spring Indices (SI-x). These models transform daily minimum and maximum temperatures into a set of consistent indices that track the timing of first leaf and first bloom for key indicator plant species. The SI-x also enables the calculation of the so-called frost damage index. Using new computational technologies and high spatial resolution gridded weather data, here we present and evaluate a multi-decadal 1 km spatial resolution version of the SI-x models, which cover North American (1980 to 2022) and European areas (1950 to 2020). Because of the generally good agreement with ground phenological observations, this continental-scale and high spatial resolution product can support both scientists and decision makers in their quest to hind- and forecast weather and climate change impacts.

Comparing expedient and proactive approaches to the planning of protected area networks on Borneo

Protected areas are an important tool for wildlife conservation; however, research is increasingly revealing both biases and inadequacies in the global protected area network. One common criticism is that protected areas are frequently located in remote, high-elevation regions, which may face fewer threats compared to more accessible locations. To explore the conservation implications of this issue, we consider a thought experiment with seven different counterfactual scenarios for the Sunda clouded leopard’s conservation on Borneo. This allows us to examine two contrasting paradigms for conservation: “proactive conservation” which prioritises areas with high biodiversity and high risk of development, and “expedient conservation” which focusses on areas with the lowest development risk. We select clouded leopards as our focal species not only because of their emerging conservation importance, but also because, as top predators, they represent both keystone species and ambassadors for wider forest biodiversity. Furthermore, a published analysis of the likely impacts of forest loss in their habitat provides a benchmark for evaluating the modelled outcomes of alternative hypothetical conservation scenarios. We find that, across all metrics, expedient reserve design offered few benefits over the business-as-usual scenario, in contrast to the much greater conservation effectiveness of proactive protected area design. This paper sheds light on the challenging trade-offs between conservation goals and the competing land uses essential for the economic development and well-being of local communities.

Re-establishing historic ecosystem links through targeted species reintroduction: Beaver-mediated wetlands support increased bat activity

Despite the global significance of wetlands, conservation strategies often fall short in preserving these ecosystems due to failures in incorporating processes that sustain the ecosystem functioning, hydrological dynamics, ecological processes, and biodiversity of wetlands. Nature-based solutions, such as the reintroduction of beavers, have emerged as effective tools for promoting wetland restoration. Whilst the impact of beavers on wetland restoration is well known, their broader influence on ecosystem health, particularly in modifying habitats for other species, remains inadequately understood. Here we assess the impact that habitat modification through the reintroduction of beavers has on bat populations. There were significantly greater activity levels within beaver-modified wetland habitats for multiple bat species, including higher activity levels of 393 % for Barbastella barbastellus and 313 % for Plecotus spp.. Additionally, we observed positive effects on bat populations in the woodland habitat surrounding beaver-modified wetland for certain taxa. In the face of escalating challenges posed by climate change and habitat loss, addressing biodiversity loss necessitates a shift toward ecosystem-centric mitigation measures. Our study demonstrates that the reintroduction of keystone species like beavers can re-establish historical facilitative links between aquatic and terrestrial food webs, highlighting the importance of such interventions in fostering the resilience and sustainability of entire ecosystems.

A Thorium(IV) metallacyclopropyne complex

Actinide metallacyclic chemistry has been of interest due to its involvement in various chemical processes. However, fundamental understanding on the key species, actinide metallacyclic complexes, is limited to metallacyclopropenes whereas little is known about the actinide metallacyclopropynes presumably due to their unusual high reactivity. Herein, we report the preparation of a thorium metallacyclopropyne complex (η2-C ≡ C)ThCl3– in the gas phase by using electrospray ionization mass spectrometry, and it is generated via a single-ligand strategy through sequential losses of CO2 and HCl from the monopropynoate precursor (HC ≡ CCO2)ThCl4– upon collision-induced dissociation. Alternatively, the dual-ligand strategy involving consecutive losses of two CO2 and one C2H2 from the dipropynoate precursor (HC ≡ CCO2)2ThCl3– works as well. According to the reactivity experiments and theoretical calculations, (η2-C ≡ C)ThCl3– possesses a dianionic ligand C22– coordinated to the Th(IV) center in a side-on fashion. Further bonding analysis demonstrates the presence of a triple bond between the two C atoms, and the Th 5 f orbitals are significantly involved in the Th-(C ≡ C) bonding. A Th metallacyclopropyne structure is thus established for (η2-C ≡ C)ThCl3–.

Pan-pathogen deep sequencing of nosocomial bacterial pathogens in Italy in spring 2020: a prospective cohort study

Nosocomial infections pose a considerable risk to patients who are susceptible, and this is particularly acute in intensive care units when hospital-associated bacteria are endemic. During the first wave of the COVID-19 pandemic, the surge of patients presented a significant obstacle to the effectiveness of infection control measures. We aimed to assess the risks and extent of nosocomial pathogen transmission under a high patient burden by designing a novel bacterial pan-pathogen deep-sequencing approach that could be integrated with standard clinical surveillance and diagnostics workflows. We did a prospective cohort study in a region of northern Italy that was severely affected by the first wave of the COVID-19 pandemic. Inpatients on both ordinary and intensive care unit (ICU) wards at the San Matteo hospital, Pavia were sampled on multiple occasions to identify bacterial pathogens from respiratory, nasal, and rectal samples. Diagnostic samples collected between April 7 and May 10, 2020were cultured on six different selective media designed to enrich for Acinetobacter baumannii, Escherichia coli, Enterococcus faecium, Enterococcus faecalis, Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus aureus, and Streptococcus pneumoniae, and DNA from each plate with positive growth was deep sequenced en masse. We used mSWEEP and mGEMS to bin sequencing reads by sequence cluster for each species, followed by mapping with snippy to generate high quality alignments. Antimicrobial resistance genes were detected by use of ARIBA and CARD. Estimates of hospital transmission were obtained from pairwise bacterial single nucleotide polymorphism distances, partitioned by within-patient and between-patient samples. Finally, we compared the accuracy of our binned Acinetobacter baumannii genomes with those obtained by single colony whole-genome sequencing of isolates from the same hospital. We recruited patients from March 1to May 7, 2020. The pathogen population among the patients was large and diverse, with 2148species detections overall among the 2418sequenced samples from the 256patients. In total, 55sequence clusters from key pathogen species were detected at least five times. The antimicrobial resistance gene prevalence was correspondingly high, with key carbapenemase and extended spectrum ß-lactamase genes detected in at least 50 (40%) of 125patients in ICUs. Using high-resolution mapping to infer transmission, we established that hospital transmission was likely to be a significant mode of acquisition for each of the pathogen species. Finally, comparison with single colony Acinetobacter baumannii genomes showed that the resolution offered by deep sequencing was equivalent to single-colony sequencing, with the additional benefit of detection of co-colonisation of highly similar strains. Our study shows that a culture-based deep-sequencing approach is a possible route towards improving future pathogen surveillance and infection control at hospitals. Future studies should be designed to directly compare the accuracy, cost, and feasibility of culture-based deep sequencing with single colony whole-genome sequencing on a range of bacterial species. Wellcome Trust, European Research Council, Academy of Finland Flagship program, Trond Mohn Foundation, and Research Council of Norway.

Dynamical behavior of obligatory mutualistic-cheater interactions under the influence of white noise

Intraspecific mutualism is vital for ecosystems. Some interactions involve one species benefiting without reciprocating. Recent experiments suggest stable co-existence between mutualists and cheaters. This paper focuses on interactions between obligate mutualistic species and their cheaters, using a modified Lotka-Volterra model to analyze the negative impact of cheaters. We establish conditions for stability and verify a diffusive system's stability under spatial effects. Additionally, we study population dynamics fluctuations in the presence of Gaussian noise.

Declines and shifts in morphological diversity of ciscoes (Coregonus spp.) in lakes Huron and Michigan, 1917–2019

Ciscoes ( Coregonus spp .) were historically abundant and ecologically important in Laurentian Great Lakes ecosystems. Despite well-documented declines in their abundance and taxonomic diversity, declines in morphological diversity remain understudied. This knowledge gap is especially pertinent for lakes Michigan and Huron, which have each lost six of eight historical species. Improved understanding of historical and contemporary morphological diversity of Great Lakes ciscoes can inform ongoing restoration efforts and further elucidate the factors that contributed to declines. Our goal was to characterize shifts in morphological diversity of ciscoes in lakes Michigan and Huron over a century (1917–2019). We analyzed size-corrected morphometric and meristic measurements from three periods: Early (1917–1923), Middle (1950–1972), and Contemporary (2015–2019). We then identified morphologically distinct clusters while remaining agnostic to species identifications. We found that morphological diversity and the number of distinct clusters declined over time. We then leveraged species identifications to highlight key species losses and examine morphological shifts among extant species. Our findings provide insights into the historical and contemporary morphological diversity of ciscoes and will inform restoration efforts.

Microbiota-driven vaccination in soft ticks: Implications for survival, fitness and reproductive capabilities in Ornithodoros moubata.

The Ornithodoros moubata (Om) soft tick, a vector for diseases like tick-borne human relapsing fever and African swine fever, poses challenges to conventional control methods. With diminishing insecticide efficacy, harnessing the tick's microbiota through innovative approaches like microbiota-driven vaccination emerges as a promising strategy for sustainable and targeted disease control. This study investigated the intricate relationship between Pseudomonas, a keystone taxon in the Om microbiome, and its impact on tick fitness, microbiome structure and network dynamics. Utilizing in silico analyses and empirical vaccination experiments, the role of Pseudomonas within microbial networks in the tick midguts (MG) and salivary glands (SG) of Om was studied. Additionally, the consequences of anti-microbiota vaccines targeting Pseudomonas and Lactobacillus on tick fitness, microbiome diversity and community assembly were explored. The result of the study shows that in Om, Pseudomonas plays a central role in microbial networks, influencing keystone species despite being categorized as peripheral (interacting with 47 different taxa, 13 of which are keystone species). Anti-microbiota vaccination targeting Pseudomonas and Lactobacillus yields distinct effects on tick fitness, with Pseudomonas vaccination significantly impacting female tick survival, while Lactobacillus significantly reduced oviposition and fertility. Microbiome changes post-vaccination reveal diversity alterations, emphasizing the impact of vaccine choice. Community assembly dynamics and network robustness analyses highlight Pseudomonas' pivotal role, in influencing topological features and network resilience. The findings of the study provide comprehensive insights into the intricate dynamics of Om microbial networks and the potential of targeted microbiota-driven vaccines for tick control.

Fish eggs in the diet of White Sea cod Gadus morhua marisalbi (Gadiformes: Gadidae): species identification using DNA-based methods

Trophic relationships reflect the peculiarities of the functioning of communities of aquatic organisms and analysis of their structure and dynamics can be used to improve fisheries management and assess the state of marine ecosystems. Populations at the margins of the species' range have particular adaptations, including feeding habits, to extreme conditions, which makes them a convenient model object for studying the possible consequences of ecosystem changes under the influence of global factors. The cod Gadus morhua marisalbi Derjugin, 1920 permanently inhabits the coastal waters of the subarctic White Sea, located at the northeastern margin of the geographic range of the Atlantic cod G. morhua Linnaeus, 1758. This coastal cod population strongly depends on the local environmental conditions and available food resources during the summer feeding period. In addition to the main food organisms (fish, polychaetes, crustaceans), the eggs of fish spawning in shallow coastal areas in summer are also important in the diet of cod at this time. According to published data, fish eggs found in significant quantities and most often in the stomachs of cod belonged to threespine stickleback and lumpfish, but this has not been confirmed by any experimental research. Besides, the possible presence of herring eggs in the diet of cod remains unproven due to the difficulties of its visual identification. In this work, we used molecular genetic methods for species identification of fish eggs found in cod stomachs. At the first stage, the species identification of DNA isolated from eggs was done using two sets of species-specific primers: the first which we designed for the mitochondrial COI gene of stickleback, cod, and herring, and the second, published for a microsatellite locus of herring. At the second stage, the species identity of DNA extracted from fish eggs was checked using DNA barcoding. The results showed that cod stomachs contained herring and stickleback eggs, and in a number of cases we found the co-occurrence of eggs of these species. Of the 29 DNA preparations studied, fourteen were successfully amplified with microsatellite primers for herring, and thirteen amplified with primers for stickleback. Interannual differences in the occurrence of herring eggs in samples were insignificant, while the frequency of occurrence of stickleback eggs in 2018 was higher than in 2017. Our analysis did not reveal significant intra-annual differences between the observed and theoretically expected number of cases of simultaneous occurrences of herring and stickleback eggs. The high frequency of occurrence of herring and stickleback eggs in cod stomachs revealed in this study indicates the importance of these components in the diet of cod and provides new knowledge on the trophic role of cod as a key species in the White Sea ecosystem. Analysis of available data on the spatial and temporal diet patterns of coastal White Sea cod shows that fish eggs can significantly contribute to the total amount of food consumed by this species during the summer.

Genetics and ontogeny are key factors influencing thermal resilience in a culturally and economically important bivalve

Increasing seawater temperatures coupled with more intense and frequent heatwaves pose an increasing threat to marine species. In this study, the New Zealand green-lipped mussel, Perna canaliculus, was used to investigate the effect of genetics and ontogeny on thermal resilience. The culturally and economically significant mussel P. canaliculus (Gmelin, 1971) has been selectively-bred in New Zealand for two decades, making it a unique biological resource to investigate genetic interactions in a temperate bivalve species. Six selectively-bred full sibling families and four different ages, from early juveniles (6, 8, 10 weeks post-fertilisation) to sub-adults (52 weeks post-fertilisation), were used for experimentation. At each age, each family was exposed to a three-hour heat challenge, followed by recovery, and survival assessments. The shell lengths of live and dead juvenile mussels were also measured. Gill tissue samples from sub-adults were collected after the thermal challenge to quantify the 70 kDa heat shock protein gene (hsp70). Results showed that genetics, ontogeny and size influence thermal resilience in P. canaliculus, with LT50 values ranging between 31.3 and 34.4 °C for all studied families and ages. Juveniles showed greater thermotolerance compared to sub-adults, while the largest individuals within each family/age class tended to be more heat sensitive than their siblings. Sub-adults differentially upregulated hsp70 in a pattern that correlated with net family survival following heat challenge, reinforcing the perceived role of inducible HSP70 protein in molluscs. This study provides insights into the complex interactions of age and genotype in determining heat tolerance of a key mussel species. As marine temperatures increase, equally complex selection pressure responses may therefore occur. Future research should focus on transcriptomic and genomic approaches for key species such as P. canaliculus to further understand and predict the effect of genetic variation and ontogeny on their survival in the context of climate change.