Cryptorchidism, a prevalent congenital defect in pigs, raises animal welfare and economic concerns in the breeding industry. This study utilized a genome-wide transcriptome analysis, examining samples from the pituitary gland, cremaster muscle and testis of one-week-old piglets. In the cremaster muscle of cryptorchid piglets,1225 genes exhibited significant differential expression (log2FoldChange = |2.0|, p-adjusted value ≤ 0.01). Downregulated genes were linked to biological processes like muscle tissue development and actin cytoskeleton organization. Pathway analysis further revealed the suppression of metabolic pathways including ‘Oxidative phosphorylation’, ‘TCA cycle’ and ‘Motor Proteins’. Notably, several genes integral to the motor protein pathway were significantly downregulated. Additionally, crucial genes in the noncanonical Wnt signalling pathway that regulates tissue morphogenesis and repair during the embryonic stage, were also suppressed. Our results indicate that a disruption in the normal testicular descent is accompanied by the suppression of major genes in the motor protein pathway, potentially hampering the presumed role of the cremaster muscle in testicular descent. However, we propose this to be a consequence of the down regulation of key genes in the noncanonical Wnt signalling pathway. Based on our findings, future research might be able to uncover causal mutations related to the expression of these genes.

Investigating marine species population structure in a multidisciplinary framework can reveal signatures of potential local adaptation and the consequences for management and conservation. In this study we delineate the population structure of common sole (Solea solea) in the Mediterranean Sea using genomic and otolith data, based on single nucleotide polymorphism (SNPs) markers, otolith shape and otolith trace element composition data. We correlated SNPs with environmental and spatial variables to evaluate the impact of the selected features on the actual population structure. Specifically, we used a seascape genetics approach with redundancy (RDA) and genetic-environmental association (GEA) analysis to identify loci potentially involved in local adaptation. Finally, putative functional annotation was investigated to detect genes associated with the detected patterns of neutral and adaptive genetic variation. Results from both genetic and otolith data suggested significant divergence among putative populations of common sole, confirming a clear separation between the Western and Eastern Mediterranean Sea, as well as a distinct genetic cluster corresponding to the Adriatic Sea. Evidence of fine-scale population structure in the Western Mediterranean Sea was observed at outlier loci level and further differentiation in the Adriatic. Longitude and salinity variation accounted for most of the wide and fine spatial structure. The GEA detected significant associated outlier loci potentially involved in local adaptation processes under highly structured differentiation. In the RDA both spatial distribution and environmental features could partially explain the genetic structure. Our study not only indicates that separation among Mediterranean sole population is led primarily by neutral processes because of low connectivity due to spatial segregation and limited dispersal, but it also suggests the presence of local adaptation. These results should be taken into account to support and optimize the assessment of stock units, including a review and possible redefinition of fishery management units.

Animals used in research often have to be euthanised, especially when tissue sampling is essential. Recently, a euthanasia method, utilizing an inhalant anaesthetic 'nitrogen gas in foam' in an anoxia box (ANOXIATM), has gained considerable interest as it claimed to be more animal-friendly. However, it is not clear whether the use of this euthanasia method has an influence on RNA measurements. Moreover, there are no studies on the interaction effect of different euthanasia methods on the tissue sample storage conditions. The current study compared RNA measurements from two euthanasia methods (ANOXIATM vs. T-61® injection) and two storage conditions (RNAlater™ vs. snap freezing) in 12 male piglets. The nitrogen anoxia method had a significantly higher RNA yield (p < 0.01) compared to the T-61® method. However, no effect of the euthanasia methods on the A260/230 ratio and RIN value was observed. Tissues stored in RNAlater™ had significantly higher RIN values (p < 0.001) compared to snap frozen samples. The present study could not find a significant difference between the two euthanasia methods in piglets, with regard to RNA quality measurements. Hence, the nitrogen anoxia technique (ANOXIATM) might be considered as a suitable alternative to T-61® for euthanasia of piglets used in research.

Shrimp are a valuable aquaculture species globally; however, disease remains a major hindrance to shrimp aquaculture sustainability and growth. Mechanisms mediated by endogenous viral elements (EVEs) have been proposed as a means by which shrimp that encounter a new virus start to accommodate rather than succumb to infection over time. However, evidence on the nature of such EVEs and how they mediate viral accommodation is limited. More extensive genomic data on Penaeid shrimp from different geographical locations should assist in exposing the diversity of EVEs. In this context, reported here is a PacBio Sequel-based draft genome assembly of an Australian black tiger shrimp ( Penaeus monodon ) inbred for one generation. The 1.89 Gbp draft genome is comprised of 31,922 scaffolds (N50: 496,398 bp) covering 85.9% of the projected genome size. The genome repeat content (61.8% with 30% representing simple sequence repeats) is almost the highest identified for any species. The functional annotation identified 35,517 gene models, of which 25,809 were protein-coding and 17,158 were annotated using interproscan. Scaffold scanning for specific EVEs identified an element comprised of a 9,045 bp stretch of repeated, inverted and jumbled genome fragments of Infectious hypodermal and hematopoietic necrosis virus (IHHNV) bounded by a repeated 591/590 bp host sequence. As only near complete linear ~4 kb IHHNV genomes have been found integrated in the genome of P. monodon previously, its discovery has implications regarding the validity of PCR tests designed to specifically detect such linear EVE types. The existence of joined inverted IHHNV genome fragments also provides a means by which hairpin dsRNAs could be expressed and processed by the shrimp RNA interference (RNAi) machinery.

Cephalopods have evolved nervous systems that parallel the complexity of mammalian brains in terms of neuronal numbers and richness in behavioral output. How the cephalopod brain develops has only been described at the morphological level, and it remains unclear where the progenitor cells are located and what molecular factors drive neurogenesis. Using histological techniques, we located dividing cells, neural progenitors and postmitotic neurons in Octopus vulgaris embryos. Our results indicate that an important pool of progenitors, expressing the conserved bHLH transcription factors achaete-scute or neurogenin, is located outside the central brain cords in the lateral lips adjacent to the eyes, suggesting that newly formed neurons migrate into the cords. Lineage-tracing experiments then showed that progenitors, depending on their location in the lateral lips, generate neurons for the different lobes, similar to the squid Doryteuthis pealeii. The finding that octopus newborn neurons migrate over long distances is reminiscent of vertebrate neurogenesis and suggests it might be a fundamental strategy for large brain development.

The European eel is critically endangered. Although the quality of silver eels is essential for their reproduction, little is known about the effects of multiple contaminants on the spawning migration and the European eel management plan does not take this into account. To address this knowledge gap, we sampled 482 silver eels from 12 catchments across Europe and developed methods to assess three aspects of eel quality: muscular lipid content (N = 169 eels), infection with Anguillicola crassus (N = 482), and contamination by persistent organic pollutants (POPs, N = 169) and trace elements (TEs, N = 75). We developed a standardized eel quality risks index (EQR) using these aspects for the subsample of 75 female eels. Among 169 eels, 33% seem to have enough muscular lipids content to reach the Sargasso Sea to reproduce. Among 482 silver eels, 93% were infected by A. crassus at least once during their lifetime. All contaminants were above the limit of quantification, except the 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE), Ag and V. The contamination by POPs was heterogeneous between catchments while TEs were relatively homogeneous, suggesting a multi-scale adaptation of management plans. The EQR revealed that eels from Warwickshire were most impacted by brominated flame-retardants and agricultural contaminants, those from Scheldt were most impacted by agricultural and construction activities, PCBs, coal burning, and land use, while Frémur eels were best characterized by lower lipid contents and high parasitic and BTBPE levels. There was a positive correlation between EQR and a human footprint index highlighting the capacity of silver eels for biomonitoring human activities and the potential impact on the suitability of the aquatic environment for eel population health. EQR therefore represents a step forward in the standardization and mapping of eel quality risks, which will help identify priorities and strategies for restocking freshwater ecosystems.

The natural flight response in shrimp is powered by rapid contractions of the abdominal muscle fibres to propel themselves backwards away from perceived danger. This muscle contraction is dependent on repetitive depolarization of muscle plasma membrane, triggering tightly spaced cytoplasmic [Ca2+] transients and rapidly rising tetanic force responses. To achieve such high amplitude and high frequency of Ca2+ transients requires a high abundance of sarcoplasmic/endoplasmic reticulum Ca2+ ATPase (SERCA) to rapidly clear cytoplasmic Ca2+ between each transient and an efficient Ca2+ release system consisting of the Ryanodine Receptor (RyR), and voltage gated Ca2+ channels (CaVs). With the aim to expand our knowledge of muscle gene function and identify orthologous genes regulating muscle excitation-contraction (EC) coupling, this study assembled nine Penaeid shrimp muscle transcriptomes. On average, the nine transcriptomes contained 27,000 contigs, with an annotation rate of 36% and a BUSCO completeness of 70%. Despite maintaining their function, the crustacean RyR and CaV proteins showed evidence of significant diversification from mammalian orthologs, while SERCA remained more conserved. Several key components of protein interaction were conserved, while others showed distinct crustacean specific evolutionary adaptations. Lastly, this study revealed approximately 1,000 orthologous genes involved in muscle specific processes present across all nine species.

Background and Objective: Human-induced physical and environmental barriers especially hydropower dams and dense anoxic vegetation along riverine-lacustrine connectivity are known to isolate and fragment fish populations, leading to variation.This study explored possible morphological variations among populations of Barbus altianalis from Uganda with the intent to provide a more costeffective and reliable platform for elucidating the stocks under combined environmental and anthropogenic influence as a tool for improved fisheries management and conservation.Materials and Methods: Multivariate analysis of morphometric variables was performed to determine the morphological variation and discreteness among three populations of B. altianalis (N = 251) from the lacustrine (Lake Edward) and riverine (River Nile and Kazinga channel) systems in Uganda.Morphological variation was determined using a multivariate analysis of advanced truss and non-truss network systems on all individuals collected from commercial catches.Results: There was a significantly (p<0.001) higher level of heterogeneity among populations.Group means on the DFA1 showed that River Nile (-0.89) separated furthest from Lake Edward (0.79) and the Kazinga channel (0.68).River Nile had the highest number (80.5%) of individuals correctly classified while Lake Edward (67.2%) and Kazinga channel (60.5%) had more misclassifications between them, an indication that they could be much harder to separate.Conclusion: The observed patterns of variation were consistent with the geographical locations of the different water bodies, that the isolating mechanisms are subjecting the different populations to different selection pressure hence different phenotypic responses by the populations.

Uncertainty hampers innovative mixed-fisheries management by the scales at which connectivity dynamics are relevant to management objectives. The spatial scale of sustainable stock management is species-specific and depends on ecology, life history and population connectivity. One valuable approach to understand these spatial scales is to determine to what extent population genetic structure correlates with the oceanographic environment. Here, we compare the level of genetic connectivity in three codistributed and commercially exploited demersal flatfish species living in the North East Atlantic Ocean. Population genetic structure was analysed based on 14, 14 and 10 neutral DNA microsatellite markers for turbot, brill and sole, respectively. We then used redundancy analysis (RDA) to attribute the genetic variation to spatial (geographical location), temporal (sampling year) and oceanographic (water column characteristics) components. The genetic structure of turbot was composed of three clusters and correlated with variation in the depth of the pycnocline, in addition to spatial factors. The genetic structure of brill was homogenous, but correlated with average annual stratification and spatial factors. In sole, the genetic structure was composed of three clusters, but was only linked to a temporal factor. We explored whether the management of data poor commercial fisheries, such as in brill and turbot, might benefit from population-specific information. We conclude that the management of fish stocks has to consider species-specific genetic structures and may benefit from the documentation of the genetic seascape and life-history traits.

The common octopus, Octopus vulgaris , is an active marine predator known for the richness and plasticity of its behavioral repertoire, and remarkable learning and memory capabilities. Octopus and other coleoid cephalopods, cuttlefish and squid, possess the largest nervous system among invertebrates, both for cell counts and body to brain size. O . vulgaris has been at the center of a long-tradition of research into diverse aspects of its biology. To leverage research in this iconic species, we generated 270 Gb of genomic sequencing data, complementing those available for the only other sequenced congeneric octopus, Octopus bimaculoides . We show that both genomes are similar in size, but display different levels of heterozygosity and repeats. Our data give a first quantitative glimpse into the rate of coding and non-coding regions and support the view that hundreds of novel genes may have arisen independently despite the close phylogenetic distance. We furthermore describe a reference-guided assembly and an open genomic resource (CephRes-gdatabase), opening new avenues in the study of genomic novelties in cephalopods and their biology.

Preeclampsia (PE) has been associated with placental dysfunction, resulting in fetal hypoxia, accelerated erythropoiesis, and increased erythroblast count in the umbilical cord blood (UCB). Although the detailed effects remain unknown, placental dysfunction can also cause inflammation, nutritional, and oxidative stress in the fetus that can affect erythropoiesis. Here, we compared the expression of surface adhesion molecules and the erythroid differentiation capacity of UCB hematopoietic stem/progenitor cells (HSPCs), UCB erythroid profiles along with the transcriptome and proteome of these cells between male and female fetuses from PE and normotensive pregnancies. While no significant differences were observed in UCB HSPC migration/homing and in vitro erythroid colony differentiation, the UCB HSPC transcriptome and the proteomic profile of the in vitro differentiated erythroid cells differed between PE vs. normotensive samples. Accordingly, despite the absence of significant differences in the UCB erythroid populations in male or female fetuses from PE or normotensive pregnancies, transcriptional changes were observed during erythropoiesis, particularly affecting male fetuses. Pathway analysis suggested deregulation in the mammalian target of rapamycin complex 1/AMP-activated protein kinase (mTORC1/AMPK) signaling pathways controlling cell cycle, differentiation, and protein synthesis. These results associate PE with transcriptional and proteomic changes in fetal HSPCs and erythroid cells that may underlie the higher erythroblast count in the UCB in PE.

With just a handful of documented cases of hybridisation in cartilaginous fishes, shark hybridisation remains poorly investigated. Small amounts of admixture have been detected between Galapagos (Carcharhinus galapagensis) and dusky (Carcharhinus obscurus) sharks previously, generating a hypothesis of ongoing hybridisation. We sampled a large number of individuals from areas where the species co-occur (contact zones) across the Pacific Ocean and used both mitochondrial and nuclear-encoded SNPs to examine genetic admixture and introgression between the two species. Using empirical analytical approaches and simulations, we first developed a set of 1873 highly informative SNPs for these two species to evaluate the degree of admixture between them. Overall, results indicate a high discriminatory power of nuclear SNPs (FST = 0.47, p < 0.05) between the two species, unlike mitochondrial DNA (ΦST = 0.00 p > 0.05), which failed to differentiate these species. We identified four hybrid individuals (∼1%) and detected bi-directional introgression between C. galapagensis and C. obscurus in the Gulf of California along the east Pacific coast of the Americas. We emphasize the importance of including a combination of mtDNA and diagnostic nuclear markers to properly assess species identification, detect patterns of hybridisation, and better inform management and conservation of these sharks, especially given the morphological similarities within the genus Carcharhinus.

Abstract Fishing represents a major problem for conservation of chondrichthyans, with a quarter of all species being overexploited. School sharks, Galeorhinus galeus, are targeted by commercial fisheries in Australia and New Zealand. The Australian stock has been depleted to below 20% of its virgin biomass, and the species is recorded as Conservation Dependent within Australia. Individuals are known to move between both countries, but it is disputed whether the stocks are reproductively linked. Accurate and unbiased determination of stock and population connectivity is crucial to inform effective management. In this study, we assess the genetic composition and population connectivity between Australian and New Zealand school sharks using genome‐wide SNPs, while accounting for non‐random kin sampling. Between 2009 and 2013, 88 neonate and juvenile individuals from Tasmanian and New Zealand nurseries were collected and genotyped. Neutral loci were analyzed to detect fine‐scale signals of reproductive connectivity. Seven full‐sibling groups were identified and removed for unbiased analysis. Based on 6,587 neutral SNPs, pairwise genetic differentiation from Tasmanian and New Zealand neonates was non‐significant (F ST = 0.0003, CI95 = [−0.0002, 0.0009], p = 0.1163; D est = 0.0006 ± 0.0002). This pattern was supported by clustering results. In conclusion, we show a significant effect of non‐random sampling of kin and identify fine‐scale reproductive connectivity between Australian and New Zealand school sharks. OPEN RESEARCH BADGES This article has earned an Open Data Badge for making publicly available the digitally‐shareable data necessary to reproduce the reported results. The data is available at https://doi.org/10.5061/dryad.pd8612j.

Identifying biologically relevant levels of population structure and demographically independent populations is imperative for sustainable fisheries management, but challenging because of high levels of gene flow and large population sizes leading to weak genetic structure. However, increasingly good access to genome-wide variation and architecture have facilitated accurate determination of fine scale genetic population structure. Here, we studied the population structure of European seabass (Dicentrarchus labrax L.), a commercially exploited and farmed fish with high dispersal capacity. In addition, we examined the influence of geographic distance and abiotic environmental variables on the observed genetic structure with a seascape genomics approach. Seabass showed a largely panmictic pattern within the Atlantic Ocean, whereas several genetic clusters were distinguished within the Mediterranean Sea based on 2,549 SNP markers genotyped using ddRAD sequencing. Introgression of Atlantic alleles was detected throughout the western Mediterranean Sea, but introgression of Mediterranean alleles was only found in a restricted area in the Atlantic Ocean off the Strait of Gibraltar. Seascape analysis suggested that genetic population structure is mediated by both dispersal limitation and environmental gradients, pointing to local adaptation. As such the study provides key information for fisheries and conservation management of European seabass.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

The clear relationship between the microbiome and the general well-being of metazoans has motivated the characterization of bacterial communities in cultured species for future microbiome monitoring and modulation to improve productivity. To study the bacterial diversity associated with farmed adult P. monodon at harvest, guts, gastric mills (GM), pond water and sediments were investigated using next-generation sequencing technology in two control ponds (CP1 and CP2) where animals showed a healthy appearance, and two low productive ponds (LP1 and LP2) where animals showed signs of disease. Animals from CP2 were on average at least 4 g heavier than animals from other ponds, and the final yield of both CP was more than double that of LP. LP2 showed the lowest diversity indices, which can potentially be attributed to high abundance of Vibrio spp. and warm water conditions (31.6 +/- 0.3 degrees C on average). The structure of the bacterial community in the gut, GM and water samples was different between CP and LP. Vibrio spp. and anaerobic bacteria (e.g. Fusibacter) were enriched in the gastrointestinal tract of animals from LP (LDA >= 4). While Vibrio can potentially act against the host and other members of the bacterial community, Fusibacter might be an indicator of sulfur compounds accumulation in the animal as the hepatopancreas becomes affected by a PirA toxin. Enrichment of Cyanobacteria in the water (LDA = 4.38) and members of Desulfobacteraceae in sediments of LP (5% on average) could be environmental stress indicators in summer conditions. Characterizing bacterial microbiomes in aquaculture is important to detect indicators of health and productivity that can be used as monitoring tools in the animal s gastrointestinal tract and the environment, ultimately enabling a targeted modulation of the bacterial community for improved production.

This study presents the first case of the joint DNA metabarcoding of prey items and microbiome community analysis in wild juvenile fish. Juvenile European plaice (Pleuronectes platessa) were caught at 11 locations in the southern North Sea and eastern English Channel. Stomach fullness varied ontogenetically in time and space. Food uptake seemed to be slightly limited for the smallest plaice individuals up to a size of 20 to 30 mm. Furthermore, strong homogeneity for microbiome and prey item composition prevailed. Little seasonal, annual and regional (on-offshore/depth) variation was observed in prey item composition. Brown shrimp Crangon crangon made up > 70% of the reads in all stomachs, length classes, regions, seasons and years. Offshore samples differentiated with a distinct lack of beta-Proteobacteria in the gut microbiome. Based on a visual similarity network analysis, there was no observable correlation between prey item and microbiome composition, indicating that the microbiome composition wasn't driven by diet, but might be determined by the benthic bacterial community. DNA metabarcoding yields clear insights in the prey and microbiome composition of plaice, even for seemingly empty stomachs, and should therefore be considered for future dietary and microbiome studies.

Tropical reefs are highly diverse ecosystems, and reliable biomonitoring, through diet metabarcoding, is needed to understand present and future trophic relationships in this changing habitat. Several studies have assessed the reliability and effectiveness of single molecular markers; however, a cross-marker validation has rarely been performed. This study identified crucial properties for 12S rDNA, 16S rDNA and COI metabarcoding in tropical-reef piscivores (Plectropomus spp.). In addition, three new versatile primer sets for 16S were designed in silico for metabarcoding of reef fish. Results showed that COI was overall better at recovering true diversity because of a well-supported database. Second, optimal 16S amplicon sizes ranged between 160 and 440 base pairs for full diversity recovery, with increased species detection for the 270-base pairs region. Finally, blocking of predator-specific COI sequences was not equally effective in all host species, potentially introducing bias when diet compositions are directly compared. In conclusion, this novel study showed that marker success for prey identification is highly dependent on the reference database, taxonomic scope, DNA quality, amplicon length and sequencing platform. Results suggest that COI, complemented with 16S, yields the best outcome for diet metabarcoding in reef piscivores. Findings in this paper are relevant to other piscivores and other metabarcoding applications.