Detection and characterization of bacterial endosymbionts in Southeast Asian tephritid fruit fly populations.

BACKGROUND: Various endosymbiotic bacteria, including Wolbachia of the Alphaproteobacteria, infect a wide range of insects and are capable of inducing reproductive abnormalities to their hosts such as cytoplasmic incompatibility (CI), parthenogenesis, feminization and male-killing. These extended phenotypes can be potentially exploited in enhancing environmentally friendly methods, such as the sterile insect technique (SIT), for controlling natural populations of agricultural pests. The goal of the present study is to investigate the presence of Wolbachia, Spiroplasma, Arsenophonus and Cardinium among Bactrocera, Dacus and Zeugodacus flies of Southeast Asian populations, and to genotype any detected Wolbachia strains. RESULTS: A specific 16S rRNA PCR assay was used to investigate the presence of reproductive parasites in natural populations of nine different tephritid species originating from three Asian countries, Bangladesh, China and India. Wolbachia infections were identified in Bactrocera dorsalis, B. correcta, B. scutellaris and B. zonata, with 12.2-42.9% occurrence, Entomoplasmatales in B. dorsalis, B. correcta, B. scutellaris, B. zonata, Zeugodacus cucurbitae and Z. tau (0.8-14.3%) and Cardinium in B. dorsalis and Z. tau (0.9-5.8%), while none of the species tested, harbored infections with Arsenophonus. Infected populations showed a medium (between 10 and 90%) or low (< 10%) prevalence, ranging from 3 to 80% for Wolbachia, 2 to 33% for Entomoplasmatales and 5 to 45% for Cardinium. Wolbachia and Entomoplasmatales infections were found both in tropical and subtropical populations, the former mostly in India and the latter in various regions of India and Bangladesh. Cardinium infections were identified in both countries but only in subtropical populations. Phylogenetic analysis revealed the presence of Wolbachia with some strains belonging either to supergroup B or supergroup A. Sequence analysis revealed deletions of variable length and nucleotide variation in three Wolbachia genes. Spiroplasma strains were characterized as citri-chrysopicola-mirum and ixodetis strains while the remaining Entomoplasmatales to the Mycoides-Entomoplasmataceae clade. Cardinium strains were characterized as group A, similar to strains infecting Encarsia pergandiella. CONCLUSIONS: Our results indicated that in the Southeast natural populations examined, supergroup A Wolbachia strain infections were the most common, followed by Entomoplasmatales and Cardinium. In terms of diversity, most strains of each bacterial genus detected clustered in a common group. Interestingly, the deletions detected in three Wolbachia genes were either new or similar to those of previously identified pseudogenes that were integrated in the host genome indicating putative horizontal gene transfer events in B. dorsalis, B. correcta and B. zonata.

Insights in Pharmaceutical Pollution: The Prospective Role of eDNA Metabarcoding.

Environmental pollution is a growing threat to natural ecosystems and one of the world's most pressing concerns. The increasing worldwide use of pharmaceuticals has elevated their status as significant emerging contaminants. Pharmaceuticals enter aquatic environments through multiple pathways related to anthropogenic activity. Their high consumption, insufficient waste treatment, and the incapacity of organisms to completely metabolize them contribute to their accumulation in aquatic environments, posing a threat to all life forms. Various analytical methods have been used to quantify pharmaceuticals. Biotechnology advancements based on next-generation sequencing (NGS) techniques, like eDNA metabarcoding, have enabled the development of new methods for assessing and monitoring the ecotoxicological effects of pharmaceuticals. eDNA metabarcoding is a valuable biomonitoring tool for pharmaceutical pollution because it (a) provides an efficient method to assess and predict pollution status, (b) identifies pollution sources, (c) tracks changes in pharmaceutical pollution levels over time, (d) assesses the ecological impact of pharmaceutical pollution, (e) helps prioritize cleanup and mitigation efforts, and (f) offers insights into the diversity and composition of microbial and other bioindicator communities. This review highlights the issue of aquatic pharmaceutical pollution while emphasizing the importance of using modern NGS-based biomonitoring actions to assess its environmental effects more consistently and effectively.

Characterization of the Bacterial Profile from Natural and Laboratory Glossina Populations.

Tsetse flies (Glossina spp.; Diptera: Glossinidae) are viviparous flies that feed on blood and are found exclusively in sub-Saharan Africa. They are the only cyclic vectors of African trypanosomes, responsible for human African trypanosomiasis (HAT) and animal African trypanosomiasis (AAT). In this study, we employed high throughput sequencing of the 16S rRNA gene to unravel the diversity of symbiotic bacteria in five wild and three laboratory populations of tsetse species (Glossina pallidipes, G. morsitans, G. swynnertoni, and G. austeni). The aim was to assess the dynamics of bacterial diversity both within each laboratory and wild population in relation to the developmental stage, insect age, gender, and location. Our results indicated that the bacterial communities associated with the four studied Glossina species were significantly influenced by their region of origin, with wild samples being more diverse compared to the laboratory samples. We also observed that the larval microbiota was significantly different than the adults. Furthermore, the sex and the species did not significantly influence the formation of the bacterial profile of the laboratory colonies once these populations were kept under the same rearing conditions. In addition, Wigglesworthia, Acinetobacter, and Sodalis were the most abundant bacterial genera in all the samples, while Wolbachia was significantly abundant in G. morsitans compared to the other studied species. The operational taxonomic unit (OTU) co-occurrence network for each location (VVBD insectary, Doma, Makao, and Msubugwe) indicated a high variability between G. pallidipes and the other species in terms of the number of mutual exclusion and copresence interactions. In particular, some bacterial genera, like Wigglesworthia and Sodalis, with high relative abundance, were also characterized by a high degree of interactions.

Heritability of cortisol response to confinement stress in European sea bass dicentrarchus labrax.

BACKGROUND: In fish, the most studied production traits in terms of heritability are body weight or growth, stress or disease resistance, while heritability of cortisol levels, widely used as a measure of response to stress, is less studied. In this study, we have estimated heritabilities of two growth traits (body weight and length) and of cortisol response to confinement stress in the European sea bass. FINDINGS: The F1 progeny analysed (n = 922) belonged to a small effective breeding population with contributions from an unbalanced family structure of just 10 males and 2 females. Heritability values ranged from 0.54 (± 0.21) for body weight to 0.65 (± 0.22) for standard body length and were low for cortisol response i.e. 0.08 (± 0.06). Genetic correlations were positive (0.94) between standard body length and body weight and negative between cortisol and body weight and between cortisol and standard body length (-0.60 and -0.55, respectively). CONCLUSION: This study confirms that in European sea bass, heritability of growth-related traits is high and that selection on such traits has potential. However, heritability of cortisol response to stress is low in European sea bass and since it is known to vary greatly among species, further studies are necessary to understand the reasons for these differences.

Chromosome genome assembly for the meagre, Argyrosomus regius, reveals species adaptations and sciaenid sex-related locus evolution.

The meagre, Argyrosomus regius, has recently become a species of increasing economic interest for the Mediterranean aquaculture and there is ongoing work to boost production efficiency through selective breeding. Access to the complete genomic sequence will provide an essential resource for studying quantitative trait-associated loci and exploring the genetic diversity of different wild populations and aquaculture stocks in more detail. Here, we present the first complete genome for A. regius, produced through a combination of long and short read technologies and an efficient in-house developed pipeline for assembly and polishing. Scaffolding using previous linkage map data allowed us to reconstruct a chromosome level assembly with high completeness, complemented with gene annotation and repeat masking. The 696 Mb long assembly has an N50 = 27.87 Mb and an L50 = 12, with 92.85% of its length placed in 24 chromosomes. We use this new resource to study the evolution of the meagre genome and other Sciaenids, via a comparative analysis of 25 high-quality teleost genomes. Combining a rigorous investigation of gene duplications with base-wise conservation analysis, we identify candidate loci related to immune, fat metabolism and growth adaptations in the meagre. Following phylogenomic reconstruction, we show highly conserved synteny within Sciaenidae. In contrast, we report rapidly evolving syntenic rearrangements and gene copy changes in the sex-related dmrt1 neighbourhood in meagre and other members of the family. These novel genomic datasets and findings will add important new tools for aquaculture studies and greatly facilitate husbandry and breeding work in the species.

Body-shape trajectories and their genetic variance component in Gilthead seabream (Sparus aurata L.).

The phenotype of juvenile fish is closely associated with the adult phenotype, thus consisting an important quality trait for reared fish stocks. In this study, we estimated the correlation between the juvenile and adult body-shape in Gilthead seabream, and examined the genetic basis of the ontogenetic trajectories. The body shape of 959 pit-tagged fish was periodically examined during the juvenile-to-adult period. Individual shape ontogenetic trajectories were studied in respect to the initial (juvenile) and final (adult) phenotypes, as well as to the rate that adult phenotype is attained (phenotypic integration rate). We found that the juvenile body-shape presented a rapid change up to 192.7 ± 1.9 mm standard length, followed by a phenotypically stable period (plateau). Depending on the shape component considered, body-shape correlations between juvenile and adult stages ranged from 0.22 to 0.76. Heritability estimates (h2) of the final phenotype ranged from 0.370 ± 0.077 to 0.511 ± 0.089, whereas h2 for the phenotypic integration rate was 0.173 ± 0.062. To our knowledge, this is the first study demonstrating that the variance of the ontogenetic trajectories has a substantial additive genetic component. Results are discussed in respect to their potential use in selective breeding programs of Gilthead seabream.

New Insights on the Zeugodacus cucurbitae (Coquillett) Bacteriome.

Various factors, including the insect host, diet, and surrounding ecosystem can shape the structure of the bacterial communities of insects. We have employed next generation, high-throughput sequencing of the 16S rRNA to characterize the bacteriome of wild Zeugodacus (Bactrocera) cucurbitae (Coquillett) flies from three regions of Bangladesh. The tested populations developed distinct bacterial communities with differences in bacterial composition, suggesting that geography has an impact on the fly bacteriome. The dominant bacteria belonged to the families Enterobacteriaceae, Dysgomonadaceae and Orbaceae, with the genera Dysgonomonas, Orbus and Citrobacter showing the highest relative abundance across populations. Network analysis indicated variable interactions between operational taxonomic units (OTUs), with cases of mutual exclusion and copresence. Certain bacterial genera with high relative abundance were also characterized by a high degree of interactions. Interestingly, genera with a low relative abundance like Shimwellia, Gilliamella, and Chishuiella were among those that showed abundant interactions, suggesting that they are also important components of the bacterial community. Such knowledge could help us identify ideal wild populations for domestication in the context of the sterile insect technique or similar biotechnological methods. Further characterization of this bacterial diversity with transcriptomic and metabolic approaches, could also reveal their specific role in Z. cucurbitae physiology.

The Implication of Vibrio Bacteria in the Winter Mortalities of the Critically Endangered Pinna nobilis.

Pinna nobilis populations, constituting the largest bivalve mollusk endemic to the Mediterranean, is characterized as critically endangered, threatened by extinction. Among the various factors proposed as etiological agents are the Haplosporidium pinnae and Mycobacterium sp. parasites. Nevertheless, devastation of the fan mussel populations is still far from clear. The current work is undertaken under a broader study aiming to evaluate the health status of Pinna nobilis population in Aegean Sea, after the mass mortalities that occurred in 2019. A significant objective was also (a) the investigation of the etiological agents of small-scale winter mortalities in the remaining populations after the devastating results of Haplosporidium pinnae and Mycobacterium sp. infections, as well as (b) the examination of the susceptibility of the identified bacterial strains in antibiotics for future laboratory experiments. Microbiological assays were used in order to detect the presence of potential bacterial pathogens in moribund animals in combination with molecular tools for their identification. Our results provide evidence that Vibrio bacterial species are directly implicated in the winter mortalities, particularly in cases where the haplosporidian parasite was absent. Additionally, this is the first report of Vibrio mediterranei and V. splendidus hosted by any bivalve on the Greek coastline.

Detection of Wolbachia Infections in Natural and Laboratory Populations of the Moroccan Hessian Fly, Mayetiola destructor (Say).

Mayetiola destructor (Hessian fly) is a destructive pest of wheat in several parts of the world. Here, we investigated the presence of reproductive symbionts and the effect of the geographical location on the bacterial community associated to adult Hessian flies derived from four major wheat producing areas in Morocco. Using specific 16S rDNA PCR assay, Wolbachia infection was observed in 3% of the natural populations and 10% of the laboratory population. High throughput sequencing of V3-V4 region of the bacterial 16S rRNA gene revealed that the microbiota of adult Hessian flies was significantly influenced by their native regions. A total of 6 phyla, 10 classes and 79 genera were obtained from all the samples. Confirming the screening results, Wolbachia was identified as well in the natural Hessian flies. Phylogenetic analysis using the sequences obtained in this study indicated that there is one Wolbachia strain belonging to supergroup A. To our knowledge, this is the first report of Wolbachia in Hessian fly populations. The observed low abundance of Wolbachia most likely does not indicate induction of reproductive incompatibility. Yet, this infection may give a new insight into the use of Wolbachia for the fight against Hessian fly populations.

Near-Complete Genome Sequence of a Fish Nervous Necrosis Virus Isolated from a Clinical Disease Outbreak in Farm-Reared Bream Sparus aurata in Spain.

Sparus aurata larvae infected by viral nervous necrosis were collected from an aquaculture fish farm. The isolated viral genome, composed of two segments (RNA1 and RNA2), was sequenced and analyzed comparatively. Phylogenetic tree analyses revealed that the isolated strain is a reassortant, exhibiting a red-spotted grouper nervous necrosis virus (RGNNV)-type RNA1 and a striped jack nervous necrosis virus (SJNNV)-type RNA2.

Quantitative trait loci involved in sex determination and body growth in the gilthead sea bream (Sparus aurata L.) through targeted genome scan.

Among vertebrates, teleost fish exhibit a considerably wide range of sex determination patterns that may be influenced by extrinsic parameters. However even for model fish species like the zebrafish Danio rerio the precise mechanisms involved in primary sex determination have not been studied extensively. The zebrafish, a gonochoristic species, is lacking discernible sex chromosomes and the sex of juvenile fish is difficult to determine. Sequential protandrous hermaphrodite species provide distinct determination of the gender and allow studying the sex determination process by looking at the mechanism of sex reversal. This is the first attempt to understand the genetic basis of phenotypic variation for sex determination and body weight in a sequential protandrous hermaphrodite species, the gilthead sea bream (Sparus aurata). This work demonstrates a fast and efficient strategy for Quantitative Trait Loci (QTL) detection in the gilthead sea bream, a non-model but target hermaphrodite fish species. Therefore a comparative mapping approach was performed to query syntenies against two other Perciformes, the European sea bass (Dicentrarchus labrax), a gonochoristic species and the Asian sea bass (Lates calcarifer) a protandrous hermaphrodite. In this manner two significant QTLs, one QTL affecting both body weight and sex and one QTL affecting sex, were detected on the same linkage group. The co-segregation of the two QTLs provides a genomic base to the observed genetic correlation between these two traits in sea bream as well as in other teleosts. The identification of QTLs linked to sex reversal and growth, will contribute significantly to a better understanding of the complex nature of sex determination in S. aurata where most individuals reverse to the female sex at the age of two years through development and maturation of the ovarian portion of the gonad and regression of the testicular area. [Genomic sequences reported in this manuscript have been submitted to GenBank under accession numbers HQ021443-HQ021749.].