Draft genome of a biparental beetle species, Lethrus apterus.

BACKGROUND: The lack of an understanding about the genomic architecture underpinning parental behaviour in subsocial insects displaying simple parental behaviours prevents the development of a full understanding about the evolutionary origin of sociality. Lethrus apterus is one of the few insect species that has biparental care. Division of labour can be observed between parents during the reproductive period in order to provide food and protection for their offspring. RESULTS: Here, we report the draft genome of L. apterus, the first genome in the family Geotrupidae. The final assembly consisted of 286.93 Mbp in 66,933 scaffolds. Completeness analysis found the assembly contained 93.5% of the Endopterygota core BUSCO gene set. Ab initio gene prediction resulted in 25,385 coding genes, whereas homology-based analyses predicted 22,551 protein coding genes. After merging, 20,734 were found during functional annotation. Compared to other publicly available beetle genomes, 23,528 genes among the predicted genes were assigned to orthogroups of which 1664 were in species-specific groups. Additionally, reproduction related genes were found among the predicted genes based on which a reduction in the number of odorant- and pheromone-binding proteins was detected. CONCLUSIONS: These genes can be used in further comparative and functional genomic researches which can advance our understanding of the genetic basis and hence the evolution of parental behaviour.

Insulin/IGF Signaling and Life History Traits in Response to Food Availability and Perceived Density in the Cnidarian Hydra vulgaris.

Insulin/insulin-like growth factor signaling (IIS) is thought to be a central mediator of life history traits, but the generality of its role is not clear. Here, we investigated mRNA expression levels of three insulin-like peptide genes, the insulin-like receptor htk7, as well as several antioxidant genes, and the heat-shock protein hsp70 in the freshwater cnidarian Hydra vulgaris. Hydra polyps were exposed to a combination of different levels of food and perceived population density to manipulate life history traits (asexual reproduction and oxidative stress tolerance). We found that stress tolerance and the rate of asexual reproduction increased with food, and that these two effects were in significant interaction. Exposing animals to high perceived density resulted in increased stress tolerance or reduced reproduction only on lower food levels, but not on high food. The insulin-like receptor htk7 and the antioxidant gene catalase were significantly upregulated in the high density treatments. However, the expression level of insulin-like peptide genes, most antioxidant genes, and hsp70 were not affected by the experimental treatments. The higher expression level of htk7 may suggest that animals maintain a higher level of preparedness for insulin-like ligands at high population densities. However, the lack of difference between food levels suggests that IIS is not involved in regulating asexual reproduction and stress tolerance in hydra, or that its role is more subtle than a simple model of life history regulation would suggest.

Effects of Prior Contest Experience and Contest Outcome on Female Reproductive Decisions and Offspring Fitness.

Winning or losing a prior contest can influence the outcome of future contests, but it might also alter subsequent reproductive decisions. For example, losers may increase their investment in the current breeding attempt if losing a contest indicates limited prospects for future breeding. Using the burying beetle Nicrophorus vespilloides, we tested whether females adjust their prehatching and posthatching reproductive effort after winning or losing a contest with a same-sex conspecific. Burying beetles breed on carcasses of small vertebrates for which there is fierce intrasexual competition. We found no evidence that winning or losing a contest influenced reproductive investment decisions in this species. Instead, we show that a female's prior contest experience (regardless of its outcome) influenced the amount of posthatching care provided, with downstream consequences for the female's reproductive output; both winners and losers spent more time provisioning food to their offspring and produced larger broods than females with no contest experience. We discuss the wider implications of our findings and present a conceptual model linking contest-mediated adjustments in parental investment to population-level processes. We propose that the frequency of intraspecific contests could both influence and be influenced by population dynamics in species where contest experience influences the size and/or number of offspring produced.

Range-wide phylogeography of the flightless steppe beetle Lethrus apterus (Geotrupidae) reveals recent arrival to the Pontic Steppes from the west.

The Eurasian Steppe belt is one of the largest biomes in the Northern Hemisphere. We provide here a range-wide phylogeography of the flightless steppe beetle Lethrus apterus that inhabits the western part of the Steppe belt through the study of population-level variance of mitochondrial cytochrome oxidase I sequences and nuclear microsatellites. We detected a concordant geographic structure of genetic data with a significant isolation-by-distance pattern. We found more genetic variation in the western part of the area and identified Northern Bulgaria and the Pannonian Basin as possible refugia. Genetic clusters were separated by main rivers in the eastern part of the area. This implies west-to-east colonisation and argues for an evolutionarily recent arrival of this species to its current main distribution area, the Pontic Steppes. This contradicts the classical biogeographical wisdom that assumed an east-to-west colonisation pattern.

Diagnostic accuracy of SARS-CoV-2 Panbio™ rapid antigen diagnostic tests in a 4,440-case clinical follow-up.

Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) Rapid Antigen Detection Testing (RADT) has been subjected to several evaluations in reference to diagnostic accuracy, ranging from small scale up to large population studies including nation-wide community-based studies. All confirmed the diagnostic accuracy of the tests which were strongly dependent upon the infection's population prevalence. In our retrospective study, parallel SARS-CoV-2 Panbio™ RADT assay, including real-time reverse transcription quantitative polymerase chain reaction (RT-qPCR) tests, were aimed to evaluate diagnostic performance regarding the rapid antigen diagnostic testing. Out of 4,440 paired tests, 609 samples tested positive using RT-qPCR, resulting in a prevalence of 13.7%. Panbio detected 251 (5.7%) positive tested samples. Overall sensitivity was 41.2% (95% CI 37.4-45.2%) and overall specificity was 99.7% (95% CI 99.4-99.8%). Positive predictive value (PPV) was 95.1% (95% CI 91.8-97.1%) and the negative predictive value (NPV) was 91.4% (95% CI 90.5-92.2%). RADT sensitivity increased with stratification in reference to the results according to PCR Cycle threshold (Ct) and presence of the symptoms considerably influenced PPV and NPV. Sensitivity in the group of Ct values ≤ 20 was 91.2%, 68.6% within the Ct range of 20-25, 47.9% in the group of Ct values between 25 and 30, and 12.6% in the group of Ct values between 30 and 35. A follow-up of the positive cases aligned with RT-qPCR testing and comparison of the general population enrolled in the testing in which the fatal cases occurred enabled us to estimate real clinical diagnostic performance regarding the SARS-CoV-2 Panbio RADT. Based upon our results, we recommend the SARS-CoV-2 Panbio RADT tests be carried out as the primary test, without parallel PCR testing, only among high population prevalence rates of the infection and to be used for symptomatic individuals with average or low severe disease developmental risk. In the case of high risk regarding the development of severe infection complications, a parallel SARS-CoV-2 RT-qPCR is needed to be carried out to attain proper diagnostic accuracy and avoid delaying appropriate medical care.

Inotocin, a potential modulator of reproductive behaviours in a biparental beetle, Lethrus apterus.

Several members of the highly conserved oxytocin/vasopressin neuropeptide family are involved in the regulation of reproductive and affiliative behaviours in numerous vertebrate and invertebrate species. Here we investigate gene expression patterns of inotocin, the insect ortholog of this peptide family, and its receptor to decipher their possible role in the control of reproductive behaviour in a beetle, Lethrus apterus, with biparental care. In an experiment performed on individuals of a wild population, we found that inotocin is not related to the control of water balance in this species because expression patterns did not change as a response to drought exposure. The expression levels of inotocin and its receptor, however, increased over the reproductive season i.e., when behaviour shifts from pair formation to parental care, suggesting that inotocin might be involved in the regulation of parental care in this insect. No difference was, however, found between sexes; a finding which might indicate that inotocin plays a similar role in both parents.

Evaluation of potential reference genes for real-time qPCR analysis in a biparental beetle, Lethrus apterus (Coleoptera: Geotrupidae).

Hormones play an important role in the regulation of physiological, developmental and behavioural processes. Many of these mechanisms in insects, however, are still not well understood. One way to investigate hormonal regulation is to analyse gene expression patterns of hormones and their receptors by real-time quantitative polymerase chain reaction (RT-qPCR). This method, however, requires stably expressed reference genes for normalisation. In the present study, we evaluated 11 candidate housekeeping genes as reference genes in samples of Lethrus apterus, an earth-boring beetle with biparental care, collected from a natural population. For identifying the most stable genes we used the following computational methods: geNorm, NormFinder, BestKeeper, comparative delta Ct method and RefFinder. Based on our results, the two body regions sampled (head and thorax) differ in which genes are most stably expressed. We identified two candidate reference genes for each region investigated: ribosomal protein L7A and RP18 in samples extracted from the head, and ribosomal protein L7A and RP4 extracted from the muscles of the thorax. Additionally, L7A and RP18 appear to be the best reference genes for normalisation in all samples irrespective of body region. These reference genes can be used to study the hormonal regulation of reproduction and parental care in Lethrus apterus in the future.