Chorion formation in panoistic ovaries requires windei and trimethylation of histone 3 lysine 9.

Epigenetic modifications play key roles in transcriptional regulation. Trimethylation of histone 3 lysine 9 (H3K9me3) is one of the most widely studied histone post-translational modifications, and has been linked to transcriptional repression. In Drosophila melanogaster, Windei is needed for H3K9me3 in female germ line cells. Here, we report the occurrence of a D. melanogaster Windei (Wde) ortholog in the ovary of the hemimetabolous insect Blattella germanica, which we named BgWde. Depletion of BgWde by RNAi reduced H3K9me3 in follicular cells, which triggered changes in transcriptional regulation that led to the prevention of chorion gene expression. In turn, this impaired oviposition (and the formation of the ootheca) and, therefore, prevented reproduction. Windei and H3K9me3 have already been reported in follicular cells of D. melanogaster, but this is the first time that the function of these modifications has been demonstrated in the said cells. This is also the first time that an epigenetic marker is reported as having a key role in choriogenesis.

Identification and functional characterization of an ovarian aquaporin from the cockroach Blattella germanica L. (Dictyoptera, Blattellidae).

Aquaporins (AQPs) are membrane proteins that form water channels, allowing rapid movement of water across cell membranes. AQPs have been reported in species of all life kingdoms and in almost all tissues, but little is known about them in insects. Our purpose was to explore the occurrence of AQPs in the ovary of the phylogenetically basal insect Blattella germanica (L.) and to study their possible role in fluid homeostasis during oogenesis. We isolated an ovarian AQP from B. germanica (BgAQP) that has a deduced amino acid sequence showing six potential transmembrane domains, two NPA motifs and an ar/R constriction region, which are typical features of the AQP family. Phylogenetic analyses indicated that BgAQP belongs to the PRIP group of insect AQPs, previously suggested to be water specific. However, ectopic expression of BgAQP in Xenopus laevis oocytes demonstrated that this AQP transports water and modest amounts of urea, but not glycerol, which suggests that the PRIP group of insect AQPs may have heterogeneous solute preferences. BgAQP was shown to be highly expressed in the ovary, followed by the fat body and muscle tissues, but water stress did not significantly modify the ovarian expression levels. RNA interference (RNAi) reduced BgAQP mRNA levels in the ovary but the oocytes developed normally. The absence of an apparent ovarian phenotype after BgAQP RNAi suggests that other functionally redundant AQPs that were not silenced in our experiments might exist in the ovary of B. germanica.

Behavior and season affect crayfish detection and density inference using environmental DNA.

Although the presence/absence of aquatic invertebrates using environmental DNA (eDNA) has been established for several species, inferring population densities has remained problematic. The invasive American signal crayfish, Pacifastacus leniusculus (Dana), is the leading cause of decline in the UK's only native crayfish species, Austropotamobius pallipes (Lereboullet). Methods to detect species at low abundances offer the opportunity for the early detection, and potential eradication, of P. leniusculus before population densities reach threatening levels in areas occupied by A. pallipes. Using a factorial experimental design with aquaria, we investigated the impacts of biomass, sex ratio, and fighting behavior on the amount of eDNA released by P. leniusculus, with the aim to infer density per aquarium depending on treatments. The amount of target eDNA in water samples from each aquarium was measured using the quantitative Polymerase Chain Reaction. We show that the presence of eggs significantly increases the concentration of crayfish eDNA per unit of mass, and that there is a significant relationship between eDNA concentration and biomass when females are egg-bearing. However, the relationship between crayfish biomass and eDNA concentration is lost in aquaria without ovigerous females. Female-specific tanks had significantly higher eDNA concentrations than male-specific tanks, and the prevention of fighting did not impact the amount of eDNA in the water. These results indicate that detection and estimate of crayfish abundance using eDNA may be more effective while females are ovigerous. This information should guide further research for an accurate estimation of crayfish biomass in the field depending on the season. Our results indicate that detection and quantification of egg-laying aquatic invertebrate species using eDNA could be most successful during periods when eggs are developing in the water. We recommend that practitioners consider the reproductive cycle of target species when attempting to study or detect aquatic species using eDNA in the field.