Taxonomic bias in AMP prediction of invertebrate peptides.

Invertebrate antimicrobial peptides (AMPs) are at the forefront in the search for agents of therapeutic utility against multi-resistant microbial pathogens, and in recent years substantial advances took place in the in silico prediction of antimicrobial function of amino acid sequences. A yet neglected aspect is taxonomic bias in the performance of these tools. Owing to differences in the prediction algorithms and used training data sets between tools, and phylogenetic differences in sequence diversity, physicochemical properties and evolved biological functions of AMPs between taxa, notable discrepancies may exist in performance between the currently available prediction tools. Here we tested if there is taxonomic bias in the prediction power in 10 tools with a total of 20 prediction algorithms in 19 invertebrate taxa, using a data set containing 1525 AMP and 3050 non-AMP sequences. We found that most of the tools exhibited considerable variation in performance between tested invertebrate groups. Based on the per-taxa performances and on the variation in performances across taxa we provide guidance in choosing the best-performing prediction tool for all assessed taxa, by listing the highest scoring tool for each of them.

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.

Consequences of rapid development owing to cohort splitting: just how costly is it to hurry?

In cohort splitting, diverging sub-cohorts may show substantial differences in their growth and developmental rates. Although in the past, causes and adaptive value of cohort splitting were studied in detail, individual-level consequences of cohort splitting are still rather overlooked. Life history theory predicts that considerably increased growth and developmental rates should be traded off against other costly life history traits. However, it is not clear whether one should expect such associations in adaptive developmental plasticity scenarios, because natural selection might have promoted genotypes that mitigate those potential costs of rapid development. To address these contrasting propositions, we assessed life history traits in the wolf spider Pardosa agrestis, both collected from natural habitat and reared in laboratory. We found that some traits are negatively associated with developmental rates in spiders collected from the wild, but these associations were relaxed to a considerable extent in laboratory-reared specimens. In general, we observed no consistent trend for the presence of developmental costs, although some results might suggest higher relative fecundity costs in rapidly developing females. Our study provides a detailed approach to the understanding of individual-level consequences of cohort splitting, and to the associations between key life history traits in adaptive developmental plasticity scenarios.

Seasonal changes in immune response and reproductive investment in a biparental beetle.

Immunity and reproduction are physiologically demanding processes, therefore trade-offs are expected between these life history traits. Furthermore, investments in these traits are also known to be affected by factors such as sex, body size, individual condition, seasonal changes and parasite infection. The relationship between immunity and reproduction and the effect of other factors on this relationship were investigated in many species, but there are a small number of studies on these patterns in biparental invertebrates. Lethrus apterus is an iteroparous biparental beetle with predominant female care in respect of collecting and processing food for larvae. Males guard the nest built underground and also their mate. Here we investigate how sex, body size, time within the reproductive season and parasite load may influence the relationship between immunocompetence and reproductive investment in this species. In beetles from a natural population we quantified immune response by measuring the encapsulation response, antimicrobial activity of hemolymph, the investment into reproductive tissues by measuring the size of testis follicles in males and total egg size in females, and parasite load by counting the number of mites on the beetles. We found that the encapsulation response is condition-dependent, as large individuals showed significantly higher encapsulation ability than small ones. Antimicrobial capacity was significantly higher in females than in males. In case of antimicrobial activity there was also a seasonal change in the relationship between immunity and reproductive investment, but only under heavy mite load. Reproductive investment was influenced by the interaction between body size and season (in females) and by body size and season (in males). Furthermore in females the interaction between antimicrobial activity and season indicated that reproductive investment increased with antimicrobial activity early in the reproductive season. By investigating the relationship between immunity and reproductive investment in a natural population of a biparental beetle species, we can conclude that investments into these important life history traits are governed by complex interactions between physiological and environmental factors. Our results are discussed in the context of life history evolution, highlighting the role of the assessed factors in shaping trade-offs themselves (in invertebrates).

Deuterium oxide dilution: a novel method to study apical water layers and transepithelial water transport.

Lung epithelia regulate the water flux between gas filled airways and the interstitial compartment in order to maintain organ function. Current methodology to assess transepithelial water transport is limited. We present a D2O dilution method to quantify submicroliter volumes of aqueous solutions on epithelial cell layers. Evaluating D2O/H2O mixtures using mid-infrared (2-25 µm) attenuated total reflection (ATR) spectroscopy, with a resolution of 0.06% vol/vol change, corresponding to 24 nL, was achieved. Using this method, we demonstrate that water transport across NCI-H441 lung epithelial cell layers and apical surface liquid (ASL) volumes are coupled to dexamethasone dependent amiloride-sensitive ion transport. However, contrary to current dogma, electrogenic transport is not rate-limiting for water transport. This clearly indicates the need to directly assess net water rather than ion transport across epithelial cell layers. The presented D2O dilution method enables such direct and quick quantification of transepithelial water transport with high resolution.