Maturation at a young age and small size of European smelt (<Emphasis Type="Italic">Osmerus eperlanus</Emphasis>): A consequence of population overexploitation or climate change?

Age of fish at maturation depends on the species and environmental factors but, in general, investment in growth is prioritized until the first sexual maturity, after which a considerable and increasing proportion of resources are used for reproduction. The present study summarizes for the first the key elements of the maturation of European smelt (Osmerus eperlanus) young of the year (YoY) in the North-eastern Gulf of Riga (the Baltic Sea). Prior to the changes in climatic conditions and collapse of smelt fishery in the 1990s in the Gulf of Riga, smelt attained sexual maturity at the age of 3–4 years. We found a substantial share (22%) of YoY smelt with maturing gonads after the collapse of the smelt fisheries. Maturing individuals had a significantly higher weight, length and condition factor than immature YOY, indicating the importance of individual growth rates in the maturation process. The proportion of maturing YoY individuals increased with fish size. We discuss the factors behind prioritizing reproduction overgrowth in early life and its implications for the smelt population dynamics.     

Cascading effects of variation in plant vigour on the relative performance of insect herbivores and their parasitoids

Abstract 1. Consequences of variation in food plant quality were estimated for a system consisting of two monophagous noctuid herbivores and three ichneumonid parasitoids.
2. In a natural population, pupal weights of the herbivores in this system, Nonagria typhae and Archanara sparganii , were found to be highly variable. Pupal weights increased strongly and consistently with the increase in the vigour of the host plant, Typha latifolia , providing support for the plant vigour hypothesis. Correspondingly, as the moths do not feed as adults, a strong, positive correlation between host vigour and fecundity of the herbivores would be expected.
3. There were strong and positive relationships between adult body sizes of the parasitoids and the sizes of their lepidopteran hosts. Moreover, a direct, positive link between plant quality and parasitoid size was documented.
4. For all three parasitoids, cascading effects of plant quality on body size were weaker than for the herbivores. Differences in the importance of adult feeding and oviposition behaviour suggest that dependence of fitness on body size is also weaker in the parasitoids than in the moths. It is therefore concluded that the numerical response of the herbivore population to a change in plant quality should exceed the corresponding response in the parasitoids.
5. The results of this work imply that variation in plant variables may affect performance of different trophic levels to a different extent. It is suggested that the importance of adult feeding for the reproductive success (capital vs. income breeding strategies) in both herbivores and parasitoids is an essential aspect to consider when predicting responses of such a system to changes in plant quality.     

Systematic evaluation of NIPT aneuploidy detection software tools with clinically validated NIPT samples

Non-invasive prenatal testing (NIPT) is a powerful screening method for fetal aneuploidy detection, relying on laboratory and computational analysis of cell-free DNA. Although several published computational NIPT analysis tools are available, no prior comprehensive, head-to-head accuracy comparison of the various tools has been published. Here, we compared the outcome accuracies obtained for clinically validated samples with five commonly used computational NIPT aneuploidy analysis tools (WisecondorX, NIPTeR, NIPTmer, RAPIDR, and GIPseq) across various sequencing depths (coverage) and fetal DNA fractions. The sample set included cases of fetal trisomy 21 (Down syndrome), trisomy 18 (Edwards syndrome), and trisomy 13 (Patau syndrome). We determined that all of the compared tools were considerably affected by lower sequencing depths, such that increasing proportions of undetected trisomy cases (false negatives) were observed as the sequencing depth decreased. We summarised our benchmarking results and highlighted the advantages and disadvantages of each computational NIPT software. To conclude, trisomy detection for lower coverage NIPT samples (e.g. 2.5M reads per sample) is technically possible but can, with some NIPT tools, produce troubling rates of inaccurate trisomy detection, especially in low-FF samples.     

Exogeneous cyclic AMP blocks the muscarinic receptor-mediated intracellular Ca2+-release in the gastrulating chick embryo cells

Summary Exogeneous cyclic AMP (cAMP, 10^–8M), when added together with acetylcholine (ACh, 500 M) to dissociated chick embryo cells, blocked the ACh-stimulated increase in the level of cytosolic free Ca²⁺ ([Ca²⁺]_i). This inhibiting action of exogeneous cAMP is probably mediated by intracellular cyclic GMP (cGMP) and cAMP.     

Age and size at maturity: A quantitative review of diet‐induced reaction norms in insects

Optimality models predict that diet‐induced bivariate reaction norms for age and size at maturity can have diverse shapes, with the slope varying from negative to positive. To evaluate these predictions, we perform a quantitative review of relevant data, using a literature‐derived database of body sizes and development times for over 200 insect species. We show that bivariate reaction norms with a negative slope prevail in nearly all taxonomic and ecological categories of insects as well as in some other ectotherm taxa with comparable life histories (arachnids and amphibians). In insects, positive slopes are largely limited to species, which feed on discrete resource items, parasitoids in particular. By contrast, with virtually no meaningful exceptions, herbivorous and predatory insects display reaction norms with a negative slope. This is consistent with the idea that predictable resource depletion, a scenario selecting for positively sloped reaction norms, is not frequent for these insects. Another source of such selection—a positive correlation between resource levels and juvenile mortality rates—should similarly be rare among insects. Positive slopes can also be predicted by models which integrate life‐history evolution and population dynamics. As bottom‐up regulation is not common in most insect groups, such models may not be most appropriate for insects.     

Contrasting effects of plant population size on florivory and pollination

Changes in plant population size, induced by various forms of habitat degradation, can affect the performance of plants by altering their interactions with other organisms such as pollinators and herbivores. However, studies on plant reproductive response to variation in population size that simultaneously consider different interactions are rare. In this study, we examined (1) how levels of pollinator visitation and florivory vary with population size of a self-incompatible herb, Verbascum nigrum (Scrophulariaceae), (2) the relative effect of these two interactions on host seed set, and (3) whether the intensity of florivory influences pollinator visitation rate. The intensity of florivory increased, whereas pollinator visitation rate decreased with host population size. Although average seed production was negatively affected by the intensity of florivory, seed production was independent of population size. The direct negative effect of florivores on plant seed set was indirectly enforced by their negative effect on pollinator visitation rate. Our results emphasize the complexity of responses of different plant–animal interactions to plant population size. However, interactions involving specialized organisms are likely to disrupt first as plant population size decreases.     

Light- and CO2-saturated photosynthesis: enhancement by oxygen

Oxygen may enhance CO₂-saturated photosynthesis in intact leaves, which display the Warburg effect when illuminated at the current atmospheric level of CO₂ and O₂, of about 350 μl l⁻¹ and 21%, respectively. The magnitude of the stimulation depends on irradiance. The K _M(O₂) of the stimulation is 128 μM (10.6% O₂). Maximum enhancement in wheat leaves is 6.1 and 5.3 μmol m⁻² s⁻¹ under 27.9 and 18.7 mW cm⁻², respectively, corresponding to a 25–30% increase in the ribulose 1,5-bisphosphate (RuBP) turnover rate if compared with O₂-free ambient gas phase. The stimulation appears in 5–10 s after a sharp increase in O₂. In response to a decrease in O₂, the new stabilized rate is reached in 5–7 min. The stimulation does not involve any increase in the activity of Rubisco. The effect correlates with increased concentration of RuBP. Oxygen enhances CO₂-saturated photosynthesis by acting as a terminal electron acceptor in the photosynthetic electron transport. The magnitude of the effect may be adopted as an index of the pseudocyclic photophosphorylation in vivo.     

Altered mitochondrial apparent affinity for ADP and impaired function of mitochondrial creatine kinase in gluteus medius of patients with hip osteoarthritis

The cellular energy metabolism in human musculus gluteus medius (MGM) under normal conditions and hip osteoarthritis (OA) was explored. The functions of oxidative phosphorylation and energy transport systems were analyzed in permeabilized (skinned) muscle fibers by oxygraphy, in relation to myosin heavy chain (MHC) isoform distribution profile analyzed by SDS-PAGE, and to creatine kinase (CK) and adenylate kinase (AK) activities measured spectrophotometrically in the intact muscle. The results revealed high apparent Km for ADP in regulation of respiration that decreased after addition of creatine in MGM of traumatic patients (controls). OA was associated with increased sensitivity of mitochondrial respiration to ADP, decreased total activities of AK and CK with major reduction in mi-CK fraction, and attenuated effect of creatine on apparent Km for ADP compared with control group. It also included a complete loss of type II fibers in a subgroup of patients with the severest disease grade. It is concluded that energy metabolism in MGM cells is organized into functional complexes of mitochondria and ATPases. It is suggested that because of degenerative remodeling occurring during development of OA, these complexes become structurally and functionally impaired, which results in increased access of exogenous ADP to mitochondria and dysfunction of CK-phosphotransfer system.     

Sexual differences in weight loss upon eclosion are related to life history strategy in Lepidoptera

Given that immature and adult insects have different life styles, different target body compositions can be expected. For adults, such targets will also differ depending on life history strategy, and thus vary among the sexes, and in females depend on the degree of capital versus income breeding and ovigeny. Since these targets may in part be approximated by loss of substances upon eclosion, comparing sexual differences in such losses upon eclosion among species that differ in life history would provide insights into insect functional ecology. We studied weight loss in eclosing insects using original data on pupal and adult live weights of 38 species of Lepidoptera (mainly Geometridae) and further literature data on 15 species of Lepidoptera and six representatives of other insect orders, and applied the phylogenetic independent contrasts approach. In addition, data on live and dry weights of pupae of four species of Lepidoptera are presented. We documented that Lepidoptera typically lose a large proportion (20-80%) of their pupal weight upon adult eclosion. Sexual differences in weight loss varied between absent and strongly male biased. Most of the weight loss was water loss, and sexual differences in adult water content correlate strongly with differences in weight loss. Using feeding habits (feeds or does not feed as an adult) and female biased sexual size dimorphism as measures of degree of capital breeding, we found that the difference among the sexes in weight loss tends to be more pronounced in capital breeding species. Additionally, females of more pro-ovigenic species (large proportion of eggs mature upon emergence) tend to have higher water contents. Our results suggests that metamorphosis is generally facilitated by a high water content, while adults excrete water upon eclosion to benefit flight unless water has been allocated to eggs, or is treated as a capital resource for adult survival or future allocation to eggs.