Duration of the parasitic phase determines subsequent performance in juvenile freshwater pearl mussels (Margaritifera margaritifera)

Host–parasite systems have been useful in understanding coevolutionary patterns in sympatric species. Based on the exceptional interaction of the long‐lived and highly host‐specific freshwater pearl mussel (FPM; Margaritifera margaritifera) with its much shorter‐lived host fish (Salmo trutta or Salmo salar), we tested the hypotheses that a longer duration of the parasitic phase increases fitness‐related performance of mussels in their subsequent post parasitic phase, and that temperature is the main factor governing the duration of the parasitic phase. We collected juvenile mussels from naturally and artificially infested fish from eight rivers in Norway. Excysted juvenile mussels were maintained separately for each collection day, under similar temperature and food regimes, for up to 56 days. We recorded size at excystment, post excystment growth, and survival as indicators of juvenile fitness in relation to the duration of the parasitic phase. We also recorded the daily average temperatures for the entire excystment period. We observed strong positive relationships between the length of the parasitic phase and the post parasitic growth rate, size at excystment and post parasitic survival. Temperature was identified as an important factor governing excystment, with higher temperatures decreasing the duration of the parasitic phase. Our results indicate that juvenile mussels with the longest parasitic phase have better resources (larger size and better growth rate) to start their benthic developmental phase and therefore to survive their first winter. Consequently, the parasitic phase is crucial in determining subsequent survival. The temperature dependence of this interaction suggests that climate change may affect the sensitive relationship between endangered FPMs and their fish hosts.publishedVersio

Molecular characterization and exclusion of porcine GUSB as a candidate gene for congenital hernia inguinalis/scrotalis

BACKGROUND: Inguinal hernias are usually caused by a congenital defect, which occurs as a weakness of the inguinal canal. Porcine β-glucuronidase gene (GUSB) was chosen as functional candidate gene because of its involvement in degradation of hyaluronan within gubernacular tissue during descent of testes. Since a genome-wide linkage analysis approach has shown evidence that two regions on porcine chromosome 3 (SSC 3) are involved in the inheritance of hernia inguinalis/scrotalis in German pig breeds, GUSB also attained status as a positional candidate gene by its localization within a hernia-associated chromosomal region. RESULTS: A contig spanning 17,157 bp, which contains the entire GUSB, was assembled. Comparative sequence analyses were conducted for the GUSB gene locus. Single nucleotide polymorphisms (SNPs) located within the coding region of GUSB were genotyped in 512 animals. Results of transmission disequilibrium test (TDT) for two out of a total of five detected SNPs gave no significant association with the outcome of hernia in pigs. CONCLUSION: On the basis of our studies we are able to exclude the two analyzed SNPs within the porcine GUSB gene as causative for the transmission of inguinal hernia

Population-level variation in senescence suggests an important role for temperature in an endangered mollusc

Age-related declines in survival and function (senescence) were thought not to exist in wild populations as organisms, and particularly in invertebrates, do not live long enough. While, recent evidence has demonstrated that senescence is both common and measurable even in wild populations under field conditions, there are still organisms that are thought to exhibit “negligible senescence”. We explore variation in rates and patterns of senescence in the biogerontological model organism Margaritifera margaritifera across five populations, which differ in their age profile. In particular, we tested the theory of negligible senescence using time-at-death records for 1091 specimens of M. margaritifera. There is clear evidence of senescence in all populations, as indicated by an increase in mortality with age, but the nature of the relationship varies subtly between populations. We find strong evidence of a mortality plateau at later ages in some populations but this is unequivocally absent from others. We then demonstrate that the temporal scaling of the rates of senescence between five populations of M. margaritifera can be explained by the variation in the thermal environment of the population. Hence climate change may pose a threat to the demography of this long-lived, endangered species, and a greater understanding of the relationship between river temperature and population structure will be essential to secure the species against global temperature increases. Our findings demonstrate that useful insights can be drawn from a non-invasive monitoring method to derive demographic data, and we suggest a wide-scale application of this method to monitor populations across the whole latitudinal (and, hence, thermal) range of the species

Maternal iron status in early pregnancy and DNA methylation in offspring: an epigenome-wide meta-analysis

This is the final version. Available on open access from BMC via the DOI in this recordAvailability of data and materials: Full meta-analysis results will be made available through an open access database upon acceptance. Cohort-level data are available from the cohort senior authors upon reasonable request and may be subject to local regulations.BACKGROUND: Unbalanced iron homeostasis in pregnancy is associated with an increased risk of adverse birth and childhood health outcomes. DNA methylation has been suggested as a potential underlying mechanism linking environmental exposures such as micronutrient status during pregnancy with offspring health. We performed a meta-analysis on the association of maternal early-pregnancy serum ferritin concentrations, as a marker of body iron stores, and cord blood DNA methylation. We included 1286 mother-newborn pairs from two population-based prospective cohorts. Serum ferritin concentrations were measured in early pregnancy. DNA methylation was measured with the Infinium HumanMethylation450 BeadChip (Illumina). We examined epigenome-wide associations of maternal early-pregnancy serum ferritin and cord blood DNA methylation using robust linear regression analyses, with adjustment for confounders and performed fixed-effects meta-analyses. We additionally examined whether associations of any CpGs identified in cord blood persisted in the peripheral blood of older children and explored associations with other markers of maternal iron status. We also examined whether similar findings were present in the association of cord blood serum ferritin concentrations with cord blood DNA methylation. RESULTS: Maternal early-pregnancy serum ferritin concentrations were inversely associated with DNA methylation at two CpGs (cg02806645 and cg06322988) in PRR23A and one CpG (cg04468817) in PRSS22. Associations at two of these CpG sites persisted at each of the follow-up time points in childhood. Cord blood serum ferritin concentrations were not associated with cord blood DNA methylation levels at the three identified CpGs. CONCLUSION: Maternal early-pregnancy serum ferritin concentrations were associated with lower cord blood DNA methylation levels at three CpGs and these associations partly persisted in older children. Further studies are needed to uncover the role of these CpGs in the underlying mechanisms of the associations of maternal iron status and offspring health outcomes

Fish and mussels: importance of fish for freshwater mussel conservation

Co-extinctions are increasingly recognized as one of the major processes leading to the global biodiversity crisis, but there is still limited scientific evidence on the magnitude of potential impacts and causal mechanisms responsible for the decline of affiliate (dependent) species. Freshwater mussels (Bivalvia, Unionida), one of the most threatened faunal groups on Earth, need to pass through a parasitic larval (glochidia) phase using fishes as hosts to complete their life cycle. Here, we provide a synthesis of published evidence on the fish–mussel relationship to explore possible patterns in co-extinction risk and discuss the main threats affecting this interaction. We retrieved 205 publications until December 2015, most of which were performed in North America, completed under laboratory conditions and were aimed at characterizing the life cycle and/or determining the suitable fish hosts for freshwater mussels. Mussel species were reported to infest between one and 53 fish species, with some fish families (e.g., Cyprinidae and Percidae) being used more often as hosts than others. No relationship was found between the breadth of host use and the extinction risk of freshwater mussels. Very few studies focused on threats affecting the fish–mussel relationship, a knowledge gap that may impair the application of future conservation measures. Here, we identify a variety of threats that may negatively affect fish species, document and discuss the concomitant impacts on freshwater mussels, and suggest directions for future studies.The Portuguese Foundation for Science and Technology—FCT through POPH/FSE funds supported VM, MI and MLL under grants (SFRH/BD/108298/2015), (SFRH/BPD/90088/2012), (SFRH/BD/115728/2016), respectively. KD acknowledges the support from the Czech Science Foundation (13-05872S). RS acknowledges the support of the strategic programme UID/BIA/04050/2013 (POCI-01-0145- FEDER-007569) funded by national funds through the FCT I.P. and by the ERDF through the COMPETE2020-Programa Operacional Competitividade e Internacionalização (POCI). This study was conducted as part of the project FRESHCO: Multiple implications of invasive species on Freshwater Mussel co-extinction processes, supported by FCT (contract: PTDC/AGRFOR/1627/2014)