Distribution and microhabitats of native and non-native gammarids (Amphipoda, Crustacea) in Brittany, with particular reference to the endangered endemic sub-species Gammarus duebeni celticus

Aim  To assess temporal changes in gammarid distribution in Brittany and microhabitat-use overlap between the endangered endemic Gammarus duebeni celticus Stock & Pinkster, 1970 , the expanding natives G. pulex (Linnaeus, 1758) and Echinogammarus berilloni (Catta, 1878), and the introduced G. tigrinus Sexton, 1939.
Location  Brittany and adjacent regions in western France.
Methods  The spatial and temporal patterns in distribution of gammarids at the scale of Brittany were studied using 351 sites. Longitudinal distributions (from the source to the estuary of the river) and microhabitat-use (substratum type and water velocity) were also considered in selected rivers.
Results  At the regional scale, all species occurred together less often than expected statistically, with significant deviations from expected for G. pulex vs. both G. duebeni celticus and G. tigrinus , and for E. berilloni vs. both G. duebeni celticus and G. tigrinus . However, at the microhabitat scale, E. berilloni occurred significantly more often than expected with the endemic G. duebeni celticus , and this appears to be due to similar substratum and water velocity preferences, although at both the regional and microhabitat scales E. berilloni prefers wider streams than G. duebeni celticus . This study reveals a decline in the endangered G. duebeni celticus since 1970.
Main conclusions  The longitudinal and local distributions of G. duebeni celticus , and the higher-than-expected co-occurrence of the species with G. pulex , suggest that the decline of the endemic species may be due to changes in the environment and/or interference from native G. pulex , which is expanding its range in Brittany. The results are discussed as regards to the consequences for regional biodiversity.     

Inhibition of cathepsin B by peptidyl aldehydes and ketones: slow-binding behavior of a trifluoromethyl ketone

Inhibition of the cysteine proteinase cathepsin B by a series of N-benzyloxycarbonyl-L-phenylalanyl-L-alanine ketones and the analogous aldehyde has been investigated. Surprisingly, whereas the aldehyde was found to be almost as potent a competitive reversible inhibitor as the natural peptidyl aldehyde, leupeptin, the corresponding trifluoromethyl ketone showed comparatively weak (and slow-binding) reversible inhibition. Evaluation of competitive hydration and hemithioketal formation in a model system led to a structure-activity correlation spanning several orders of magnitude in both cathepsin B inhibition constants (Ki) and model system equilibrium data (KRSH,apparent).     

Glycosaminoglycans vary in accumulation along the neuraxis during spinal neurulation in the mouse embryo

We have utilized the method of whole embryo culture for metabolic labeling of mouse embryos with [3H]glucosamine during closure of neural folds at the posterior neuropore (27- to 29-somite stage). Accumulations of newly synthesized glycopeptides, lactosaminoglycans, hyaluronate, and sulfated glycosaminoglycans (GAG) were assessed by ion-exchange chromatography of glycoconjugates isolated from labeled embryos. Accumulation of hyaluronate and sulfated GAG was greatest in the posterior neuropore and decreased progressively toward the hindbrain where neurulation was already complete. Hyaluronate comprised a progressively smaller proportion of total newly synthesized glycoconjugate from the posterior neuropore toward the cranial region and glycopeptides showed the opposite trend. Sulfated GAG and lactosaminoglycans showed no consistent differences in relative abundance along the neuraxis. Autoradiographic analysis of newly synthesized glycoconjugates revealed especially heavy incorporation into developing basement membranes, beneath the neuroepithelium and around the notochord, in the posterior neuropore and recently closed neural tube regions, but not at more cranial levels of the neuraxis. Predigestion of sections with a specific hyaluronidase showed a significant quantity of this glycoconjugate to be hyaluronate. These results are consistent with a role for neuroepithelial and notochordal basement membrane hyaluronate in spinal neurulation.     

The habitat diversity and fish reproductive function of floodplain ecosystems

Synopsis Fish reproduction in floodplain ecosystems, based on relative abundance and total biomass of 0+ juveniles, was studied using the synchronic approach to typological analysis in conjunction with Point Abundance Sampling by modified electrofishing. In 3 different flood plains of the Upper Rhône River, 1015 point samples yielding 4573 juveniles (0+) from 21 species were collected from 48 ecosystems of various geomorphological origin. The results demonstrate the lotic-to-lentic succession of floodplain ecosystems to be a series of non-sequential reproductive zones, with spawning conditions being reflected by the specific composition and guild structure of the YOY fish assemblages. The habitat diversity and the fish reproductive potential of floodplain ecosystems are strongly influenced by geomorphological origin and by past and present hydrological conditions. The YOY assemblages of autogenically driven ecosystems (usually of anastomose or meander origin) tend to differ both in composition and in quantity from those found in allogenically driven ecosystems (generally of braided origin). Ecosystems of intermediate character, and fish reproduction thereof, occur as the result of either ecosystem rejuvenation or senescence: autogenically driven ecosystems by allogenic mechanisms, or allogenically driven ecosystems by anthropic and/or autogenic mechanisms, respectively. Because of co-occurrence of ecosystems at similar and at different successional status, the flood plain as an entity is seen as stable with respect to fish reproduction.     

New and Old World phylogeography of pumpkinseed Lepomis gibbosus (Linnaeus, 1758): the North American origin of introduced populations in Europe

Hydrobiologia - To determine the origin of introduced European populations of pumpkinseed Lepomis gibbosus (Linnaeus, 1758)—a freshwater sunfish, native to eastern North America that has...     

Induction of the Cpx Envelope Stress Pathway Contributes to Escherichia coli Tolerance to Antimicrobial Peptides

Antimicrobial peptides produced by multicellular organisms as part of their innate system of defense against microorganisms are currently considered potential alternatives to conventional antibiotics in case of infection by multiresistant bacteria. However, while the mode of action of antimicrobial peptides is relatively well described, resistance mechanisms potentially induced or selected by these peptides are still poorly understood. In this work, we studied the mechanisms of action and resistance potentially induced by ApoEdpL-W, a new antimicrobial peptide derived from human apolipoprotein E. Investigation of the genetic response of Escherichia coli upon exposure to sublethal concentrations of ApoEdpL-W revealed that this antimicrobial peptide triggers activation of RcsCDB, CpxAR, and σ^E envelope stress pathways. This genetic response is not restricted to ApoEdpL-W, since several other antimicrobial peptides, including polymyxin B, melittin, LL-37, and modified S₄ dermaseptin, also activate several E. coli envelope stress pathways. Finally, we demonstrate that induction of the CpxAR two-component system directly contributes to E. coli tolerance toward ApoEdpL-W, polymyxin B, and melittin. These results therefore show that E. coli senses and responds to different antimicrobial peptides by activation of the CpxAR pathway. While this study further extends the understanding of the array of peptide-induced stress signaling systems, it also provides insight into the contribution of Cpx envelope stress pathway to E. coli tolerance to antimicrobial peptides.     

Plasticity of diel patterns in the diet and habitat use of feral, non-native fathead minnow Pimephales promelas (Actinopterygii, Cyprinidae) in a pond-dwelling population in England

The aim of the study was to test for diel patterns in the diet and habitat use in a feral, pond-dwelling, non-native fathead minnow Pimephales promelas population in England. Fish were collected in June 2009 using traps set in four habitat types (open waters, rushes??Juncus effusus, weeds??Potamogeton natans and mixed vegetation), then sexed and measured for total length and eviscerated weight in the laboratory. Data were analysed at 6-h intervals, with Fulton??s condition index and three dietary parameters (frequency of occurrence, number and weight) calculated. Minor diurnal differences in habitat use were observed in males, females and immatures, and these may be due to predator avoidance. Body condition varied greatly in rushes during daytime, probably due to shifts in habitat suitability (e.g. food, refuge). Detritus dominates the diet of native fathead minnow; however, planktonic crustaceans were the most important food resource for this population, with a clear ontogenetic shift, irrespective of habitat, towards greater proportion of ingested detritus in larger individuals. Overall, the results demonstrate that feral fathead minnows display substantial trophic plasticity and a wide range of habitat use, which is normally associated with invasive species. However, established fathead minnow populations in Europe are rare despite its wide-spread ornamental and scientific use.     

A global review and meta-analysis of applications of the freshwater Fish Invasiveness Screening Kit

Reviews in Fish Biology and Fisheries - The freshwater Fish Invasiveness Screening Kit (FISK) has been applied in 35 risk assessment areas in 45 countries across the six inhabited continents (11...