From spring sources to springbrook: Changes in environmental characteristics and benthic fauna

Spatial patterns in macroinvertebrate communities and some abiotic factors were examined in three rheocrene springs and their springbrooks (Kraków-Cz?stochowa Upland, southern Poland). The mean discharge of particular springs ranged from 5 to 11 L s^?1, and its annual fluctuations were small. Water temperature was very stable at all sampling sites. In the eucrenon the number of benthic taxa was the smallest (9–14 determined to the family level), but the densities were the highest (approx. 14000 ind. m^?2). The biggest changes in macroinvertebrate composition were observed in the modified hypocrenon, which is an artificial pond. The lowest number of taxa were found in a natural, short springbrook with a nondiversified bottom substrate. The density of crenophilic taxa (Drusus trifidus, Dugesia gonocephala, Elmidae) diminished along the springbrooks, while the opposite trend was observed for ubiquitous taxa (some Oligochaeta, Asellus aquaticus and Chironomidae). Even in a very short natural springbrook (30 m), Drusus trifidus, the only species of Trichoptera found in the springs discussed here, goes through the entire development cycle. The strongest influence of a big river was observed at the outflow of one of the natural springbrooks, where the highest number of riverine oligochaete species were found. The benthic fauna of the springs studied here differed from that found in other springs in this area — the absence of the typical crenophilic species Bithynella austriaca (Gastropoda) and the presence of Gianus aquedulcis (Oligochaeta) may indicate the autonomy of the spring fauna in the Mstów area, possibly resulting from the postglacial geomorphological formation of this region or differences in habitat conditions.     

Interpretation of the invertebrate-based BMWP-PL index in a gravel-bed river: insight from the Polish Carpathians

Like its British prototype (Biological Monitoring Working Party score system), the Polish benthic invertebrate-based BMWP-PL index is commonly regarded as an indicator of river water quality. This interpretation of the index has been verified in a study of the gravel-bed Bia?a River. Benthic macroinvertebrates were sampled at 10 sites and compared in one channelized and one unmanaged cross-section per site. The resulting taxa richness and BMWP-PL index scores were compared with water quality and physical habitat characteristics in the cross-sections. Channelized and unmanaged cross-sections clearly differed in their physical habitat conditions, and water quality characteristics mostly varied in the downstream direction. Particular cross-sections hosted between 3 and 26 invertebrate taxa, with the respective BMWP-PL scores indicating the water in the surveyed cross-sections varied between high and poor quality. However, the BMWP-PL scores were unrelated to physicochemical characteristics of the river water, which consistently pointed to high water quality. Instead, the scores were significantly related to several physical habitat variables, with the number of low-flow channels in a cross-section explaining the largest proportion of the variance in the index values. The relationship of the scores with the complexity of flow pattern in the river and a lack of their dependence on physicochemical water characteristics show that the BMWP-PL index should not be regarded as an indicator of water quality but rather as an indicator of the ecological status of rivers, dependent both on their hydromorphological and water-quality characteristics.     

The reproductive phenology of Delesseria sanguinea and Odonthalia dentata off the Isle of Man

Samples of individual plants of Delesseria sanguinea and Odonthalia dentata were collected from shallow subtidal populations off the south end of the Isle of Man during the reproductive season. Reproductive bladelets were measured and their state of fertility noted. In Delesseria, male bladelets appeared in early September and achieved maximum size in mid October when bladelets of all sizes became fertile; the largest of these dehisced first and all were spent by mid December. Females appeared 3 weeks later; carpogonia were fertilized during October but carpospores were not released until about February when maximum bladelet length was reached. In about half the bladelets carpogonia remained unfertilized and did not grow further and only 40% of successful fertilizations resulted in carpospore release. Tetrasporangial bladelets did not appear until November and tetraspores were released in January and February while bladelets were still growing. Gametophytes and tetrasporophytes existed in about equal numbers. In Odonthalia, all three types of bladelet appeared in early November and fertilization took place in December, but later-developing carpogonia seemed to remain unfertilized in spite of a second wave of production of spermatangia, resulting in a low fertilization success of about 7%. Both carpospores and tetraspores dehisced from January to April. In this species the gametophytes formed about 58% of the population, a proportion expected from equal survival of number of spores per parent.     

Enhancing adhesion of yeast brewery strains to chamotte carriers through aminosilane surface modification

The adhesion of cells to solid supports is described as surface-dependent, being largely determined by the properties of the surface. In this study, ceramic surfaces modified using different organosilanes were tested for proadhesive properties using industrial brewery yeast strains in different physiological states. Eight brewing strains were tested: bottom-fermenting Saccharomyces pastorianus and top-fermenting Saccharomyces cerevisiae. To determine adhesion efficiency light microscopy, scanning electron microscopy and the fluorymetric method were used. Modification of chamotte carriers by 3-(3-anino-2-hydroxy-1-propoxy) propyldimethoxysilane and 3-(N, N-dimethyl-N-2-hydroxyethyl) ammonium propyldimethoxysilane groups increased their biomass load significantly.     

High genetic diversity is not essential for successful introduction

Some introduced populations thrive and evolve despite the presumed loss of diversity at introduction. We aimed to quantify the amount of genetic diversity retained at introduction in species that have shown evidence of adaptation to their introduced environments. Samples were taken from native and introduced ranges of Arctotheca populifolia and Petrorhagia nanteuilii. Using microsatellite data, we identified the source for each introduction, estimated genetic diversity in native and introduced populations, and calculated the amount of diversity retained in introduced populations. These values were compared to those from a literature review of diversity in native, confamilial populations and to estimates of genetic diversity retained at introduction. Gene diversity in the native range of both species was significantly lower than for confamilials. We found that, on average, introduced populations showing evidence of adaptation to their new environments retained 81% of the genetic diversity from the native range. Introduced populations of P. nanteuilii had higher genetic diversity than found in the native source populations, whereas introduced populations of A. populifolia retained only 14% of its native diversity in one introduction and 1% in another. Our literature review has shown that most introductions demonstrating adaptive ability have lost diversity upon introduction. The two species studied here had exceptionally low native range genetic diversity. Further, the two introductions of A. populifolia represent the largest percentage loss of genetic diversity in a species showing evidence of substantial morphological change in the introduced range. While high genetic diversity may increase the likelihood of invasion success, the species examined here adapted to their new environments with very little neutral genetic diversity. This finding suggests that even introductions founded by small numbers of individuals have the potential to become invasive.     

Essential Regulation of Lung Surfactant Homeostasis by the Orphan G Protein-Coupled Receptor GPR116

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Rat aversion to isoflurane versus carbon dioxide

Some experts suggest that sedation of laboratory rodents with isoflurane before euthanasia with carbon dioxide (CO₂) is a humane alternative to euthanasia with CO₂ alone, but little research has compared aversion with these agents. Albino rats were tested in a light–dark box where they had the choice between remaining in a dark compartment filling with isoflurane or CO₂, or escaping to a lit compartment. Experiment 1 validated the procedure by confirming that rats responded to agent and light intensity. In experiment 2, 9/16 and 0/16 rats remained in the dark compartment until recumbent when initially exposed to isoflurane and CO₂, respectively. In experiment 3, more rats remained in the dark compartment until recumbent during initial (10/16) versus re-exposure (1/16) to isoflurane. These results indicate that initial exposure to CO₂ is more aversive than isoflurane, and that re-exposure to isoflurane is more aversive than initial exposure. We conclude that sedation with isoflurane is a refinement over euthanasia with CO₂ alone for rats that have not been previously exposed to inhalant anaesthetics.     

Pseudomonas fluorescens NZI7 repels grazing by C. elegans,a natural predator

The bacteriovorous nematode Caenorhabditis elegans has been used to investigate many aspects of animal biology, including interactions with pathogenic bacteria. However, studies examining C. elegans interactions with bacteria isolated from environments in which it is found naturally are relatively scarce. C. elegans is frequently associated with cultivation of the edible mushroom Agaricus bisporus, and has been reported to increase the severity of bacterial blotch of mushrooms, a disease caused by bacteria from the Pseudomonas fluorescens complex. We observed that pseudomonads isolated from mushroom farms showed differential resistance to nematode predation. Under nutrient poor conditions, in which most pseudomonads were consumed, the mushroom pathogenic isolate P. fluorescens NZI7 was able to repel C. elegans without causing nematode death. A draft genome sequence of NZI7 showed it to be related to the biocontrol strain P. protegens Pf-5. To identify the genetic basis of nematode repellence in NZI7, we developed a grid-based screen for mutants that lacked the ability to repel C. elegans. The mutants isolated in this screen included strains with insertions in the global regulator GacS and in a previously undescribed GacS-regulated gene cluster, ‘EDB'' (‘edible''). Our results suggest that the product of the EDB cluster is a poorly diffusible or cell-associated factor that acts together with other features of NZI7 to provide a novel mechanism to deter nematode grazing. As nematodes interact with NZI7 colonies before being repelled, the EDB factor may enable NZI7 to come into contact with and be disseminated by C. elegans without being subject to intensive predation.     

Chemerin Is an Antimicrobial Agent in Human Epidermis

Chemerin, a chemoattractant ligand for chemokine-like receptor 1 (CMKLR1) is predicted to share similar tertiary structure with antibacterial cathelicidins. Recombinant chemerin has antimicrobial activity. Here we show that endogenous chemerin is abundant in human epidermis, and that inhibition of bacteria growth by exudates from organ cultures of primary human skin keratinocytes is largely chemerin-dependent. Using a panel of overlapping chemerin-derived synthetic peptides, we demonstrate that the antibacterial activity of chemerin is primarily mediated by Val⁶⁶-Pro⁸⁵, which causes direct bacterial lysis. Therefore, chemerin is an antimicrobial agent in human skin.