Fish passage experience at small-scale hydro-electric power plants in France

There are more than 1,700 small-scale hydro-electric power stations in France today, which can be found on the majority of rivers with migratory species in them. This article gives an overview of the different types of fish facilities in use at these small-scale hydro plants. The relative advantages and drawbacks of each type of fish pass are discussed, with reference to the requirements of migratory species and the site-specific constraints. Emphasis is placed on the problems of attraction and maintenance. The article also mentions the various techniques used to evaluate existing or recently constructed fish passes. Experience in using bypass facilities combined with trashracks for downstream juvenile salmonids and eels are related. The author points out the severe cumulative impact which may occur due to the existence of several small-scale hydro projects on the same river. He presents his view on the priorities for research on fish passage facilities, especially on “fish friendly” small-scale hydropower intakes. Guest editors: R. L. Welcomme & G. Marmulla Hydropower, Flood Control and Water Abstraction: Implications for Fish and Fisheries     

Reassessment of inclusion body-based production as a versatile opportunity for difficult-to-express recombinant proteins

The production of recombinant proteins in the microbial host Escherichia coli often results in the formation of cytoplasmic protein inclusion bodies (IBs). Proteins forming IBs are often branded as difficult-to-express, neglecting that IBs can be an opportunity for their production. IBs are resistant to proteolytic degradation and contain up to 90% pure recombinant protein, which does not interfere with the host metabolism. This is especially advantageous for host-toxic proteins like antimicrobial peptides (AMPs). IBs can be easily isolated by cell disruption followed by filtration and/or centrifugation, but conventional techniques for the recovery of soluble proteins from IBs are laborious. New approaches therefore simplify protein recovery by optimizing the production process conditions, and often include mild resolubilization methods that either increase the yield after refolding or avoid the necessity of refolding all together. For the AMP production, the IB-based approach is ideal, because these peptides often have simple structures and are easy to refold. The intentional IB production of almost every protein can be achieved by fusing recombinant proteins to pull-down tags. This review discusses the techniques available for IB-based protein production before considering technical approaches for the isolation of IBs from E. coli lysates followed by efficient protein resolubilization which ideally omits further refolding. The techniques are evaluated in terms of their suitability for the process-scale production and downstream processing of recombinant proteins and are discussed for AMP production as an example.     

Rapid one-step protein purification from plant material using the eight-amino acid StrepII epitope

Beyond the rewards of plant genome analysis and gene identification, characterisation of protein activities, post-translational modifications and protein complex composition remains a challenge for plant biologists. Ideally, methods should allow rapid isolation of proteins from plant material achieving a high degree of purity. We tested three purification strategies based on the eight-amino acid StrepII, six-amino acid His₆ and 181-amino acid Tandem Affinity Purification (TAP) affinity tags for enrichment of a membrane-anchored protein kinase, NtCDPK2, and a soluble protein, AtSGT1b, from leaf extracts. Transiently expressed StrepII-taggedNtCDPK2 was purified from Nicotiana benthamiana to almost complete homogeneity in less than 60min and was directly suitable for enzymatic or mass-spectrometric analyses, allowing the identification of in planta phosphorylation sites. In contrast, purification of NtCDPK2 via His₆ tag yielded partially oxidised protein of low purity. AtSGT1b could be isolated after transient expression from N. benthamiana or from transgenic Arabidopsis thaliana as either TAP-tagged or StrepII-tagged protein. While StrepII-tag purification achieved similar yield and high purity as the TAP-tag strategy, it was considerably easier and faster. Using either tagging strategy, a protein was co-purified with AtSGT1b from N. benthaniana and A. thalianaleaf extracts, suggesting that both the StrepII and TAP tags are suitable for purification of protein complexes from plant material. We propose that the StrepII epitope, in particular, may serve as a generally utilizable tag to further our understanding of protein functions, post-translational modifications and interaction dynamics in plants.     

Identifying spawning behavior in Pacific halibut, <Emphasis Type="BoldItalic">Hippoglossus stenolepis</Emphasis>, using electronic tags

Synopsis Identifying spawning behavior in Pacific halibut, Hippoglossus stenolepis, is particularly challenging because they occupy a deep, remote environment during the spawning season. To identify spawning events, a method is needed in which direct observation by humans is not employed. Spawning behavior of seven other flatfish, species has been directly observed in their natural environment by investigators using SCUBA. All of these flatfish species display almost identical spawning behavior that follows a routine. Therefore, it is reasonable to believe that this spawning behavior occurs in other flatfish species, including Pacific halibut. As part of a larger study, we recaptured two Pacific halibut on which Pop-up Archival Transmitting (PAT) tags had been attached during the winter spawning season. Because the tags were physically retrieved, we were able to collect minute-by-minute depth records for 135 and 155 days. We used these depth data to tentatively identify spawning events. On seven separate occasions between 20 January 2001 and 9 February 2001, one fish displayed a conspicuous routine only seen during the spawning season of Pacific halibut and the routine parallels the actions of other spawning flatfish directly observed by humans using SCUBA. Therefore, we propose this routine represents spawning behavior in Pacific halibut. The second tagged fish did not display the conspicuous routine, thus challenging the assumption that Pacific halibut are annual spawners. PAT tags may prove to be a useful tool for identifying spawning events of Pacific halibut, and that knowledge may be used for improved management in the future.     

Differential mortality and the Donner Party disaster

The story of the Donner Party combines powerful American themes. The beginning of the tale is immersed in the romance of the western frontier and in the American dream of improving life by taking bold steps. The end of the tale, in contrast, is awash in death and cannibalism. No wonder Americans learn the story as children; no Grimm's fairy tale can match it. However, detailed analyses of the patterning of Donner Party deaths suggest that the story is even better read as a piece of biology than as a piece of history. Virtually all aspects of Donner Party mortality can now be explained by our knowledge of the factors that cause differential mortality in human societies. The differential fates of these emigrants show us natural selection in action.     

Home range size and dispersion in the helmeted guineafowl (Numida meleagris galeata Pallas) of the Waza National Park, Cameroon

Field investigations of the home range size and emigration pattern of wild helmeted guineafowl ( Numida meleagris galeata Pallas) from 1992 to 1995 showed that home range size (±95% confidence limits (CL) ) varied with season from 3·6±1·5 km² for the dry seasons to 3·1±1·5 km² for the rainy seasons. Home range size varied depending on whether it was estimated with data for adult males, adult females or young birds, with a higher home range size for young birds, closely followed by adult males. Group size (±95%CL) varied by month, and was highest between March and April (47·0±8·1 birds/group) and lowest in August 9·0±5·1 birds/group). More young birds (±95%CL) (36·8±19·6%) dispersed than adult males (21·1±1·9%) or adult females (13·5±1·8%). There was a highly significant positive correlation between group size and the number of birds emigrating from the group. There was also a significant negative correlation between the weights of birds at tagging and the percentage that emigrated during the first year of study but not later. This is suggested to be linked to the high number of young birds emigrating, since they weigh relatively less than adults. The lack of correlation between body weight and number of birds emigrating a year or later after birds were tagged was thought to be due to the fact that birds tagged while young attained adult weight within a year.     

Translation enhancement by optimized downstream box sequences in <Emphasis Type="Italic">Escherichia coli </Emphasis>and<Emphasis Type="Italic"> Mycobacterium smegmatis</Emphasis>

The effect on translation of downstream box sequences optimized for binding to Mycobacterium smegmatis and Escherichia coli 16S rRNA in the absence of a Shine--Dalgarno (SD) region was investigated. The relative translational efficiency of each construct in either M. smegmatis or E. coli was determined. Eradication of the SD region in the absence of a downstream box abolished the translation activity. In contrast, optimized downstream box constructs resulted in a 13- and 18-fold increase in protein synthesis, relative to non-optimized DB controls in E. coli and M. smegmatis, respectively.     

Environmentally-controlled,density-dependent secondary dispersal in a local estuarine crab population

The mechanisms driving the pelagic secondary dispersal of aquatic organisms following initial settlement to benthic habitats are poorly characterized. We examined the physical environmental (wind, diel cycle, tidal phase) and biological (ontogenetic, density-dependent) factors that contribute to the secondary dispersal of a benthic marine invertebrate, the blue crab (Callinectes sapidus) in Pamlico Sound, NC, USA. Field studies conducted in relatively large (0.05 km²) seagrass beds determined that secondary dispersal is primarily undertaken by the earliest juvenile blue crab instar stages (J1 crabs). These crabs emigrated pelagically from seagrass settlement habitats using nighttime flood tides during average wind conditions (speed ~5 m s^–1). Moreover, the secondary dispersal of J1 crabs was density-dependent and regulated by intra-cohort (J1) crab density in seagrass. Our results suggest that dispersal occurs rapidly following settlement, and promotes blue crab metapopulation persistence by redistributing juveniles from high-density settlement habitats to areas characterized by low postlarval supply. Collectively, these data indicate that blue crab secondary dispersal is an active process under behavioral control and can alter initial distribution patterns established during settlement. This study highlights the necessity of considering secondary dispersal in ecological studies to improve our understanding of population dynamics of benthic organisms.