High spontaneous rate of gene duplication in Caenorhabditis elegans

Gene and genome duplications are the primary source of new genes and novel functions and have played a pivotal role in the evolution of genomic and organismal complexity. The spontaneous rate of gene duplication is a critical parameter for understanding the evolutionary dynamics of gene duplicates; yet few direct empirical estimates exist and differ widely. The presence of a large population of recently derived gene duplicates in sequenced genomes suggests a high rate of spontaneous origin, also evidenced by population genomic studies reporting rampant copy-number polymorphism at the intraspecific level. An analysis of long-term mutation accumulation lines of Caenorhabditis elegans for gene copy-number changes with array comparative genomic hybridization yields the first direct estimate of the genome-wide rate of gene duplication in a multicellular eukaryote. The gene duplication rate in C. elegans is quite high, on the order of 10(-7) duplications/gene/generation. This rate is two orders of magnitude greater than the spontaneous rate of point mutation per nucleotide site in this species and also greatly exceeds an earlier estimate derived from the frequency distribution of extant gene duplicates in the sequenced C. elegans genome.     

The Interaction of Selenate and Selenite with Selected Freshwater Sediments

Selenite and selenate at submicrogram levels were added to suspensions of two lake sediments (Buffalo Pound and Katepwa Lakes) from southeastern Saskatchewan, Canada. The sediment from Buffalo Pound Lake rapidly oxidized selenite in an Arrhenius type reaction and followed first order kinetics. The sediment from Katepwa Lake oxidized selenite, but at a much slower rate. The oxidation of selenite is an abiotic process. The sediment from Katepwa Lake also reduced selenate, while Buffalo Pound Lake sediment did not. The reduction of selenate is likely mediated by biotic activity, associated biochemical processes, and/or organic matter.     

Disintegration of a large concentration of loliginid squid as a response to predation

During hydroacoustic observations in November 2002, a large concentration of chokka squid (Loligo reynaudi) was monitored for three days during fairly constant wind speed and direction, that marginally improved during the period of observations. During this period, the concentration (estimated biomass 48 t) disintegrated into small, separate aggregations. Most often, such dispersal is weather-related, but obviously not in this case. Instead, a bottom trawl made adjacent to the concentration, as well as underwater camera observations revealed an unusually large number of predators, mostly bronze whaler sharks (Carcharhinus brachyurus). Most whaler sharks caught in the trawl had chokka in their stomachs. Therefore, one explanation for the break-up of this squid concentration was the unusual predator activity. Video observations revealed, that these attacks occurred on the bottom where squid spawn; while none were observed in the water column where squid pair, mate and swim in a circular motion preparing for descent to the egg bed. The disintegration of the whole concentration suggested that disrupted spawning affects the upper part of the typical mushroom-shaped structure as well, and squid subsequently disperse and/or move away as a result of predation by whaler sharks.     

Variation of cats under domestication: genetic assignment of domestic cats to breeds and worldwide random‐bred populations

Both cat breeders and the lay public have interests in the origins of their pets, not only in the genetic identity of the purebred individuals, but also in the historical origins of common household cats. The cat fancy is a relatively new institution with over 85% of its 40–50 breeds arising only in the past 75 years, primarily through selection on single‐gene aesthetic traits. The short, yet intense cat breed history poses a significant challenge to the development of a genetic marker–based breed identification strategy. Using different breed assignment strategies and methods, 477 cats representing 29 fancy breeds were analysed with 38 short tandem repeats, 148 intergenic and five phenotypic single nucleotide polymorphisms. Results suggest the frequentist method of Paetkau (single nucleotide polymorphisms = 0.78, short tandem repeats = 0.88) surpasses the Bayesian method of Rannala and Mountain (single nucleotide polymorphisms = 0.56, short tandem repeats = 0.83) for accurate assignment of individuals to the correct breed. Additionally, a post‐assignment verification step with the five phenotypic single nucleotide polymorphisms accurately identified between 0.31 and 0.58 of the misassigned individuals raising the sensitivity of assignment with the frequentist method to 0.89 and 0.92 for single nucleotide polymorphisms and short tandem repeats respectively. This study provides a novel multistep assignment strategy and suggests that, despite their short breed history and breed family groupings, a majority of cats can be assigned to their proper breed or population of origin, that is, race.     

Standardized Procedure for Determination of Staphylocoagulase

A simple standardized procedure for the determination of staphylocoagulase, based on thrombin clotting time measurement with euglobulin, has been developed. A standard euglobulin solution containing 0.25% of clottable protein, 0.01 M epsilon-aminocaproic acid, and 20 units of heparin per ml is employed. One unit of staphylocoagulase is defined as the amount of the enzyme which clots this standard euglobulin solution in 25 sec.     

A new direct method of stock assessment of the loliginid squid

Hydroacoustic research conducted on chokka squid (Loligo reynaudi d’Orbigny, 1845), off the east coast of South Africa from 1994–2005, has led to the development of an innovative stock assessment technique, perhaps applicable to all loliginids that migrate inshore to spawn. This technique combines hydroacoustic biomass estimates made on the spawning concentrations inshore, and minimum biomass estimates made both inshore and offshore using demersal surveys employing the swept-area method. The hydroacoustic estimate uses an improved method to obtain target strength measurements, and squid concentrations are individually mapped from a small boat with a towed transducer. This method may be used even during intense fishing operations because of the manoeuvrability of the small boat inside a tight cluster of fishing vessels. Biomasses of the individual concentrations are then summed. The inshore biomass, also includes dispersed, mature squid migrating between concentrations, this is assessed using a concentration stability factor. The biomass of dispersed squid offshore is again calculated using the swept-area method, a well known demersal survey methodology. The biomass of concentrated (spawning) squid offshore is calculated using the same proportions between concentrated and dispersed squid which were found inshore. All four components are then summed to calculate the total biomass. The result obtained is subject to the effect of complex temporal dynamics, as new animals are recruited to the adult pool and those recently assessed migrate to other sectors of the distribution area.