Mapping of earthworm distribution for the British Isles and Eire highlights the under-recording of an ecologically important group

Earthworms are important soil organisms yet we have limited knowledge on the geographical distribution of species. Using data from a variety of sources representing a total of 3,941 locality records we have produced the first distribution maps of earthworm species in the British Isles The maps highlight the paucity of knowledge on this ecologically important group. A systematic approach needs to be taken to bring earthworm species data to a level comparable with other important invertebrate groups such as nematodes and isopods. Through the recent establishment of an earthworm recording scheme, the Earthworm Society of Britain, working with the Biological Records Centre and earthworm researchers across the British Isles, aim to build comprehensive distribution information for future monitoring and research purposes.     

Genetic connectivity across marginal habitats: the elephants of the Namib Desert

Locally isolated populations in marginal habitats may be genetically distinctive and of heightened conservation concern. Elephants inhabiting the Namib Desert have been reported to show distinctive behavioral and phenotypic adaptations in that severely arid environment. The genetic distinctiveness of Namibian desert elephants relative to other African savanna elephant (Loxodonta africana) populations has not been established. To investigate the genetic structure of elephants in Namibia, we determined the mitochondrial (mt) DNA control region sequences and genotyped 17 microsatellite loci in desert elephants (n = 8) from the Hoanib River catchment and the Hoarusib River catchment. We compared these to the genotypes of elephants (n = 77) from other localities in Namibia. The mtDNA haplotype sequences and frequencies among desert elephants were similar to those of elephants in Etosha National Park, the Huab River catchment, the Ugab River catchment, and central Kunene, although the geographically distant Caprivi Strip had different mtDNA haplotypes. Likewise, analysis of the microsatellite genotypes of desert‐dwelling elephants revealed that they were not genetically distinctive from Etosha elephants, and there was no evidence for isolation by distance across the Etosha region. These results, and a review of the historical record, suggest that a high learning capacity and long‐distance migrations allowed Namibian elephants to regularly shift their ranges to survive in the face of high variability in climate and in hunting pressure.     

Assembly of the Candida albicans genome into sixteen supercontigs aligned on the eight chromosomes

Background

The 10.9× genomic sequence of Candida albicans, the most important human fungal pathogen, was published in 2004. Assembly 19 consisted of 412 supercontigs, of which 266 were a haploid set, since this fungus is diploid and contains an extensive degree of heterozygosity but lacks a complete sexual cycle. However, sequences of specific chromosomes were not determined.

Results

Supercontigs from Assembly 19 (183, representing 98.4% of the sequence) were assigned to individual chromosomes purified by pulse-field gel electrophoresis and hybridized to DNA microarrays. Nine Assembly 19 supercontigs were found to contain markers from two different chromosomes. Assembly 21 contains the sequence of each of the eight chromosomes and was determined using a synteny analysis with preliminary versions of the Candida dubliniensis genome assembly, bioinformatics, a sequence tagged site (STS) map of overlapping fosmid clones, and an optical map. The orientation and order of the contigs on each chromosome, repeat regions too large to be covered by a sequence run, such as the ribosomal DNA cluster and the major repeat sequence, and telomere placement were determined using the STS map. Sequence gaps were closed by PCR and sequencing of the products. The overall assembly was compared to an optical map; this identified some misassembled contigs and gave a size estimate for each chromosome.

Conclusion

Assembly 21 reveals an ancient chromosome fusion, a number of small internal duplications followed by inversions, and a subtelomeric arrangement, including a new gene family, the TLO genes. Correlations of position with relatedness of gene families imply a novel method of dispersion. The sequence of the individual chromosomes of C. albicans raises interesting biological questions about gene family creation and dispersion, subtelomere organization, and chromosome evolution.     

Observations on the seasonal incidence of myxomatosis and its interactions with helminth parasites in the European rabbit (Oryctolagus cuniculus)

European rabbits (Oryctolagus cuniculus) were collected monthly over a 10-yr period and the incidence of myxomatosis and the size of helminth populations were recorded. Myxomatosis occurred annually, always as an epidemic in the latter half of the year and was associated with both an increase in the percentage of animals infected and the size of the infections of the nematodes Trichostrongylus retortaeformis and Passalurus ambiguus and the cestode Mosgovoyia pectinata. It is suggested that myxomatosis had the effect of reducing the rabbits' overall immune response to infection and that due to the regular annual occurrence of myxomatosis, the resulting increase in the size of helminth infections must be considered an integral part of the population dynamics of these parasites.     

Microencapsulation of human fibroblasts in a water-insoluble polyacrylate

Viable human diploid fibroblasts have been micro-encapsulated in EUDRAGIT RL, a commercially available water-insoluble polyacrylate, by an interfacial precipitation technique. Cells in medium and polymer solution (in diethyl phthalate) were coextruded and formed into droplets by a coaxial air stream. The droplets fell into a corn-oil/mineral-oil mixture to extract the solvent to precipitate the polymer around the cells. Capsules were ca. 500 mum in diameter depending on the air flowrate with a ca. 10-mum thick wall. When collagen (1 mg/mL) was added to the cell suspension prior to encapsulation and base-washed corn oil was used, cell growth occurred with one doubling achieved after five to six days as the collagen gel contracted inside the capsule. In the absence of collagen, cells spread on the inner wall of the capsule but did not grow, presumably because the surface charge on the capsule was inadequate. In similar fashion fibroblasts spread but did not grow on films of EUDRAGIT RL but did grow on blends of EUDRAGIT RL and EUDRAGIT E containing 10-30% of the latter more highly aminated polyacrylate. Although not suitable for anchorage-dependent cell growth by itself, EUDRAGIT RL has been suitable as a model polymer to demonstrate the feasibility of using water insoluble polyacrylates and organic solvents and nonsolvents for the micro-encapsulation of fibroblasts. Such microcapsules are of potential interest as a mode of large scale tissue culture for the production of novel therapeutic agents.     

The Involvement of Aspartate and Glutamate in the Decarboxylation of Malate by Isolated Bundle Sheath Chloroplasts from Zea mays

Aspartate or glutamate stimulated the rate of light-dependent malate decarboxylation by isolated Zea mays bundle sheath chloroplasts. Stimulation involved a decrease in the apparent K_m (malate) and an increased maximum velocity of decarboxylation. In the presence of glutamate other dicarboxylates (succinate, fumarate) competitively inhibited malate decarboxylation by intact chloroplasts with respect to malate with an apparent K_i of about 6 millimolar. For comparison the K_i for inhibition of nicotinamide adenine dinucleotide phosphate-malic enzyme from freshly lysed chloroplasts by these dicarboxylates was 15 millimolar. A range of compounds structurally related to aspartate stimulated malate decarboxylation by intact chloroplasts. K_a values for stimulation at 5 millimolar malate were 1.7, 5, and 10 millimolar for l-glutamate, l-aspartate, and β-methyl-dl-aspartate, respectively. Certain compounds, notably cysteic acid, which stimulated malate decarboxylation by intact chloroplasts inhibited malate decarboxylation by nicotinamide adenine dinucleotide phosphate-malic enzyme obtained from lysed chloroplasts and assayed under comparable conditions. It was concluded that aspartate, glutamate, and related compounds affect the transport of malate into the intact chloroplasts and that malate translocation does not take place on the general dicarboxylate translocator previously reported for higher plant chloroplasts.     

DNA fingerprinting reveals relation between tail ornaments and cuckoldry in barn swallows, Hirundo rustica

In an experimental study in Denmark, it was previously foundthat male barn swallows (Hirundo rustica) with elongated tailstreamers obtained an apparent fitness advantage through earlierpairing, an increased frequency of second clutches, and highertotal reproductive success per season. In a parallel study offive barn swallow colonies in Ontario, Canada, we also foundthat elongated males paired earlier and thus were apparentlypreferred by females. Now, using DNA fingerprinting on familiesfrom two of those Ontario colonies, we show that five elongatedmales fathered only 59% of the offspring in their nests, whereassix shortened males fathered 96% of their nestlings. Thus, althoughelongated males were clearly preferred by females at the timeof pair formation, tail elongation may have hampered the abilityof a male to guard his mate, resulting in an increase in extrapairfertilizations (EPFs). A significant negative correlation betweenthe number of EPFs and natural tail length in this experimentalstudy also suggests that tail streamer length may reflect malequality. (Behav Ecol 1990; 2: 90–98)