Polymorphism and Ultrastructure of a Colpodean Ciliate of the Genus Platyophryides Foissner, 1987

ABSTRACT. A ciliate isolated from a pond in Brazil, transformed to a giant form when its food was shifted from a bacterial prey to a ciliate prey. This polymorphism is immediately reversible when the prey ciliates, either Tetrahymena or Colpidium , disappear from the culture medium. By its life cycle, morphology, and ultrastructure, this ciliate belongs to the Class Colpodea. it could belong to the genus Platyophryides Foissner, 1987, except that its micronucleus is not enveloped by the macronuclear membrane. The systematic position of the genus Platyophryides , the validity of the three species in this genus, and the characteristics of the Cyrtolophosidida are discussed.     

On the origin and colonization of house mice in the Madeira Islands

The skulls and skins of adult house mice from the Madeira Islands have been studied and compared with those from the Salvage Islands and with material from the neighbouring Portuguese mainland man-associated and wild forms, respectively Mus musclus domesticus Rutty, 1772 and M. sprelus Lataste, 1883. Differences between island and mainland populations were found in some of the analysed features. Insular skins of mice were found to be smaller than those of specimens from the mainland. However, in Madeiran and Salvage mice the toothrows were much more developed than in the mainland house mice. It is considered that the causes of these differences lie in the different characteristics of the habitats, mainly food availability, and also in the isolation of populations. Mus musculus domesticus appears to be the only form of the house mouse to have so far successfully colonized the Madeiras.     

Deficiencies in sex-regulated expression and levels of two hepatic sterol carrier proteins in a murine model of Niemann-Pick type C disease.

Hepatic sterol carrier protein-2 (SCP2) and sterol carrier protein-X (SCPx) levels in normal and in mutant Niemann-Pick Type C mice were determined by immunoblotting with antiserum against rat SCP2. A 14-kDa protein (SCP2) was detected in the cytosol fraction and a 58-kDa protein (SCPx) was found in both cytosolic and organellar fractions. Expression of hepatic SCPx protein was developmentally regulated in a sex-specific pattern. The amounts of organelle-associated SCPx increased 4-fold during sexual development of normal males but decreased dramatically during development of normal females. Levels of hepatic SCP2 increased much less dramatically during sexual maturation of normal males and females. Adult Niemann-Pick Type C mice were deficient in both hepatic SCPx and SCP2. The deficit in SCPx in affected males reflected a failure to increase hepatic SCPx levels during sexual maturation. In affected males SCPx remained at levels found in immature mice. Affected male and female mice were also unable to maintain levels of hepatic SCP2. The level of SCP2 was near normal in affected immature males and subnormal in affected immature females. During sexual maturation hepatic SCP2 declined in affected animals.     

ADAPTATION TO SEASONALITY IN A CRICKET: PATTERNS OF PHENOTYPIC AND GENOTYPIC VARIATION IN BODY SIZE AND DIAPAUSE EXPRESSION ALONG A CLINE IN SEASON LENGTH

This paper investigates patterns of phenotypic variation in the striped ground cricket (Allonemobious fasciatus) along a cline in season length and tests the hypothesis that variation in body size and diapause propensity is the result of diversifying selection due to different local conditions. We examined 83 populations and found that A. fasciatus produced a single generation per year (univoltine) north of 37°N latitude and was bivoltine south of 35°30′N. Body size generally increased with increasing season length, with a sudden drop in the region corresponding to the transition from univoltine to bivoltine life cycles, reflecting the division of total season length in two within-bivoltine populations. We reared ten populations in our laboratory and found that much of the interpopulation variance in body size observed in the field could be attributed to genetic differences. Diapause expression also varied significantly among populations and was strongly correlated with season length. The heritability of body size did not differ between populations, but full-sib estimates greatly exceeded parent–offspring estimates suggesting that there are important nonadditive genetic effects. The heritability of diapause expression, determined from analysis of full sibs, varied significantly between populations (0.33 ± 0.10 to 1.31 ± 0.21) with an average of 0.74 ± 0.16. Body size and diapause expression were genetically correlated in transition-zone populations, but not in univoltine or bivoltine populations. Our findings support the suggestion that clinal variation in body size and diapause expression in the striped ground cricket reflect adaptation to season length.     

A Comparison of the Use of In Vitro-Transcribed and Native rRNA for the Quantification of Microorganisms in the Environment

Abstract Nearly full-length, small subunit (SSU) rRNA was transcribed in vitro from clones of SSU rDNA genes. Comparing the use of in vitro-transcribed and native rRNA indicated that, when in vitro-transcribed rRNA was used as a standard for quantitative hybridizations with oligonucleotide probes, the population was consistently underestimated. The population abundance was expressed as a percentage of specific target SSU rRNA (determined with a specific oligonucleotide probe), relative to the total SSU rRNA (measured with a universal probe). Differences in hybridization signals could be related to specific probe target locations and rRNA denaturation conditions, suggesting that higher order structure is important in quantitative membrane hybridizations. Therefore, in vitro-transcribed rRNA cannot always be used for the absolute quantification of microbial populations, but can be employed as a standard to quantify shifts in population abundance over time, and to compare community structure in various environments.