Latitudinal clines in body size,but not in thermal tolerance or heat‐shock cognate 70 (HSC70), in the highly‐dispersing intertidal gastropod Littorina keenae (Gastropoda: Littorinidae)

Natural populations of widely‐distributed animals often exhibit clinal variation in phenotypic traits or in allele frequencies of a particular gene over their geographical range. A planktotrophic intertidal snail, Littorina keenae is broadly distributed along the north‐eastern Pacific coast through a large latitudinal range (24°50′N–43°18′N). We tested for latitudinal clines in two complex phenotypic traits – thermal tolerance and body size – and one single locus trait – heat shock cognate 70 (HSC70) – in L. keenae along almost its entire geographical range. We found only weak evidence for a latitudinal cline in the thermal tolerance and no evidence for a cline in allele frequencies at HSC70. However, as predicted by Bergmann's rule, we detected a strong latitudinal cline that accounted for 60% of the variance in body size (R² = 0.598; P < 0.001). In contrast, body size did not significantly affect thermal tolerance. HSC70 showed no genetic differentiation among the populations, supporting our previous mitochondrial gene‐based estimate of high gene flow during this snail's free‐swimming larval stage. Given that L. keenae experiences panmixia along its species range, the observed size cline may be partially or entirely caused by a phenotypically plastic response to local thermal environments rather than by genetic divergence in body size among populations in response to locally optimizing natural selection. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100 , 494–505.     

Expression of 5HT-1A and 5HT-1B receptor genes in brains of Wistar-Zagreb 5HT rats

By selective breeding, two sublines of rats with high or low activity of platelet serotonin (5HT) transporter (5HTt) have been developed (Wistar-Zagreb 5HT rats). Previous studies demonstrated significant differences between the sublines in the expression of platelet 5HTt at the level of both, mRNA and protein. Pharmacological studies showed marked alterations in brain 5HTt function, indicating differences in central serotonin homeostasis, although analysis of regional brain 5HTt gene expression did not show analogous differences. In this study, we searched for possible changes in the expression of the two central 5HT receptor subtypes: 5HT-1A and 5HT-1B, both participating in the regulation of brain 5HT transmission. Semi-quantitative RT-PCR, with three different housekeeping genes as internal standards, showed no differences in the levels of 5HT-receptor expression between the sublines. Results suggest that constitutional alteration of 5HT homeostasis, induced by selective breeding for the extremes of platelet 5HTt activity, did not cause measurable changes in the expression of central 5HT-1A (hippocampus) and 5HT-1B (striatum) receptors in the mentioned rat sublines under physiological conditions.     

Biochemical characterization of three nucleopolyhedrovirus isolates of Spodoptera exigua and Mamestra brassicae

Three nucleopolyhedroviruses (NPVs), of different geographical origins, were biochemically characterized and compared. Two that were isolated from Spodoptera exigua (Se-UZB and Se-SP3) in Uzbekistan and Spain were SeMNPV type, and the third which was isolated from Mamestra brassicae (Mb-PL) in Poland was MbMNPV type. The Spanish isolate Se-SP3 showed restriction endonuclease (REN) profiles that were closely related to two previously described Spanish strains Se-SP1 and Se-SP2, but had some unique and characteristic REN fragments. On the other hand, comparison between the Uzbekian (Se-UZB) and the Spanish (Se-SP1, Se-SP2, and Se-SP3) isolates from S. exigua showed unrelated REN profiles. However, the Pst I and Bgl II profiles of Se-UZB and Mb-PL were identical, and very similar to the REN profiles of the MbMNPV strain, which constitutes the active component of Mamestrin^® (NPP, Nagueres, France), a commercial bioinsecticide. It is therefore very likely that the Se-UZB samples were cross-infected by the Polish strain (Mb-PL). This work presents two new strains of SeMNPV and MbMNPV, called Se-SP3 and Mb-PL, respectively, which were surveyed in two distant areas.     

Rise of oceanographic barriers in continuous populations of a cetacean: the genetic structure of harbour porpoises in Old World waters

Background

Understanding the role of seascape in shaping genetic and demographic population structure is highly challenging for marine pelagic species such as cetaceans for which there is generally little evidence of what could effectively restrict their dispersal. In the present work, we applied a combination of recent individual-based landscape genetic approaches to investigate the population genetic structure of a highly mobile extensive range cetacean, the harbour porpoise in the eastern North Atlantic, with regards to oceanographic characteristics that could constrain its dispersal.

Results

Analyses of 10 microsatellite loci for 752 individuals revealed that most of the sampled range in the eastern North Atlantic behaves as a 'continuous' population that widely extends over thousands of kilometres with significant isolation by distance (IBD). However, strong barriers to gene flow were detected in the south-eastern part of the range. These barriers coincided with profound changes in environmental characteristics and isolated, on a relatively small scale, porpoises from Iberian waters and on a larger scale porpoises from the Black Sea.

Conclusion

The presence of these barriers to gene flow that coincide with profound changes in oceanographic features, together with the spatial variation in IBD strength, provide for the first time strong evidence that physical processes have a major impact on the demographic and genetic structure of a cetacean. This genetic pattern further suggests habitat-related fragmentation of the porpoise range that is likely to intensify with predicted surface ocean warming.     

Contractile behavior of the forelimb digital flexors during steady-state locomotion in horses (Equus caballus): an initial test of muscle architectural hypotheses about in vivo function

The forelimb digital flexors of the horse display remarkable diversity in muscle architecture despite each muscle-tendon unit having a similar mechanical advantage across the fetlock joint. We focus on two distinct muscles of the digital flexor system: short compartment deep digital flexor (DDF(sc)) and the superficial digital flexor (SDF). The objectives were to investigate force-length behavior and work performance of these two muscles in vivo during locomotion, and to determine how muscle architecture contributes to in vivo function in this system. We directly recorded muscle force (via tendon strain gauges) and muscle fascicle length (via sonomicrometry crystals) as horses walked (1.7 m s(-1)), trotted (4.1 m s(-1)) and cantered (7.0 m s(-1)) on a motorized treadmill. Over the range of gaits and speeds, DDF(sc) fascicles shortened while producing relatively low force, generating modest positive net work. In contrast, SDF fascicles initially shortened, then lengthened while producing high force, resulting in substantial negative net work. These findings suggest the long fibered, unipennate DDF(sc) supplements mechanical work during running, whereas the short fibered, multipennate SDF is specialized for economical high force and enhanced elastic energy storage. Apparent in vivo functions match well with the distinct architectural features of each muscle.     

Demographic Data of a Population of Insured Swedish Dogs Measured in a Questionnaire Study

Dogs, in the age range 1–3 years old, were randomly selected from the largest animal insurance database in Sweden for inclusion in the study. The study was performed in 1997, and a total of 680 dog owners were selected for the study. A total of 461 dog owners completed the survey, at an overall response rate of 68%. Data was compared to a recent gallup performed on a sample of all dogs in Sweden. The demographic statistics of the insured dog population were in many aspects similar to the total dog population of Sweden. Typical for both insured dogs and the total population of dogs were a low proportion of neutered dogs, that many dogs were bought at an early age, that many dogs were in contact with a "breeder" when sold, and a similar profile of health status. However, "dog breeders" seemed to have their dogs insured to a higher extent than the general dog owner. It was concluded that as the populations were alike in many respects, it is reasonable to use the insurance database for epidemiological studies on diet and exercise in Swedish dogs.     

Technical variations of the bipedicled TRAM flap in unilateral breast reconstruction: effects of conventional versus microsurgical techniques of pedicle transfer on complications rates

In cases of unilateral breast reconstruction with a transverse rectus abdominis musculocutaneous (TRAM) flap, poorly perfused tissue, which is normally excised to avoid subsequent fat necrosis, must sometimes be used to achieve adequate breast size and projection. In such cases, incorporation of a second vascular pedicle into the flap design improves perfusion. The authors retrospectively examined their experience with bipedicled TRAM flap-based unilateral breast reconstruction to determine whether the use of microsurgical rather than conventional (nonmicrosurgical) techniques for flap transfer resulted in lower incidences of flap-site fat necrosis and donor-site hernia/bulge. The authors retrospectively reviewed the medical records of all patients who underwent unilateral breast reconstruction with a bipedicled TRAM or deep inferior epigastric perforator flap between January of 1991 and March of 2001. Group 1 consisted of patients who had undergone flap transfer using a conventional technique for both pedicles; group 2, patients who had flap transfer using a conventional technique for one pedicle and a microsurgical technique for the other; and group 3, patients who had flap transfer using a microsurgical technique for both pedicles. Of the 863 patients identified, 72 (8.3 percent) had undergone reconstruction using a bipedicled flap. There were 43 patients in group 1, 24 patients in group 2, and five patients in group 3. Only one case of total flap loss had occurred (group 1). Partial flap loss occurred in two patients in group 1 (5 percent) and three patients in group 2 (13 percent). Fat necrosis occurred more frequently in groups 1 (23 percent) and 2 (29 percent) than in group 3 (0 percent) (p = 0.5, Fisher's exact test). Similarly, bulge or hernia was more common in groups 1 (12 percent) and 2 (4 percent) than in group 3 (0 percent) (p = 0.6, Fisher's exact test). In this study, patients who received a bipedicled TRAM flap using microsurgical techniques alone (group 3) appeared to have better flap perfusion and less frequent hernia/bulge than did patients who underwent flap transfer using conventional (group 1) or combined techniques (group 2). However, these differences were not statistically significant, and this trend must be verified in a larger study.     

DNA-DNA hybridization evidence of the rapid rate of muroid rodent DNA evolution

Single-copy nuclear DNAs (scnDNAs) of eight species of arvicoline and six species of murine rodents were compared using DNA-DNA hybridization. The branching pattern derived from the DNA comparisons is congruent with the fossil evidence and supported by comparative biochemical, chromosomal, and morphological studies. The recently improved fossil record for these lineages provides seven approximate divergence dates, which were used to calibrate the DNA-hybridization data. The average rate of scnDNA divergence was estimated as 2.5%/Myr. This is approximately 10 times the rate in the hominoid primates. These results agree with previous reports of accelerated DNA evolution in muroid rodents and extend the DNA-DNA hybridization data set of Brownell.