An association between the kinship and fertility of human couples

Previous studies have reported that related human couples tend to produce more children than unrelated couples but have been unable to determine whether this difference is biological or stems from socioeconomic variables. Our results, drawn from all known couples of the Icelandic population born between 1800 and 1965, show a significant positive association between kinship and fertility, with the greatest reproductive success observed for couples related at the level of third and fourth cousins. Owing to the relative socioeconomic homogeneity of Icelanders, and the observation of highly significant differences in the fertility of couples separated by very fine intervals of kinship, we conclude that this association is likely to have a biological basis.     

Atresia coli in a nine-week-old kitten

A case of blind-end atresia coli in a kitten surviving for 66 days is presented. Human cases of intestinal atresia are often attributed to injuries sustained in utero to a previously normal fetus. Neither clinical nor autopsy findings gave conclusive evidence regarding the aetiology of the condition in the kitten; the only sibling affected from a litter of five. The case is interesting because the kitten survived nine weeks without any clinical signs other than abdominal distension.     

Effects of temperature and body weight on growth rate and feed conversion ratio in turbot (Scophthalmus maximus)

Six size groups of hatchery produced turbot (2–499 g) were reared at six constant temperatures (10–25 °C). The results were used to develop a mathematical model for growth rate and feed conversion in turbot. At each temperature there were linear relationships between logarithms of (a) specific growth rate (G%/day) and body weight (W g), and (b) feed conversion ratio (FCR) and W. The slopes of the regressions were linearly related to temperature and the intercepts of the regression changed with temperature according to a second order polynomial. The optimal temperature for growth (T_opt.G) is predicted to decline with increasing body weight: T_opt.G = 22.45 − 0.713lnW, i.e. 22.5, 20.8, 19.1 and 17.5 °C for 1, 10, 100 and 1000 g fish, respectively, and the growth rates of these fish sizes at their optimal temperature (G_max) were predicted to be 7.63, 2.73, 1.03 and 0.40%/day, respectively. The optimal temperature for feed conversion (T_opt.FCR) is also predicted to decline with increasing fish size: T_opt.FCR = 18.80 − 0.625lnW, i.e. 18.8, 17.4, 15.9 and 14.5 °C for 1, 10, 100 and 1000 g fish, respectively, and the predicted feed conversions of these fish sizes (FCR_min) were 0.44, 0.56, 0.68 and 0.82 for the present feed types. The growth model predicts that 2 g turbot can reach 743 and 619 g in 1 year when reared at T_opt.G and T_opt.FCR, respectively.     

Genetic comparison of experimental farmed strains and wild Icelandic populations of Atlantic cod (Gadus morhua L.)

Microsatellite DNA loci and the Pantophysin locus (Pan I) were used to investigate levels of genetic diversity within farmed strains of Atlantic cod Gadus morhua and to compare them with the wild source population. A total of 282 farmed samples originating from a spawning ground off the south-west coast of Iceland were sampled in the years 2002 and 2003, and 258 wild cod were collected at the same spawning ground in the same years. The farmed strains exhibited a lower mean number of alleles and allelic diversity than the wild samples at the microsatellite loci. Significant differences were observed between wild and farmed samples both in allele and genotype frequencies at the Pan I locus. We argue that the genetic divergence of wild and farmed samples of Atlantic cod may be due to a small number of effective founding breeders contributing to the genetic variation of the farmed strains, inducing a reduction in allelic diversity. We discuss the potential effect of breeding practices on the genetic diversity of Atlantic cod.     

Increased mortality of fish due to changing Al-chemistry of mixing zones between limed streams and acidic tributaries

The present study is mainly focusing on mortality variations of fish due to changing Alchemistry of mixing zones. An artificial mixing zone was made by pumping water from a limed stream and an acidic tributary into a mixing channel. Atlantic salmon (Salmo salar L.) parr were exposed to the mixed water, limed stream water, and acidic tributary water. Mortality, blood haematocrit and plasma Cl^?-concentration were recorded. Neither mortality, nor changes in haematocrit and plasma Cl^? were observed when fish were exposed to limed water, while in both acidic and mixed water, mortalities and loss of plasma Cl^? were observed. The highest mortality rates were found within the initial part (0 to 20 s) of the mixing zone. Blood haematocrit increased only in fish exposed to acidic tributary water. Our results shows that changes in Al-chemistry and subsequent Al-polymerization occur when acidic tributary water is mixed with limed stream water. We have also demonstrated that the toxicity which can arise in mixing zones are greater than in the original acidic water before mixing. The variations in mortality observed are associated with the quality and quantity of Al-polymerization as well as ageing of the polymers.     

Vertebral column deformity with curved cross-stitch vertebrae in Norwegian seawater-farmed Atlantic salmon,Salmo salar L.

Pathological changes in the vertebral column of farmed Atlantic salmon in Norway have been reported since the 1990s. Based on the characteristic radiographic findings, we here present a vertebral column deformity named “curved cross-stitch vertebrae” that mainly affects the middle aspect of the vertebral column. Sixty fish, from the west/northwest coast of mid-Norway, were sampled at slaughter and examined by radiography, computed tomography (CT), necropsy, macrophotography, and histology. The vertebral deformities were radiographically graded as mild, moderate, or marked. The main differences between these grades of changes were defined by increased curving of the peripheries of endplates, reduced intervertebral spaces, and vertical displacement of the vertebrae. The curved rims of endplates were located peripheral to a continuous and approximately circular borderline. The CT studies revealed small, multifocal, hypo-attenuating, round to crescent-shaped areas in the notochord, compatible with the presence of gas. Additionally, histology revealed that the axial parts of endplates had circular zones with perforations, through which either notochordal tissue prolapsed into the vertebrae or vascularized fibrochondroid proliferations extended from the vertebrae into the notochord. Inflammation was present in many vertebral bodies. To the best of our knowledge, this is the first report of gas in the notochord of fish.     

Sequence variants in the RNF212 gene associate with genome-wide recombination rate

The genome-wide recombination rate varies between individuals, but the mechanism controlling this variation in humans has remained elusive. A genome-wide search identified sequence variants in the 4p16.3 region correlated with recombination rate in both males and females. These variants are located in the RNF212 gene, a putative ortholog of the ZHP-3 gene that is essential for recombinations and chiasma formation in Caenorhabditis elegans. It is noteworthy that the haplotype formed by two single-nucleotide polymorphisms (SNPs) associated with the highest recombination rate in males is associated with a low recombination rate in females. Consequently, if the frequency of the haplotype changes, the average recombination rate will increase for one sex and decrease for the other, but the sex-averaged recombination rate of the population can stay relatively constant.