Comparison of migratory tendency in European Quail Coturnix c. coturnix, domestic Japanese Quail Coturnix c. japonica and their hybrids

Since the 1970s, the decline of the occidental populations of European Quail Coturnix c. coturnix , a partial migrant Galliform species, has driven the release of domestic Japanese Quail Coturnix c. japonica into the wild as game birds. Recent experiments suggest that reproductive isolating mechanisms have not developed to prevent hybridization between European and Japanese Quail. To assess the potential impact of hybridization between the subspecies in the wild, this study aims to compare the migratory characteristics of captive European Quail, domestic Japanese Quail, F₁ hybrids and a backcross. In a laboratory experiment, birds hatched in summer and reared under a natural photoperiod were transferred during winter to an artificial photoperiod (light–dark) of 14 : 10 h. Behavioural (migratory restlessness, crowing activity in males) and physiological (sexual development, fat accumulation, body mass) measures were recorded. Domestic Japanese Quail showed no migratory tendency in response to the increased day length. F₁ hybrids showed rapid sexual development and few of them exhibited the typical profile of a migrant bird. Backcrosses showed great variation in their response, comparable with those of the European Quail. Therefore, hybridization could lead to an increased proportion of quail showing sedentary rather than migratory behaviour. Furthermore, hybrids that do show migratory behaviour have the potential to facilitate Japanese gene flow into areas where the release of domestic Quail as game birds is not yet practised.     

Variability in diapause propensity within populations of a temperate insect species: interactions between insecticide resistance genes and photoperiodism

Temperate insects generally use day length as a reliable cue for long-term seasonal changes in their environment. Significant variation in photoperiodism between and within populations is thought to be associated with genetic variation resulting from local adaptation. In this study, we investigated whether genetic variation associated with selection for insecticide resistance may be a source of divergence in the photoperiodic timing of diapause through pleiotropic interactions. Critical photoperiods for diapause induction were estimated in one susceptible and two insecticide-resistant homozygous strains of the codling moth Cydia pomonella , as well as in their reciprocal F₁ progeny. Diapause responses to naturally decreasing day length were subsequently followed in the laboratory strains and in two field populations of C. pomonella in south-eastern France. We found higher critical photoperiods for diapause induction in homozygous resistant individuals than in both homozygous susceptible and heterozygous ones. This partly explained the significantly earlier timings of diapause found in homozygous resistant individuals of both laboratory and field populations of C. pomonella under natural photoperiods, relative to those found in both homozygous susceptible and heterozygous ones. We assume that adaptive genetic changes associated with selection for insecticide resistance may generate substantial variation in the seasonal timing of diapause, an essential ecological feature of the fitness of insecticide resistance genes in this species.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 83 , 341–351.     

Lactate Dehydrogenase from Rhizobium. Purification and Role in Indole Metabolism

Cell-free extracts of Rhizobium meliloti contain a soluble lactate dehydrogenase (LDH-EC 1.1.1.27.). This was purified 250-fold by ammonium sulfate precipitation and filtration on different Sephadex gels. This enzyme catalyses the reduction of pyruvate to lactate in the presence of NADH and for the first time we report its ability to reduce indole-3-pyruvic acid (IPyA) to indole-3-lactic acid (ILA). Optimal conditions for activity and K_m values for both substrates were determined. In the presence of NAD the reverse reaction could be demonstrated with the aliphatic substrate (lactate), but under our conditions it was not possible to achieve the oxidation of ILA to IPyA. The role of this LDH in the indole metabolism is discussed and a general reaction scheme is suggested.