The Respiratory Transition from Water to Air Breathing During Amphibian Metamorphosis

SYNOPSIS. Profound developmental changes occur in the morphologyand physiology of the respiratory system of amphibians duringthe transition from strictly aquatic to dual aquatic-aerialbreathing. This developmental transition usually involves modificationsin ventilatory mechanisms and/or respiratory surfaces {e.g.,degeneration of gills, ventilation of functional lungs). Boththe first appearance of obligate air breathing and the subsequentdependence upon it by amphibian larvae are sensitive to a varietyof environmental stressors during critical developmental periods.These stressors include oxygen availability, ambient temperature,the risk of predation and mode of feeding.     

The Distribution of Halogeton Sativus (L.) C. A. Meyer in Morocco

In the search for natural enemies of Halogeton glomeratus (Bieb.)C. A. Meyer, a noxious weed introduced into the United States,studies were made, in 1959-61, on the distribution of H. sativus,a closely related species, occurring within Morocco. This plantis found in the Rif Mountains in the north, throughout the MoulouyaRiver Valley, along the Ziz River Valley, scattered along thesouthern slopes of the High Atlas Mountains as far west as Amerzgane,with an apparently discontinuous area of distribution on thenorthern slopes of the High Atlas in the vicinity of Asni.     

First International Workshop on Porcine Chromosome 6

Recent advances in the use of microsatellite markers and the development of comparative gene mapping techniques have made the construction of high resolution genetic maps of livestock species possible. Framework and comprehensive genetic linkage maps of porcine chromosome 6 have resulted from the first international effort to integrate genetic maps from multiple laboratories. Eleven highly polymorphic genetic markers were exchanged and mapped by four independent laboratories on a total of 583 animals derived from four reference populations. The chromosome 6 framework map consists of 10 markers ordered with high local support. The average marker interval of the framework map is 15.1 cM (sex averaged). The framework map is 135, 175 and 109 cM in length (for sex averaged, female and male maps, respectively). The comprehensive map includes a total of 48 type I and type II markers with a sex averaged interval of 3.5 cM and is 166, 196 and 126 cM (for sex averaged, female and male maps, respectively). Additional markers within framework map marker intervals can thus be selected from the comprehensive map for further analysis of quantitive trait loci (QTL) located on chromosome 6. The resulting maps of swine chromosome 6 provide a valuable tool for analysing and locating QTL.