sp.). ................................................................................ ................................................................................................................................................. 6 Participación de las Especies Reactivas de Ox. sp.). Hormones secreted by the male gonad early in gestation induce regression of potentially female structures and development of the male reproductive tract. En esta expedición se colectaron 16 especies durante un mes de trabajo de campo en la temporada seca (febrero), en cinco campamentos a alturas entre 1700 y 2100 m sobre el nivel del mar. pose two questions: (1) what are the molecular mechanisms responsible for the evolution of squamate viviparity? Biol Repro. A, lizard, Lacerta vivipara. ), una lagartija (Arthrosaura montigena, n. al segmento inicial mientras que las células claras se pro, activos y clasificaron los gránulos de secrec, almacenan en la cauda del epidídimo. Hinton, and M.C. En este documento se muestra, Las investigaciones realizadas en reptiles que involucran el estu, reproductiva, se han inclinado en aspectos que contemplan la identificación de su, capacidad de fertilizar al ovocito. Cienc. Cell Tissue Res, 1975. Artificial insemination of beef cattle and sheep is likely to increase, but not to the extent achieved for dairy cattle or swine. Mapa de distribución del genero Sceloporus [16]. Esto aumenta la abertura de las mandÃbulas y probablemente ayuda a llevar a la presa a la boca. The first scientific exploration followed immediately—the 1937–1938 Phelps Venezuelan Expedition of the American Museum of Natural History made the first zoological and general botanical collections. reproductora de este grupo tan amplio de organismos. Iguania). It was explored from the air by Jimmy Angel, a bush pilot and colorful soldier of fortune for whom the world's highest waterfall is named (Angel Falls at the northern end of Auyantepui). centriole, the number of mitochondria and dense-bodies sets, and the shape of mitochondria. Los camaleones y algunos otras lagartijas tienen colas prensiles, que también ayudan a agarrar las ramas. Access scientific knowledge from anywhere. Estadio 2. 163(4): p. 545-60. classical roles and current perspectives. Quiescencia (diciembre) [2], de espermatogonias y células de Sertoli entremezcladas, algunos túbulos presentan. ), a lizard (Arthrosaura montigena, n. Application of sexed semen in commercial dairy herds will be common, but its impact on other species of livestock may be marginal. The isolated droplet fraction was enriched in galactosyltransferase and sialyltransferase activities, and endogenous glycosylation assays identified the modification of several endogenous glycopeptides. The entire sperm duct system is under androgen control. Conversely, the purification and characterization of pituitary gonadotropin from different families of snake reveal the existence of a single gonadotropin that controls both testicular functions in squamates. Estadio 7. Oviposition is accomplished by interactions of the above hormones tempered by adrenergic innervation. By the year 2,000, spermatozoal motility, velocity and concentration probably will be measured by dipping a fiber optic probe into a semen sample. Epididymal spermatozoa were devoid of markers for the ER as well as the Golgi-associated coatamer protein beta-COP. Sin embargo, las montañas adyacentes que conforman el macizo fragmentado del Chimantá son relativamente cercanas y parecen presentar una herpetofauna unificada. 2. Vet., 2009. 1973. All rights reserved. This expedition collected 16 species during a month of fieldwork in the dry season (February), in five camps at elevations of 1700–2100 m above sea level. En algunas lagartijas, los osteodermos, que son placas óseas que se desarrollan en la dermis, subyacen a las escamas de la cabeza y del cuerpo. If the locomotor ‘costs’ of reproduction reflect all-or-none physiological changes associated with pregnancy, then the magnitude of such costs may correlate only weakly with the actual level of reproductive investment. Manipulation of the seasonal pattern in sperm production of rams and stallions also will be commonplace. siguiente, justo antes del apareamiento [31]. ................................................................................................................... .......................................................................................................... .............................................................................................................................. ...................................................................................................................... ........................................................................................................................ ................................................................................................................ ........................................................................................................... ................................................................................................ ................................................................................................... ........................................................................................................ ............................................................................................ ............................................................................ ....................................................................................................................... ................................................................................................................. ............................................................................................................... ............................................................................................................. ............................................................................................................ .................................................................................................................... ........................................................................................... ........................................................................................................................... ..................................................................................................... Este libro contiene una selección de artículos de las áreas de las Ciencias Biológicas y Ciencias.
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