Observations on the Fetal Morphology in Myocastor Coypus Bonariensis (Coypu) (Rodentia, Myocastoridae)

Abstract

The goal of this work was to characterize the morphology of fetuses of Myocastor coypus bonariensis (coypu) after 60, 90, 120 and 135 days post-coitus (d.p.c.). At all the ages, gestational sacs showed an elliptical shape. Placentas were discoidal, with a unilobular external appearance in fetuses of 60 d.p.c. and with lobulations separated by a groove in fetuses of other ages. The umbilical cord, wrapped around the fetal body, showed a proximal dilatation in 60-d.p.c. fetuses, being its course uniform and a little spiral in the other ages. The 60-d.p.c. fetuses showed differentiation of corporal regions, prominent encephalic vesicles and little developed earlobes located in the laterals of the skull, in the limit with the cervical area and in straight line with the optical vesicles. The primitive forelimbs showed differentiation of arm, forearm and hand. In the hindlimbs, the inter-digital membrane was observed joining the fingers along all their length. Fetuses of 90 d.p.c. showed developed eyelids and closed palpebral cleft, developed auricular pavilions (earlobes), hairy follicles in the facial region (vibrissae) and in the skull and bent limbs. Fetuses of 120 and 135 d.p.c. showed a bodily cover constituted by a dense pilous covering, spread palpebral clefts, open mouth, bent limbs and inter-digital membranes in the hindlimbs.