Avaliação do desenvolvimento e das alterações morfológicas congênitas de uma ninhada xântica de cascavel Crotalus durissus terrificus nascida em cativeiro

Abstract

Xanthism is a chromatic anomaly of genetic origin, with the predominance of yellow pigment, xanthine, in the animal skin. Since it influences the animal survival, it is extremely rare in nature although some specimens reach the adult stage. Congenital malformations are alterations in fetal development and the causes may be genetic, environmental and sometimes unknown. This papper describe the development and congenital morphological alterations of a captive-born xanthic clutch of Crotalus durissus terrificus. In December 2015 and June 2016 two xanthic adult specimens of Crotalus durissus terrificus, one female and one male were registered at Serpent Reception Sector of the Instituto Butantan. The female was collected in Lindóia, São Paulo (22° 31' S and 46 ° 39' W), and the male in Socorro (22o 32' S and 46o 34' W), São Paulo, both cities located in the mesoregion of Campinas (SP). After the quarantine period, the animals were placed in one enclosure of the long-term exhibition of the Museu Biológico. In March 2018 a mating took place and in December, nine months later, the female gave birth to thirteen live newborns, 08 females, 04 males and one of unknown sex, all presenting the same pigmentation anomaly and some with congenital malformations. Morphological and motor evaluations were performed biweekly and biometric quarterly (mass and snout-vent length - SVL). In motor evaluation the following parameters were considered: (1) reaction of postural straightening (RPS), (2) locomotion, (3) muscular tonus and (4) head tonus. Complementary radiographic examinations were also performed. Of the 13 born, three died before the start of the evaluations. In the morphological evaluation it was possible to observe the following alterations in two animals: microphthalmia, malformation in the scales, alteration in the insertion of the tongue and bones alterations. Imaging exams found the absence of some sacral vertebrae. The two juveniles that presented motor alterations died the following month, while the other animals remain unchanged so far. It is possible that the deaths that occurred were due to the expression of deleterious genes by crossing recessive individuals. According to the literature, it is difficult to determine the cause of congenital malformations, but it is believed that the interaction between genetic and environmental factors are important in their incidence.