Rattlesnakes use chemical stimuli in ambush site selection and for relocation of envenomated prey through atrike-induced chemosensory searching. Shifts in responsiveness to prey chemicals have been documented in many ...Rattlesnakes use chemical stimuli in ambush site selection and for relocation of envenomated prey through atrike-induced chemosensory searching. Shifts in responsiveness to prey chemicals have been documented in many snakes, and often correlate with prey commonly taken as snakes increase in age and size as well as geographical locations of the species. For instance, neonate rattlesnakes that prey primarily on ectotherms responded most strongly to chemical cues of commonly taken lizard prey, whereas adult rattlesnakes that prey primarily on small mammals responded significantly to chemical cues of com- monly taken rodents. In the current study, 11 Prairie Rattlesnakes Crotalus viridis viridis which were classified as large neonates based on measures of snout-vent length （SVL） and body mass, yet chronologically were at or near adulthood, were tested for their responsiveness to chemical extracts of natural and non-natural prey items. Although the snakes had eaten only neonate lab mice （Mus musculus）, they responded significantly more to chemical cues of natural prey items and particularly to chemical cues of prey normally taken by subadults （Peromyscus mice and Sceloporus lizard）. These results suggest that ontogenetic shifts in re- sponsiveness to natural prey chemical cues are innately programmed and are not based on body size or feeding experience in C. v. viridis. This does not imply, however, that growth and experience are without effects, especially with novel prey or rare prey that have experienced recent population expansion [Current Zoology 59 （2）： 175-179, 2013].展开更多
Neuromuscular junction is the main target for snakebites, which venoms act depending on the snake genus for paralyzing the prey （neurotoxicity） or for facilitating the digestion processes of the victim （myotoxicity...Neuromuscular junction is the main target for snakebites, which venoms act depending on the snake genus for paralyzing the prey （neurotoxicity） or for facilitating the digestion processes of the victim （myotoxicity）, and also as a defense mechanism against predators. In the present study, a mouse neuromuscular apparatus was used for testing the hexane fraction of Casearia gossypiosperma plant, that showed the better antiophidian ability than dichloromethane, ethyl acetate and methanol fractions, against the irreversible paralysis induced by two, Bothrops jararacussu （Bjssu, 40 μg/mL） and Crotalus durissus terrificus （Cdt, 10 μg/mL） snake venoms. All fractions were obtained by liquid-liquid partition from the C. gossypiosperma hydroalcoholic lyophilized extract. The preliminary chromatographic profile of this plant showed phenols and flavonols as active constituents, whereas hexane fraction expressed mainly 13-sitosterol and quercetin. In spite of hexane fraction protection （≌95% and 48% against Bjssu and Cdt, respectively）, isolately, only quercetin protected against the blockade-induced by Bjssu venom （65.5%）. This study showed that hexane fraction acts against these snake venoms by a synergistic phytocomplex mechanism.展开更多
文摘Rattlesnakes use chemical stimuli in ambush site selection and for relocation of envenomated prey through atrike-induced chemosensory searching. Shifts in responsiveness to prey chemicals have been documented in many snakes, and often correlate with prey commonly taken as snakes increase in age and size as well as geographical locations of the species. For instance, neonate rattlesnakes that prey primarily on ectotherms responded most strongly to chemical cues of commonly taken lizard prey, whereas adult rattlesnakes that prey primarily on small mammals responded significantly to chemical cues of com- monly taken rodents. In the current study, 11 Prairie Rattlesnakes Crotalus viridis viridis which were classified as large neonates based on measures of snout-vent length （SVL） and body mass, yet chronologically were at or near adulthood, were tested for their responsiveness to chemical extracts of natural and non-natural prey items. Although the snakes had eaten only neonate lab mice （Mus musculus）, they responded significantly more to chemical cues of natural prey items and particularly to chemical cues of prey normally taken by subadults （Peromyscus mice and Sceloporus lizard）. These results suggest that ontogenetic shifts in re- sponsiveness to natural prey chemical cues are innately programmed and are not based on body size or feeding experience in C. v. viridis. This does not imply, however, that growth and experience are without effects, especially with novel prey or rare prey that have experienced recent population expansion [Current Zoology 59 （2）： 175-179, 2013].
文摘Neuromuscular junction is the main target for snakebites, which venoms act depending on the snake genus for paralyzing the prey （neurotoxicity） or for facilitating the digestion processes of the victim （myotoxicity）, and also as a defense mechanism against predators. In the present study, a mouse neuromuscular apparatus was used for testing the hexane fraction of Casearia gossypiosperma plant, that showed the better antiophidian ability than dichloromethane, ethyl acetate and methanol fractions, against the irreversible paralysis induced by two, Bothrops jararacussu （Bjssu, 40 μg/mL） and Crotalus durissus terrificus （Cdt, 10 μg/mL） snake venoms. All fractions were obtained by liquid-liquid partition from the C. gossypiosperma hydroalcoholic lyophilized extract. The preliminary chromatographic profile of this plant showed phenols and flavonols as active constituents, whereas hexane fraction expressed mainly 13-sitosterol and quercetin. In spite of hexane fraction protection （≌95% and 48% against Bjssu and Cdt, respectively）, isolately, only quercetin protected against the blockade-induced by Bjssu venom （65.5%）. This study showed that hexane fraction acts against these snake venoms by a synergistic phytocomplex mechanism.
