Digestive properties of the venom of the Australian Coastal Taipan, Oxyuranus scutellatus (Peters, 1867)

Venom Variation of Neonate and Adult Chinese Cobras in Captivity Concerning Their Foraging Strategies

The venom and transcriptome profile of the captive Chinese cobra (Naja atra) is not characterized until now. Here, LC-MS/MS and illumine technology were used to unveil the venom and trascriptome of neonates and adults N. atra specimens. In captive Chinese cobra, 98 co-existing transcripts for venom-related proteins was contained. A total of 127 proteins belong to 21 protein families were found in the profile of venom. The main components of snake venom were three finger toxins (3-FTx), snake venom metalloproteinase (SVMP), cysteine-rich secretory protein (CRISP), cobra venom factor (CVF), and phosphodiesterase (PDE). During the ontogenesis of captive Chinese cobra, the rearrangement of snake venom composition occurred and with obscure gender difference. CVF, 3-FTx, PDE, phospholipase A2 (PLA2) in adults were more abundant than neonates, while SVMP and CRISP in the neonates was richer than the adults. Ontogenetic changes in the proteome of Chinese cobra venom reveals different strategies for handling prey. The levels of different types of toxin families were dramatically altered in the wild and captive specimens. Therefore, we speculate that the captive process could reshape the snake venom composition vigorously. The clear comprehension of the composition of Chinese cobra venom facilitates the understanding of the mechanism of snakebite intoxication and guides the preparation and administration of traditional antivenom and next-generation drugs for snakebite.

The Role of Feeding Specialization on Post-Prandial Metabolic Rate in Snakes of the Genus Bothrops

Feeding specialization is a recurrent issue in the evolution of snakes and is sometimes associated to morphological and/or behavioral adaptations that improve snake performance to exploit a particular food type. Despite its importance for animal fitness, the role of physiological traits has been much less studied than morphological and behavioral traits in the evolution of feeding specialization in snakes. In this context, the energetic cost of post-prandial period is an important physiological factor due to the remarkable effect on the snake energy budget. We collected data on post-prandial metabolic rate (SDA) in five species of pit vipers from the genus Bothrops with different degrees of mammal feeding specialization to test the hypothesis that feeding specialist species have lower energy costs during the digestion of their regular food item when compared to species with a more generalist diet. Our results support this hypothesis and suggest that ontogenetic changes in diet can be accompanied by changes in energy cost of the digestion process.

Comparative proteomic analysis of the venom of the taipan snake, Oxyuranus scutellatus, from Papua New Guinea and Australia: role of neurotoxic and procoagulant effects in venom toxicity

The venom proteomes of populations of the highly venomous taipan snake, Oxyuranus scutellatus, from Australia and Papua New Guinea (PNG), were characterized by reverse-phase HPLC fractionation, followed by analysis of chromatographic fractions by SDS-PAGE, N-terminal sequencing, MALDI-TOF mass fingerprinting, and collision-induced dissociation tandem mass spectrometry of tryptic peptides. Proteins belonging to the following seven protein families were identified in the two venoms: phospholipase A(2) (PLA(2)), Kunitz-type inhibitor, metalloproteinase (SVMP), three-finger toxin (3FTx), serine proteinase, cysteine-rich secretory proteins (CRISP), and coagulation factor V-like protein. In addition, C-type lectin/lectin-like protein and venom natriuretic peptide were identified in the venom of specimens from PNG. PLA(2)s comprised more than 65% of the venoms of these two populations. Antivenoms generated against the venoms of these populations showed a pattern of cross-neutralization, corroborating the immunological kinship of these venoms. Toxicity experiments performed in mice suggest that, at low venom doses, neurotoxicity leading to respiratory paralysis represents the predominant mechanism of prey immobilization and death. However, at high doses, such as those injected in natural bites, intravascular thrombosis due to the action of the prothrombin activator may constitute a potent and very rapid mechanism for killing prey.

Digestive performance in neonatal Southern Pacific Rattlesnakes (Crotalus oreganus helleri)

Despite significant research on the metabolic characteristics of digestion in adult snakes, the digestive performance of neonatal snakes is poorly characterized. We examined the energetic costs associated with digestion and the energetic profit derived from the first meal eaten by neonatal Southern Pacific Rattlesnakes ( Crotalus oreganus helleri Meek, 1905). Composition of venom of C. o. helleri changes through ontogeny, becoming richer in proteolytic components that are hypothesized by some to enhance the rate of digestion. Therefore, we also investigated whether venom type (proteolytic-component-rich “adult” versus neurotoxin-rich “neonate” venom) affected digestive performance. We examined specific dynamic action (SDA), apparent assimilation efficiency, rate of digestion, and gut passage time in snakes fed prey killed with either “adult” or “neonate” venom at 22 and 30 °C. Although digestion progressed more quickly at 30 °C compared with 22 °C, there were no significant differences in digestion rate or assimilation efficiency owing to venom type; however, our statistical power was limited by small sample size. Despite the lack of “digestive experience”, the apparent assimilation efficiency was remarkably high (mean of 92%) and greater than published values for Crotalinae species. Based on these results, we hypothesize that neonatal C. o. helleri make a big energetic profit from their first meal by digesting efficiently and economically.

Characterisation of a mannose-binding C-type lectin from Oxyuranus scutellatus snake venom

C-type lectins are calcium-dependent sugar binding proteins and are distributed ubiquitously amongst vertebrate organisms. As part of a wider study on Australian snake venom components, we have identified and characterised a C-type lectin from the venom of Oxyuranus scutellatus (Australian coastal taipan) with mannose-binding activity. This protein exhibited a subunit molecular mass of 15 kDa and was found to bind mannose and also bind to and agglutinate erythrocytes in a Ca(2+)-dependent manner. cDNA transcripts coding for C-lectin proteins were cloned and sequenced from six Australian elapid snake species and an antibody generated against the O. scutellatus mannose-binding C-lectin identified C-lectin proteins in the venom of 13 Australian elapid snakes by immunoblotting. Experimental evidence and molecular modelling also suggest that this protein exhibits a unique dimeric structure. This is the first confirmed example of a snake venom C-lectin with mannose-binding activity.

Prey envenomation does not improve digestive performance in Taiwanese pit vipers (Trimeresurus gracilis and T. stejnegeri stejnegeri)

It has been a common belief that snake venom may help in the digestion of its prey, although direct examples and supporting evidence have not been sufficient. To address this, the present study examined whether preinjecting natural amounts of pit viper venom into experimental mice may accelerate their digestion by the snakes or gain energy benefit as compared to the control without the envenomation. Live adults of two Asian pit viper species Trimeresurus gracilis and T. stejnegeri stejnegeri, which inhabit the cold and warm environment respectively, were the subjects studied herein. A natural dose of 1.2 mg of each of the pit viper venom in phosphate-buffered saline (PBS) was injected into the mouse (about 10% of the snake mass) before it was being fed to the same species of vipers, while the pit vipers in control group were given mouse injected with sterile PBS. The snakes were kept at 14 degrees C or 24 degrees C, and parameters of gut passage time, costs of digestion, and/or digestive efficiency were measured. The results did not support the hypotheses that envenomation facilitates prey digestion. The venom in fact caused longer first defecation time and lower assimilation energy at 14 degrees C. Besides, the time to reach the oxygen consumption peak, and the first defecation time of T. s. stejnegeri were longer than that of T. gracilis.

Nucleotidase and DNase activities in Brazilian snake venoms

Among the myriad of enzymes present in animal venoms, nucleotidases and nucleases are poorly investigated. Herein, we studied such enzymes in 28 crude venoms of animals found in Brazil. Higher levels of ATPase, 5'-nucleotidase, ADPase, phosphodiesterase and DNase activities were observed in snake venoms belonging to Bothrops, Crotalus and Lachesis genera than to Micrurus genus. The venom of Bothrops brazili snake showed the highest nucleotidase and DNase activities, whereas that of Micrurus frontalis snake the highest alkaline phosphatase activity. On the other hand, the venoms of the snake Philodryas olfersii and the spider Loxosceles gaucho were devoid of most nucleotidase and DNase activities. Species that exhibited similar nucleotidase activities by colorimetric assays showed different banding pattern by zymography, suggesting the occurrence of structural differences among them. Hydrolysis of nucleotides showed that 1 mol of ATP is cleaved in 1 mol of pyrophosphate and 1 mol of orthophosphate, whereas 1 mol of ADP is cleaved exclusively in 2 mol of orthophosphates. Pyrophosphate is barely hydrolyzed by snake venoms. Phosphodiesterase activity was better correlated with 5'-nucleotidase, ADPase and ATPase activities than with DNase activity, evidencing that phosphodiesterases are not the main agent of DNA hydrolysis in animal venoms. The omnipresence of nucleotidase and DNase activities in viperid venoms implies a role for them within the repertoire of enzymes involved in immobilization and death of preys.