Small-eyed Snake Research Articles

HERPETOFAUNA DAN HABITATNYA DI AREA FAKULTAS KEHUTANAN UNIVERSITAS PAPUA, MANOKWARI

Herpetofauna is a group of animal that make up the ecosystem and has an important role both ecologically and economically. Along with the fragmentation of ​​the Faculty of Forestry area at the University of Papua due to campus development, the diversity of the existing Herpetofauna may change. Therefore, this study aims to investigate the diversity of Herpetofauna and the habitat in the area of Faculty of Forestry at the University of Papua. The collection of data was carried out for one month using visual encounter survey with timed count technique. The results showed that there were 14 species of Herpetofauna consisting of one species of Frog (Platymanthis papuensis), ten species of lizards (Sphenomorphus muelleri, Sphenomorphus jobiensis, Emoia caeruleocauda, ​​Emoia jakati, Eutrophis multifasciata, Nactus pelagicus, Lemprolephis smaragdina, Cyrtodactylus sp., Gehira sp. and Hemydactylus frenatus) and three species of snakes (Micropechis ikaheka, Boiga irregularis and Candoia carinata). The most of Herpetofauna were found in the Arboretum Fahutan, seven species. Amphibians are only found at night while lizards and snakes were discovered both during the day and at night.

Can a common snake provide conservation insights?

The small-eyed snake (Cryptophis nigrescens) is a common non-threatened species in eastern Australia. It coexists with the threatened broad-headed snake (Hoplocephalus bungaroides), a species adversely affected by habitat disturbance and subject to poaching. The small-eyed snake is a habitat generalist and not subject to poaching. It may prey on other snakes, including the broad-headed snake, and, like the broad-headed snake, may shelter under thermally favourable loose rocks during the cooler months of the year. This may lead to interactions between these species due to the limited availability of such rocks, and possibly exacerbate other threats to the broad-headed snake, such as poaching and the loss of thermally favourable rocks. I conducted repeat surveys for snakes at 64 rock outcrops in Royal National Park over a 16-year period. I predicted that site use by the small-eyed snake would not be influenced by a disturbance variable previously documented to influence site use by the broad-headed snake. Observations were consistent with this prediction, confirming the unique vulnerability of the broad-headed snake. I used my long-term data to analyse the co-occurrence of the two species. The broad-headed snake was detected as frequently at sites with and without the small-eyed snake, suggesting that these species occupy outcrops independently of each other. Therefore, interactions with the small-eyed snake will not reduce the effectiveness of habitat restoration for the broad-headed snake in Royal National Park.

Absolute venomics: Absolute quantification of intact venom proteins through elemental mass spectrometry

We report the application of a hybrid element and molecular MS configuration for the parallel absolute quantification of μHPLC-separated intact sulfur-containing venom proteins, via ICP triple quadrupole MS and 32S/34S isotope dilution analysis, and identification by ESI-QToF-MS of the toxins of the medically important African black-necked spitting cobra, Naja nigricollis (Tanzania); New Guinea small-eyed snake, Micropechis ikaheka; and Papuan black snake, Pseudechis papuanus. The main advantage of this approach is that only one generic sulfur-containing standard is required to quantify each and all intact Cys- and/or Met-containing toxins of the venom proteome. The results of absolute quantification are in reasonably good agreement with previously reported relative quantification of the most abundant protein families. However, both datasets depart in the quantification of the minor ones, showing a tendency for this set of proteins to be underestimated in standard peptide-centric venomics approaches. The molecular identity, specific toxic activity, and concentration in the venom, are the pillars on which the toxicovenomics-aimed discovery of the most medically-relevant venom toxins, e.g. those that need to be neutralized by an effective therapeutic antivenom, should be based. The pioneering venom proteome-wide absolute quantification shown in this paper represents thus a significant advance towards this goal. The potential of ICP triple quadrupole MS in proteomics in general, and venomics in particular, is critically discussed. Biological significanceAnimal venoms provide excellent model systems for investigating interactions between predators and prey, and the molecular mechanisms that contribute to adaptive protein evolution. On the other hand, numerous cases of snake bites occur yearly by encounters of humans and snakes in their shared natural environment. Snakebite envenoming is a serious global public health issue that affects the most impoverished and geopolitically disadvantaged rural communities in many tropical and subtropical countries. Unveiling the temporal and spatial patterns of venom variability is of fundamental importance to understand the molecular basis of envenoming, a prerequisite for developing therapeutic strategies against snakebite envenoming. Research on venoms has been continuously enhanced by advances in technology. The combined application of next-generation transcriptomic and venomic workflows has demonstrated unparalleled capabilities for venom characterization in unprecedented detail. However, mass spectrometry is not inherently quantitative, and this analytical limitation has sparked the development of methods to determine absolute abundance of proteins in biological samples. Here we show the potential of a hybrid element and molecular MS configuration for the parallel ESI-QToF-MS and ICP-QQQ detection and absolute quantification of intact sulfur-containing venom proteins via 32S/34S isotope dilution analysis. This configuration has been applied to quantify the toxins of the medically important African snake Naja nigricollis (Tanzania), and the Papuan species Micropechis ikaheka and Pseudechis papuanus.

A New Species of New Guinea Worm-Eating Snake, GenusToxicocalamus(Serpentes: Elapidae), From the Star Mountains of Western Province, Papua New Guinea, With a Revised Dichotomous Key to the Genus

Abstract We describe a new species of New Guinea vermivorous snake (Toxicocalamus) from a single specimen collected at Wangbin in the Star Mountains, Western Province, Papua New Guinea. The new species is the largest known member of the genus and can be differentiated from all other Toxicocalamus by a combination of the following characters: large size (total length of the holotype 1,200 mm), dorsal head scutes in the typical “colubrid-elapid dorsal nine-scute arrangement”; separate, single preocular and paired postoculars; single anterior temporal and single or paired posterior temporals; six supralabials, with third and fourth supralabial contacting the orbit; dorsal scales in 15–15–15 rows; 203 ventral scales, 29 subcaudal scales; and a divided anal plate. Its erstwhile status, misidentified as Micropechis ikaheka in the collection of the Museum of Comparative Zoology, demonstrates the need for detailed examination of existing collections and is indicative of hidden diversity yet to be identified, not ...

Combined venom gland cDNA sequencing and venomics of the New Guinea small-eyed snake, Micropechis ikaheka.

The poorly understood venom proteome of the New Guinea small-eyed snake, Micropechis ikaheka, a large and powerfully built elapid endemic to Papua New Guinea and Indonesian West Papua province, was investigated through a combined venomics and venom gland transcriptomics approach. Although M. ikaheka accounts for only a small proportion of snakebites on the mainland, 40% of snakebites on Karkar Island are attributed to bites by this snake. Major effects of envenomings include life-threatening post-synaptic neuromuscular blockade resulting in respiratory paralysis, myotoxicity, severe bleeding, hypotension and cardiovascular abnormalities. We have investigated the contribution of 3FTxs and PLA₂ molecules in venom lethality, myotoxicity, and cardiovascular function. Our work provides important correlations between venom composition and its pharmacological activity. In conjunction with the antivenomics work reported in the companion paper, our study may contribute to improve treatment outcomes for snakebite victims of M. ikaheka.

Preclinical efficacy of Australian antivenoms against the venom of the small-eyed snake, Micropechis ikaheka, from Papua New Guinea: An antivenomics and neutralization study

There is no specific antivenom for the treatment of envenoming by the small-eyed snake, Micropechis ikaheka, a dangerous fossorial species endemic to Papua New Guinea, Irian Jaya (West Papua) and neighbouring islands. This study evaluated one marine (sea snake) and four terrestrial (tiger snake, brown snake, black snake and polyvalent) antivenoms, manufactured in Australia by bioCSL Limited, for their ability to immunoreact ('antivenomic' analysis) and neutralize enzymatic and toxic activities of M. ikaheka venom. All antivenoms neutralized lethality of the venom and attenuated, dose-dependently, myotoxic activity. The polyvalent antivenom also neutralized cardiotoxic activity. In contrast, antivenoms were ineffective in the neutralization of phospholipase A₂ (PLA₂) and anticoagulant activities. Antivenomics outcomes were in concordance with neutralization tests, for chromatographic peaks corresponding to α-neurotoxins of the three finger family, responsible for lethality, were quantitatively retained in the immunoaffinity columns, whereas peaks corresponding to PLA₂s were immunocaptured only to a partial extent. The ability of antivenoms to neutralize lethal, i.e. neurotoxic, and myotoxic activities of M. ikaheka venom, which represent the most relevant clinical manifestations of envenoming, suggests that these antivenoms may provide paraspecific protection in humans, although the poor neutralization of PLA₂ supports the need for well-designed clinical studies to not only determine which antivenoms are most appropriate for treatment of M. ikaheka envenoming, but to also fully describe the syndrome of envenoming caused by this beautiful, but lethal species. Snakebite by the small-eyed snake, Micropechis ikaheka, in Papua New Guinea can be life-threatening. The predominant clinical features in this envenoming are neurotoxicity and systemic myotoxicity. Although it accounts for only a small proportion of snakebites on the mainland, 40% of snakebites on Karkar Island are attributed to bites by the Ikaheka snake. However, no specific antivenom is available for the treatment of M. ikaheka envenoming in Papua New Guinea. This study evaluated a panel of Australian bioCSL antivenoms for their paraspecific immunoreaction and neutralization of the toxic activities of M. ikaheka venom. All antivenoms exhibited strong immunorecognition of α-neurotoxins of the 3FTx family and neutralized the lethal, i.e. neurotoxic, and myotoxic activities of M. ikaheka venom. However, these antivenoms exhibited poor neutralization of PLA₂ and anticoagulant activities. This study suggests that the Australian antivenoms may provide paraspecific protection against M. ikaheka venom in humans, a hypothesis that demands studies aimed at assessing whether these antivenoms neutralize neurotoxicity and myotoxicity in the clinical setting.

Chemosensory discrimination of social cues mediates space use in snakes, Cryptophis nigrescens (Elapidae)

Snakes have traditionally been viewed as solitary, asocial animals whose habitat use is driven by temperature, prey and predators. However, recent studies suggest that snake spatial ecology may also be socially mediated. We examined the influence of conspecific chemical cues on refuge selection in a small nocturnal snake (the small-eyed snake) that engages in male contest competition. Females preferred refuges containing scent cues from conspecifics (of either sex) rather than scentless refuges. Males preferred female-scented rather than male-scented refuges, and preferred the scent of larger (and hence, more fecund) females than smaller females. Males spent more time in refuges containing the scent of smaller rather than larger males, but males that lost a contest did not avoid the refuge scented by the winner and therefore did not show evidence of the winner–loser effect. Females preferred refuges scented by larger males. Small-eyed snakes can distinguish conspecific sex and body size using chemical cues, and they use these cues to select alternative refuge sites. We suggest that social factors play a significant role in driving snake spatial distribution patterns in the wild and that snakes may exhibit more complex social systems than has generally been believed.

Skin Histology and Microtopography of Papuan White Snake (Micropechis ikaheka) in Relation to Their Zoogeographical Distribution

Papuan white snake ( Micropechis ikaheka ) is endemic to New Guinea (the region of the Papua and Papua New Guinea). Internal histology of skin layer and the microtopography structure on the surface scales of M. ikaheka were the aims of the study. This study also related to zoogeographical of the snake in Papua. Geographical skin color variation of M. ikaheka can be described in three groups, i.e. brown, yellow and black group. The three groups of the snake have specific zoogeography in the mainland of Papua and satellite islands to Papua New Guinea. Paraffin method used in this work showed approximately five layers i.e. oberhautchen, the beta ( b ) - layer, the mesos layer, the alpha ( a ) - layer, and the dermis in the snake skin. Although the paraffin method cannot explain the arrangement of pigment cells, however, the dark color on the dermis might contain melanophores that might cause dark color of the snake body. Overlapping scales formed the hinge region were flexible to assist the snakes when they moved across substrate. Scanning electron microscopy (SEM) of the oberhautchen of all of M. ikaheka revealed no microornamentation . However, dorsal and ventral scales showed many follicles on the entire surface of the boundary scales.

Area Distribusi dan Variasi Morfologi Ular Putih (Micropechis ikaheka) di Papua

<em>The objectives of the research were to identify the area of distribution and the specific habitat of the white snake (Micropechis ikaheka) in Papua (Western New Guinea), and to explain the morphological variation among the populations of that snake.  About eight months of field work were taken to conduct the survey (April 2002; June 2006; and March to Augusts 2007) in several areas in the mainland and off-shore islands of Papua. Observation were carried out in the field at night and during the day to collect the snake. The studies were done on a collection of specimens that were found in the Museum Zoologicum Bogoriense LIPI in Cibinong, Conservation International in Jayapura and the Biology Laboratory of the Papua State University in Manokwari.The results showed that the white snake Micropechis ikahekacan be divided into three separate groups based on the color of the scales, i.e. Black, Brown and Yellow. The black one is the new group found in this research, and also there was one individual snake with transitional coloration between the brown group and the yellow group. However, M. ikahekais common and has a relatively wide distribution in New Guinea, but every group has a specific and limited area of distribution. The group with black color is distributed in the islands of Waigeo and Batanta and the group with yellow color is distributed from Manokwari, Sorong, upto the islands of Salawati, Batanta and Waigeo. Meanwhile, the brown colored sanke is distributed from the island of Yapen, mainland of Waropen, Mamberamo,  Jayawijaya, Mindiptana up to Papua New Guinea.</em>

Olfactory recognition of predators by nocturnal lizards: safety outweighs thermal benefits

Many prey species are faced with multiple predators that differ in the degree of danger posed. The threat-sensitive predator avoidance hypothesis predicts that prey should assess the degree of threat posed by different predators and match their behavior according to current levels of risk. To test this prediction, we compared the behavioral responses of nocturnal velvet geckos, Oedura lesueurii, to chemicals from 2 snakes that pose different threats: the dangerous broad-headed snake Hoplocephalus bungaroides that eats geckos and the less dangerous small-eyed snake Cryptophis nigrescens that eats skinks (i.e., does not consume geckos). We also tested whether predator avoidance by prey was modulated by thermal costs associated with retreat-site selection. In both the presence and absence of thermal costs, velvet geckos avoided crevices scented by both dangerous and less dangerous snake species. When given the choice between a crevice scented by a broad-headed snake and a crevice scented by a small-eyed snake, most geckos avoided either retreat site. These results suggest that velvet geckos treat both snake predators as equally dangerous. To further explore these results, we quantified patterns of retreat-site selection by free-living velvet geckos on 2 sandstone plateaux. As in the laboratory, velvet geckos avoided thermally suitable rocks previously used by both snake species. Hence, a gecko's choice of retreat site is influenced by the presence of snake chemicals but is independent of thermal costs or the level of danger posed by the predator. To minimize their risk of predation, geckos may use a simple rule of thumb: “all snakes are dangerous.”

Chemical cues from both dangerous and nondangerous snakes elicit antipredator behaviours from a nocturnal lizard

Many prey species use chemical cues to detect predators. According to the threat sensitivity hypothesis, prey should match the intensity of their antipredator behaviour to the degree of threat posed by the predator. Several species of lizards display antipredator behaviours in the presence of snake chemical cues, but how species specific are these responses? In Australia, most snake species eat lizards, and are therefore potentially dangerous. Hence, we predicted that lizards should display generalized rather than species-specific antipredator behaviours. To test this prediction, we quantified the behavioural responses of velvet geckos, Oedura lesueurii, to chemical cues from five species of elapid snakes that are syntopic with velvet geckos but differ in their degree of danger. These five snake species included two nocturnal ambush foragers that eat geckos (broad-headed snake Hoplocephalus bungaroides, and death adder, Acanthophis antarcticus), two active foragers that eat skinks (but rarely eat geckos) and that differ in their activity times (nocturnal small-eyed snake, Cryptophis nigrescens, and diurnal whip snake, Demansia psammophis), and a nocturnal nonthreatening species that feeds entirely on blind snakes (bandy-bandy, Vermicella annulata). Geckos showed similar antisnake behaviours (tail waving, tail vibration), and a similar intensity of responses (reducing activity, freezing), to chemical cues from all five snake species, even though the snakes differed in their degree of danger and foraging modes. Our results suggest that velvet geckos display generalized antipredator responses to chemicals from elapid snakes, rather than responding in a graded fashion depending upon the degree of threat posed by a particular snake species.

Intraguild predation, thermoregulation, and microhabitat selection by snakes

Intraguild (IG) predation, the killing and eating of potential competitors, can be a powerful force within faunal assemblages. If both the IG predator and its prey prefer similar microhabitats in spatially structured environments, avoidance of the predator may relegate IG prey to suboptimal habitats. In southeastern Australia, the broad-headed snake (Hoplocephalus bungaroides )i s an endangered species sympatric with the small-eyed snake (Cryptophis nigrescens), an abundant and geographically widespread species known to eat other snakes. Both of these nocturnal ectotherms shelter diurnally beneath thermally distinctive ‘‘hot rocks,’’ which are in limited supply. When selecting shelter sites, broad-headed snakes thus face a trade-off between predation risk and habitat quality. In laboratory experiments, we allowed broad-headed snakes to choose between retreat sites differing in thermal regimes, in scent cues from predators, and in the actual presence of the predator. Broad-headed snakes displayed an aversion to sites with live predators and predator scent, yet nonetheless frequently selected those sites to obtain thermal benefits. In trials with live predators, adult broad-headed snakes shared hot rocks with small-eyed snakes, but most juveniles did not; data from a 16-year field study likewise suggest that broad-headed snakes only cohabit with small-eyed snakes if the two snakes are similar in body size. Our results suggest that thermoregulatory considerations are sufficient to prompt juvenile (but not adult) broad-headed snakes to risk IG predation, emphasizing the importance of microhabitat quality and body size in mediating IG predator–prey interactions. Key words: disturbance, endangered species, habitat selection, predation risk, refuge, snakes. [Behav Ecol]

Does foraging mode influence life history traits? A comparative study of growth, maturation and survival of two species of sympatric snakes from south-eastern Australia

Abstract Theory predicts that compared with active searchers, ambush foragers should have lower rates of energy intake, slower growth, and higher survival rates. We tested these predictions with data on two species of sympatric, saurophagous, small-bodied, viviparous elapid snakes: the broad-headed snake, Hoplocephalus bungaroides, and the small-eyed snake, Rhinoplocephalus nigrescens. Demographic parameters and growth curves for both species were estimated from a long-term (9 years) mark-recapture study in Morton National Park, south-eastern Australia. The ambush predator (H. bungaroides) displayed slower juvenile growth and later maturation (5 years for males, 6 years for females) than did the active forager (R. nigrescens, 3 years). Litter sizes were similar in both species, but reproductive frequency was higher in R. nigrescens (90–100%) than in H. bungaroides (50%). Juvenile survival was lower in the active searcher (31%) than in the ambush forager (55%), but adult survivorship was similar (74% vs 82%). Our results support the hypothesis that ambush foragers display ‘slow’ life history traits, but additional phylogenetically independent comparisons are needed to evaluate the generality of this pattern.

Phospholipase A2‐dependent effects of the venom from the new guinean small‐eyed snake Micropechis ikaheka

The New Guinean small-eyed snake (Micropechis ikaheka) is a cause of life-threatening envenoming. Previous studies on M. ikaheka venom have indicated the presence of neurotoxins as well as myotoxins. This study examined the in vitro myotoxic effects of M. ikaheka venom and the efficacy of a polyvalent antivenom in neutralizing these effects. Venom (50 microg/ml) produced a slowly developing contracture and inhibition of direct twitches of the chick biventer cervicis nerve-muscle preparation in the presence of tubocurarine (10 microM). Myotoxicity was confirmed by subsequent histological examination of tissues. This myotoxicity was prevented by the prior addition of polyvalent snake antivenom (30 U/ml). However, the addition of antivenom (30 U/ml) 1 h after venom administration failed to reverse or prevent the further inhibition of direct twitches. In addition, venom (1-10 microg/ml) produced concentration-dependent contractions of the guinea-pig isolated ileum. These effects were dependent on phospholipase A2 (PLA2) activity of the venom as evidenced by the ability of the PLA2 inhibitor 4-bromophenacyl bromide (4-BPB; 1.8 mM) to prevent this activity. This study indicates that M. ikaheka venom causes significant myotoxicity and that polyvalent snake antivenom may be a potential treatment for the myotoxic effects in patients envenomed by this species.

Structure and function comparison of Micropechis ikaheka snake venom phospholipase A2 isoenzymes

Comparison of the crystal structures of three Micropechis ikaheka phospholipase A2 isoenzymes (MiPLA2, MiPLA3 and MiPLA4, which exhibit different levels of pharmacological effects) shows that their C-terminus (residues 110-124) is the most variable. M-Type receptor binding affinity of the isoenzymes has also been investigated and MiPLA4 binds to the rabbit M-type receptor with high affinity. Examination of surface charges of the isoenzymes reveals a trend of increase in positive charges with potency. The isoenzymes are shown to oligomerize in a concentration-dependent manner in a semi-denaturing gel. The C-termini of the medium (MiPLA4) and highly potent (MiPLA2) isoenzyme molecules cluster together, forming a highly exposed area. A BLAST search using the sequence of the most potent MiPLA2 results in high similarity to Staphylococcus aureus clotting factor A and cadherin 11. This might explain the myotoxicity, anticoagulant and hemoglobinuria effects of MiPLA2s.

How Do Nocturnal Snakes Select Diurnal Retreat Sites?

Abstract Theoretical and empirical studies of habitat selection suggest that reptiles should use “fixed” structural features (perch diameter, vegetation) or light intensity (sun and shade) to select thermally suitable microhabitats. But how do nocturnal species select thermally suitable diurnal retreat sites at night in the absence of visual cues? To investigate this question, we studied habitat selection by two sympatric nocturnal snakes, the endangered Broad-Headed Snake Hoplocephalus bungaroides and the common Small-Eyed Snake Cryptophis nigrescens. In the field, we investigated whether snakes selected diurnal retreat sites nonrandomly with respect to vegetation structure and rock temperature. In the laboratory, we offered snakes a choice between rocks with different crevice sizes, temperatures, and degree of shading. In the field, rocks used by snakes received significantly higher levels of incident radiation intensity (and therefore had higher temperatures) than random rocks but had similar levels of...

Cardiovascular, haematological and neurological effects of the venom of the Papua New Guinean small-eyed snake ( Micropechis ikaheka) and their neutralisation with CSL polyvalent and black snake antivenoms

Cardiovascular and haematological effects of venom of the small-eyed Snake ( Micropechis ikaheka) were examined in ventilated anaesthetised piglets. Neurotoxic effects were examined in chick biventer cervicis nerve-muscle preparations. Immunoreactivity of venom was tested against the monovalent antivenom components in a CSL Ltd Venom Detection Kit. Neutralisation was tested in vivo and in vitro with CSL Ltd polyvalent snake and Black Snake ( Pseudechis australis) antivenoms. Venom in 0.1% bovine serum albumin in saline was infused into piglets in doses 1–2000 μg/kg. Pulmonary hypertension ( P=0.0007) and depression of cardiac output ( P=0.002) were observed up to 3 h after 150–160 μg/kg. The concentration of plasma free-haemoglobin increased more than 50-fold, indicating haemolysis. Neither coagulopathy nor thrombocytopenia occurred. Creatine phosphokinase and serum potassium levels did not increase suggesting absence of acute rhabdomyolysis. The venom caused post-synaptic neurotoxicty. Immunoreactivity of venom with Black Snake antivenom was observed at very high venom concentrations. Cardiovascular effects were absent and haemolysis was less after venom was pre-incubated at 37 °C for 30 min with polyvalent antivenom. Neutralisation by Black Snake antivenom was less effective. The neurotoxicity was neutralised by polyvalent or Black Snake antivenoms. Human envenomation may be treated with CSL Ltd polyvalent snake antivenom.

A novel prothrombin activator from the venom of Micropechis ikaheka: isolation and characterization.

A novel prothrombin activator, Mikarin, has been isolated from Micropechis ikaheka venom. It is a single polypeptide chain metalloproteinase with the apparent molecular weight of 47kDa. Mikarin exhibits Ca(2+)-independent prothrombin activation, but no effects on other blood coagulation factors, such as factor X and fibrinogen. Mikarin is the first member of group I prothrombin activators from elapid venom. Like other high-molecular-weight snake venom proteinases, it has three structural domains, metalloproteinase and disintegrin-like and Cys-rich domains, and belongs to the P-III class of snake venom metalloproteinases. The N-terminal of Mikarin exhibits 76% sequence identity with Cobrin, a metalloproteinase identified from Naja naja venom, but very lower identities were found when compared with those from viperid and crotalid venom. In addition, the presence of disintegrin-like and Cys-rich domains in snake venom metalloproteinases with diverse biological activities suggests that these domains may be important for their function.

Pharmacological characterization of mikatoxin, an α-neurotoxin isolated from the venom of the New-Guinean small-eyed snake Micropechis ikaheka

Symptoms of envenomation by the New-Guinean small-eyed snake Micropechis ikaheka (Elapidae) include peripheral neurotoxicity and myotoxicity. We have now purified to homogeneity a long-chain neurotoxin, mikatoxin, from M. ikaheka venom by successive gel filtration and reverse-phase chromatography. Electrospray ionization mass spectrometry showed mikatoxin to be a homogenous peptide of MW 7775.6. Mikatoxin was devoid of any phospholipase A2 activity associated with the crude venom and did not exhibit any intrinsic anticholinesterase activity. In the chick biventer cervicis muscle, it produced an irreversible, concentration-dependent block of responses to exogenously applied acetylcholine and carbachol as well as twitches evoked by nerve, but not by direct muscle stimulation. Moreover, mikatoxin, like α-bungarotoxin and erabutoxin-b, did not show significant fade response to train-of-four stimulation of the mouse phrenic nerve-hemi diaphragm muscle. It also failed to block ganglionic transmission in the guinea pig ileum and muscarinic responses in the rat anococcygeus muscle. Our study provides strong evidence for the presence of a neurotoxin (mikatoxin) in M. ikaheka venom that produces neuromuscular blockade in skeletal muscle attributable to selective and irreversible antagonism of postsynaptic nicotinic acetylcholine receptors of the neuromuscular junction and likely contributes to the peripheral neurotoxicity observed in M. ikaheka envenomation.

The inhibition of platelet aggregation and blood coagulation by Micropechis ikaheka venom.

Uncoagulable blood and life-threatening bleeding can result from the action of some snake venom toxins on haemostatic components of blood and vessel walls. Although envenoming by Micropechis ikaheka primarily affects neurones and muscle cells causing post-synaptic neuromuscular blockade and rhabdomyolysis, disturbances of haemostasis also occur. Therefore, the present study explored the effects of M. ikaheka venom on platelets and endothelium, which are important components of the haemostatic mechanism. The venom inhibited platelet aggregation in response to ADP and collagen, and also delayed clotting dependent on platelet activation or endothelial cell tissue factor expression. Some of these effects were reduced by the incubation of venom with a phospholipase A2 (PLA2) inhibitor and could be reproduced by a 17 kDa venom fraction containing a PLA2. In addition, an 11 kDa fraction containing a long-chain neurotoxin reduced ADP-induced aggregation. The venom was also found to reduce endothelial cell adherence to vitronectin-, fibronectin- and collagen-coated surfaces. These results suggest that, by inhibiting procoagulant activities of platelets and endothelial cells, a 17 kDa PLA2 plays an important role in the anticoagulant action of M. ikaheka venom.