Coral Snake Micrurus Research Articles

Case history. “Coral snake” Micrurus mipartitus bite in 1968. A herpetologist's ordeal

Historical clinical case that presented back in 1968 at a time when respiratory support and intensive care techniques were just emerging, with many shortcomings in hospital care areas and monitoring devices. The case is of a 58 year-old patient, outstanding citizen, recent winner in a television contest on snakes, who was bitten accidentally by a coral snake Micrurus mipartitus. The poison of this snake is a macromolecule that induces complete depolarizing muscle blockade which, if not reverted, leads to death from respiratory failure. A group of social leaders in the region managed to obtain the specific anti-venom that was not produced in the country, as well as the mechanical ventilation equipment, a negative pressure “iron lung” and a Bird Mark 7 positive pressure device. Manual ventilation was initiated by the anaesthesia team with the support of the medical students. Then, with the Bird Mark 7, the patient survived under empirical “intensive” care after 17 days of respiratory depression and 33 days in the hospital. Voluntary contributions of the community in an effort to solve the clinical problem are narrated.

Caso clínico histórico. Mordedura de serpiente «rabo de ají» en el año de 1968. Viacrucis de un herpetólogo

Historical clinical case that presented back in 1968 at a time when respiratory support and intensive care techniques were just emerging, with many shortcomings in hospital care areas and monitoring devices. The case is of a 58 year-old patient, outstanding citizen, recent winner in a television contest on snakes, who was bitten accidentally by a coral snake Micrurus mipartitus. The poison of this snake is a macromolecule that induces complete depolarizing muscle blockade which, if not reverted, leads to death from respiratory failure. A group of social leaders in the region managed to obtain the specific anti-venom that was not produced in the country, as well as the mechanical ventilation equipment, a negativepressure «iron lung» and a Bird Mark 7 positive pressure device. Manual ventilation was initiated by the anaesthesia team with the support of the medical students. Then, with the Bird Mark 7, the patient survived under empirical «intensive» care after 17 days of respiratory depression and 33 days in the hospital. Voluntary contributions of the community in an effort to solve the clinical problem are narrated.

Integrative characterization of the venom of the coral snake Micrurus dumerilii (Elapidae) from Colombia: Proteome, toxicity, and cross-neutralization by antivenom

In Colombia, nearly 2.8% of the 4200 snakebite accidents recorded annually are inflicted by coral snakes (genus Micrurus). Micrurus dumerilii has a broad distribution in this country, especially in densely populated areas. The proteomic profile of its venom was here studied by a bottom-up approach combining RP-HPLC, SDS-PAGE and MALDI-TOF/TOF. Venom proteins were assigned to eleven families, the most abundant being phospholipases A2 (PLA2; 52.0%) and three-finger toxins (3FTx; 28.1%). This compositional profile shows that M. dumerilii venom belongs to the ‘PLA2-rich’ phenotype, in the recently proposed dichotomy for Micrurus venoms. Enzymatic and toxic venom activities correlated with protein family abundances. Whole venom induced a conspicuous myotoxic, cytotoxic and anticoagulant effect, and was mildly edematogenic and proteolytic, whereas it lacked hemorrhagic activity. Some 3FTxs and PLA2s reproduced the lethal effect of venom. A coral snake antivenom to Micrurus nigrocinctus demonstrated significant cross-recognition of M. dumerilii venom proteins, and accordingly, ability to neutralize its lethal effect. The combined compositional, functional, and immunological data here reported for M. dumerilii venom may contribute to a better understanding of these envenomings, and support the possible use of anti-M. nigrocinctus coral snake antivenom in their treatment. Biological significanceCoral snakes represent a highly diversified group of elapids in the New World, with nearly 70 species within the genus Micrurus. Owing to their scarce yields, the biochemical composition and toxic activities of coral snake venoms have been less well characterized than those of viperid species. In this work, an integrative view of the venom of M. dumerilii, a medically relevant coral snake from Colombia, was obtained by a combined proteomic, functional, and immunological approach. The venom contains proteins from at least eleven families, with a predominance of phospholipases A2 (PLA2), followed by three-finger toxins (3FTx). According to its compositional profile, M. dumerilii venom can be grouped with those of several Micrurus species from North and Central America that present a PLA2-predominant phenotype, to date it is the most southerly coral snake species to do so. Other coral snake species that a ‘PLA2-rich’ venom, M. dumerilii venom contains both components that form MitTx, a pain-inducing heterodimeric complex recently characterized from the venom of Micrurus tener, also present in Micrurus mosquitensis and M. nigrocinctus venoms. In addition to a lethal three-finger toxin, PLA2s participate in the toxicity of M. dumerilii venom, some of them displaying ability to induce cytolysis, muscle necrosis, and lethality to mice. An antivenom to M. nigrocinctus demonstrated significant cross-recognition of M. dumerilii venom proteins, and accordingly, ability to neutralize its lethal effect, being of potential therapeutic usefulness in these envenomings.

Eastern coral snake Micrurus fulvius venom toxicity in mice is mainly determined by neurotoxic phospholipases A2

Here we show for the first time that the venom from an elapid (Micrurus fulvius) contains three finger toxin (3FTxs) peptides with low toxicity but high content of lethal phospholipases A2 (PLA2). The intravenous venom LD50 in mice was 0.3μg/g. Fractionation on a C18 column yielded 22 fractions; in terms of abundance, 58.3% of them were components of 13-14kDa and 24.9% were molecules of 6-7kDa. Two fractions with PLA2 activity represented 33.4% of the whole venom and were the most lethal fractions. Fractions with low molecular mass (<7000Da) partially and reversibly blocked the nicotinic acetylcholine receptor (nAChR), with the exception of one that blocked it completely. The fraction that blocked 100% contained two protein species whose dose-response was determined; the IC50s were 13±1 and 9.5±0.3nM. Despite the apparent effect on nAChR none of the low molecular mass fractions were lethal in mice, at concentrations of 1μg/g. From 2D-PAGE and LC-MS/MS, we identified fourteen species of PLA2, four protein species of C-type lectin, three zinc metalloproteinases, one phosphodiesterase and one 3FTx. The N-terminal amino acid sequence of fractions with biological interest was obtained. In contrast with coral snake venoms from South America, M. fulvius has minor amounts of low molecular mass components, but high content of PLA2, which is responsible for the venom lethality of this species. The results reported here contribute to better understanding of envenomation development and to improve antivenom design and production. These findings break from the paradigm that neurotoxicity caused by Micrurus venoms is mainly attributable to 3FTx neurotoxins and encourage future studies on Micrurus evolution and venom specialization. This article is part of a Special Issue entitled Non-model organisms.

Biochemical characterization of the venom of the coral snake Micrurus tener and comparative biological activities in the mouse and a reptile model

The objective of this study was to identify the venom components that could play a relevant role during envenomation caused by the coral snake Micrurus tener, through its biochemical characterization as well as the analysis of its effects on a murine model. Furthermore, it aimed to evaluate crude venom, in addition to its components, for possible specificity of action on a natural prey model (Conopsis lineata). The toxicity of the crude venom (delivered subcutaneously) showed a significant difference between the Median Lethal Dose (LD50) in mice (4.4 μg/g) and in Conopsis lineata (12.1 μg/g) that was not observed when comparing the Median Paralyzing Dose (PD50) values (mice = 4.7 μg/g; snakes = 4.1 μg/g). These results are evidence that the choice of study model strongly influences the apparent effects of crude venom. Moreover, based on the observed physical signs in the animal models, it was concluded that the most important physical effect caused by the venom is flaccid paralysis, which facilitates capture and subduing of prey regardless of whether it is alive; death is a logical consequence of the lack of oxygenation. Venom fractionation using a C18 reverse phase column yielded 35 fractions from which 16.6% caused paralysis and/or death to both animal models, 21.9% caused paralysis and/or death only to C. lineata and 1.6% were murine specific. Surprisingly, the diversity of snake-specific fractions did not reflect a difference between the PD50s of the crude venom in mice and snakes, making it impossible to assume some type of specificity for either of the study models. Finally, the great diversity and abundance of fractions with no observable effect in snakes or mice (42.7%) suggested that the observed lethal fractions are not the only relevant toxic fractions within the venom and emphasized the possible relevance of interaction between components to generate the syndrome caused by the venom as a whole.

Review of Eastern coral snake (Micrurus fulvius fulvius) exposures managed by the Florida Poison Information Center Network: 1998–2010

Context. Envenomation by the Eastern coral snake is rare but may be associated with significant morbidity. While effective, acquisition of North American Coral Snake Antivenin (NACSAV) is difficult because production was discontinued for many years. Objective. The purpose of this study is to characterize coral snake exposures in Florida and determine the effects of varying treatment paradigms on patient outcomes. Methods. This study is an observational case series of cases received at Florida poison centers. Included cases were Eastern coral snake exposures occurring between January 1, 1998 and October 31, 2010. Excluded cases included those found to be unrelated or those not followed for at least 24 h post envenomation. Case comments were reviewed to obtain data. Comparisons were made between asymptomatic patients receiving empiric antivenom therapy (empiric group) and those asymptomatic patients who received antivenom upon developing signs of systemic envenomation (withhold group). Results. Of the 553 cases identified, 387 were included in the final analysis. According to case comments, 56.3% of patients had no reported systemic symptoms. Most commonly, patients were reported to have pain (40.6%), paresthesias (28.4%), nausea (12.7%), and emesis (11.4%). NACSAV was administered to 252 patients (65%). Of those patients receiving NACSAV, 18.25% were reported to have had an adverse reaction. Patients in the withhold group (n = 106) had significantly fewer minor, moderate, and major outcomes than patients in the empiric group (n = 134, p < 0.01). Discussion. While patients in the withhold group had favorable outcomes compared with those in the empiric group, this strategy cannot be applied to all patients presenting asymptomatic to healthcare facilities due to study limitations.Conclusion. Further studies are needed to determine what treatment strategy is most appropriate for asymptomatic patients presenting to healthcare facilities.

Endoparasites infecting the semiaquatic coral snake Micrurus surinamensis (Squamata: Elapidae) in the southern amazonian region, Mato Grosso state, Brazil

A parasitological survey was conducted in specimens of the semiaquatic coral snake Micrurus surinamensis, a poorly known South American elapid. Four specimens collected at the southern Amazon region in the Brazilian state of Mato Grosso were analyzed for endoparasites. Three parasite species were recovered from the snake hosts: the pentastomid Sebekia oxycephala, the nematode Physaloptera sp. and the trematode Opisthogonimus lecithonotus. This represents new locality and host record for S. oxycephala and O. lecithonotus.

Isolation, characterization, cloning and expression of an alpha-neurotoxin from the venom of the Mexican coral snake Micrurus laticollaris (Squamata: Elapidae)

A new member of short chain α-neurotoxic protein family from venom of the Mexican coral snake, Micrurus laticollaris, was characterized. This protein, named MlatA1, possesses 61 amino acids with 8 conserved cysteine residues, sharing 30–91% sequence identity with other fully sequenced Micrurus toxins. MlatA1 (LD50i.v. = 0.064 mg/kg) antagonizes with both fetal and adult nicotinic acetylcholine receptor (nAChR) as well as α-7 neuronal nAChR in a dose-dependent way. Specific rabbit anti-Mlat serum (titer higher than 18,000) does not show any protective ability against this toxin, nevertheless it was able to recognize protein bands in six out of twelve Micrurus venoms showing the existence of two distinct antigenic groups for α-neurotoxins in North American coral snakes species. The MlatA1 gene was cloned and used to produce recombinant toxin (rMlatA1) that was recognized by rabbit anti-native toxin but was depleted of toxic activity.

A Batesian mimic and its model share color production mechanisms

Abstract Batesian mimics are harmless prey species that resemble dangerous ones (models), and thus receive protection from predators. How such adaptive resemblances evolve is a classical problem in evolutionary biology. Mimicry is typically thought to be difficult to evolve, especially if the model and mimic produce the convergent phenotype through different proximate mechanisms. However, mimicry may evolve more readily if mimic and model share similar pathways for producing the convergent phenotype. In such cases, these pathways can be co-opted in ancestral mimic populations to produce high-fidelity mimicry without the need for major evolutionary innovations. Here, we show that a Batesian mimic, the scarlet kingsnake Lampropeltis elapsoides, produces its coloration using the same physiological mechanisms as does its model, the eastern coral snake Micrurus fulvius. Therefore, precise color mimicry may have been able to evolve easily in this system. Generally, we know relatively little about the proximate mechanisms underlying mimicry.

Micrurus annellatus annellatus (Peters, 1871) (Serpentes: Elapidae): distribution extension in the state of Acre, northern Brazil

The annellated coral snake Micrurus annellatus (Peters, 1871) occurs from southern Ecuador and southeastern Colombia to southeastern Peru and north of Bolivia. Only Micrurus a. bolivianus has been recorded in Brazil, in the state of Amazonas. Herein we provide two records of Micrurus a. annellatus from Brazil in the state of Acre.

Characterization of a new muscarinic toxin from the venom of the Brazilian coral snake Micrurus lemniscatus in rat hippocampus

AimsWe have isolated a new muscarinic protein (MT-Mlα) from the venom of the Brazilian coral snake Micrurus lemniscatus. Main methodsThis small protein, which had a molecular mass of 7,048Da, shared high sequence homology with three-finger proteins that act on cholinergic receptors. The first 12 amino acid residues of the N-terminal sequence were determined to be: Leu-Ile-Cys-Phe-Ile-Cys-Phe-Ser-Pro-Thr-Ala-His. Key findingsThe MT-Mlα was able to displace the [3H]QNB binding in the hippocampus of rats. The binding curve in competition experiments with MT-Mlα was indicative of two types of [3H]QNB-binding site with pKi values of 9.08±0.67 and 6.17±0.19, n=4, suggesting that various muscarinic acetylcholine receptor (mAChR) subtypes may be the target proteins of MT-Mlα. The MT-Mlα and the M1 antagonist pirenzepine caused a dose-dependent block on total [3H]inositol phosphate accumulation induced by carbachol. The IC50 values for MT-Mlα and pirenzepine were, respectively, 33.1 and 2.26 nM. Taken together, these studies indicate that the MT-Mlα has antagonist effect on mAChRs in rat hippocampus. SignificanceThe results of the present study show, for the first time, that mAChRs function is drastically affected by MT-Mlα since it not only has affinity for mAChRs but also has the ability to inhibit mAChRs.

Hemostatic and toxinological diversities in venom of Micrurus tener tener, Micrurus fulvius fulvius and Micrurus isozonus coral snakes

The coral snake Micrurus tener tener (Mtt) from the Elapidae family inhabits the southwestern United States and produces severe cases of envenomations. Although the majority of Mtt venom components are neurotoxins and phospholipase A2s, this study demonstrated, by SDS-PAGE and molecular exclusion chromatography (MEC), that these venoms also contain high-molecular-weight proteins between 50 and 150 kDa that target the hemostatic system. The biological aspects of other Micrurus venoms were also studied, such as the LD50s of Micrurus isozonus (from 0.52 to 0.61 mg/kg). A pool from these venoms presented a LD50 of 0.57 mg/kg, Micrurus f. fulvius (Mff) and Mtt had LD50s of 0.32 and 0.78 mg/kg, respectively. These venoms contained fibrino(geno)lytic activity, they inhibited platelet aggregation, as well as factor Xa and/or plasmin-like activities. M. isozonus venoms from different Venezuelan geographical regions inhibited ADP-induced platelet aggregation (from 50 to 68%). Micrurus tener tener venom from the United States was the most active with a 95.2% inhibitory effect. This venom showed thrombin-like activity on fibrinogen and human plasma. Fractions of Mtt showed fibrino(geno)lytic activity and inhibition on plasmin amidolytic activity. Several fractions degraded the fibrinogen Aα chains, and fractions F2 and F7 completely degraded both fibrinogen Aα and Bβ chains. To our knowledge, this is the first report on thrombin-like and fibrino(geno)lytic activity and plasmin or factor Xa inhibitors described in Micrurus venoms. Further purification and characterization of these Micrurus venom components could be of therapeutic use in the treatment of hemostatic disorders.

Envenomation by Micrurus coral snakes in the Brazilian Amazon region: report of two cases

Two cases of proven coral snake bites were reported in Belém, Pará State, Brazil. The first case was a severe one caused by Micrurus surinamensis. The patient required mechanical ventilation due to acute respiratory failure. The second case showed just mild signs of envenomation caused by Micrurus filiformis. Both patients received specific Micrurus antivenom and were discharged without further complications. Coral snake bites are scarcely reported in the Amazon region and there is a broad spectrum of clinical manifestations, varying from extremely mild to those which may rapidly lead to death if the patient is not treated as soon as possible.

Frontoxins, three-finger toxins from Micrurus frontalis venom, decrease miniature endplate potential amplitude at frog neuromuscular junction

Neurotoxicity is a major symptom of envenomation caused by Brazilian coral snake Micrurus frontalis. Due to the small amount of material that can be collected, no neurotoxin has been fully sequenced from this venom. In this work we report six new three-finger like toxins isolated from the venom of the coral snake M. frontalis which we named Frontoxin (FTx) I–VI. Toxins were purified using multiple steps of RP-HPLC. Molecular masses were determined by MALDI-TOF and ESI ion-trap mass spectrometry. The complete amino acid sequence of FTx II, III, IV and V were determined by sequencing of overlapping proteolytic fragments by Edman degradation and by de novo sequencing. The amino acid sequences of FTx I, II, III and VI predict 4 conserved disulphide bonds and structural similarity to previously reported short-chain α-neurotoxins. FTx IV and V each contained 10 conserved cysteines and share high similarity with long-chain α-neurotoxins. At the frog neuromuscular junction FTx II, III and IV reduced miniature endplate potential amplitudes in a time-and concentration-dependent manner suggesting Frontoxins block nicotinic acetylcholine receptors.

Proteomic analysis of the venom from the fish eating coral snake Micrurus surinamensis: Novel toxins, their function and phylogeny

The protein composition of the soluble venom from the South American fish-eating coral snake Micrurus surinamensis surinamensis, here abbreviated M. surinamensis, was separated by RP-HPLC and 2-DE, and their components were analyzed by automatic Edman degradation, MALDI-TOF and ESI-MS/MS. Approximately 100 different molecules were identified. Sixty-two components possess molecular masses between 6 and 8 kDa, are basically charged molecules, among which are cytotoxins and neurotoxins lethal to fish (Brachidanios rerio). Six new toxins (abbreviated Ms1-Ms5 and Ms11) were fully sequenced. Amino acid sequences similar to the enzymes phospholipase A2 and amino acid oxidase were identified. Over 20 additional peptides were identified by sequencing minor components of the HPLC separation and from 2-DE gels. A functional assessment of the physiological activity of the six toxins was also performed by patch clamp using muscular nicotinic acetylcholine receptor assays. Variable degrees of blockade were observed, most of them reversible. The structural and functional data obtained were used for phylogenetic analysis, providing information on some evolutionary aspects of the venom components of this snake. This contribution increases by a factor of two the total number of alpha-neurotoxins sequenced from the Micrurus genus in currently available literature.

82: Onset of Systemic Effects from Bites of the Texas Coral Snake (Micrurus tener)

Coral snake antivenom is indicated for all victims envenomated by Micrurus coral snakes in North America. However, recent studies have demonstrated that antivenom does not need to be administered to victims of Texas coral snakes (Micrurus tener previously Micrurus fulvius tenere) who do not have any systemic effects. Since these symptoms may begin long after the bite, the time required to observe these patients is unknown. Our goal was to determine the appropriate duration of the observation period for systemic effects.

Pharmacological and structural characterization of a novel phospholipase A 2 from Micrurus dumerilii carinicauda venom

We have isolated a new phospholipase A 2 (MiDCA1) from the venom of the coral snake Micrurus dumerilii carinicauda. This toxin, which had a molecular mass of 15,552 Da, shared high sequence homology with the PLA 2 toxins MICNI A and B from Micrurus nigrocinctus venom (77.7% and 73.1%, respectively). In chick biventer cervicis preparations, MiDCA1 produced concentration- and time-dependent neuromuscular blockade that reached 100% after 120 min (2.4 μM, n=6); contractures to exogenously applied carbachol (8 μM) and KCl (13 mM) were still seen after complete blockade. In mouse phrenic-nerve diaphragm preparations, MiDCA1 (2.4 μM; n=6) caused triphasic changes followed by partial neuromuscular blockade. Intracellular recordings of end-plate potentials (EPPs) and miniature end-plate potentials (MEPPs) from mouse diaphragm preparations showed that MiDCA1 increased the quantal content by 386±12% after 10 min ( n=14; p<0.05) and caused a triphasic change in the frequency of MEPPs. MiDCA1 also decreased the resting membrane potential, an effect that was prevented by tetrodotoxin and/or low extracellular calcium, but not by d-tubocurarine. The toxin increased the amplitude of mouse sciatic-nerve compound action potentials by 30±9% (0.6 μM; p<0.05). Potassium currents elicited in freshly dissociated dorsal root ganglia neurones were blocked by 31±1% ( n=4; p<0.05) in the presence of 2.4 μM MiDCA1. These results show that MiDCA1 is a new presynaptic phospholipase A 2 that produces neuromuscular blockade in vertebrate nerve-muscle preparations. The triphasic effects seen in mammalian preparations and the facilitatory response were probably caused mainly by the activation of sodium channels, complemented by the blockade of nerve terminal potassium channels. The inability of d-turocurarine to prevent the depolarization by MiDCA1 indicated that cholinergic nicotinic receptors were not involved in this phenomenon.

A fish prey found in the coral snake Micrurus alleni (Serpentes: Elapidae) in Costa Rica

A fish prey found in the coral snake Micrurus alleni (Serpentes: Elapidae) in Costa Rica. The presence of a small specimen of the swamp eel Synbranchus marmoratus (84 mm total length) in the stomach contents of an adult coral snake Micrurus alleni with 692 mm total length from the Caribbean versant of Costa Rica is reported. This eel was swallowed headfirst.

Efficacy of a Pressure-Immobilization bandage in delaying the onset of systemic toxicity in a porcine model of eastern coral snake (Micrurus fulvius) envenomation

Study objectives: Pressure-immobilization bandages (PIBs) are first-aid devices that are used in foreign regions where neurotoxic elapid envenomations are common. These devices are theorized to impede lymphatic return to the central circulation, thereby sequestering venom at the bite site and delaying systemic toxicity, which allows additional time to provide the victim with definitive care in the form of antivenom and advanced airway management. Coral snakes are New World elapids with primarily neurotoxic venoms. PIB use has never been formally examined in coral snake envenomations. We evaluate the efficacy of these devices in delaying the onset of systemic toxicity in a porcine model of Micrurus fulvius envenomation. Methods: The study design was a randomized, controlled trial of PIBs in a porcine model of M fulvius envenomation. The setting was a university animal laboratory. Subjects were 12 pigs, ranging from 9.1 to 11.4 kg. The animals were sedated, intubated, and anesthetized. Volatile anesthesia was maintained by animal care technicians at a level to ensure animal comfort and that all pigs were breathing spontaneously. Lyophilized venom was obtained from Natural Toxins Research Center (Kingsville, TX) and resuspended in pure water at a concentration of 10 mg/mL. The lethal dose of M fulvius venom in a human has been estimated at 5 mg, and the venom yield of a large snake can be 20 mg. We chose a 10-mg dose to ensure that all animals would develop severe toxicity during the study. The subjects were injected with 10 mg of M fulvius venom in the subcutaneous tissue of the left distal foreleg. Immediately after injection, the subjects were randomized to either receive a PIB 1 minute after envenomation or to have no treatment. The PIB consisted of an elastic bandage applied to the entire extremity at a pressure such that a finger could be easily passed under. The same operator applied all bandages. Aluminum and foam splints were then loosely taped on either side to immobilize the extremity. Pulse rate, respiratory rate, pulse oximetry, and quality of respirations were recorded at 10-minute intervals. The primary endpoint was survival to 8 hours, and groups were compared using χ 2 analysis. Groups were also compared with respect to time to onset of systemic toxicity in the form of respiratory compromise, and total time of survival. A veterinary pathologist performed necropsies on all animals, and the histology of the envenomation site was examined. One animal from each group was removed because of the discovery of preexisting respiratory pathology. Results: Four of 5 pigs in the treatment group survived to 8 hours, but none in the control group did ( P =.0036). Time to onset of signs of respiratory compromise was 170±33.3 minutes in the control group. Two pigs in the treatment group showed signs of respiratory compromise before 8 hours, 1 at 310 minutes and 1 at 460 minutes. One of these subjects did survive to 8 hours. None of the pigs had histologic changes at the envenomation site consistent with ischemic or pressure-related injury. Conclusion: Pressure immobilization bandages were effective in delaying the onset of systemic venom toxicity in this model of M fulvius envenomation. According to this study, the use of PIBs can be recommended as initial treatment in human envenomations by coral snakes.

Feeding behavior and venom toxicity of coral snake Micrurus nigrocinctus (Serpentes: Elapidae) on its natural prey in captivity

The feeding behavior and venom toxicity of the coral snake Micrurus nigrocinctus (Serpentes: Elapidae) on its natural prey in captivity were investigated. Coral snakes searched for their prey (the colubrid snake Geophis godmani) in the cages. Once their preys were located, coral snakes stroke them with a rapid forward movement, biting predominantly in the anterior region of the body. In order to assess the role of venom in prey restraint and ingestion, a group of coral snakes was ‘milked’ in order to drastically reduce the venom content in their glands. Significant differences were observed between snakes with venom, i.e., ‘nonmilked’ snakes, and ‘milked’ snakes regarding their behavior after the bite. The former remained hold to the prey until paralysis was achieved, whereas the latter, in the absence of paralysis, moved their head towards the head of the prey and bit the skull to achieve prey immobilization by mechanical means. There were no significant differences in the time of ingestion between these two groups of coral snakes. Susceptibility to the lethal effect of coral snake venom greatly differed in four colubrid species; G. godmani showed the highest susceptibility, followed by Geophis brachycephalus, whereas Ninia psephota and Ninia maculata were highly resistant to this venom. In addition, the blood serum of N. maculata, but not that of G. brachycephalus, prolonged the time of death of mice injected with 2 LD 50s of M. nigrocinctus venom, when venom and blood serum were incubated before testing. Subcutaneous injection of coral snake venom in G. godmani induced neurotoxicity and myotoxicity, without causing hemorrhage and without affecting heart and lungs. It is concluded that (a) M. nigrocinctus venom plays a role in prey immobilization, (b) venom induces neurotoxic and myotoxic effects in colubrid snakes which comprise part of their natural prey, and (c) some colubrid snakes of the genus Ninia present a conspicuous resistance to the toxic action of M. nigrocinctus venom.