African Snake Research Articles

Intrageneric cross-reactivity of monospecific rabbit antisera against venoms of the medically most important Bitis spp. and Echis spp. African snakes.

BackgroundSnakebite envenomation exerts a heavy toll in sub-Saharan Africa. The design and production of effective polyspecific antivenoms for this region demand a better understanding of the immunological characteristics of the different venoms from the most medically important snakes, to select the most appropriate venom combinations for generating antivenoms of wide neutralizing scope. Bitis spp. and Echis spp. represent the most important viperid snake genera in Africa.Methodology/Principal findingsEight rabbit-derived monospecific antisera were raised against the venoms of four species of Bitis spp. and four species of Echis spp. The effects of immunization in the rabbits were assessed, as well as the development of antibody titers, as judged by immunochemical assays and neutralization of lethal, hemorrhagic, and in vitro coagulant effects. At the end of immunizations, local and pulmonary hemorrhage, together with slight increments in the plasma activity of creatine kinase (CK), were observed owing to the action of hemorrhagic and myotoxic venom components. Immunologic analyses revealed a considerable extent of cross-reactivity of monospecific antisera against heterologous venoms within each genus, although some antisera provided a more extensive cross-reactivity than others. The venoms that generated antisera with the broadest coverage were those of Bitis gabonica and B. rhinoceros within Bitis spp. and Echis leucogaster within Echis spp.Conclusions/SignificanceThe methodology followed in this study provides a rational basis for the selection of the best combination of venoms for generating antivenoms of high cross-reactivity against viperid venoms in sub-Saharan Africa. Results suggest that the venoms of B. gabonica, B. rhinoceros, and E. leucogaster generate antisera with the broadest cross-reactivity within their genera. These experimental results in rabbits need to be translated to large animals used in antivenom production to assess whether these predictions are reproduced in horses or sheep.

Non-compartmental toxicokinetic studies of the Nigerian Naja nigricollis venom.

Snakebite envenoming (SBE) is a neglected public health problem, especially in Asia, Latin America and Africa. There is inadequate knowledge of venom toxicokinetics especially from African snakes. To mimic a likely scenario of a snakebite envenoming, we used an enzyme-linked immunosorbent assay (ELISA) approach to study the toxicokinetic parameters in rabbits, following a single intramuscular (IM) administration of Northern Nigeria Naja nigricollis venom. We used a developed and validated non-compartmental approach in the R package PK to determine the toxicokinetic parameters of the venom and subsequently used pharmacometrics modelling to predict the movement of the toxin within biological systems. We found that N. nigricollis venom contained sixteen venom protein families following a mass spectrometric analysis of the whole venom. Most of these proteins belong to the three-finger toxins family (3FTx) and venom phospholipase A2 (PLA2) with molecular weight ranging from 3 to 16 kDa. Other venom protein families were in small proportions with higher molecular weights. The N. nigricollis venom was rapidly absorbed at 0.5 h, increased after 1 h and continued to decrease until the 16th hour (Tmax), where maximum concentration (Cmax) was observed. This was followed by a decrease in concentration at the 32nd hour. The venom of N. nigricollis was found to have high volume of distribution (1250 ± 245 mL) and low clearance (29.0 ± 2.5 mL/h) with an elimination half-life of 29 h. The area under the curve (AUC) showed that the venom remaining in the plasma over 32 h was 0.0392 ± 0.0025 mg h.L−1, and the mean residence time was 43.17 ± 8.04 h. The pharmacometrics simulation suggests that the venom toxins were instantly and rapidly absorbed into the extravascular compartment and slowly moved into the central compartment. Our study demonstrates that Nigerian N. nigricollis venom contains low molecular weight toxins that are well absorbed into the blood and deep tissues. The venom could be detected in rabbit blood 48 h after intramuscular envenoming.

Profiling the Murine Acute Phase and Inflammatory Responses to African Snake Venom: An Approach to Inform Acute Snakebite Pathology

Snake envenoming causes rapid systemic and local effects that often result in fatal or long-term disability outcomes. It seems likely that acute phase and inflammatory responses contribute to these haemorrhagic, coagulopathic, neurotoxic, nephrotoxic and local tissue destructive pathologies. However, the contributory role of acute phase/inflammatory responses to envenoming is under-researched and poorly understood—particularly for envenoming by sub-Saharan African venomous snakes. To provide data to help guide future studies of human patients, and to explore the rationale for adjunct anti-inflammatory medication, here we used an in vivo murine model to systematically assess acute phase and inflammatory responses of mice to ten African snake venoms. In addition to investigating snake species-specific effects of venom on the cardiovascular system and other key organs and tissues, we examined the response to intravascular envenoming by acute phase reactants, including serum amyloid A, P-selectin and haptoglobin, and several cytokines. Venoms of the spitting (Naja nigricollis) and forest (N. melanoleuca) cobras resulted in higher acute phase and inflammatory responses than venoms from the other cobras, mambas and vipers tested. Naja nigricollis venom also stimulated a 100-fold increase in systemic interleukin 6. Thin blood films from venom-treated mice revealed species-specific changes in red blood cell morphology, indicative of membrane abnormalities and functional damage, lymphopenia and neutrophil leukocytosis. Our ex vivo assays with healthy human blood treated with these venoms identified that N. nigricollis venom induced marked levels of haemolysis and platelet aggregation. We conclude that African snake venoms stimulate very diverse responses in this mouse model of acute systemic envenoming, and that venoms of the African cobras N. nigricollis and N. melanoleuca, in particular, cause marked inflammatory and non-specific acute phase responses. We also report that several African snake venoms cause haemolytic changes. These findings emphasise the importance of understanding acute responses to envenoming, and that further research in this area may facilitate new diagnostic and treatment approaches, which in turn may lead to better clinical outcomes for snakebite patients.

05. Defensive behaviour by the African snakes [Amblyodipsas unicolor] and [Atractaspis andersonii

05. Defensive behaviour by the African snakes [Amblyodipsas unicolor] and [Atractaspis andersonii

Defensive behaviour by the African snakes Amblyodipsas unicolor and Atractaspis andersonii

Coiling into a spiral as a way of concealing and protecting the head is described in species of two African snake genera – Amblyodipsas and Atractaspis, the latter otherwise known for a very different and distinctive ‘snout to ground’ avoidance behaviour. Spiralling and balling are considered in other snakes worldwide and the individualism of animal behaviour warned against. It is to be hoped that recognition of ‘spiralling’ as a distinctive form of ‘coiling’ or ‘balling’ behaviour will lead to more critical analysis of snake defensive behaviour

Snakebites in Jordan: A clinical and epidemiological study

The epidemiology features and clinical symptoms associated with 121 cases of snakebite requiring admission to 24 hospitals in Jordan, during 2018–2020, are discussed. Ninety-six of them (79%) brought with them to the hospital the snake that bit them or a photograph of it. Echis coloratus was responsible for 68 of the bites and 6 fatalities. Sex ratio was 3.2 males: 1 female, with an overall average age of 27 ± 14.36 years. The highest incidence of bites was reported in September. Bites were most common on hands and legs. The period of hospitalization ranged from 1 to 36 days. Irbid and Karak governorates had the highest number of snakebites, most cases being reported from agricultural areas and among farmers.Clinical symptoms associated with five species of venomous snakes are described along with illustrative case histories. Symptoms associated with Echis coloratus bites included local swelling and necrosis, coagulopathy and bleeding, microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury (AKI) and chronic renal failure. Daboia palaestinae victims exhibited ecchymoses, local swelling and necrosis, with one case of angioedema. Other symptoms included thrombocytopenia, coagulopathy, microangiopathic hemolysis and local and systemic bleeding, as well as AKI. A single case of envenoming by Macrovipera lebetinus developed the following symptoms; swelling, severe pain, extensive ecchymoses, neutrophil leukocytosis, normochromic normocytic anemia and aggregated platelets with thrombocytopenia. Symptoms associated with two cases of Pseudocerastes fieldi included swelling that spread from bitten hands, and mild abnormalities of platelet count and bleeding time. Four cases of envenoming by Atractaspis engaddensis exhibited severe pain, local swelling, erythema, numbness and tissue necrosis. One of them developed acute systemic symptoms.The only antivenom currently available in Jordan, is VINS “Snake venom antitoxin (Biosnake)”, manufactured in India using venoms of three African snakes that do not occur in Jordan. It proved clinically ineffective against envenoming by Jordanian Viperidae, failing to correct coagulopathy and life-threatening hemorrhage, and to prevent AKI.

Effect of hybridization of novel African teff and snake grass fibers reinforced epoxy composites with bio castor seed shell filler: Experimental investigation

The main aim of this research was to fabricate novel African teff and snake grass fibers reinforced hybrid epoxy composites with bio castor seed shell powder as filler using compression molding method as a function of varying fiber weight fraction from 5 to 25 wt%. The African teff and snake grass fibers were chemically treated with 5% NaOH to enhance fiber outer surface by removing hemicellulose, lignin, wax, and oil contents. The tensile, flexural, impact, interlaminar shear strength, and hardness of the alkaline treated hybrid composites were determined as per ASTM standards to evaluate the effect of fiber weight fraction on the developed composites. The chemical bonding between the treated fiber and NaOH agents was verified through Fourier transform infrared analysis. The adhesion between the treated fiber and matrix was analyzed by using a scanning electron microscope. The results of the investigation indicated that the mechanical properties improved with the increase in African teff fiber up to 20 wt. % and deteriorated thereafter. It was also observed that the combined influence of bio castor seed shell powder along with natural fibers over the mechanical properties was higher.

Assessing a 6-h endpoint observation time in the lethality neutralization assay used to evaluate the preclinical efficacy of snake antivenoms.

The lethality neutralization assay in mice is the gold standard for the evaluation of the preclinical efficacy and specification fulfillment of snake antivenoms. However, owing to the animal suffering involved, this assay is a candidate to be replaced by in vitro alternatives or, at least, improved by the reduction of the number of animals used per experiment, the introduction of analgesia, and the refinement of the test. Since these tests are usually run for 24 or 48 h, one possibility to refine it is to shorten the endpoint observation time of the assay and so limiting the duration of suffering. To assess the effect of this modification of the standard procedure on the analytical properties of the assay, we compared the median lethal dose (LD50) and median effective dose (ED50) values, estimated through observation times of 6, 24 and 48 h. We used African and Latin American snake venoms and several batches of two polyspecific antivenoms. A significant correlation was found between LD50 and ED50 values estimated at the three observation times. Although some LD50 and ED50 values were significantly different at these time points, results of 6 h were robust enough to be used in the characterization of new antivenoms, the verification of specification compliance, and the parallel comparison of formulations. Our observations support the modification of the standard procedures used for assessing neutralizing ability of antivenoms by carrying out the observations at 6 h instead of 24 or 48 h, with the consequent reduction in the suffering inflicted upon mice during these assays. However, the shortening of the observation time in the lethality tests must be validated for each venom and antivenom before its introduction in the routine procedures.

A can of worms: Identification issues and morphological conservatism in a large sample of African Green and Bush Snakes (Colubridae: Philothamnus) from Minziro Forest, Tanzania

ABSTRACT The African green snakes of the genus Philothamnus include c. 21 recognised species distributed across sub-Saharan Africa. Many of the species exhibit high morphological conservatism, exist sympatrically, and can have high population densities. This is presumably the reason why the number of species, their systematics, and taxonomy remain debated, and this may compromise the ability to conduct accurate species identifications based on morphological characters. To investigate and quantify this problem, we examined a large sympatric sample of ethanol-preserved Philothamnus specimens from Minziro Forest, Tanzania. Of the 248 specimens examined, 55 were P. heterolepidotus, 49 were P. hoplogaster, 33 were P. angolensis, and one was P. ornatus. A further 110 specimens could not be assigned to any species based on existing identification keys. Thus, this unidentified sample of Philothamnus comprises new forms or undescribed polymorphisms within recognised forms. We examined diagnostic morphological characters using a multivariate approach. Results revealed that if the presence or absence of the white spot character is ignored, many unidentified individuals fall within well-defined clusters based on other characters. These include the heart position, which we explore here as a new diagnostic character for this genus. A thorough revision using integrative taxonomy, for example combining morphological and genetic characteristics from across the spectrum of variability in this genus, could provide a better understanding of species limits, diversity, evolutionary history, and radiation of some of the most commonly encountered snakes in sub-Saharan Africa. This would also improve the taxonomic accuracy of regional herpetological biodiversity assessments.

Snakes on an African plain: the radiation of Crotaphopeltis and Philothamnus into open habitat (Serpentes: Colubridae).

BackgroundThe African continent is comprised of several different biomes, although savanna is the most prevalent. The current heterogeneous landscape was formed through long-term vegetation shifts as a result of the global cooling trend since the Oligocene epoch. The overwhelming trend was a shift from primarily forest, to primarily savanna. As such, faunal groups that emerged during the Paleogene/Neogene period and have species distributed in both forest and savanna habitat should show a genetic signature of the possible evolutionary impact of these biome developments. Crotaphopeltis and Philothamnus (Colubridae) are excellent taxa to investigate the evolutionary impact of these biome developments on widespread African colubrid snakes, and whether timing and patterns of radiation are synchronous with biome reorganisation.MethodsA phylogenetic framework was used to investigate timing of lineage diversification. Phylogenetic analysis included both genera as well as other Colubridae to construct a temporal framework in order to estimate radiation times for Crotaphopeltis and Philothamnus. Lineage diversification was estimated in Bayesian Evolutionary Analysis Sampling Trees (BEAST), using two mitochondrial markers (cyt–b, ND4), one nuclear marker (c–mos), and incorporating one fossil and two biogeographical calibration points. Vegetation layers were used to classify and confirm species association with broad biome types (‘closed’ = forest, ‘open’ = savanna/other), and the ancestral habitat state for each genus was estimated.ResultsPhilothamnus showed an ancestral state of closed habitat, but the ancestral habitat type for Crotaphopeltis was equivocal. Both genera showed similar timing of lineage diversification diverging from their sister genera during the Oligocene/Miocene transition (ca. 25 Mya), with subsequent species radiation in the Mid-Miocene. Philothamnus appeared to have undergone allopatric speciation during Mid-Miocene forest fragmentation. Habitat generalist and open habitat specialist species emerged as savanna became more prevalent, while at least two forest associated lineages within Crotaphopeltis moved into Afromontane forest habitat secondarily and independently.DiscussionWith similar diversification times, but contrasting ancestral habitat reconstructions, we show that these genera have responded very differently to the same broad biome shifts. Differences in biogeographical patterns for the two African colubrid genera is likely an effect of distinct life-history traits, such as the arboreous habits of Philothamnus compared to the terrestrial lifestyle of Crotaphopeltis.

Rivers, not refugia, drove diversification in arboreal, sub-Saharan African snakes.

The relative roles of rivers versus refugia in shaping the high levels of species diversity in tropical rainforests have been widely debated for decades. Only recently has it become possible to take an integrative approach to test predictions derived from these hypotheses using genomic sequencing and paleo‐species distribution modeling. Herein, we tested the predictions of the classic river, refuge, and river‐refuge hypotheses on diversification in the arboreal sub‐Saharan African snake genus Toxicodryas. We used dated phylogeographic inferences, population clustering analyses, demographic model selection, and paleo‐distribution modeling to conduct a phylogenomic and historical demographic analysis of this genus. Our results revealed significant population genetic structure within both Toxicodryas species, corresponding geographically to river barriers and divergence times from the mid‐Miocene to Pliocene. Our demographic analyses supported the interpretation that rivers are indications of strong barriers to gene flow among populations since their divergence. Additionally, we found no support for a major contraction of suitable habitat during the last glacial maximum, allowing us to reject both the refuge and river‐refuge hypotheses in favor of the river‐barrier hypothesis. Based on conservative interpretations of our species delimitation analyses with the Sanger and ddRAD data sets, two new cryptic species are identified from east‐central Africa. This study highlights the complexity of diversification dynamics in the African tropics and the advantages of integrative approaches to studying speciation in tropical regions.

Unexpected lack of specialisation in the flow properties of spitting cobra venom.

Venom spitting is a defence mechanism based on airborne venom delivery used by a number of different African and Asian elapid snake species ('spitting cobras'; Naja spp. and Hemachatus spp.). Adaptations underpinning venom spitting have been studied extensively at both behavioural and morphological level in cobras, but the role of the physical properties of venom itself in its effective projection remains largely unstudied. We hereby provide the first comparative study of the physical properties of venom in spitting and non-spitting cobras. We measured the viscosity, protein concentration and pH of the venom of 13 cobra species of the genus Naja from Africa and Asia, alongside the spitting elapid Hemachatus haemachatus and the non-spitting viper Bitis arietans. By using published microCT scans, we calculated the pressure required to eject venom through the fangs of a spitting and a non-spitting cobra. Despite the differences in the modes of venom delivery, we found no significant differences between spitters and non-spitters in the rheological and physical properties of the studied venoms. Furthermore, all analysed venoms showed a Newtonian flow behaviour, in contrast to previous reports. Although our results imply that the evolution of venom spitting did not significantly affect venom viscosity, our models of fang pressure suggests that the pressure requirements to eject venom are lower in spitting cobras than in non-spitting cobras.

Molecular phylogenetics of sub-Saharan African natricine snakes, and the biogeographic origins of the Seychelles endemic Lycognathophis seychellensis

Phylogenetic relationships of sub-Saharan African natricine snakes are understudied and poorly understood, which in turn has precluded analyses of the historical biogeography of the Seychelles endemic Lycognathophis seychellensis. We inferred the phylogenetic relationships of Seychelles and mainland sub-Saharan natricines by analysing a multilocus DNA sequence dataset for three mitochondrial (mt) and four nuclear (nu) genes. The mainland sub-Saharan natricines and L. seychellensis comprise a well-supported clade. Two maximally supported sets of relationships within this clade are (Limnophis,Natriciteres) and (Afronatrix,(Hydraethiops,Helophis)). The relationships of L. seychellensis with respect to these two lineages are not clearly resolved by analysing concatenated mt and nu data. Analysed separately, nu data best support a sister relationship of L. seychellensis with (Afronatrix,(Hydraethiops,Helophis)) and mt data best support a sister relationship with all mainland sub-Saharan natricines. Methods designed to cope with incomplete lineage sorting strongly favour the former hypothesis. Genetic variation among up to 33 L. seychellensis from five Seychelles islands is low. Fossil calibrated divergence time estimates support an overseas dispersal of the L. seychellensis lineage to the Seychelles from mainland Africa ca. 43–25 million years before present (Ma), rather than this taxon being a Gondwanan relic.

Two case reports of local envenoming by the Spotted grass snake, Psammophylax rhombeatus (Linnæus, 1758) (Serpentes, Psammophiidae)

Two cases of bites by a South African psammophiid snake, Psammophylax rhombeatus, are described and analyzed. These are the first detailed reports of local envenoming by a Psammophylax spp. While handling a wild-collected 1 m P. rhombeatus, the snake inflicted a protracted bite proximal to the metacarpophalangeal joint of digit #5, left hand of a 24−year-old male amateur herpetologist. Local edema persisted for three days, but no pain or other signs or symptoms including non-specific autonomic effects (e.g. headache, nausea) occurred. In a second case, a 28−year-old male herpetologist-photographer was repositioning a 0.58 m female P. rhombeatus in order to photograph the snake and her egg clutch, when the snake bit the metacarpophalangeal joint of digit #5, left hand, and briefly advanced its jaws. The bite caused mild local pain, progressive edema of the left hand, and arthralgia; resolution required almost 1 week. Bites from non-front-fanged snakes such as these by P. rhombeatus are uncommonly reported in comparison with those described for front-fanged snakes (e.g. Viperidae, Elapidae). Therefore, documentation of bites even with minimal effects provides information essential for the construction of an accurate medical risk profile for these less-known species.

Moringa oleifera Extract Extenuates Echis ocellatus Venom-Induced Toxicities, Histopathological Impairments and Inflammation via Enhancement of Nrf2 Expression in Rats.

Echis ocellatus snakebite causes more fatalities than all other African snake species combined. Moringa oleifera reportedly possesses an antivenom property. Therefore, we evaluated the effectiveness of M. oleifera ethanol extract (MOE) against E. ocellatus venom (EOV) toxicities. Thirty male rats were grouped as follows (n = 5): Group 1 (normal control received saline), groups 2 to 6 were administered intraperitoneally, 0.22 mg/kg (LD50) of EOV. Group 2 was left untreated while group 3 to 6 were treated post-envenoming with 0.2 mL of polyvalent antivenom, 200, 400, and 600 mg/kg of MOE respectively. MOE significantly (p < 0.05) normalized the altered haematological indices and blood electrolytes profiles. MOE attenuated venom-induced cellular dysfunctions, characterized by a significant increase in NRF2, and concomitant downregulation of increased antioxidant enzymes (SOD and CAT) activities in the serum and heart of the treated rats. MOE normalized the elevated TNF-α and IL-1β in serum and heart tissues. Furthermore, the IgG titre value was significantly (p < 0.5) higher in the envenomed untreated group compared to the MOE-treated groups. Hemorrhagic, hemolytic and coagulant activities of the venom were strongly inhibited by the MOE dose, dependently. Lesions noticed on tissues of vital organs of untreated rats were abolished by MOE. Our findings substantiate the effectiveness of MOE as a potential remedy against EOV toxicities.

Taxonomic revision of the Jita snakes (Lamprophiidae: Boaedon) from São Tomé and Príncipe (Gulf of Guinea), with the description of a new species

ABSTRACT The taxonomic status of the São Tomé and Príncipe islands ‘Cobras Jitas’, genus Boaedon, has been a subject of confusion. Historically, these island populations have been referred to as part of either the Boaedon fuliginosus species complex or Boaedon capensis species complex, two of the most taxonomically challenging groups of African snakes, or considered a distinct taxonomic entity, B. bedriagae. Here we review the São Tomé and Príncipe populations through a combination of morphological and molecular data. Our results suggest that each island population represents a unique species. After a thorough review of the taxonomic and nomenclatural history of the group, we revalidate B. bedriagae, restricting the application of this name to the São Tomé population by the designation of a lectotype. We also describe the Príncipe population as a new species, Boaedon mendesi sp. nov. This description has implications to our understanding of the diversity and phylogeographic patterns of the Gulf of Guinea Oceanic Islands.

The oldest lamprophiid (Serpentes, Caenophidia) fossil from the late Oligocene Rukwa Rift Basin, Tanzania and the origins of African snake diversity

Extant snake faunas have their origins in the mid-Cenozoic, when colubroids replaced booid-grade snakes as the dominant species. The timing of this faunal changeover in North America and Europe based on fossils is thought to have occurred in the early Neogene, after a period of global cooling opened environments and made them suitable for more active predators. However, new fossils from the late Oligocene of Tanzania have revealed an early colubroid-dominated fauna in Africa suggesting a different pattern of faunal turnover there. Additionally, molecular divergence times suggest colubroid diversification began sometime in the Paleogene, although the exact timing and driving forces behind the diversification are not clear. Here we present the first fossil snake referred to the African clade Lamprophiinae, and the oldest fossil known of Lamprophiidae. As such, this specimen provides the only potential fossil calibration point for the African snake radiation represented by Lamprophiidae, and is the oldest snake referred to Elapoidea. A molecular clock analysis using this and other previously reported fossils as calibration points reveals colubroid diversification minimally occurred in the earliest Paleogene, although a Cretaceous origin cannot be excluded. The elapoid and colubrid lineages diverged during the period of global warming near the Paleocene-Eocene boundary, with both clades diversifying beginning in the early Eocene (proximate to the Early Eocene Climate Optimum) and continuing into the cooler Miocene. The majority of subclades diverge well before the appearance of colubroid dominance in the fossil record. These results suggest an earlier diversification of colubroids than generally previously thought, with hypothesized origins of these clades in Asia and Africa where the fossil record is relatively poorly known. Further work in these regions may provide new insights into the timing of, and environmental influences contributing to, the rise of colubroid snakes.

A much-needed tonic for African snakes (review of Jean-Philippe Chippaux and Kate Jackson, Snakes of Central and Western Africa)

A much-needed tonic for African snakes (review of Jean-Philippe Chippaux and Kate Jackson, Snakes of Central and Western Africa)

Heterochronic Developmental Shifts Underlying Squamate Cerebellar Diversity Unveil the Key Features of Amniote Cerebellogenesis.

Despite a remarkable conservation of architecture and function, the cerebellum of vertebrates shows extensive variation in morphology, size, and foliation pattern. These features make this brain subdivision a powerful model to investigate the evolutionary developmental mechanisms underlying neuroanatomical complexity both within and between anamniote and amniote species. Here, we fill a major evolutionary gap by characterizing the developing cerebellum in two non-avian reptile species—bearded dragon lizard and African house snake—representative of extreme cerebellar morphologies and neuronal arrangement patterns found in squamates. Our data suggest that developmental strategies regarded as exclusive hallmark of birds and mammals, including transit amplification in an external granule layer (EGL) and Sonic hedgehog expression by underlying Purkinje cells (PCs), contribute to squamate cerebellogenesis independently from foliation pattern. Furthermore, direct comparison of our models suggests the key importance of spatiotemporal patterning and dynamic interaction between granule cells and PCs in defining cortical organization. Especially, the observed heterochronic shifts in early cerebellogenesis events, including upper rhombic lip progenitor activity and EGL maintenance, are strongly expected to affect the dynamics of molecular interaction between neuronal cell types in snakes. Altogether, these findings help clarifying some of the morphogenetic and molecular underpinnings of amniote cerebellar corticogenesis, but also suggest new potential molecular mechanisms underlying cerebellar complexity in squamates. Furthermore, squamate models analyzed here are revealed as key animal models to further understand mechanisms of brain organization.

Bitis arietans Snake Venom Induces an Inflammatory Response Which Is Partially Dependent on Lipid Mediators.

Bitis arietans is a snake of medical importance, as it is responsible for more accidents in humans and domestic animals than all other African snakes put together. The accidents are characterized by local and systemic alterations, such as inflammation, cardiovascular and hemostatic disturbances, which can lead victims to death or permanent disability. However, little is known about the envenomation mechanism, especially regarding the inflammatory response, which is related to severe clinical conditions triggered by the venom. Therefore, the aim of the present study was to evaluate the inflammatory response related to the B. arietans envenomation using a peritonitis mice model. By pharmacological interventions and use of mice genetically deficient of the 5-lipoxygenase enzyme (5-LO−/−) or platelet-activating factor (PAF) receptor (PAFR−/− the participation of eicosanoids and PAF in this response was also investigated. The obtained results demonstrated that the venom induces an in vivo inflammatory response, characterized by an early increased vascular permeability, followed by an accumulation of polymorphonuclear (PMN) cells in the peritoneal cavity, accompanied by the production of the eicosanoids LTB4, LTC4, TXB2 and PGE2, as well as the local and systemic production of IL-6 and MCP-1. These inflammatory events were attenuated by the pre-treatment with anti-inflammatory drugs that interfere in lipid mediators’ functions. However, 5-LO−/− mice did not show a reduction of inflammatory response induced by the venom, while PAFR−/− mice showed a reduction in both the PMN leukocytes number and the local and systemic production of IL-6 and MCP-1. This study demonstrated that the Bitis arietans venom contains toxins that trigger an inflammatory process, which is partially dependent on lipid mediators, and may contribute to the envenomation pathology.