Intersexual variations in the venom of the Brazilian 'armed' spider Phoneutria nigriventer (Keyserling, 1891)

Intersexual Differences in the Gene Expression of Phoneutria depilata (Araneae, Ctenidae) Toxins Revealed by Venom Gland Transcriptome Analyses

The wandering spider, Phoneutria depilata, is one of Colombia's most active nocturnal arthropod predators of vertebrates and invertebrates. Its venom has been a relevant subject of study in the last two decades. However, the scarcity of transcriptomic data for the species limits our knowledge of the distinct components present in its venom for linking the mainly neurotoxic effects of the spider venom to a particular molecular target. The transcriptome of the P. depilata venom gland was analyzed to understand the effect of different diets or sex and the impact of these variables on the composition of the venom. We sequenced venom glands obtained from ten males and ten females from three diet treatments: (i) invertebrate: Tenebrio molitor, (ii) vertebrate: Hemidactylus frenatus, and (iii) mixed (T. molitor + H. frenatus). Of 17,354 assembled transcripts from all samples, 65 transcripts relating to venom production differed between males and females. Among them, 36 were classified as neurotoxins, 14 as serine endopeptidases, 11 as other proteins related to venom production, three as metalloprotease toxins, and one as a venom potentiator. There were no differences in transcripts across the analyzed diets, but when considering the effect of diets on differences between the sexes, 59 transcripts were differentially expressed. Our findings provide essential information on toxins differentially expressed that can be related to sex and the plasticity of the diet of P. depilata and thus can be used as a reference for venomics of other wandering spider species.

Worldwide Web: High Venom Potency and Ability to Optimize Venom Usage Make the Globally Invasive Noble False Widow Spider Steatoda nobilis (Thorell, 1875) (Theridiidae) Highly Competitive against Native European Spiders Sharing the Same Habitats

Venom compositions include complex mixtures of toxic proteins that evolved to immobilize/dissuade organisms by disrupting biological functions. Venom production is metabolically expensive, and parsimonious use is expected, as suggested by the venom optimisation hypothesis. The decision-making capacity to regulate venom usage has never been demonstrated for the globally invasive Noble false widow Steatoda nobilis (Thorell, 1875) (Theridiidae). Here, we investigated variations of venom quantities available in a wild population of S. nobilis and prey choice depending on venom availability. To partially determine their competitiveness, we compared their attack rate success, median effective dose (ED₅₀) and lethal dose (LD₅₀), with four sympatric synanthropic species: the lace webbed spider Amaurobius similis, the giant house spider Eratigena atrica, the missing sector orb-weaver Zygiella x-notata, and the cellar spider Pholcus phalangioides. We show that S. nobilis regulates its venom usage based on availability, and its venom is up to 230-fold (0.56 mg/kg) more potent than native spiders. The high potency of S. nobilis venom and its ability to optimize its usage make this species highly competitive against native European spiders sharing the same habitats.

Comparative venomic profiles of three spiders of the genus Phoneutria

Background:

Spider venoms induce different physio-pharmacological effects by binding with high affinity on molecular targets, therefore being of biotechnological interest. Some of these toxins, acting on different types of ion channels, have been identified in the venom of spiders of the genus Phoneutria, mainly from P. nigriventer. In spite of the pharmaceutical potential demonstrated by P. nigriventer toxins, there is limited information on molecules from venoms of the same genus, as their toxins remain poorly characterized. Understanding this diversity and clarifying the differences in the mechanisms of action of spider toxins is of great importance for establishing their true biotechnological potential. This prompted us to compare three different venoms of the Phoneutria genus: P. nigriventer (Pn-V), P. eickstedtae (Pe-V) and P. pertyi (Pp-V).

Methods:

Biochemical and functional comparison of the venoms were carried out by SDS-PAGE, HPLC, mass spectrometry, enzymatic activities and electrophysiological assays (whole-cell patch clamp).

Results:

The employed approach revealed that all three venoms had an overall similarity in their components, with only minor differences. The presence of a high number of similar proteins was evident, particularly toxins in the mass range of ~6.0 kDa. Hyaluronidase and proteolytic activities were detected in all venoms, in addition to isoforms of the toxins Tx1 and Tx2-6. All Tx1 isoforms blocked Nav1.6 ion currents, with slight differences.

Conclusion:

Our findings showed that Pn-V, Pe-V and Pp-V are highly similar concerning protein composition and enzymatic activities, containing isoforms of the same toxins sharing high sequence homology, with minor modifications. However, these structural and functional variations are very important for venom diversity. In addition, our findings will contribute to the comprehension of the molecular diversity of the venoms of the other species from Phoneutria genus, exposing their biotechnological potential as a source for searching for new active molecules.

Linking toxicity and predation in a venomous arthropod: the case of Tityus fuhrmanni (Scorpiones: Buthidae), a generalist predator scorpion

Background:

Scorpions are arachnids that have a generalist diet, which use venom to subdue their prey. The study of their trophic ecology and capture behavior is still limited compared to other organisms, and aspects such as trophic specialization in this group have been little explored.

Methods:

In order to determine the relationship between feeding behavior and venom toxicity in the scorpion species Tityus fuhrmanni, 33 specimens were offered prey with different morphologies and defense mechanisms: spiders, cockroaches and crickets. In each of the experiments we recorded the following aspects: acceptance rate, immobilization time and the number of capture attempts. The median lethal dose of T. fuhrmanni venom against the three different types of prey was also evaluated.

Results:

We found that this species does not have a marked difference in acceptance for any of the evaluated prey, but the number of capture attempts of spiders is higher when compared to the other types of prey. The immobilization time is shorter in spiders compared to other prey and the LD₅₀ was higher for cockroaches.

Conclusions:

These results indicate that T. fuhrmanni is a scorpion with a generalist diet, has a venom with a different potency among prey and is capable of discriminating between prey types and employing distinct strategies to subdue them.

The biology and evolution of spider venoms

Spiders are diverse, predatory arthropods that have inhabited Earth for around 400 million years. They are well known for their complex venom systems that are used to overpower their prey. Spider venoms contain many proteins and peptides with highly specific and potent activities suitable for biomedical or agrochemical applications, but the key role of venoms as an evolutionary innovation is often overlooked, even though this has enabled spiders to emerge as one of the most successful animal lineages. In this review, we discuss these neglected biological aspects of spider venoms. We focus on the morphology of spider venom systems, their major components, biochemical and chemical plasticity, as well as ecological and evolutionary trends. We argue that the effectiveness of spider venoms is due to their unprecedented complexity, with diverse components working synergistically to increase the overall potency. The analysis of spider venoms is difficult to standardize because they are dynamic systems, fine-tuned and modified by factors such as sex, life-history stage and biological role. Finally, we summarize the mechanisms that drive spider venom evolution and highlight the need for genome-based studies to reconstruct the evolutionary history and physiological networks of spider venom compounds with more certainty.

Deciphering the diet of a wandering spider (Phoneutria boliviensis; Araneae: Ctenidae) by DNA metabarcoding of gut contents

Arachnids are the most abundant land predators. Despite the importance of their functional roles as predators and the necessity to understand their diet for conservation, the trophic ecology of many arachnid species has not been sufficiently studied. In the case of the wandering spider, Phoneutria boliviensis F. O. Pickard-Cambridge, 1897, only field and laboratory observational studies on their diet exist. By using a DNA metabarcoding approach, we compared the prey found in the gut content of males and females from three distant Colombian populations of P. boliviensis. By DNA metabarcoding of the cytochrome c oxidase subunit I (COI), we detected and identified 234 prey items (individual captured by the spider) belonging to 96 operational taxonomic units (OTUs), as prey for this wandering predator. Our results broaden the known diet of P. boliviensis with at least 75 prey taxa not previously registered in fieldwork or laboratory experimental trials. These results suggest that P. boliviensis feeds predominantly on invertebrates (Diptera, Lepidoptera, Coleoptera, and Orthoptera) and opportunistically on small squamates. Intersex and interpopulation differences were also observed. Assuming that prey preference does not vary between populations, these differences are likely associated with a higher local prey availability. Finally, we suggest that DNA metabarcoding can be used for evaluating subtle differences in the diet of distinct populations of P. boliviensis, particularly when predation records in the field cannot be established or quantified using direct observation.

Proteotranscriptomic Insights into the Venom Composition of the Wolf Spider Lycosa tarantula

Spider venoms represent an original source of novel compounds with therapeutic and agrochemical potential. Whereas most of the research efforts have focused on large mygalomorph spiders, araneomorph spiders are equally promising but require more sensitive and sophisticated approaches given their limited size and reduced venom yield. Belonging to the latter group, the genus Lycosa ("wolf spiders") contains many species widely distributed throughout the world. These spiders are ambush predators that do not build webs but instead rely strongly on their venom for prey capture. Lycosa tarantula is one of the largest species of wolf spider, but its venom composition is unknown. Using a combination of RNA sequencing of the venom glands and venom proteomics, we provide the first overview of the peptides and proteins produced by this iconic Mediterranean spider. Beside the typical small disulfide rich neurotoxins, several families of proteins were also identified, including cysteine-rich secretory proteins (CRISP) and Hyaluronidases. Proteomic analysis of the electrically stimulated venom validated 30 of these transcriptomic sequences, including nine putative neurotoxins and eight venom proteins. Interestingly, LC-MS venom profiles of manual versus electric stimulation, as well as female versus male, showed some marked differences in mass distribution. Finally, we also present some preliminary data on the biological activity of L. tarantula crude venom.

Sexual dimorphism in the biomechanical and toxicological performance in prey incapacitation of two morphologically distinct scorpion species (Chactas sp. and Centruroides sp.)

Morphological differences between the sexes are a common feature in many groups of animals and can have important ecological implications for courtship, mating, access to prey and, in some cases, intersex niche partitioning. In this study, we evaluated the role of sexual dimorphism in the performance of the two structures that mediate the ability to access prey, the pinchers or chelae and the venomous stinger, in two species of scorpions with contrasting morphologies: Chactas sp., which has marked sexual dimorphism in the chelae, and Centruroides sp., which does not have such marked dimorphism in the chelae. We evaluated aspects such as chela pinch force, toxicity to prey (LD50) and the volume of venom in males and females of each species. We found significant differences between males and females of Chactas sp. in the chela pinch force, volume of venom and LD50. In contrast, for Centruroides sp., no differences between males and females were found in any of these traits. We discuss several potential selective regimes that could account for the pattern observed.

Prey and Venom Efficacy of Male and Female Wandering Spider, Phoneutria boliviensis (Araneae: Ctenidae)

Spiders rely on venom to catch prey and few species are even capable of capturing vertebrates. The majority of spiders are generalist predators, possessing complex venom, in which different toxins seem to target different types of prey. In this study, we focused on the trophic ecology and venom toxicity of Phoneutria boliviensis F. O. Pickard-Cambridge, 1897, a Central American spider of medical importance. We tested the hypothesis that its venom is adapted to catch vertebrate prey by studying its trophic ecology and venom toxicity against selected vertebrate and invertebrate prey. We compared both trophic ecology (based on acceptance experiments) and toxicity (based on bioassays) among sexes of this species. We found that P. boliviensis accepted geckos, spiders, and cockroaches as prey, but rejected frogs. There was no difference in acceptance between males and females. The venom of P. boliviensis was far more efficient against vertebrate (geckos) than invertebrate (spiders) prey in both immobilization time and LD50. Surprisingly, venom of males was more efficient than that of females. Our results suggest that P. boliviensis has adapted its venom to catch vertebrates, which may explain its toxicity to humans.

Evolutionary Ecology of Fish Venom: Adaptations and Consequences of Evolving a Venom System

Research on venomous animals has mainly focused on the molecular, biochemical, and pharmacological aspects of venom toxins. However, it is the relatively neglected broader study of evolutionary ecology that is crucial for understanding the biological relevance of venom systems. As fish have convergently evolved venom systems multiple times, it makes them ideal organisms to investigate the evolutionary ecology of venom on a broader scale. This review outlines what is known about how fish venom systems evolved as a result of natural enemy interactions and about the ecological consequences of evolving a venom system. This review will show how research on the evolutionary ecology of venom in fish can aid in understanding the evolutionary ecology of animal venoms more generally. Further, understanding these broad ecological questions can shed more light on the other areas of toxinology, with applications across multiple disciplinary fields.

Phoneutria nigriventer Spider Toxin PnTx2-1 (δ-Ctenitoxin-Pn1a) Is a Modulator of Sodium Channel Gating

Spider venoms are complex mixtures of biologically active components with potentially interesting applications for drug discovery or for agricultural purposes. The spider Phoneutria nigriventer is responsible for a number of envenomations with sometimes severe clinical manifestations in humans. A more efficient treatment requires a comprehensive knowledge of the venom composition and of the action mechanism of the constituting components. PnTx2-1 (also called δ-ctenitoxin-Pn1a) is a 53-amino-acid-residue peptide isolated from the venom fraction PhTx2. Although PnTx2-1 is classified as a neurotoxin, its molecular target has remained unknown. This study describes the electrophysiological characterization of PnTx2-1 as a modulator of voltage-gated sodium channels. PnTx2-1 is investigated for its activity on seven mammalian Na_V-channel isoforms, one insect Na_V channel and one arachnid Na_V channel. Furthermore, comparison of the activity of both PnTx2-1 and PnTx2-6 on Na_V1.5 channels reveals that this family of Phoneutria toxins modulates the cardiac Na_V channel in a bifunctional manner, resulting in an alteration of the inactivation process and a reduction of the sodium peak current.

Female-biased population divergence in the venom of the Hentz striped scorpion (Centruroides hentzi)

Sex-biased genes are expressed at higher levels in one sex and contribute to phenotypic differences between males and females, as well as overall phenotypic variation within and among populations. Venom has evolved primarily for predation and defense, making venom expression a highly variable phenotype as a result of local adaptation. Several scorpion species have shown both intraspecific and intersexual venom variation, and males have been observed using venom in courtship and mating, suggesting the existence of venom-specific, sex-biased genes that may contribute to population divergence. We used reversed-phase high-performance liquid chromatography (RP-HPLC), Agilent protein bioanalyzer chips, nano-liquid chromatography mass spectrometry (nLC/MS/MS), and median lethal dose (LD₅₀) assays in fruit flies (Drosophila melanogaster) and banded crickets (Gryllodes sigillatus) to investigate proteomic and functional venom variation within and among three Florida populations of the Hentz striped scorpion (Centruroides hentzi). We found significant venom variation among populations, with females, not males, being responsible for this divergence. We also found significant variation in venom expression within populations, with males contributing more to within population variation than females. Our results provide evidence that male and female scorpions experience different natural and sexual selective pressures that have led to the expression of sex-biased venom genes and that these genes may be consequential in population divergence.

Sexually dimorphic venom proteins in long-jawed orb-weaving spiders (Tetragnatha) comprise novel gene families

Venom has been associated with the ecological success of many groups of organisms, most notably reptiles, gastropods, and arachnids. In some cases, diversification has been directly linked to tailoring of venoms for dietary specialization. Spiders in particular are known for their diverse venoms and wide range of predatory behaviors, although there is much to learn about scales of variation in venom composition and function. The current study focuses on venom characteristics in different sexes within a species of spider. We chose the genus Tetragnatha (Tetragnathidae) because of its unusual courtship behavior involving interlocking of the venom delivering chelicerae (i.e., the jaws), and several species in the genus are already known to have sexually dimorphic venoms. Here, we use transcriptome and proteome analyses to identify venom components that are dimorphic in Tetragnatha versicolor. We present cDNA sequences including unique, male-specific high molecular weight proteins that have remote, if any, detectable similarity to known venom components in spiders or other venomous lineages and have no detectable homologs in existing databases. While the function of these proteins is not known, their presence in association with the cheliceral locking mechanism during mating together with the presence of prolonged male-male mating attempts in a related, cheliceral-locking species (Doryonychus raptor) lacking the dimorphism suggests potential for a role in sexual communication.

Lethality and histopathological alterations caused by Phoneutria nigriventer spider venom from Argentina: Neutralization of lethality by experimental and therapeutic antivenoms

Although the spiders of the genus Phoneutria cause envenomation and their presence has been described in several provinces of the north of Argentina, they are not as common as other spiders of sanitary importance. In the present work, we studied the toxicity of samples of venom of Phoneutria spiders from the provinces of Misiones (where severe envenomation and deaths by Phoneutria have been recorded) and Jujuy (where no deaths have been recorded and severe envenomations are not frequent). To this end, we assessed the lethal potency in mice and guinea pigs and the histopathological alterations caused by both venoms, as well as the neutralization by the commonly used therapeutic antivenom produced by the Butantan Institute in Brazil and by an experimental antivenom developed with venom of P. nigriventer from Misiones. There were no differences in the lethality of the venoms of spiders from both regions. Post mortem examination showed that the heart and lungs were the most affected organs, while important pulmonary edema was seen macroscopically. Histological analysis showed edema, atelectasis, emphysema and cardiac lesion in both experimental models. The antivenoms assayed showed good neutralization of the venoms in the two experimental models. Despite the different geographic origins, the venoms showed similar toxicity and both the experimental antivenom and therapeutic antivenmos were able to neutralize the venoms of Argentinean P. nigriventer.

Sex Differences in Defensive Behavior and Venom of The Striped Bark Scorpion Centruroides vittatus (Scorpiones: Buthidae)

Studies of venom variability have advanced from describing the mechanisms of action and relative potency of medically important toxins to understanding the ecological and evolutionary causes of the variability itself. While most studies have focused on differences in venoms among taxa, populations, or age-classes, there may be intersexual effects as well. Striped bark scorpions (Centruroides vittatus) provide a good model for examining sex differences in venom composition and efficacy, as this species exhibits dramatic sexual dimorphism in both size and defensive behavior; when threatened by an enemy, larger, slower females stand and fight while smaller, fleeter males prefer to run. We here add evidence suggesting that male and female C. vittatus indeed have different defensive propensities; when threatened via an electrical stimulus, females were more likely to sting than were males. We reasoned that intersexual differences in defensive phenotypes would select for venoms with different functions in the two sexes; female venoms should be effective at predator deterrence, whereas male venoms, less utilized defensively, might be better suited to capturing prey or courting females. This rationale led to our predictions that females would inject more venom and/or possess more painful venom than males. We were wrong. While females do inject more venom than males in a defensive sting, females are also larger; when adjusted for body size, male and female C. vittatus commit equal masses of venom in a sting to a potential enemy. Additionally, house mice (Mus musculus) find an injection of male venom more irritating than an equal amount of female venom, likely because male venom contains more of the toxins that induce pain. Taken together, our results suggest that identifying the ultimate causes of venom variability will, as we move beyond adaptive storytelling, be hard-won.

Biochemical and electrophysiological characterization of two sea anemone type 1 potassium toxins from a geographically distant population of Bunodosoma caissarum

Sea anemone (Cnidaria, Anthozoa) venom is an important source of bioactive compounds used as tools to study the pharmacology and structure-function of voltage-gated K+ channels (KV). These neurotoxins can be divided into four different types, according to their structure and mode of action. In this work, for the first time, two toxins were purified from the venom of Bunodosoma caissarum population from Saint Peter and Saint Paul Archipelago, Brazil. Sequence alignment and phylogenetic analysis reveals that BcsTx1 and BcsTx2 are the newest members of the sea anemone type 1 potassium channel toxins. Their functional characterization was performed by means of a wide electrophysiological screening on 12 different subtypes of KV channels (KV1.1-KV1.6; KV2.1; KV3.1; KV4.2; KV4.3; hERG and Shaker IR). BcsTx1 shows a high affinity for rKv1.2 over rKv1.6, hKv1.3, Shaker IR and rKv1.1, while Bcstx2 potently blocked rKv1.6 over hKv1.3, rKv1.1, Shaker IR and rKv1.2. Furthermore, we also report for the first time a venom composition and biological activity comparison between two geographically distant populations of sea anemones.

Developmental biology of the Brazilian 'Armed' spider Phoneutria nigriventer (Keyserling, 1891): microanatomical and molecular analysis of the embryonic stages

Phoneutria (Ctenidae) is among the most dangerous venomous spiders in Brazil. Its venom is composed of a mixture of pharmacologically active components, some of which have been quite extensively studied due to their potentiality as models for new pharmaceutical drugs. Nevertheless, literature data on the venom-producing glands are very limited. In the present study, we follow the biological development of intra-cocoon stages of Phoneutria nigriventer spiders, mainly regarding the formation of the venomous apparatus and venom production. The results showed that the venom glands of Phoneutria are already present in the early 1st pre-larva stage. The venomous apparatus is completely formed in the larva, a stage that precedes the spider eclosion from the cocoon. At embryo stages, transcripts of a vertebrate-active neurotoxin (PhTx1) were shown to be present, as well as, unidentified venom proteins that were immunolabeled by anti-venom antibodies. It seems that venom toxins play roles in the protection and survival of those early developmental stages of Phoneutria spiders.

Venom apparatus of the Brazilian tarantula Vitalius dubius Mello-Leitão 1923 (Theraphosidae)

Tarantula venoms are a cocktail of proteins and peptides that have been increasingly studied in recent years. In contrast, less attention has been given to analyzing the structure of the paired cephalic glands that produce the venom. We have used light, electron, and confocal microscopy to study the organization and structure of the venom gland of the Brazilian tarantula Vitalius dubius. The chelicerae are hairy chitinous structures, each with a single curved hollow fang that opens via an orifice on the anterior surface. Internally, each chelicera contains striated muscle fiber bundles that control fang extension and retraction, and a cylindrical conical venom gland surrounded by a thick well-developed layer of obliquely arranged muscle fibers. Light microscopy of longitudinal and transverse sections showed that the gland secretory epithelium consists of a sponge-like network of slender epithelial cell processes with numerous bridges and interconnections that form lacunae containing secretion. This secretory epithelium is supported by a basement membrane containing elastic fibers. The entire epithelial structure of the venom-secreting cells is reinforced by a dense network of F-actin intermediate filaments, as shown by staining with phalloidin. Neural elements (axons and acetylcholinesterase activity) are also associated with the venom gland. Transmission electron microscopy of the epithelium revealed an ultrastructure typical of secretory cells, including abundant rough and smooth endoplasmic reticulum, an extensive Golgi apparatus, and numerous mitochondria.

Ctenus medius and Phoneutria nigriventer spiders venoms share noxious proinflammatory activities

Ctenus medius Keyserling, 1891 (Araneae: Ctenidae) co-occurs in various microhabitats of the Brazilian Atlantic Forest and can be easily misidentified as the medically important spider Phoneutria nigriventer Keyserling, 1981 (Ctenidae). Despite being phylogenetically close to Phoneutria, no data are available about the toxic potential of Ctenus medius venom. Here we show that, although presenting different profile of protein composition, C. medius venom displays some of the toxic properties exhibited by P. nigriventer venom, including proteolytic, hyaluronidasic and phospholipasic activities, as well as the ability of causing hyperalgesia and edema. Moreover, C. medius venom interferes in the activation of the complement system in concentrations that P. nigriventer venom is inactive. Thus, these data show that venoms of spiders from Ctenidae family share important proinflammatory properties and suggest that the C. medius bite may have an important noxious effect in human accidents.

Venom from spiders of the genus Hippasa: biochemical and pharmacological studies

The venoms from female spiders of the genus Hippasa namely H. partita, H. agelenoides and H. lycosina are compared for biochemical and pharmacological properties. SDS-PAGE pattern revealed varied protein composition. Marked variability is seen with casein hydrolyzing enzymes in SDS-PAGE zymogram. H. partita venom was the only venom that hydrolyzed gelatin while the other two venoms did not. The venoms shared similar hyaluronidase activity, showing a single activity band in SDS-PAGE zymogram. The PLA2 activity varied as H. partita>H. agelenoides>H. lycosina venoms. Marked differences were noted in the ability to induce edema, cytotoxicity, myotoxicity and neurotoxicity, while hemorrhage was associated exclusively with H. partita venom.

Comparison of the partial proteomes of the venoms of Brazilian spiders of the genus Phoneutria

The proteomes of the venoms of the Brazilian wandering "armed" spiders Phoneutria nigriventer, Phoneutria reidyi, and Phoneutria keyserlingi, were compared using two-dimensional gel electrophoresis. The venom components were also fractionated using a combination of preparative reverse phase HPLC on Vydac C4, analytical RP-HPLC on Vydac C8 and C18 and cation exchange FPLC on Resource S at pH 6.1 and 4.7, or anion exchange HPLC on Synchropak AX-300 at pH 8.6. The amino acid sequences of the native and S-pyridyl-ethylated proteins and peptides derived from them by enzymatic digestion and chemical cleavages were determined using a Shimadzu PPSQ-21(A) automated protein sequencer, and by MS/MS collision induced dissociations. To date nearly 400 peptides and proteins (1.2-27 kDa) have been isolated in a pure state and, of these, more than 100 have had their complete or partial amino acid sequences determined. These sequences demonstrate, as might be expected, that the venoms of P. reidyi and P. keyserlingi (Family: Ctenidae) both contain a similar range of isoforms of the neurotoxins as those previously isolated from P. nigriventer which are active on neuronal ion (Ca(2+), Na(+) and K(+)) channels and NMDA-type glutamate receptors. In addition two new families of small (3-4 kDa) toxins, some larger protein (>10 kDa) components, and two serine proteinases of the venom of P. nigriventer are described. These enzymes may be responsible for some of the post-translational modification observed in some of the venom components.

Ontogenetic changes in Phoneutria nigriventer (Araneae, Ctenidae) spider venom

Venom-yield and composition of differently sized individuals of the medically most important Brazilian spider Phoneutria nigriventer (Keyserling, 1891) was analysed. During growth the venom-mass increases according to a fourth order function of the prosoma size, which mainly reflects an increase of the venom gland volume. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed increasing percentages of proteins < or = 17 kDa from 4.1% in the smallest analysed spiders (2-3 months-old) to 79.1% in adult female venom. Additionally, high-pressure liquid-chromatography showed an increase of a single ('main') peak from 4.6 to 64.9%, while the overall number of other major-peaks decreased. Venom from young instars completely lacked lethality in mice up to a dose of 3.28 mg/kg i.v. as compared to a LD(50) of 0.63 mg/kg for adult female or 1.57 mg/kg for adult male venom that we reported previously. In conclusion, ontogenetic changes in venom protein-composition of growing P. nigriventer are suggested to produce increasing lethality in vertebrates.