Arthropod assassins: Crawling biochemists with diverse toxin pharmacopeias

Abstract

The millions of extant arthropod species are testament to their evolutionary success that can at least partially be attributed to venom usage, which evolved independently in at least arthropod lineages. While some arthropods primarily use venom for predation (e.g., spiders and centipedes) or defense (e.g., bees and caterpillars), it can also have more specialised functions (e.g. in parasitoid wasps to paralyse arthropods for their brood to feed on) or even a combination of functions (e.g. the scorpion Parabuthus transvaalicus can deliver a prevenom for predator deterrence and a venom for predation). Most arthropod venoms are complex cocktails of water, salts, small bioactive molecules, peptides, enzymes and larger proteins, with peptides usually comprising the majority of toxins. Some spider venoms have been reported to contain > 1,000 peptide toxins, which function as combinatorial libraries to provide an evolutionary advantage. The astounding diversity of venomous arthropods multiplied by their enormous toxin arsenals results in an almost infinite resource for novel bioactive molecules. The main challenge for exploiting this resource is the small size of most arthropods, which can be a limitation for current venom extraction techniques. Fortunately, recent decades have seen an incredible improvement in transcriptomic and proteomic techniques that have provided increasing sensitivity while reducing sample requirements. In turn, this has provided a much larger variety of arthropod venom compounds for potential applications such as therapeutics, molecular probes for basic research, bioinsecticides or anti-parasitic drugs. This special issue of Toxicon aims to cover the breadth of arthropod venom research, including toxin evolution, pharmacology, toxin discovery and characterisation, toxin structures, clinical aspects, and potential applications. 1. Diversity of arthropod venom systems

Animal toxins — Nature’s evolutionary-refined toolkit for basic research and drug discovery

“…During the course of evolution, venom has evolved independently at least 100 times across eight different phyla [11]. It has been estimated that there are > 220,000 venomous species on the planet, representing~15% of extant animal biodiversity [12], spanning invertebrates such as annelids, arthropods, cnidarians, molluscs, nematodes, sea urchins, star fish, and vertebrates such as snakes, lizards, fish, shrews, and platypus [1,[12][13][14]. Chemically, venoms are complex mixtures of salts, small molecules, peptides, and proteins [15,16], with an estimated 20 million compounds in spider venoms alone [17].…”

An economic dilemma between weapon systems may explain an arachno-atypical venom in wasp spiders (Argiope bruennichi)

“…Spider venoms tend to be chemically more complex than other animal venoms and up to 1000 different venom components can be present in a single species (Herzig, 2019;Langenegger et al, 2019). It has been estimated, that the sum of all spider venoms could ultimately yield 10 million bioactive molecules, but only 0.02% of this diversity has been discovered thus far (Pineda et al, 2018;Lüddecke et al, 2019).…”

“…This restricted analysis to members of the families Atracidae, Ctenidae, Theraphosidae, Sicariidae and Theridiidae, which represent a narrow sample of spider diversity (Lüddecke et al, 2019;World Spider Catalog, 2020). More recently, the advent of high-throughput methods compatible with miniscule samples has provided the means to expand the scope of such studies to less-accessible species Herzig, 2019). Combinations of genomics, transcriptomics, proteomics and microbiomics (e.g.…”

Arthropod Venom Components and Their Potential Usage

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Arthropods comprise a predominant and well-succeeded phylum of the animal kingdom that evolved and diversified in millions of species grouped in four subphyla, namely, Chelicerata (arachnids), Crustacea, Myriapoda (centipedes), and Hexapoda (insects). It is agreed that the success of the arthropods' flourishment and evolutionary story are in great part due to the diversification of venom apparatus and venom usage [1,2]. Thousands of arthropod species, ranging from arachnids (spiders and scorpions) to hymenopterans (ants, bees, and wasps) and myriapods (centipedes), are venomous and utilize their venoms for chemical ecological warfare that includes individual and colonial defense, predation, and paralysis of coexistent species to nourish their brood.

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