Characterisation of protein families in spider digestive fluids and their role in extra-oral digestion

André Walter,Jesper Bechsgaard,Kristian W Sanggaard,Jan J Enghild,Carsten Scavenius,Trine Bilde,Thomas S Dyrlund

doi:10.1186/s12864-017-3987-9

Abstract

BackgroundSpiders are predaceous arthropods that are capable of subduing and consuming relatively large prey items compared to their own body size. For this purpose, spiders have evolved potent venoms to immobilise prey and digestive fluids that break down nutrients inside the prey’s body by means of extra-oral digestion (EOD). Both secretions contain an array of active proteins, and an overlap of some components has been anecdotally reported, but not quantified. We systematically investigated the extent of such protein overlap. As venom injection and EOD succeed each other, we further infer functional explanations, and, by comparing two spider species belonging to different clades, assess its adaptive significance for spider EOD in general.ResultsWe describe the protein composition of the digestive fluids of the mygalomorph Acanthoscurria geniculata and the araneomorph Stegodyphus mimosarum, in comparison with previously published data on a third spider species. We found a number of similar hydrolases being highly abundant in all three species. Among them, members of the family of astacin-like metalloproteases were particularly abundant. While the importance of these proteases in spider venom and digestive fluid was previously noted, we now highlight their widespread use across different spider taxa. Finally, we found species specific differences in the protein overlap between venom and digestive fluid, with the difference being significantly greater in S. mimosarum compared to A. geniculata.ConclusionsThe injection of venom precedes the injection with digestive fluid, and the overlap of proteins between venom and digestive fluid suggests an early involvement in EOD. Species specific differences in the overlap may reflect differences in ecology between our two study species. The protein composition of the digestive fluid of all the three species we compared is highly similar, suggesting that the cocktail of enzymes is highly conserved and adapted to spider EOD.

Highlights

Spiders are predaceous arthropods that are capable of subduing and consuming relatively large prey items compared to their own body size
527 proteins were identified in Stegodyphus mimosarum and 305 proteins in Acanthoscurria geniculata, out of which 71 and 37 respectively were quantified based on ion intensities
Apart from the proteins that we discuss in the context of either venom or digestive activities, we found a number of cellular proteins in low concentrations that most likely derive from gut cells, since the spiders were not physically damaged during the digestive fluid sampling

Summary

Introduction

Spiders are predaceous arthropods that are capable of subduing and consuming relatively large prey items compared to their own body size For this purpose, spiders have evolved potent venoms to immobilise prey and digestive fluids that break down nutrients inside the prey’s body by means of extra-oral digestion (EOD). Spiders have evolved potent venoms to immobilise prey and digestive fluids that break down nutrients inside the prey’s body by means of extra-oral digestion (EOD) Both secretions contain an array of active proteins, and an overlap of some components has been anecdotally reported, but not quantified. The mode of digesting extra-orally may have a beneficial side effect as it allows spiders to defend themselves against infections before potential pathogens enter their body It may not surprise if immune proteins are found in digestive fluids [15]

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Results

Conclusion