Spit and Venom from Scytodes Spiders: A Diverse and Distinct Cocktail

Spiders
from the family Scytodidae have a unique prey capturing
technique: they spit a zig-zagged silken glue to tether prey to a
surface. Effectiveness of this sticky mixture is based on a combination
of contraction and adhesion, trapping prey until the spider immobilizes
it by envenomation and then feeds. We identify components expressed
in Scytodes thoracica venom glands
using combined transcriptomic and proteomic analyses. These include
homologues of toxic proteins astacin metalloproteases and potentially
toxic proteins including venom allergen, longistatin, and translationally
controlled tumor protein (TCTP). We classify 19 distinct groups of
candidate peptide toxins; 13 of these were detected in the venom,
making up 35% of the proteome. Six have significant similarity to
toxins from spider species spanning mygalomorph and nonhaplogyne araneomorph
lineages, suggesting their expression in venom is phylogenetically
widespread. Twelve peptide toxin groups have homologues in venom gland
transcriptomes of other haplogynes. Of the transcripts, approximately
50% encode glycine-rich peptides that may contribute to sticky fibers
in Scytodes spit. Fifty-one percent
of the identified venom proteome is a family of proteins that is homologous
to sequences from Drosophila sp. and Latrodectus hesperus with uncharacterized function.
Characterization of these components holds promise for discovering
new functional activity.