Uloborus plumipes has lost venom but not toxicity

In this project, we performed RNA-Seq on various tissues of the venomless spider Uloborus plumipes to assess whether Uloboridae spiders have lost their toxins along with their venom apparatus. We sampled chelicerae, whole prosoma, midgut gland, silk glands, and gonads. We detected several toxin-like transcripts in the midgut samples, including transcripts with predicted neurotoxic activity. Midgut gland extract had comparable toxicity levels to that of the venomous spider, Parasteatoda tepidariorum. However, no inhibitory effects were observed on the potassium channel Shaker IR and the sodium channel BgNav1, indicating a different toxic mechanisms.These findings support the hypothesis that Uloboridae spiders have lost their venom apparatus while retaining toxin-like genes. The potent toxicity of their digestive fluids, a trait conserved across spiders, likely compensate for the absence of venom, ensuring effective prey immobilisation and digestion.