Revealing the venomous secrets of the spider's web

Golden silk orb-weaver Nephila clavipes / Charles J Sharp / CC BY-SA

Not a British spider, but this is interesting:

Revealing the venomous secrets of the spider's web. (2020) J Proteome Res. https://pubs.acs.org/doi/10.1021/acs.jproteome.0c00086

Orb-weaving spiders use a highly strong, sticky and elastic web to catch their prey. These web properties alone would be enough for the entrapment of prey; however, these spiders may be hiding venomous secrets in the web, which current research is revealing. Here, we provide strong proteotranscriptomic evidence for the presence of toxin/neurotoxin-like proteins, defensins and proteolytic enzymes on the web silk from Nephila clavipes spider. The results from quantitative-based transcriptomics and proteomic approaches showed that silk-producing glands produce an extensive repertoire of toxin/neurotoxin-like proteins, similar to those already reported in spider venoms. Meanwhile, the insect toxicity results demonstrated that these toxic components can be lethal and/or paralytic chemical weapons used for prey capture on the web; and the presence of fatty acids in the web may be responsible mechanism for open the way to the web-toxins for accessing the interior of prey's body. Comparative phylogenomic-level evolutionary analyses revealed orthologous genes among two spider groups - Araneomorphae and Mygalomorphae; and the findings showed protein sequences similar to toxins found in the taxa Scorpiones and Hymenoptera in addition to Araneae. Overall, these data represent a valuable resource to further investigate other spider web toxin systems; these data also suggest that N. clavipes web is not a passive mechanical trap for prey capture, but it exerts an active role in prey paralysis/killing using a series of neurotoxins.

 

Woodlice Change the Habitat Use of Spiders in a Different Food Chain

This is an interesting one:

Woodlice change the habitat use of spiders in a different food chain. (2020) PeerJ. 2020; 8: e9184. https://doi.org/10.7717/peerj.9184

Background: In old field systems, the common woodlouse may have an indirect effect on a nursery web spider. Woodlice and nursery web spiders feed in different food chains, yet previous work demonstrated that the presence of woodlice is correlated with higher predation success by nursery web spiders upon their grasshopper prey. This finding suggested a new hypothesis which links two seemingly disparate food chains: when woodlice are present, the spider predator or the grasshopper prey changes their location in the vegetative canopy in a way that increases their spatial overlap and therefore predation rate. However, warming temperatures may complicate this phenomenon. The spider cannot tolerate thermal stress, meaning warming temperatures may cause the spider to move downwards in the vegetative canopy or otherwise alter its response to woodlice. Therefore, we would expect warming and woodlice presence to have an interactive effect on predation rate. Results: Habitat domain observations revealed that spiders shift upward in the canopy when woodlice are present, but the corresponding effect on grasshopper prey survival was variable over the different years of study. Under warming conditions, spiders remained lower in the canopy regardless of the presence of woodlice, suggesting that thermal stress is more important than the effect of woodlice. Our modelling results suggest that spiders do not need to move away from woodlice to maximize net energy gain (expected net energy gain and signal detection theory models). Instead spider behavior is consistent with the null hypothesis that they move away from unsuccessful encounters with woodlice (individual-based simulation). We conclude that mapping how predator behavior changes across biotic (e.g. woodlouse presence) and abiotic conditions (e.g. temperature) may be critical to anticipate changes in ecosystem dynamics.

A time of change

Blogger has forced the new interface on me. I hate it and had to go back to the legacy interface to publish this because I couldn't insert an image in the new version. I'm wondering if it's time to go back to Wordpress again, but more realistically, since most of my posts are image-oriented, it's likely to be Flickr. After 24 years of Photoshop, I've moved to Affinity Photo. I'm finding it quite a learning curve. But now the important stuff. I've been a Zerene Stacker user for years but for a number of reasons felt I ought to try Helicon Focus, so I grabbed the nearest spider and took a 27 photo stack, then ran them both through Zerene (PMax) and Helicon (Method C):


Spot the difference? Actually there is one, but maybe not what you think. There are lots of reviews of Zerene versus Helicon online, and I can now confirm what they all say! Zerene is *marginally* sharper - but only if you pixel-peep, Helicon is much faster (4-5 times on my setup). What does this mean in practice? A 27 image stack that takes 3 minutes 14 seconds to process with Zerene runs in 40 seconds with Helicon. But Helicon is over a hundred quid and marginally less sharp. I may be better investing in hardware. Opinions welcome!

(Update: partial solution to the Blogger problem, a browser conflict).

In the vernacular

Hypomma bituberculatum

The old discussion about English Common Names has reared it's head again. It goes like this: Latin binomials are not memorable to the general public and off-puttingly technical to casual observers. Spiders would be more popular if they had accessible common names like flowers, birds, dragonflies and moths. Wouldn't you like to spend an afternoon in a beautiful water meadow with Swallows buzzing around your ears, head down looking for the Wrinkly-Arsed Marsh Knobhead?

Scorched Earth

The highlight of my spider year in 2019 was documenting the remarkable range expansion of Agelena labyrinthica in VC55 (Cann, A., Cann, J. (2020) 2019: A Remarkable Year For Agelena labyrinthica. https://doi.org/10.6084/m9.figshare.11918838.v1). Having been somewhat lockdown limited until recently I haven't recorded this species yet in 2020, but they are now appearing and records are being submitted. One remarkable observation caught my attention, the occurrence of the characteristic funnel webs in bare ploughed soil. I've never seen this before, but what this also makes clear is the the seemingly unstoppable march of Agelena labyrinthica continues: