Arachnews: March 2, 2020
Your weekly roundup of art, news, and science about our arachnid friends.
Published in
10 min readMar 2, 2020
Words in bold are defined in the glossary at the end of the post.
Art & Social Media
- Caitlin Henderson has a great video of a wolf spider making her egg sac. Wolf spiders are known for carrying their egg sacs around under their abdomens until the eggs hatch, after which the spiderlings ride around on their mother’s back. [Twitter]
- Fishing spiders (family Pisauridae) also carry around their egg sacs, but in their jaws. This Dolomedes captured by @bufoninus has her egg sac submerged in the water. [Twitter]
- Old (from 2016), but still very cool: Jay Keller’s observations of a two-tailed Arizona bark scorpion (Centruroides sculpturatus). He reported that it stung its prey with both stingers at once! It also molted successfully in captivity. [iNaturalist]
Memes and Stuff
Education & Outreach
- The wonderful Damaris Brisco has a short video showing what California turret spiders (Atypoides riversi) burrows look like and telling us a little bit about their life history. Her subsequent tweets have close-up photos of the “turrets”. [Twitter]
- Nicky Bay’s photos of a beautiful cork-lid trapdoor spider (Cyclocosmia) from Thailand have been circulating again, this time attached to false claims that the spider is deadly. He has posted a thread with actual facts about the spider, as well as many more photos. Diego Barrales (@Arachno_Cosas) also has a thread correcting misinformation and explaining the usefulness of this fascinating adaptation. [Nicky Bay’s thread] [@Arachno_Cosas’ thread (in Spanish)]
- In a hole in the ground there lived a red-jawed bearded wishbone spider (Xamiatus rubrifrons). A nasty, dirty, wet hole, filled with the ends of worms and an oozy smell. Because that’s how they like it. [Caitlin Henderson]
Events & News
- The Technical University of Denmark has a press release about bioengineering Masters student Sofie Føns, who recently finished her thesis on making spider antivenoms based on human antibodies. Current antivenoms are made with animal antibodies, which can cause allergic reactions in humans. [DTU Bioengineering]
#PruittData
- At Discover Magazine, longtime science blogger Neuroskeptic—for whom scientific fraud and data misuse has been a key interest—offers their take on #PruittData, comparing it to the cases of Diederik Stapel and Jan Hendrik Schön. “I can’t see any way that these anomalies could arise in 3 different datasets except if Pruitt were a serial data fraud…What’s interesting about this case is that Pruitt seems to have had a similar modus operandi to other famous serial frauds. Namely, he operates by providing data to (completely innocent) collaborators who approach him with ideas for experiments.” [Discover Magazine]
- P. O. Montiglio, one of the other authors of the retracted 2016 American Naturalist paper, weighs in. “There is something absurd (in the literary sense, think Kafka) in seeing months or years of work disappear because we spent them on unreliable data…These retractions might have wasted our time also by leading us to think that it is possible to describe and understand the implications of individual variation using relatively small datasets or crude experimental designs.” [Montiglio Lab]
- “It’s easy for both empiricists and analysts to be snobby, to build up the skills and expertise of their side and dismiss or minimize the skills and expertise on the other side. When the goal is to do good science, and be confident in the results, this approach is counterproductive.” Elizabeth Hobson reflects on her experience on both sides of the equation. [Hobson Lab]
Research
- Voltage-gated sodium channels are a kind of ion channel: big, complex protein molecules that are part of a cell’s membrane. They form pores that automatically let ions—sodium, potassium, or calcium molecules with electrical charges—in and out. This lets nerve and muscle cells transmit electrical signals to each other very quickly. In humans, pain-sensing neurons use two particular voltage-gated sodium channels, Naᵥ1.7 and Naᵥ1.8. Mutations in the genes for those ion channels can lead to people feeling too much pain or too little. A lot of venom has powerful effects on voltage-gated sodium channels, and can potentially be used to develop drugs treating those conditions. Recently researchers tested the venom of the (very beautiful and endangered) tarantula Poecilotheria metallica to look for any new peptides that interact strongly with Naᵥ1.7 and Naᵥ1.8. They found a couple of candidates, but suspect there are even more powerful Poecilotheria peptides waiting to be discovered. [Paper 🔓️]
- Some mites (Macrocheles muscaedomesticae) are clingier than others. Like, literally. These mites prey on small invertebrates drawn to rotting food, and adult females get around by attaching themselves to flies. They might even drink some fly hæmolymph en route. This opportunistic kind of parasitism might be an evolutionary stepping-stone to obligate parasitism — where the parasite can’t live without a host. Scientists at the University of Florida found that individual mites were consistent in how likely they were — or weren’t — to hop on flies. In other words, this behaviour might not be purely a response to environmental conditions, but also depend on mites’ individual personalities. [Paper] [Sci‑Hub]
- Paradise jumping spiders (Habronattus) in Arizona’s Santa Rita Mountains can really take the heat! Spiders who lived at various elevations could all withstand temperatures up to 52–55°C. However, there were bigger differences in the minimum temperatures they could tolerate (6–12°C), and that depended on where the spiders lived. This is in keeping with “Brett’s Rule”, named after a 1956 paper by J. R. Brett. He was writing about fish, but it has held true for many kinds of animals. [Paper] [Sci‑Hub]
- Some flowers have stems covered in sticky secretions that ensnare small arthropods, sometimes including spiders. A series of observations by Abhijith A. P. C. and David E. Hill show the victims — such as a jumper that dropped a leg in a failed attempt to escape — and the victors — such as a lynx spider that uses the sticky traps as an extension of its web. [Paper]
A couple Steatoda grossa papers from the Gries lab:
- Why do male false widow spiders (Steatoda grossa) modify females’ webs by cutting away parts and wrapping it with their own silk? Does it help deter rival males, or is it a signal to the female? According to recent experiments, it’s the latter. The researchers also found that North American false widow males don’t stridulate during courtship as European ones do, although they are physically capable of it. [Paper 🔓️]
- Female false widow spiders put a lot of energy into making their webs—it’s where they spend most of their time, how they catch their food, and (as seen in the previous paper) where they communicate with potential mates. Strangely, if forced to evacuate, they don’t seem to care whether they go back to their own web or a fellow female false widow’s. They are equally indifferent to whether an egg sac is theirs or not! [Paper] [Sci‑Hub]
And yet more spider-related papers from the Development Genes and Evolution special issue…
- This paper on the embryonic development of the Brazilian white-knee tarantula (Acanthoscurria geniculata) is blowing my mind. There are detailed photos (and even videos!) of the eggs developing from just clumps of cells to freshly hatched “eggs with legs”. You can see what I mentioned last week, how the chelicerae and spinnerets and so on are all modified appendages. The abdomen, one round chunk in the grown-up spider, starts as distinct segments with leg buds that disappear later in development. (Other, weirder spiders still retain visible segments.) [Paper 🔓️]
- Remember the transcription factor FoxB from last week, and how it regulates genes that make the top half of a spider different from the bottom half? Here’s a paper about foxQ2 and six3, a couple of the transcription factors that make the front end of an animal different from the back end. All kinds of animals have the genes to make them, although they don’t always work the same—the authors call it “an evolutionary playground of anterior [front] interactions”. In the house spider Parasteatoda tepidariorum, it seems that six3 activates foxQ2, and they are needed to form a mouthpart called the labrum. This is a similar order to other animals, which suggests that insects like the red flour beetle (Tribolium castaneum), where foxQ2 and six3 activate each other, are outliers. [Paper 🔓️]
Taxonomy
- Remember the weird eyestalk boi Electroblemma pinnae from last week? Meet two of its modern-day family members, the newly described Tetrablemma tatacoa from Colombia and T. mochima from Venezuela. As well as their heavily armoured butts, they have upward-pointing horns on their chelicerae and a little turret of eyes at the very top of their head. [Paper]
- The crevice weaver Filistatoides insignis, common in and around buildings, was spotted in Chiapas, Mexico for the first time. [Paper (in Spanish) 🔓️]
- Three new Arnoliseus jumping spiders from Brazil (as well as an ID key for all Arnoliseus species.) [Paper 🔓️]
- I am disappointed to report that Spintharus leverger, a newly described species of smiley-faced cobweb spider from Brazil, does not actually have a smiley face on it. [Paper 🔓️]
- The discovery of Ischnocolus jickelii and a new species, I. vanandelae, in Iran and Oman means that this mostly Mediterranean genus of tarantulas lives much further south and east than previously thought. [Paper] [Sci‑Hub]
- We thought the linyphiid spider Proislandiana pallida, found in the Russian Arctic, was the only one of its kind—until now. Specimens from Turkey and Armenia have been named Proislandiana beroni. [Paper]
- A new species of South Asian jumping spider was originally classified as Schenkelia. On further examination, the Asian Schenkelia species were all quite different from the African ones. They have been placed in their own genus, Orientattus. [Paper 🔓️]
- Does “Tschank-hoa”, or a place that sounds like it, ring a bell for anyone? Back in 1963, Ehrenfried Schenkel named a tarantula Chilobrachys tschankhoensis, but the specimens don’t seem to be fully grown, and no one knows where “Tschank-hoa” is. It’s probably in Asia, if that helps. [Paper]
As always, thank you for reading, and thanks to Sebastian Alejandro Echeverri for edits! Suggestions and corrections are always welcome; just drop us a (silk) line at @arachnofiles. 🕷️
Glossary
- anterior: front. As opposed to posterior, rear. In nearly all animals (including us), the anterior end is different from the posterior end, and the dorsal (top; literally “back”) side is different from the ventral (lower; literally “belly”) side. This is called the bilaterian body plan.
- bilaterian: having a body with a front end and a back end, and a top side and a bottom side. The first animals with this body plan arrived on the scene around 600 million years ago, and probably resembled small worms with some kind of eyes and maybe a digestive tract. Nearly all animals are descended from them, including arachnids and humans. Can’t you see the family resemblance?
- chelicerae: arachnid mouthparts. In spiders, they house the fangs. Spiders use their chelicerae for injecting venom, chewing, and grooming; they suck up food and water through their mouth, a separate opening just behind the chelicerae. This opening is surrounded by tough plates called the labrum and labium.
- hæmolymph: arthropod “blood”. One way it is different from ours is that it uses copper, not iron, to carry oxygen. This makes it look greenish or bluish rather than red.
- labrum: literally “lip”; the upper mouthpart in arthropods. The lower mouthpart is called the labium, which also means “lip”. Apparently the question of how the labrum develops is extremely controversial.
- peptide: a molecule made of a bunch of amino acids strung together. A bunch of peptides strung together is a protein.
- stridulation: making noises by rubbing body parts together. The animals most well-known for this are crickets, but some spiders and harvestpeople can also stridulate.
- transcription factor: a type of protein that gloms onto DNA and affects how often genes are expressed. Because there are so many different kinds of transcription factors, their effects can be varied: some turn genes on and off, others only do so in specific parts of the body or at specific times in development. Changes in how genes are expressed, as done by transcription factors and other systems, are a big reason that we can share most of our DNA with other animals and yet look so different.
- voltage-gated ion channel: a large protein that acts as a kind of door in a cell membrane, letting electrically charged molecules (like sodium, potassium, and calcium) in and out. The “gate” can be shut, allowing these ions to build up on one side. Once there’s a big enough difference in electric charge (voltage) between the two sides of the membrane, the gate quickly swings open. This releases a flood of ions to the other side, creating an electrical current that can be transmitted very quickly between cells. The many types of voltage-gated ion channels are important parts of nerve and muscle cells.
