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Reposted by James McCulloch

bioRxiv Genomics @biorxiv-genomic.bsky.social · 23/09/2026

An atlas of eukaryotic centromere architecture reveals recurrent evolutionary dynamics www.biorxiv.org/content/10.64898/20…

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KamilSJaron.bsky.social @kamilsjaron.bsky.social · 18/09/2026

I am so excited to see this preprint out. I started working on springtails with @laurarossevo.bsky.social in 2019, but this pinnacle of our efforts manifested only with heroric leadership of Sam Ebdon! So, what's the deal? 👇

Globular springtail Allacma fusca. Female, one of the samples in the linked preprint.

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Soil Organisms Journal @soilorganismsj.bsky.social · 18/09/2026

📢✨NEW✨ species of Collembola! ✨ONLINE FIRST✨ Check out the paper by James McCulloch on a new species of Collembola found at the Cambridge University Botanic Garden in the latest ONLINE FIRST article ⬇️ soil-organisms.org/SO/article/v...

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James McCulloch @jamesimcc.bsky.social · 17/09/2026

This is a problem. Naming a species is the first step. But there are many other undescribed species of springtail in the UK, likely imported via the horticultural trade. Where are they coming from? What do they do in their native environment, and how may they affect UK ecosystems? Work continues.

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James McCulloch @jamesimcc.bsky.social · 17/09/2026

This allowed its naming as a new species. I chose the epithet "terraeincognitae" (roughly "of an unknown land") to portray how it is probably a non-native greenhouse species (@finleyhutchins2.bsky.social has now also found it in the Inverness botanics) but we don't know where it has come from!

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James McCulloch @jamesimcc.bsky.social · 17/09/2026

So, my attention turned further afield. The most similar species are in the Neotropics, yet my specimens still differed in their chaetotaxy. There are additional differences in the body shape, pattern, claw structure, and the labial papillae (sensory structures near the mouth).

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James McCulloch @jamesimcc.bsky.social · 17/09/2026

What is notable about these diagrams is that there are many fewer hairs than there normally are. In fact, out of all the species known from the Palearctic realm, my specimens had the fewest of these taxonomically-important hairs!

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James McCulloch @jamesimcc.bsky.social · 17/09/2026

This time, I found dozens of specimens, mostly on a few floating plants of water lettuce in a tank in one of the nurseries. This allowed me to draw diagrams like these, recording which hairs were present on the head, thorax, and abdomen.

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James McCulloch @jamesimcc.bsky.social · 17/09/2026

Entomobrya is a large (>300 spp.) and taxonomically difficult genus, and often identification relies on this so-called chaetotaxy. Each dorsal hair has a name, and it's important to record which of these hairs are present. To collect the specimens needed to do this, I returned in September.

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James McCulloch @jamesimcc.bsky.social · 17/09/2026

I immediately recognised it as a species of Entomobrya, but unlike anything known in the UK. The problem was that I only had the one specimen, from this unassuming plant pot, but identifying it further would require dissolving its insides to look closer at which hairs were present.

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James McCulloch @jamesimcc.bsky.social · 17/09/2026

It all started last August. I tagged along with @sashabliznina.bsky.social, who was collecting fungus gnats for genome sequencing to study their unusual germline-restricted chromosomes. Greenhouses also have cool springtails I wanted to sequence, and among those I found was this odd one.

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James McCulloch @jamesimcc.bsky.social · 17/09/2026

New species now out in @soilorganismsj.bsky.social! soil-organisms.org/SO/article/v... The latest addition to the UK's springtail fauna: Entomobrya terraeincognitae sp. nov. I found this species on fieldwork for my PhD @sangerinstitute.bsky.social at the Cambridge botanics. 🧵

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James McCulloch @jamesimcc.bsky.social · 02/09/2026

Of course, that should be @nhm-london.bsky.social. I have never been to Los Angeles and I'm sure that it's nice (especially the museum), but I'm glad I don't have to go all the way there every time I have some types to deposit.

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James McCulloch @jamesimcc.bsky.social · 02/09/2026

I keep erring between getting on with that and focusing on making sure that everything is described, though if I do wait until we have descriptions for all our fauna I may well be waiting indefinitely!

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James McCulloch @jamesimcc.bsky.social · 02/09/2026

The UK has a new species of springtail (to science)! I’m on my way to @nhm.org to drop off the type specimens. Name withheld so as not to violate the ICZN… but keep an eye out for the publication dropping shortly!

The slide-mounted holotype specimen held against a background of the paper describing the species new to science.

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James McCulloch @jamesimcc.bsky.social · 03/08/2026

Go out at night and you might find springtails all over logs or trees where they're absent in the day. Why? I was glad to collaborate on this new paper, where we show that even in dry-tolerant Willowsia, nocturnal activity is related to environmental moisture. soil-organisms.org/SO/article/v...

The trap used for passively sampling Willowsia throughout the summer.

Figure 2, illustrating the predicted abundance of Willowsia japonica in tree-trunk traps depending on precipitation, comparing both daytime and nighttime sampling.

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Reposted by James McCulloch

Matt Bertone @bertonemyia.bsky.social · 30/07/2026

Be a dipterist. Be in Costa Rica for #FlySchool2026. See a muscoid #fly perching on a leaf. Tell student so they can collect it. Success!! Wait a minute 🤔 That's not a fly, but weevil mimicking one! This was so convincing, even rapidly moving & poking its wings out 🥰 #Curculionidae: cf. #Mnemynurus

A weevil with red around its neck, resembling the eyes of a fly. It has large brown eyes and a long yellow proboscis curving under the body. It's on a white background facing the viewer.

A weevil with red around its neck, resembling the eyes of a fly. It has large brown eyes and a long yellow proboscis curving under the body. The wing cover are mottled brown and white. It is on a white background facing left.

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Reposted by James McCulloch

KamilSJaron.bsky.social @kamilsjaron.bsky.social · 23/07/2026

New preprint: 338 coleopteran genomes reveal exceptional rearrangement variation compared to other insect orders. Big congrats to @arf-mln.bsky.social, for getting this giant piece together. Big collaboration of @joanameier.bsky.social's and my groups. 🧵👇 doi.org/10.64898/202...

Phylogeny of 338 species with tips painted by the chromosomal ancestry of their contemporary genomes (well separated colours indicate only few changes, while blending indicates rearrangements). Colouring of the branches is by the number of rearrangements. The ring between paints and phylogeny indicates wether the chromosomal rearrangement was fusion dominated (brown) or fission dominated (teal) process.
Photo credits: Udo Schmidt, Lech Borowiec, JL Tachet, David Navrátil, Fred Chevaillot, Siga, Cosmin Manci, John Hallmén, Igor Souza-Gonçalves, Alex Hyde, H. Coiffait, David Ignace, Yves Bousquet.

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Alex Kingston @alexjkingston.bsky.social · 20/07/2026

Pleased to say that the first half of my PhD project is now out in preprint format! Using cortical organoids to model the mechanical transitions involved in early neurogenesis, we find that nuclear mechanotransduction is a crucial regulator of the timing and outcome of neuronal differentiation:

biorxiv.org

Organoids reveal niche-specific mechanotransduction-guided human cortical patterning and cell fate acquisition

The highly dynamic mechanical environment of the developing cerebral cortex has the potential to encode information vital for neuronal differentiation. Changes in local biophysical properties have bee...

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Reposted by James McCulloch

bioRxiv Developmental Biology @biorxiv-devbio.bsky.social · 16/07/2026

Organoids reveal niche-specific mechanotransduction-guided human cortical patterning and cell fate acquisition www.biorxiv.org/content/10.64898/20…

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James McCulloch @jamesimcc.bsky.social · 06/07/2026

Another springtail to find this summer! ☀️ Fab photo from @josscarr.bsky.social of Fasciosminthurus quinquefasciatus from Dorset yesterday. The 1st UK record outside Cornwall, where it was found new to Britain 2 yrs ago! www.researchgate.net/publication/... Can we track its expansion further?

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James McCulloch @jamesimcc.bsky.social · 30/06/2026

Exploring Copenhagen while at #SMBE2026 Visit The Little Mermaid & look a few m along the shoreline. You’ll see some impressive (and polycentric) Bolboschoenus (club-rush). Their polycentromeres are likely underpinned by satellites I called Garrett and Colleen More: www.biorxiv.org/content/10.6...

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James McCulloch @jamesimcc.bsky.social · 30/06/2026

I’m excited to be at #SMBE2026! I’m keen to talk to people about chromosome evolution/centromeres in the polycentric sedges and rushes (see poster or www.biorxiv.org/content/10.6...) … … or about population genomics of soil arthropods!

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James McCulloch @jamesimcc.bsky.social · 25/06/2026

Alongside the Life in the Undergrowth clip above, there's a detailed description of the ritual here: www.collembola.org/publicat/cou... It also notes that pallipes and bicinctus differ slightly in their dance moves. Their yellow forms are morphologically identical, but behaviourally different.

collembola.org

Checklist of the Collembola: Note on the courtship ritual of Deuterosminthurus pallipes (Bourletiellidae)

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James McCulloch @jamesimcc.bsky.social · 25/06/2026

Deuterosminthurus have an amazing courtship ritual. The male and female "dance" until the male determines the female to be suitably impressed, at which point he deposits a sperm droplet and guides the female onto it using a sticky thread derived from the droplet. www.youtube.com/watch?v=mcjx...

youtube.com

Spirngtail collembole mating dance, collembola danse de reproduction

YouTube video by remyposees

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James McCulloch @jamesimcc.bsky.social · 25/06/2026

Deuterosminthurus sulphureus, though, only comes in yellow and is hard to distinguish from yellow morphs of the other two. However, some setae (hairs) on the tibiotarsus (lower leg) are longer than others (2nd pic) and there is a pair of thickened setae at the tip of the abdomen in the males.

Deuterosminthurus sulphureus male habitus.

Some hairs on the outer side of the tibiotarsus are longer than others.

The end of the abdomen (small abdomen) of a male D. sulphureus with an arrow pointing to one of the pair of thickened setae. Lateral view.

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James McCulloch @jamesimcc.bsky.social · 25/06/2026

All UK Deuterosminthurus species can be fully yellow, but populations of bicinctus and pallipes can be easily recognised by having some individuals of a different morph (bicoloured and violet respectively). Males & females can be either morph. How the polymorphism is maintained is enigmatic!

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James McCulloch @jamesimcc.bsky.social · 25/06/2026

It's certainly not classic springtail weather out there. Most are reliant on the cool & damp and have hidden themselves away. But there are some summer specialists: on Monday, I found all 3 of the UK's Deuterosminthurus species in the grounds of the @sangerinstitute.bsky.social ☀️ 🧵⬇️

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James McCulloch @jamesimcc.bsky.social · 22/06/2026

The abdomen pattern is a bit unusual for Deuterosminthurus but reminds me more of Heterosminthurus. The dark head is odd, though!

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Reposted by James McCulloch

Camille Cornet @camillecornet.bsky.social · 18/06/2026

🧬🦋 New preprint out! 🦋🧬 What mechanisms underlie large-scale chromosomal rearrangements? Why do rearrangement rates vary so massively across taxa? We explored these questions in Erebia butterflies, a genus with extraordinary chromosome number diversity, from 7 to 52! www.biorxiv.org/content/10.6...

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Carmen Denman Hume @carmcdhume.bsky.social · 09/06/2026

When I sat down with @jamesimcc.bsky.social to learn about all things springtails, I never imagined I'd leave our conversation so inspired about the future of natural science research. I can't wait to see what the future has in store for James. I certainly look forward to following the journey! 😊

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Reposted by James McCulloch

KamilSJaron.bsky.social @kamilsjaron.bsky.social · 05/06/2026

A big preprint from my group! Muller Elements are considered to be conserved in flies. We tested it by reconstructing the ancestral dipteran karyotype using 340 chromosomal genomes and suprise suprise, they're not... Led by @juliagries.bsky.social and Sam Ebdon. www.biorxiv.org/content/10.6... 🧵👇

Schema of three major chromosomal rearrangements leading to Muller Elements of Drosophila melanogaster since the common ancestor of Diptera.

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Laurie Belcher @lauriebelch.bsky.social · 27/05/2026

Huge congratulations to @stuwest.bsky.social on his election as a Fellow of the Royal Society! From fig wasps to Pseudomonas, he’s shown just how powerful behavioural ecology can be. I couldn't think of anyone more deserving. www.biology.ox.ac.uk/article/prof...

biology.ox.ac.uk

Professors Tim Coulson, Stuart West, and Kathy Willis elected as Fellows of the Royal Society

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Reposted by James McCulloch

Wellcome Sanger Institute @sangerinstitute.bsky.social · 23/05/2026

No clue what a springtail is? Never fret. We've interviewed the UK's national springtail biological recorder and PhD student @jamesimcc.bsky.social . Head to our blog to learn more ⤵️ sangerinstitute.blog/2026/03/26/stu… 📸 Tim Jonas #NameItToSaveIt

Close-up of a brown and yellow springtail with a round, speckled body and fine hair, standing on mossy ground.

Close-up of a white, translucent springtail with fine hairs crawling on wet, textured soil or rock surface.

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Frank Ashwood @frankashwood.bsky.social · 03/04/2026

Want to start doing soil animal macrophotography? Or fancy a rare glimpse into mine and @mesofauna.bsky.social's minds? An article has just dropped in @soilorganismsj.bsky.social, showcasing mine and Andy's love for documenting soil biodiversity! 🧪🪱 Open Access: soil-organisms.org/SO/article/v...

A screenshot of the title and abstract page of an article in Soil Organisms journal, entitled 'Advocating for the lobe and protection of soil animals through photography: the work of Frank Ashwood and Andy Murray'.

A photograph of a round, hard-bodied mite walking among a cluster of lollipop-shaped slime mold fruiting bodies.

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KamilSJaron.bsky.social @kamilsjaron.bsky.social · 02/04/2026

Is there anyone around Newcastle owning a patch of green where we could collect springtails this Tuesday by any chance? More about the project in @jamesimcc.bsky.social's blog post: sangerinstitute.blog/2026/03/26/s...

sangerinstitute.blog

Studying soil’s unsung heroes - Wellcome Sanger Institute Blog

In this blog, we hear from Wellcome Sanger Institute PhD student James McCulloch about his favourite invertebrates, the springtails, and their extraordinary cryptic diversity.

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NBN Trust: National Biodiversity Network Trust @nbntrust.bsky.social · 08/03/2026

This #IWD2026 we’re shining a light on the incredible women who’ve been nominated, highly commended or won an NBN Award for Wildlife Recording since 2015💛 Huge thanks to all. Know an inspirational woman who records or verifies wildlife? Nominations for #NBNawards26 are open! bit.ly/NBNawards26n...

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KamilSJaron.bsky.social @kamilsjaron.bsky.social · 04/03/2026

And this is my favourite figure, nicely illustrating diversity and turnover of oligocentromeric satelites. Look at Carol and Sandra - one invaded the other at least 2x, which I find particularly amusing.

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KamilSJaron.bsky.social @kamilsjaron.bsky.social · 04/03/2026

Very proud of @jamesimcc.bsky.social to submit his first PhD paper about evolution of genomes and centromeres in taxa with oligocentromeric organisation. Lots of interesting discoveries including possibly the first reported re-evolution of monocentricity.

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Charlotte Wright @charlottewright.bsky.social · 03/03/2026

Chromosomes are often classified as either monocentric (single centromere per chr) or holocentric (centromeric activity spread across each chr). In reality, there is a continuum in centromere organisation - and cyperids are a fascinating system to explore this in as James shows in this preprint! 🌱

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James McCulloch @jamesimcc.bsky.social · 03/03/2026

Thank you to my co-authors: @marcelauliano.bsky.social, @charlottewright.bsky.social, @hendersi.bsky.social, Sam Ebdon, @kamilsjaron.bsky.social & Mark Blaxter. Finally, this would not have been possible without the Darwin Tree of Life sequencing & assembly teams @sangerinstitute.bsky.social! 🧵12/12

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James McCulloch @jamesimcc.bsky.social · 03/03/2026

There are further tidbits in the preprint. E.g., what's the effect of oligocentromeres on the gene & TE landscape of chromosomes? The same as classical monocentromeres? Spoiler: surprisingly, yes, oligocentromeres are associated with ⬆️ TE & ⬇️ gene density. 🧵11/12 www.biorxiv.org/content/10.6...

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James McCulloch @jamesimcc.bsky.social · 03/03/2026

In annotating centromeres, we also came across another surprise. Some chromosomes of the sedge Carex myosuroides seem to have a single centromere. "Monocentricity" is considered ancestral for eukaryotes, but if confirmed, this would represent the first known reversion to this state! 🧵10/12

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James McCulloch @jamesimcc.bsky.social · 03/03/2026

This is despite fusion & fission breakpoints themselves being enriched for oligocentromeres! So, having multiple centromeres per chromosome may promote fission & fusion, but having too many also seems destabilising. A balance is needed for rapid chromosomal rearrangement. 🧵9/12

Breakpoint regions are generally enriched for oligocentromeres. This is more noticeable for fusions as fusion regions are easier to identify at a greater resolution than fission regions.

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James McCulloch @jamesimcc.bsky.social · 03/03/2026

This might be partly explained by our finding that longer chromosomes have centromeric sequence taking up more of their length. Fission could result in disproportion, causing spindle geometry problems. Meanwhile, the fusion of two centromere-rich chromosomes may increase the risk of merotely. 🧵8/12

Larger chromosomes have greater oligocentromere share and density. Each line corresponds to a species.

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James McCulloch @jamesimcc.bsky.social · 03/03/2026

We'd expect denser and longer oligocentromeres to correlate with chromosomal fusions, or vice versa depending on the direction of drive. However, we find that both fissions and fusions seem more stable when there are sparser, shorter oligocentromeres. 🧵7/12

The relationship between whether a chromosome is a fission product and the scaled median length of oligocentromeric arrays on that chromosome, with glm fits for each species. Generally, recently-split chromosomes have shorter oligocentromeres.

Inter-specific relationships between oligocentromere organisation and rearrangement rates. Greater fusion rate is associated with sparser oligocentromeres and lower oligocentromeric share of the genome, and greater fission rate with longer inter-array gaps.

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