iiinova — where your digital self keeps evolving

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

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

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

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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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

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

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

They also vary in their organisation. We calculated oligocentromere length, inter-oligocentromere gap length, density, and oligocentromeric share of the chromosome. 🧵5/12

A phylogeny of the cyperid species for which candidate oligocentromeric arrays could be identified, showing for each species the values of four oligocentromeric arrangement variables: array length, inter-array gap length, oligocentromeric share of the chromosome, and array density. The points correspond to either individual arrays or gaps (array length and gap length) or chromosomes (oligocentromeric share and array density). The rearrangement rates are the rates along the terminal branches of the phylogeny.

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

We identified where the oligocentromeres were in each genome using CAP. There's a lot of turnover - across 35 species, we could classify candidate centromere-related satellite DNA into no fewer than 25 families (named after Superstore characters). 🧵4/12

The candidate oligocentromere-associated satellites vary within the cyperid clade. The heatmap shows families of candidate oligocentromeric satellites, defined as repeats with > 0.1 Jaccard similarity using 8-mers. The phylogeny inset illustrates the distribution of each family in the cyperid clade. The arrays of the candidate oligocentromere-associated satellites on chromosomes of a selection of species are illustrated beneath to demonstrate the wide variation in the organisation of oligocentromeres across the clade. The phylogeny was made using iTOL (https://itol.embl.de/)

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

Sedges and rushes are known to have 2 - 114 pairs of chromosomes. This variation is driven by fissions and fusions, and comparing whole genome sequences allows us to quantify these rearrangements accurately. Many dozens underlie even small chromosome number variation. 🧵 2/12

Figure 1. Dynamic chromosomal evolution in cyperids. A. Phylogeny of cyperid species analysed. The number of ALGs at the internal nodes and the karyotypes at the tip nodes are represented by the numbered circles. Grey branches lack rearrangements. Rearrangements were not inferred for the black branches given the unreliability of the ALG inference at the base of the cyperid clade.
B. A ribbon plot showing the macrosynteny of Carex pendula and C. sylvatica, two sister taxa. Ribbons connect groups of at least 10 syntenic markers, illustrating how roughly similar chromosome numbers in closely related species hide a plethora of independent fissions and fusions.
C. The macrosynteny of C. caryophyllea and C. distans, which are less closely related than C. pendula and C. sylvatica and, accordingly, are even more rearranged despite similar karyotypes.

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

Why do the chromosomes of cyperids (sedges & rushes) split and fuse so regularly on evolutionary timescales? Is it because they have so many centromeres? Our new preprint, the first major paper of my PhD, addresses this question. 🧵⬇️ 1/12 www.biorxiv.org/content/10.6...

A sedge. It may look unassuming but its genome has several unusual features.

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James McCulloch @jamesimcc.bsky.social · 07/12/2025

Finding a colony of Hypogastrura springtails on this wall in Peterhouse, Cambridge started me on a trail through old papers, concluding that there may be another - morphologically distinguishable! - species in Britain. The story is in the latest issue of BJENH: www.researchgate.net/publication/...

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James McCulloch @jamesimcc.bsky.social · 02/10/2025

366 days ago I started my PhD at the @sangerinstitute.bsky.social. No better time to publish my profile on the Sanger website ⬇️ www.sanger.ac.uk/person/mccul... I tend to have my taxonomic hat on when posting here, but there is a bigger picture!

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James McCulloch @jamesimcc.bsky.social · 24/08/2025

Finally, this is the tiny Sminthurides bifidus. These are synanthropic aquatic springtails found on the edge of glasshouse water features and fish tanks. The dorsal black marking is quite variable. The males are smaller and have antennal clasping organs to grasp the females in courtship! 🧵6/7

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James McCulloch @jamesimcc.bsky.social · 24/08/2025

This is Seira domestica, a slender springtail almost never found outdoors (in the UK, at least). Lepidocyrtus have similar iridescent scales but have 2 teeth on the mucro (furca apex), not 1. When assembled, this will be the first reference-quality genome from the subfamily Seirinae! 🧵5/7

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James McCulloch @jamesimcc.bsky.social · 24/08/2025

This is Sminthurinus igniceps, a relative but less distinctive. It can be told from dark S. aureus by having a head paler than the body, and from S. domesticus by having mostly orangey antennae. This species is also synanthropic, but seemingly moving out more into the wider countryside. 🧵4/7

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James McCulloch @jamesimcc.bsky.social · 24/08/2025

Despite its spots which seem to glow among the woodchips, S. bimaculatus is very similar to S. trinotatus. You need to look for a pair of hairs called subapical ventral setae on the dens, part of the springing organ (furca) that gives springtails their name. This arrow shows where they'd be! 🧵3/7

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James McCulloch @jamesimcc.bsky.social · 24/08/2025

This beautiful species, Sminthurinus bimaculatus, has been the British springtail I've most wanted to see. As with the other 3 spp., it's primarily synanthropic, meaning it's associated with human habitats like this flowerpot. 🧵2/7

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James McCulloch @jamesimcc.bsky.social · 24/08/2025

I've reached 100 British springtail species! This was helped by a recent glasshouse sampling trip, where I added these 4 species. 3 are now in the pipeline to have reference-quality genomes sequenced for the first time, by the @sangerinstitute.bsky.social. More info in the thread below! 🧵1/7

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James McCulloch @jamesimcc.bsky.social · 16/07/2025

While it appears similar to true E. imitabilis, described from a single Chinese specimen, the pattern of E. petri is unique. The chaetotaxy - the arrangement of hairs (setae) on different parts of the body - is also unique. Click the Alt text on these images for explanations of what they depict!

A composite of illustrations of different body parts. Elements A and B show the dorsal and ventral pattern respectively; to the right of the dorsal pattern illustration is the chaetotaxy formula for the relevant body segments. Each of the five most taxonomically useful segments in terms of their chaetotaxy - the head, the 2nd thoracic segment, and the 2nd, 3rd, and 4th abdominal segments - has between 2 and 5 somewhat arbitrarily-chosen "compartments" with the formula detailing the number of macrosetae (the thickest type of "hair") in each compartment.

Element C shows the configuration of a small part of the manubrium - the basal part of the furca (springing organ). This is a combination of pseudopores (two in this case - the open circles) surrounded by a number of setae (four here).

Element D shows the shape of the "apical bulb" at the very tip of the fourth antennal segment. E. petri has a bilobate apical bulb.

Element E shows the foot and the dentation of the claw - one of the ways in which E. petri differs from true E. imitabilis beyond colour pattern.

Finally, element F shows the apex of the dens and the mucro (the other two parts of the furca other than the manubrium). The mucro of E. petri has two teeth and a basal spine which reaches the tip of the basal tooth.

This rather complicated looking figure provides the chaetotaxy (arrangement of setae (hairs)) for the taxonomically important body segments. These are the head, 2nd and 3rd thoracic segments, and 2nd, 3rd, and 4th abdominal segments (in order from A-F). The diagram of the head also includes the relative size and position of each ocellus which makes up the eye.

The dotted boxes delimit the "compartments" of each segment, which is how you get the standard chaetotaxy formula as given in the other figure.

This chaetotaxy scheme was first introduced by Jordana in his 2012 volume of the Synopses on Palaearctic Collembola, which covers the subfamily Capbryinae and tribe Entomobryini of the family Entomobryidae. The chaetotaxy of any of the members of these groups should, in theory, be able to be represented using this scheme.

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James McCulloch @jamesimcc.bsky.social · 16/07/2025

Formerly known as Entomobrya nr imitabilis, this morphospecies was first spotted in 2015. Since then it has appeared across the whole length of the British Isles - the type specimens were found on an Edinburgh gravestone. Where it has come from and how it has spread so quickly is a mystery...

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James McCulloch @jamesimcc.bsky.social · 21/04/2025

Good news! >6000 springtail records have been imported from iRecord and are now available on the NBN Atlas: species.nbnatlas.org/species/NBNS... Massive thanks to @duerden.bsky.social for his investment in verifying iRecord records. Keep them coming!

A particularly luminous individual of Sminthurinus aureus (orange form)

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James McCulloch @jamesimcc.bsky.social · 13/04/2025

New to Britain! These springtails are Dicyrtomina signata, a European species that's never previously been seen in the UK. I found these while out and about in Wanstead Park, London (with @josscarr.bsky.social, @nmaybury4.bsky.social). One to look out for!

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James McCulloch @jamesimcc.bsky.social · 18/03/2025

In 1924, Womersley referred to Orchesella flavescens as "the most magnificent spring-tail". Today, 101 years later, the first reference genome for this species has been assembled and published, from a specimen I collected at Wytham Woods! wellcomeopenresearch.org/articles/10-...

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James McCulloch @jamesimcc.bsky.social · 28/02/2025

Let’s see if we can give it a name before too long!

A specimen of Entomobrya near imitabilis on its side

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James McCulloch @jamesimcc.bsky.social · 26/01/2025

A rainy afternoon looking for Smews near St Ives (Cambs) was sadly smewless. But this was somewhat compensated by us (specifically @joeparham19.bsky.social) finding this first-winter drake Lesser Scaup (right). A vagrant from North America and a new sp. for me! + some drake goldeneyes! 🪶

A male tufted duck (left) and a first-winter male lesser scaup (right). The lesser scaup can be distinguished from a greater scaup by the "peak" on the crown of the head (not smoothly rounded) and the very similar size to the tufted duck. This might be the same bird as was at Ouse Fen RSPB earlier in the winter.

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James McCulloch @jamesimcc.bsky.social · 21/01/2025

Send me records: I am excited to be taking on the role of national springtail recorder. I have huge shoes to fill, but I hope to continue the progress Peter Shaw made in understanding the taxonomy and biology of the UK's #springtails. www.brc.ac.uk/scheme/colle...

Orchesella flavescens, one of the UK's largest springtails. It's an elongate springtail, with long antennae, often with a differing number of segments on each antenna (but with a maximum of six). It can be identified by the pattern consisting of parallel longitudinal dark lines running the length of the abdomen, contrasting against a paler ground colour. This is a relatively scarce woodland species.

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James McCulloch @jamesimcc.bsky.social · 11/01/2025

Today was a day for skulking reedbed birds: two Bitterns and three Water Rails at @wwtworldwide.bsky.social's London Wetland Centre in the winter sun ☀️🪶

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James McCulloch @jamesimcc.bsky.social · 08/01/2025

This may look like an amorphous blob, but it’s an exciting one (and new for me)! This is the <1mm springtail Neelus murinus. The second photo gives a sense of scale in comparison to my gloved finger. Let’s hope we can sequence its genome, and reveal what secrets it’s hiding #springtails

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James McCulloch @jamesimcc.bsky.social · 31/12/2024

Feeling lucky to have been able to watch this drake Goosander expertly fishing in the rapids of the River Mersey in Manchester yesterday 🪶 The last one I saw was on the pond at the Sanger Institute last month… a little lost!

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James McCulloch @jamesimcc.bsky.social · 29/12/2024

A lifer for me in Austria! It has been a joy watching a flock of c50 Alpine Choughs coming to drink meltwater from the gutters of neighbouring buildings each morning. Apparently this species holds the record for breeding at the highest altitude! 🪶

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James McCulloch @jamesimcc.bsky.social · 26/12/2024

It may have been -12°C with a foot of snow on the ground in Seefeld, Austria, but that didn't seem to be an issue for this Western Conifer Seed Bug (Leptoglossus occidentalis)... They often hibernate indoors, but this one seemed satisfied with the outside wall!

An adult Western Conifer Seed Bug on the outside wall of my hotel.

The snowy vista; a thick coating of snow on the terrace, with a view of the Tyrolean alps behind.

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James McCulloch @jamesimcc.bsky.social · 24/11/2024

An adorable fly from South Africa this past summer - a species of Atriadops, in the family Nemestrinidae (which has no representatives in the U.K.). Despite its cute appearance, its larvae are endoparasitoids of grasshoppers and praying mantises!

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James McCulloch @jamesimcc.bsky.social · 19/11/2024

Having long lost the motivation to post on Twitter, I have quite the backlog of photos to share! Top of my list is this comical shot of a pair of Iberian Azure-winged Magpies curious as to what’s unfolding in front of them 🪶

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James McCulloch @jamesimcc.bsky.social · 17/11/2024

A nippy November day and face-to-face views of two beautiful Black-necked Grebes at Walthamstow Wetlands this morning 🌅 #londonbirds

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