Tim Petzold

Hypotheses of stripe pattern homology between nymphalids and hesperiids. (A) Current summary of the nymphalid ground plan, mainly based on the terminology of Schwanwitsch (Nijhout, 1991; Schwanwitsch, 1924) and including recent updates by Otaki and Mazo-Vargas et al. (Mazo-Vargas et al., 2017; Otaki, 2012; Otaki, 2021; Schwanwitsch, 1956). Discalis elements (D1 and D2); CSS, central symmetry system (cyan); BoSS, border ocelli symmetry system (magenta); Oc, forewing border ocelli; pPf and dPf, proximal and distal parafocal elements; MBS, marginal band system (green). Colored vignettes denote vein intersection landmarks. Magenta square, junction between R and M vein trunks; yellow dot, M1-M2 junction; red star, junction between discal crossvein and M3; blue cross, M3-Cu2 junction; green triangle, Cu1-Cu2 junction. Rectangles feature the name of marker genes. (B) Ventral wing patterns of the nymphalid Prepona eugenes with ground plan annotations proposed by Schwanwitsch, 1956 (left: reproduction of published drawings; right: equivalent annotations as color overlays). (C) Phylogenetic relationship between Papilionoidae families. (D) Ventral wing patterns of the hesperiid P. sidae annotated as in panel A, and highlighting the inferred CSS predicted by Schwanwitsch, 1956 (left panel). According to this author, the CSS marks a grey pattern in forewings, and a dislocated white stripe pattern in hindwings, suggesting uncoupling of pattern and color state in fore/hindwings in skippers. The forewing CSS is markedly dislocated along the Cu1 vein (arrowhead).

#WntA is a crucial marker of stripe elements early in development for the Nymphalidae butterfly family. @jasminealqassar.bsky.social & co explore if WntA has maintained its role in stripe elements over 95 million years of evolution in the Hesperiidae family of butterflies. doi.org/10.1242/bio....

Enhancer-promoter compatibility is mediated by the promoter-proximal region Gene promoters induce transcription in response to distal enhancers. How enhancers specifically activate their target promoter while bypassing other promoters remains unclear. Here, we find that the p...

What is a promoter? And how does it work?

We very happy to share our latest work trying to understand enhancer-promoter compatibility.
I am very excited about the results of @blanka-majchrzycka.bsky.social, which changed the way I think about promoters

www.biorxiv.org/content/10.1...

📣 Paper alert!

I am delighted that our paper exploring the impact of Neanderthal-derived variants on the activity of a disease-associated craniofacial enhancer has been published in Development today!
journals.biologists.com/dev/article/...

cx41.8 is expressed in presumptive haemogenic endothelial cells of the dorsal aorta. (A) Design of the cx41.8:EGFP plasmid. The upper line indicates the cx41.8 locus structure. The lower line indicates the construct design. Purple boxes indicate the cx41.8 exons; blue boxes indicate the open reading frame; yellow boxes indicate the 4.5 kb sequence upstream of the cx41.8 start codon; black boxes indicate the transposon sequences and the green box indicates the EGFP coding sequence. (B) cx41.8:EGFP expression in the presumptive floor of the aorta at 24 and 28 hpf and in presumptive budding HSPCs (48 hpf). White arrowheads denote presumptive haemogenic endothelial cells in the floor of the aorta and budding HSPCs (48 hpf). (C) Flow cytometry analysis of double-positive cells in 48 hpf kdrl:mCherry+ or cx41.8:EGFP+; kdrl:mCherry+ embryos. (D) Expression of cx41.8:EGFP and kdrl:mCherry from 24-48 hpf. White arrowheads denote cx41.8:EGFP and kdrl:mCherry double-positive endothelial cells in the floor of the dorsal aorta. Scale bars: 100 μm (B and D).

Blood stem and progenitor cells give rise to all blood cell types. Tim Petzold & co show that when Connexin 41.8 is present but impaired, it delays their initial formation and disrupts the timely activation of a key signalling pathway in #zebrafish embryos. doi.org/10.1242/bio....

How Did Hands Evolve? The Answer Is Behind You.

Our work exploring a new explanation for the regulation of Hoxd genes and the #fin-to-limb transition. 🧪

It was an absolute joy working on this w/ @aurhin.bsky.social and @homeobox.bsky.social @denisduboule.bsky.social @neilshubin.bsky.social

#evo-devo #InHoxWeTrust

Is enhancer-driven gene regulation all wrapped up? - Nature Reviews Genetics In this Comment, Wendy Bickmore discusses mechanistic models of how 3D genome organization facilitates communication between distant enhancers and their target promoters to regulate gene expression.

Very interesting new @wbickmor.bsky.social commentary on the mechanistic mystery that is very distal enhancer-promoter interactions www.nature.com/articles/s41...

This is figure 2, which shows M. ibericus queens lay males from two different species.

Living organisms are assumed to produce same-species offspring. A study in Nature reports a shift from this norm in Messor ibericus, an ant that lays individuals from two distinct species. go.nature.com/3V68MP0 🧪

Our humble gata2b in situ hybridization image made it onto the cover of @biologyopen.bsky.social!

If you'd like to check out the story behind the image, the link to our new paper is:

journals.biologists.com/bio/article/...

Connexin 41.8 governs timely haematopoietic stem and progenitor cell specification Summary: Cx41.8 is necessary to launch the haemogenic program and induce HSPC formation at the correct time during zebrafish development via a ROS-Hif-Notch-Gata2b pathway.

Excited to share that the final version of our work on Connexin 41.8 in HSPC specification is out now in @biologyopen.bsky.social!

If you're curious about how a connexin helps turn endothelial cells into blood stem cells, please have a read!

journals.biologists.com/bio/article/...

How the functional architecture of the zebrafish heart is shaped during development

📹 @tobyandrews.bsky.social et al @rashmi-priya.bsky.social
lab @crick.ac.uk in @cellpress.bsky.social Developmental Cell

➡️ bpod.org.uk/archive/2025...

Mechanochemical coupling of cell shape and organ function optimizes heart size and contractile efficiency in zebrafish Andrews et al. demonstrate that multiscale feedback between mechanical and chemical cues builds a functional heart to support zebrafish embryonic life. Cell recruitment and organ-scale forces drive tr...

Thrilled to bits to see our latest work online in Dev Cell! 🥳

We wanted to know how cells build functional organs with precision🫀🫁📏 Here we show how coupling of cell shape and organ function fine tunes the form and contractile power of the developing #zebrafish heart 1/n

tinyurl.com/cell-stretch

Juvenile Heermann's gull (very dark all over) in flight, flying over very very shallow water. Flying to the right maybe two feet off the ground. It's shadow is to the right. Just below the shadow is a reflection on the sheen of water.

Got this really cool, ghostly picture by accident the other day in Dillon Beach, CA. It is a Heermann's gull with both it's shadow and reflection.

#birds

Issue 14 is complete!

On the cover: Drosophila eye imaginal discs stained for the pan-neuronal marker Elav (red or blue) and cell fate-specific markers to investigate basic cell-biological processes such as cell proliferation and morphogenesis during development. See:
doi.org/10.1242/dev.204373

A monarch butterfly on a pink zinnia

This is my first time seeing a Monarch on our property! I literally just purchased milkweed seeds and began preparing the area I’m going to plant in this fall. That’s quite the synchronicity. #gardening #bugsky #bloomscrolling #photography

Somites are a source of nephron progenitors in zebrafish - Nature Communications This study reveals that cells of the zebrafish kidney can originate from the somites, structures traditionally held as precursors to the skeletal muscle, challenging a century-old paradigm and prompti...

Beautiful work using lineage-tracing, transplantation experiments and fate mapping to show that somites give rise to nephron progenitors

www.nature.com/articles/s41...

🐌💫 Snail embryos never looked so fabulous!
Tubulin (white), phospho-histone H3 (pink), and F-Actin (cyan) light up this early stage like a cytoskeletal disco ball.
Image from Clemens Cabernard & Adam von Barnau Sythoff 🪩🧬 #FluorescenceFriday

Wow. Scientists have edited mosquito DNA to prevent the spread of malaria to humans "while supporting essential physiological functions... and negligible fitness costs" to the mosquito population.

Potentially ending the mosquito-born spread of malaria to humans.

www.nature.com/articles/s41...

It just takes one change Here, I run though three examples of evolutionary novelty driven by single non-coding DNA changes: limb loss in snakes, gliding in sugar gliders, and coat coloration in African striped mice. These …

Mustering the courage to share my latest scicomm endeavour: I channelled my love for writing into a blog where I can hopefully bring the marvels of evolutionary biology and non-coding DNA to all Science lovers!

darkgenomevo.wordpress.com/2025/06/22/i...

No new genes needed to fly - just rewire what you have! 🦇🧬

Great new paper from the labs of @fany-real.bsky.social @stemundi.bsky.social @dariloops.bsky.social

doi.org/10.1038/s415...

#EvoDevo #SingleCell #BatWings

A photo of six butterflies which depicts the many different colours and patterns of butterflies in the genus Morpho. The top left is Morpho menelaus, the top middle is Morpho helenor, the top right is Morpho cypris. On the bottom left is Morpho rhetenor, the bottom middle is Morpho sulkowskyi, and the bottom right is Morpho hecuba. Photo credit: Emilie Snell-Rood.

In her Perspective, Emilie Snell-Rood discusses the value of basic science, using the Morpho butterfly as an example of how this type of research has driven later innovation & highlights the value of government and institutional support for basic research

journals.biologists.com/jeb/article/...

The first 22 hours of #Zebrafish development. Blood vessels labeled in green #WeinsteinLab 🔬🧪

Chemical and mechanical patterning of tortoise skin scales occur in different regions of the head Biological sciences; Zoology; Evolutionary biology

Excited to share our new research in @cp-iscience.bsky.social! We reveal that tortoise head scales are sculpted through two distinct developmental processes - chemical signalling and mechanical folding 🐢🔬🧪
@lanevol.bsky.social @genevunige.bsky.social

www.cell.com/iscience/ful...

Maternal iron deficiency causes male-to-female sex reversal in mouse embryos - Nature Iron-deficient conditions in pregnant mice can cause XY mouse embryos to develop female rather than male genitalia, revealing that iron metabolism has a role in determining male sex in mice.

www.nature.com/articles/s41...

Dev bio is amazing !!

Check out our latest work on the evolution of animal genome regulation out today in @nature.com. Nicely summarized below by @ianakim.bsky.social.
www.nature.com/articles/s41...

This is a major output from our ERC-StG project Evocellmap @erc.europa.eu at @crg.eu

Zebrafishology, study design guidelines for rigorous and reproducible data using zebrafish - Communications Biology A review emphasizes the advantages of using zebrafish in research, outlines key differences in experimental approaches, and offers guidelines for designing studies in a way that enhances experimental ...

A review emphasizes the advantages of using zebrafish in research, outlines key differences in experimental approaches, and offers guidelines for designing studies in a way that enhances experimental rigor and reproducibility. www.nature.com/articles/s42...

Interphase cell morphology defines the mode, symmetry, and outcome of mitosis During tissue formation, dynamic cell shape changes drive morphogenesis while asymmetric divisions create cellular diversity. We found that the shifts in cell morphology that shape tissues could conco...

My first post on Bluesky! Very excited to share our work just published in @science.org. We find that “Interphase cell morphology defines the mode, symmetry, and outcome of mitosis” - in angiogenesis and other tissues! www.science.org/doi/abs/10.1... www.science.org/doi/abs/10.1...

Look familiar? This beautiful video of #zebrafish embryogenesis was used for a 'one-frame per page' flipbook in the December 1996 edition of @dev-journal.bsky.social. Credit to Rolf Karlstrom and Don Kane. #ZebrafishFunFacts 🧪

Awesome new paper by @lucalivraghi.bsky.social et al.
doi.org/10.1016/j.cu...
in @currentbiology.bsky.social
on the evo-devo of a butterfly color variation

enjoy the show!

Thrilled that our image was selected for the cover of @royalsocietypublishing.org's Open Biology! We experimentally induced a developmental shift from normal footpad scales to mechanically-driven folding on chicken embryo digits 🐣🔬. Stay tuned—the full article is coming soon! 🧪 #DevBio

It's the moment you've all been waiting for... Invertebrate of the year voting is now open! 🗳️ Who will be your winner? theguardian.com/invertebrateoftheyear25