Lightnews — Scholar-powered news

Reposted by Callum Bucklow

James Hammond @jamesehammond.bsky.social · Sep 8

Out now in Seminars in Cell & Dev Biol!

doi.org/10.1016/j.se...

With thanks to co-authors @callumbucklow.bsky.social and @bertaverd.bsky.social

6 4

Callum Bucklow @callumbucklow.bsky.social · May 29

That's great, thank you. Also just read the article you posted, fantastic summary and breakdown of the evidence.

1

Callum Bucklow @callumbucklow.bsky.social · May 29

This is an absolutely amazing picture of a mouthbrooder -- I've only been able to get pics of eggs. Would you mind if I used this image for presentations and for teaching? Full credit given, of course.

1 1

Callum Bucklow @callumbucklow.bsky.social · May 29

Our findings reveal the dynamic interplay between somitogenesis and homeotic transformations driving vertebral diversity, reinforcing cichlids as an incredible model for unraveling axial evolution in teleosts. Not to mention exciting work bridging developmental biology, evo bio, and macroevolution!

Callum Bucklow @callumbucklow.bsky.social · May 29

We previously showed vertebral addition drives body elongation in African cichlids. But intraspecific variation in vertebral count doesn’t predict body shape, having more vertebrae doesn’t mean you’re more elongate. So, intraspecific variation is decoupled from macroevolutionary body shape patterns.

1 1

Callum Bucklow @callumbucklow.bsky.social · May 29

Therefore, evolutionary modification of somitic 'fidelity' (at least in African cichlids) has not been important in driving evolution of total counts and the intraspecific variation has not changed as African cichlids diversified... in other words, somite counts within species are highly canalised.

1

Callum Bucklow @callumbucklow.bsky.social · May 29

Despite high evolvability, vertebral counts in African cichlids show low intraspecific variation. Correcting for phylogeny: (1) variation doesn't scale with count (no sign of selection), and (2) doesn't differ between lakes & rivers, even if each system is subject to its own rate of count evolution.

1

Callum Bucklow @callumbucklow.bsky.social · May 29

Intraspecific variation in vertebral count is common across vertebrates, including in teleosts (and cichlids). The presence of intraspecific variation suggests developmental lability in somitogenesis, how has this variation evolved? What might it tell us about the evolution of somitogenesis?

1

Callum Bucklow @callumbucklow.bsky.social · May 29

Using vertebral count data from >4,500 African cichlids (~500 species), we show that axial regionalisation can shift via changes to AP patterning. However, most variation reflects differences in somite number, with homeotic transformations emerging mainly as a consequence of these somitic changes.

1

Callum Bucklow @callumbucklow.bsky.social · May 29

Interspecific differences in vertebral count and axial regionalisation reflect evolutionary shifts in somite number and homeotic identity post-divergence. By mapping these traits across clades, we can infer how somitogenesis and AP patterning have evolved alongside lineage diversification.

1

Callum Bucklow @callumbucklow.bsky.social · May 29

The total number of vertebrae and their morphological identity along the anterior–posterior (AP) axis are established during development, through the processes of somitogenesis and subsequent regionalisation of the somites which is governed by Hox gene patterning.

1

Callum Bucklow @callumbucklow.bsky.social · May 29

My third PhD manuscript is on BioRxiv: "Somitic Change Drives Changes in Vertebral Regionalisation in African Cichlids Despite Strong Canalisation of Somite Number" (www.biorxiv.org/content/10.1...). Thanks to my co-authors and supervisors @bertaverd.bsky.social and Roger Benson. Thread below...

Somitic Change Drives Changes in Vertebral Regionalisation in African Cichlids Despite Strong Canalisation of Somite Number

Vertebrae arise from somites, transient embryonic segments that rhythmically bud from the presomitic mesoderm during axial elongation. The number and identity of vertebrae are ultimately determined by...

www.biorxiv.org

1 2 9

Reposted by Callum Bucklow

George Turner @dlimnothrissa.bsky.social · May 26

Lake Malawi cichlids: even common, big, spectacular species are often a taxonomic mess, like these Taeniolethrinops species. Much work needed!

3 7

Reposted by Callum Bucklow

Berta Verd @bertaverd.bsky.social · May 19

Experimental embryology postdoc available in my lab at the @biology.ox.ac.uk @ox.ac.uk working on the evolution of vertebral counts. Reach out if you’re passionate about EvoDevo, enjoy lab work and microscopy and are into or could get into cichlid fishes. Deadline on the 16th June. Please share!

3 66 63

Reposted by Callum Bucklow

Virtual Gastrulation Zoom Talks @vgzt2021.bsky.social · May 16

Please join next week‘s Western 🌙 VGZT:
🗓️ Thursday, May 22
⏰ 9:30 PDT / 12:30 EDT / 16:30 UTC / 17:30 BST / 18:30 CET

@aliseleit.bsky.social
👉Developmental heterochrony & evolution of segmentation in eels

@laura-rustarazo.bsky.social
👉Rigidity transitions & epithelial organization in 🐟 embryos

7 9

Callum Bucklow @callumbucklow.bsky.social · May 16

Thank you Ali!!

Callum Bucklow @callumbucklow.bsky.social · May 16

Our work highlights the need for comparative approaches to understand cichlid evolution and demonstrates that African cichlids can be very powerful models for the study of vertebral column evolution. More cichlid-related research to come!!

2

Callum Bucklow @callumbucklow.bsky.social · May 16

Finally, we show that the common ancestor of African cichlids had a distinctly riverine axial morphology—deep-bodied with relatively few vertebrae and equal proportions of precaudal and caudal vertebrae. Axial diversity in lakes radiated outward from this ancestral form.

1

Callum Bucklow @callumbucklow.bsky.social · May 16

Interestingly, axial morphospace correlates with radiation age—Tanganyikan cichlids (oldest) show the widest occupation. But rates of vertebral evolution vary between lake radiations and accumulated variation is not just a function of divergence time! Lake-specific dynamics??

1

Callum Bucklow @callumbucklow.bsky.social · May 16

However, despite the focus on the lacustrine radiations, riverine taxa occupy a much wider axial morphospace than the lacustrine species. Which is partly being driven by a stochastic rate of total vertebral count evolution twice that of the highest lacustrine rate.

1

Callum Bucklow @callumbucklow.bsky.social · May 16

Elongation of the body is important for ecological adaptation. Lacustrine cichlids (those living in lakes) have repeatedly (and independently) evolved elongate, fusiform bodies supported by higher total vertebral counts, linked to demersal, pelagic, and piscivorous lifestyles.

1

Callum Bucklow @callumbucklow.bsky.social · May 16

Consistent with other teleosts, cichlid body elongation often involves adding vertebrae—but it's not the only route. Cranial and post-cranial elongation have co-evolved, revealing multiple axes of morphological change.

1

Callum Bucklow @callumbucklow.bsky.social · May 16

Despite its critical role in locomotion, the evolution of the vertebral column in cichlids has rarely been studied. We set out to change that—with the first macroevolutionary analysis of axial morphology across 4861 individuals from 583 species.

1 2

Callum Bucklow @callumbucklow.bsky.social · May 16

African cichlids are a powerful system in evolutionary biology, with over 1800 species and iconic radiations in Lakes Tanganyika, Malawi, and Victoria. But one feature has been overlooked: their axial skeletons.

1 1

Callum Bucklow @callumbucklow.bsky.social · May 16

Excited to announce my second PhD manuscript is on bioRvix (biorxiv.org/content/10.1...). Thanks to all co-authors, including my supervisors @bertaverd.bsky.social and Roger Benson. Thread below...

African Cichlid Lake Radiations Recapitulate Riverine Axial Morphologies Through Repeated Exploration of Morphospace

African cichlids comprise more than 1800 species of freshwater fishes, with remarkable adaptive radiations in Lakes Tanganyika, Malawi, and Victoria that have given rise to extraordinary morphological...

biorxiv.org

2 9 25