Matt Simon (https://instagram.com/crawly.creepy) made me recently aware of a new article from Matthew Graham and co-workers on the mitochondrial genome for the genus Smeringurus Haradon, 1983 (Vajeovidae). This stuff is way over my head and I had planned to not blog about it, but it turns out that the results have implications for vaejovid systematics and should be mentioned in the blog.
Fortunately, I have been allowed to use Matt's review of the papers content and bring them to you in this post. And those interested can check out the article to see if you understand more than I do. :)
The researchers of the study set out to recover the first mitochondrial genome for the genus Smeringurus. However, one part of the genome was persistently difficult to recover. "What first appeared to be an incomplete or problematic portion of the genome gradually resolved...into a large and remarkably orderly tandem-repeat array in the control region" of the mitochondrial genome.
This is a new finding. It is significant because it shows "the control region as a structured and, potentially, an evolutionarily informative component of scorpion mitogenomes." The authors believe that this finding brings clarity to a difficult mitogenomic region that in the past was under-recognized because researchers were unable to make sense of it.
However, it's complicated. The researchers observe that this repeat array in the mitogenomic control region occurs in some other scorpion taxa, but it does not occur in all scorpion groups.
Lastly, the authors note that their study has implications for vaejovid systematics. "Within the limits of currently available mitogenomic sampling, S. mesaensis was recovered as sister to the remaining sampled vaejovids. That placement is notable because it is broadly consistent with earlier studies that also placed Smeringurus or Smeringurinae near the base of Vaejovidae."
However, the researchers note, prior work by Santibáñez-López et al. with phylogenomic data "recovered Smeringurinae...not as sister to the remaining vaejovids, but as a long branch nested within the family." That means the two techniques led to different systematic pictures. "That contrast suggests that the placement of Smeringurinae may remain sensitive to character sampling and analytical scale."
Abstract:
Repetitive regions of animal mitochondrial genomes are biologically informative but often difficult to assemble, raising the possibility that structured variation in mitochondrial control regions may be overlooked, especially in short-read datasets. We used Oxford Nanopore long-read sequencing to assemble five complete mitochondrial genomes of the dune scorpion Smeringurus mesaensis and resolve and validate the structure of the mitochondrial control region. In all five individuals, the 1598–1600 bp control region contained six complete 202 bp tandem repeats and one 92 bp terminal partial repeat. Mean control-region coverage ranged from 15.9× to 49.8×, with 10–33 reads spanning the 5′ repeat-array boundary, 14–25 spanning a central repeat junction, and three reads spanning the complete repeat array. Despite this repetitive architecture, the arrays were highly organized: repeats R2–R6 were identical within individuals, whereas R1 and the terminal partial repeat retained consistent positional differences. The 5′ non-repeat region showed significant local similarity to the control regions of Vaejovis mexicanus and V. smithi (72.8% and 69.6% identity), whereas the 202 bp repeat produced only short, nonsignificant matches. This pattern suggests that replication slippage and sequence homogenization have jointly shaped control-region evolution. A comparative survey of published scorpion mitogenomes further indicated that tandem repeats are more widespread and structurally diverse than generally reported. These results demonstrate the value of long reads for direct validation of repeat-rich mitochondrial architecture and highlight control-region structure as an underappreciated feature of scorpion mitogenome evolution.
Reference:
Graham MR, Santibáñez-López CE, Murdoch B. Long-Read Mitogenomes Reveal Hidden Control-Region Architecture in Smeringurus mesaensis and Overlooked Tandem Repeats in Scorpions. Arthropoda. 2026;4(4):16. [Open Access]
Thanks to Matt Simon for informing me about the article and for allowing me to use his review of it!
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