Big Spider, Big Genome: Chromosome-level genome of a North American tarantula (Aphonopelma marxi) and comparative genomics across 300 million years of spider evolution

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  Image Credit: WikiCommons Big Spider, Big Genome: Chromosome-level genome of a North American tarantula (Aphonopelma marxi) and comparative genomics across 300 million years of spider evolution Abstract The comparison of chromosome-level genomes allows biologists to investigate new axes of organismal evolution. Spiders comprise a significant proportion of known arachnid diversity, with many complex morphologies and unique natural histories, yet comparative genomics in spiders has been limited due to the number of available genomes. We present a de novo chromosomal reference genome of a mature male tarantula, Aphonopelma marxi, and comparatively examine spider genome evolution across the Order Araneae. Using PacBio HiFi and Hi-C sequencing, the final 6.5 Gb assembly consists of 17 autosomes, 1 X chromosome, and 127 unplaced scaffolds, with an N50 of 370 Mb and Arachnida (odb10; 2934 genes) BUSCO of 96.7%. By comparing 20 additional spider genomes from 15 families, we find mygalomo...

Digestion in the arachnid Mischonyx squalidus as a probable source of lipids to synthesize opiliones defense and communication molecules

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Digestion in the arachnid Mischonyx squalidus as a probable source of lipids to synthesize opiliones defense and communication molecules

Abstract

Opiliones (Arachnida) comprises approximately 7,000 species. Due to their lack of venom glands, their defense is mainly based on the secretion of scent glands, which also play roles in communication and antimicrobial activity. This odoriferous secretion has a diverse composition according to harvestmen species but frequently contains benzoquinones. Studies of benzoquinone synthesis intermediates suggest a pathway based on lipid metabolism from diet. This study provides the first transcriptomic and enzymatic analysis of the midgut of Mischonyx squalidus to understand the acquisition of nutrients. The enzymatic analysis tested 11 digestive enzymes and found high lipase activity and moderate and low activity for peptidases and carbohydrases, respectively. Transcriptome sequencing yielded 19,658 unigenes, predominating enzymes and binding proteins closely associated with Xiphosura and Scorpiones proteins; a third of which are hydrolases. A multigene lipase family is expressed. Cathepsin L peptidases were prominently abundant, indicating their relevance for protein digestion. Additionally, toxin-like proteins and lipid metabolism-related enzymes, such as phospholipase A2 and NPC cholesterol transporters, were represented, indicating a sophisticated digestive and metabolic system for lipids. These findings suggest a link between lipid digestive metabolism and defensive and communicative molecule synthesis, underscoring Opiliones’ unique evolutionary adaptations.

Silva, J. O., Viala, V. L., Dias, R. O., Ferreira, C., Terra, W. R., & Lopes, A. R. (2025). Digestion in the arachnid Mischonyx squalidus as a probable source of lipids to synthesize opiliones defense and communication molecules. Scientific Reports, 15(1), 1-15. https://doi.org/10.1038/s41598-025-18180-x