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...

Polar bodies serve as a landmark for anteroposterior axis formation in spiders

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Polar bodies serve as a landmark for anteroposterior axis formation in spiders

Abstract

The early embryogenesis of many spiders involves the formation of a radially symmetric germ disc. While the cells of the rim of this germ disc develops into anterior structures, the center of the disc will form the posteriorly located segment addition zone of the embryo. Therefore, germ disc formation sets the anterior-posterior (AP) body axis of spider embryos. The early spider egg is a spherical structure with no apparent asymmetry, and it is believed that germ disc formation is a stochastic process. For this study, we have re-analyzed early spider embryogenesis and found a strong correlation of the position of the polar bodies and the formation of the germ disc. Our results suggest that germ disc formation in the common house spider Parasteatoda tepidariorum is not a stochastic but a pre-determined process. Furthermore, we provide evidence that this correlation might be conserved between araneomorph and mygalomorph spider species.

Polar bodies serve as a landmark for anteroposterior axis formation in spiders, Ruixun Wang, Matthias Pechmann, bioRxiv 2024.09.30.615744; doi: https://doi.org/10.1101/2024.09.30.615744