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...

Accessing the challenges of descriptive morphology in Barychelidae and Theraphosidae through a morphometric approach (Araneae, Mygalomorphae)

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Accessing the challenges of descriptive morphology in Barychelidae and Theraphosidae through a morphometric approach (Araneae, Mygalomorphae)

Abstract

Phylogenetic studies have confirmed that Barychelidae is a sister group of Theraphosidae. However, taxonomic instability has led to the transfer of genera between the two families, both families show overlapping diagnostic characteristics, indicating a similarity making species differentiation challenging. In this study, we conducted an evaluation of three morphological characters that are commonly used to distinguish Barychelidae and Theraphosidae. We employed geometric morphometric to analyze variations in the shapes of the maxilla, labium, and the eyes arrangement. Our results revealed that these characters show continuous variation, which can make it problematic for discrete categorization and differentiation between Barychelidae and Theraphosidae. On the other hand, our analysis showed that the shape of the eye arrangement is effective in distinguishing the subfamilies within Barychelidae. Furthermore, we found notable distinctions between these characters on the Neotropical Sasoninae genera compared to the Sason Simon, 1887. Therefore, highlights the importance of incorporation of morphometric analyses into taxonomic and cladistics studies to improve the understanding of distinctions between families that are considered as sister groups.

Hector M. O. GONZALEZ-FILHO, Maria T. COLPANI-SARTORI, Arthur GALLETI-LIMA et al. Accessing the challenges of descriptive morphology in Barychelidae and Theraphosidae through a morphometric approach (Araneae, Mygalomorphae), 30 January 2026, PREPRINT (Version 1) available at Research Square [https://doi.org/10.21203/rs.3.rs-8385809/v1]