The world's fastest spider tops 3.5 metres per second

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  Evolutionary biomechanics of maximum running speed in spiders (Araneae)    Abstract Background Maximum running speed is a central performance trait, linking morphology, physiology and behaviour to fitness. It is shaped by physical capacity and ecological selection but may also be constrained by ancestry. To examine how these forces interact across macroevolutionary timescales, we conducted an allometric study in a hyper-diverse arthropod taxon—spiders (Araneae). Results Drawing on running performance data for 258 species from 64 of the 139 extant spider families, we integrated phylogenetic comparative methods and biomechanical modelling to disentangle the effects of body size, ancestry, leg morphology, ecological guild and preferred locomotor orientation. Maximum running speed varied substantially, both across body mass and among species of similar body mass. By accounting for body mass with a recent biomechanical model, we show that size-specific performance carries ...

Evolutionary dynamics of the chromosomal changes in the genus Cyphophthalmus (Arachnida: Opiliones) on the Balkan Peninsula

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Evolutionary dynamics of the chromosomal changes in the genus Cyphophthalmus (Arachnida: Opiliones) on the Balkan Peninsula

Abstract

We investigated the genus Cyphophthalmus within the suborder Cyphophthalmi (Arachnida: Opiliones), focusing on its cytogenetic evolution in the Balkan Peninsula. Our comprehensive analysis of 21 species revealed a notable range in diploid chromosome numbers (2n = 24–30), challenging previous assumptions of genetic uniformity within this group. Using fluorescent in situ hybridization (FISH) with an 18S rDNA probe, we detected variability in the number of loci, with evidence of independent increases in this cluster (up to five pairs). This study combines the results of phylogenetic reconstruction based on analysis of mitochondrial gene cytochrome c oxidase subunit I (COI) (including karyotyped individuals) with standard and molecular cytogenetic techniques, making it the first of its kind in harvestman research. The findings reveal a significantly higher level of biodiversity in the Balkan Peninsula than previously recognized, suggesting complex differentiation within the genus Cyphophthalmus. Additionally, our results highlight the efficacy of cytogenetics as a tool for species’ delineation, enriching our understanding of the evolutionary history of the genus and emphasizing the intricate genetic diversity shaped by the unique geological and environmental history of the Balkan Peninsula.

Hiřman, M., Karaman, I., Štundlová, J., Just, P., & Šťáhlavský, F. (2025). Evolutionary dynamics of the chromosomal changes in the genus Cyphophthalmus (Arachnida: Opiliones) on the Balkan Peninsula. Zoological Journal of the Linnean Society, 204(3). https://doi.org/10.1093/zoolinnean/zlaf068