Photoreceptor physiology of two species of crab spiders (Araneae: Thomisidae)

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  Photoreceptor physiology of two species of crab spiders (Araneae: Thomisidae) Abstract Spiders are a diverse order of predatory arachnids with more than 53.000 described species, most of which have eight eyes. Many webless hunting spiders, most noticeably the jumping spiders (Salticidae) have been shown to have excellent eyes with high spatial resolution and colour vision. The family of crab spiders (Thomisidae) is also hypothesized to be visual hunters, employing a “sit and wait” or ambush hunting technique; however, little is currently known about their visual capacity. Here we use extracellular electrophysiology to examine the photoreceptor physiology of two crab spiders living in two different ecological niches.  Ozyptila praticola  (C.L. Koch, 1837) hunts on the ground in dim habitats whereas  Xysticus cristatus  (Clerck, 1757) hunts in the typical bright open grasslands. We test the hypotheses that (1) each species has special-purpose eyes, (2) that male...

Size matters: a new genus of tarantula with the longest male palps, and an integrative revision of Monocentropus Pocock, 1897 (Araneae, Theraphosidae, Eumenophorinae)

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Size matters: a new genus of tarantula with the longest male palps, and an integrative revision of Monocentropus Pocock, 1897 (Araneae, Theraphosidae, Eumenophorinae)

Abstract

A taxonomic revision of the eumenophorine tarantula genus Monocentropus Pocock, 1897, which currently comprises three species, M. balfouri Pocock, 1897 (♂♀; Socotra, Yemen), M. lambertoni Fage, 1922 (♂♀; Madagascar), and M. longimanus Pocock, 1903 (♂♀; Yemen), is presented. By integrating both morphological data and a molecular phylogeny based on mitochondrial (cox1) and nuclear (28S, 18S) markers, the genus is herein redefined to include only the type species, M. balfouri. A new genus, Satyrex Zamani & von Wirth, gen. nov., is established to comprise S. longimanus comb. nov., along with four new species from the Arabian Peninsula and the Horn of Africa described herein: S. arabicus Zamani & von Wirth, sp. nov. (♂; Saudi Arabia), S. ferox Zamani, von Wirth & Stockmann, sp. nov. (♂♀; Yemen, Oman), S. somalicus Zamani & von Wirth, sp. nov. (♂; Somaliland), and S. speciosus Zamani, von Wirth & Just, sp. nov. (♂♀; Somaliland). The new genus is partially characterised by possessing the longest male palps known in tarantulas, possibly functioning in cannibalism avoidance during mating. Both the molecular phylogeny and morphological characters suggest that M. lambertoni is probably not congeneric with M. balfouri, and also indicate that multiple species may be currently subsumed under the former name. Therefore, M. lambertoni is regarded as incerta sedis pending further studies to clarify its taxonomic placement, as it is also considered to represent a species complex. Finally, the distribution of all studied taxa is discussed within a biogeographic framework.


Zamani A, von Wirth V, Fabiánek P, Höfling J, Just P, Korba J, Petzold A, Stockmann M, Elmi HSA, Vences M, Opatova V (2025) Size matters: a new genus of tarantula with the longest male palps, and an integrative revision of Monocentropus Pocock, 1897 (Araneae, Theraphosidae, Eumenophorinae). ZooKeys 1247: 89-126. https://doi.org/10.3897/zookeys.1247.162886