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...

A comparative morphology of trichobothrial bases in araneoid spiders and its significance for the phylogeny and system of the superfamily Araneoidea (Arachnida, Araneae)

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A comparative morphology of trichobothrial bases in araneoid spiders and its significance for the phylogeny and system of the superfamily Araneoidea (Arachnida, Araneae)

Abstract

Bothrial morphology was studied by SEM in 137 araneoid genera representing all 22 currently recognized extant families and all 42 conventional subfamilies of the Araneoidea. The ancestral type in the superfamily Araneoidea is a ‘hooded’ bothrium with a single well-developed transverse ridge, dividing its proximal and distal plates (‘Erigone-type’); the advanced type is a solid dome-like bothrium without vestiges of the ridge (‘Theridion-type’); there are several intermediate types reflecting various pathways and stages of the ridge reduction (united here as ‘Argiope-type’). The parallel trends in bothrial evolution, recognized as continuous series from the ancestral type up to the advanced one through some intermediate stages, are distinguished in each of the seven main phylogenetic lineages of the superfamily: ‘tetragnathoids’, ‘araneoids’, ‘cyatholipoids’, and ‘theridioids’ possess a complete set of the three types, while ‘malkariods’, ‘symphytognathoids’. and ‘linyphioids’ lack the advanced, dome-like type (‘Theridion-type’). Only three taxa have been proposed earlier as the sister group of the superfamily Araneoidea: Nicodamoidea, Deinopoidea, and Leptonetoidea; morphology of bothria, as well as other cuticular microstructures, clearly supports the araneoid-nicodamoid relationship hypothesis, purely ‘molecular’ to date. Bothrial morphology provides the additional arguments for several taxonomic acts, e.g., for the reranking the Agnarsson’s (2004) ‘clade 35’ (Theonoe, Carniella, Robertus, and Pholcomma) up to the Theonoeinae Simon, 1894, stat. nov., and for the revalidation the micropholcommatid Plectochetos Butler, 1932, gen. revalid. and zygiellid Parazygiella Wunderlich, 2004, gen. revalid.

Eskov KY, Marusik YM (2024) A comparative morphology of trichobothrial bases in araneoid spiders and its significance for the phylogeny and system of the superfamily Araneoidea (Arachnida, Araneae). ZooKeys 1219: 1-60. https://doi.org/10.3897/zookeys.1219.133002