Genomic and transcriptomic analyses reveal the adaptation to semi-aquatic and aquatic life in spiders

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  Genomic and transcriptomic analyses reveal the adaptation to semi-aquatic and aquatic life in spiders Abstract Spiders are largely terrestrial, but some lineages have independently adapted to marine and freshwater habitats. Although physiological and behavioral traits supporting these evolutionary transitions have been characterized, the genomic basis of adaptation to aquatic and semi-aquatic habitats in spiders remains unclear. Here, we report a chromosome-level genome assembly for the aquatic spider Argyroneta aquatica. Comparative analysis of 22 spider species supports two independent transitions in semi-aquatic (∼56 Mya) and aquatic (∼44 Mya) lineages. The aquatic spider show distinct respiratory morphology compared with terrestrial spiders, including anterior spiracles and denser tracheoles. Molecular evolution analyses identified lineage-specific shifts in selective constraint or evidence of positive selection linked to trachea development (e.g., Wnt-1, Catenin beta, TMEM23...

A three-dimensional immunofluorescence atlas of the brain of the hackled-orb weaver spider, Uloborus diversus

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A three-dimensional immunofluorescence atlas of the brain of the hackled-orb weaver spider, Uloborus diversus

Abstract

Spider orb-web building is a captivating, rare example of animal construction, whose neural underpinnings remain undiscovered. We created a three-dimensional atlas for the hackled-orb weaver, Uloborus diversus, based on immunostaining for the presynaptic component, synapsin, in whole-mounted spider synganglia. Whereas spider neuroanatomy has thus far been most comprehensively studied in cursorial species, this optically sectioned atlas contributes a continuous, finely resolved model of the central nervous system of an orb-web building spider. Aligned to this volume, we examined the expression patterns of neuronal populations representing many of the classical neurotransmitters and neuromodulators (GABA, acetylcholine, serotonin, and octopamine/tyramine), as well as a subset of neuropeptides (allatostatin A, crustacean cardioactive peptide (CCAP), FMRFamide, proctolin) – detailing immunoreactivity in an unbiased fashion throughout the synganglion to reveal co-expression in known structures (such as the arcuate body), as well as novel neuropils not readily apparent in prior spider research, including the tonsillar neuropil as well as a potential protocerebral bridge. These structures provide targets for future functional studies, and taken together, could represent a spider equivalent of the central complex, contributing to behaviors such as web-building.

Gregory Artiushin, Abel Corver, Andrew Gordus (2026) A three-dimensional immunofluorescence atlas of the brain of the hackled-orb weaver spider, Uloborus diversus eLife 14:RP107732. https://doi.org/10.7554/eLife.107732.3