Olfactory learning in two Amblypygi species Paraphrynus laevifrons and Phrynus pseudoparvulus

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  Olfactory learning in two Amblypygi species Paraphrynus laevifrons and Phrynus pseudoparvulus Abstract A wide diversity of arthropod taxa have demonstrated the capacity for learning, but most of our current understanding comes from only a select subset of this highly diverse clade, with most studies focusing on various insect groups. Amblypygids (Order Amblypygi, Class Arachnida), however, are emerging as a model group for studying sensory integration and the neural substrates associated with learning and memory, especially as it relates to navigation. These nocturnal creatures possess specialized sensory appendages and one of the largest and most complex mushroom bodies - the part of the arthropod brain associated with learning and memory - of any arthropod. Prior field studies on multiple species demonstrate sophisticated homing abilities while laboratory-based behavioral assays in  Phrynus marginemaculatus  confirm olfactory-based learning associated with a refuge. I...

Circadian rhythms of locomotor activity in the New World tarantula Neoholothele incei (Araneae: Theraphosidae)

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Circadian rhythms of locomotor activity in the New World tarantula Neoholothele incei (Araneae: Theraphosidae)

Abstract

Circadian rhythms in behavior are intrinsically linked to organismal fitness, supporting the theory that Earth’s near 24 h day selects against dissonant rhythms. However, in arthropods, particularly spiders, circadian free-running periods (FRPs) exhibit significant population variation. Some spider species possess rhythms that deviate by up to 5–6 h from 24 h. These findings are restricted to a large clade of web-building spiders, leaving it unknown whether this chronobiological strategy extends beyond that group. To explore this, we monitored the locomotor activity of a distant outgroup species, the New World tarantula Neoholothele incei F.O. Pickard-Cambridge, under a controlled photic cycle. Our efforts determined that its bimodal diel activity is governed by circadian (endogenous) components. Spiders usually had both a diurnal and nocturnal peak in locomotor activity. Each peak showed strong support for its regulation by endogenous circadian control under constant conditions. FRPs averaged within an hour of 24 h but ranged from ~ 21 to 25 h, similar to the variation observed in some insects and spiders. These results offer initial evidence that FRP variation, though not always extreme deviations from 24 h, is a common strategy among spiders.

Giulian, J., Toporikova, N., Petko, J. et al. Circadian rhythms of locomotor activity in the New World tarantula Neoholothele incei (Araneae: Theraphosidae). J Ethol (2025). https://doi.org/10.1007/s10164-025-00842-y