Seasonal Variation in Whole-Body Elemental Concentrations and Excreta Production of a Riparian Orb-Weaving Spider (Larinioides cornutus)

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  Seasonal Variation in Whole-Body Elemental Concentrations and Excreta Production of a Riparian Orb-Weaving Spider (Larinioides cornutus) ABSTRACT Predators influence nutrient cycling by assimilating elements from their prey and returning nutrients to ecosystems via excretion and discarded prey remains. However, seasonal variation in the contribution of predators to nutrient cycling remains poorly understood, particularly for terrestrial arthropod predators such as spiders. We examined temporal variation in whole-body elemental concentrations, excreta C and N concentrations, and cumulative excreta output in a riparian orb-weaving spider ( Larinioides cornutus ) across the growing season of 2024. Adult females were collected across seven sampling periods spanning mid-June to early October, and whole-body concentrations of macronutrients (carbon [C], nitrogen [N], phosphorus [P]) and multiple trace elements were quantified. Whole-body N and P concentrations, and several trace elemen...

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