A new species of Strotarchus Simon, 1888 from Mexico and description of the male of the type species S. nebulosus Simon, 1888 (Araneae: Cheiracanthiidae)

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  A new species of Strotarchus Simon, 1888 from Mexico and description of the male of the type species S. nebulosus Simon, 1888 (Araneae: Cheiracanthiidae) Abstract A new sac spider of the genus Strotarchus Simon, 1888, S. adrianae spec. nov., is described based on specimens of both sexes collected from Jalisco, Mexico. In addition, the previously unknown male of Strotarchus nebulosus Simon, 1888 is described for the first time. Orozco-Gil, M., Jiménez, M.-L. & Chamé-Vázquez, D. (2026) A new species of Strotarchus Simon, 1888 from Mexico and description of the male of the type species S. nebulosus Simon, 1888 (Araneae: Cheiracanthiidae). Zootaxa, 5821 (2), 263–273. https://doi.org/10.11646/zootaxa.5821.2.7

Small Brains: Body Shape Constrains Tissue Allocation to the Central Nervous System in Ant-Mimicking Spiders

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Small Brains: Body Shape Constrains Tissue Allocation to the Central Nervous System in Ant-Mimicking Spiders

ABSTRACT

In Batesian mimicry, mimetic traits are not always as convincing as predicted by theory—in fact, inaccurate mimicry with only a superficial model resemblance is common and taxonomically widespread. The “selection trade-offs hypothesis” proposes a life-history trade-off between accurate mimetic traits and one or more vital biological functions. Here, using an accurate myrmecomorphic (ant-mimicking) jumping spider species, Myrmarachne smaragdina, we investigate how myrmecomorphic modifications to the body shape impact the internal anatomy in a way that could be functionally limiting. Specifically, via x-ray micro-computed tomography (microCT), we quantify how the spider's constricted prosoma, which emulates the head and thorax of ants, impacts the size of the central nervous system (CNS) and the venom glands. Although, relative to their whole-body mass, we found no significant difference in venom gland volume, the CNS of the ant-mimicking jumping spider was significantly smaller when compared with a relatively closely related non-mimic jumping spider, indicating that some trade-off between mimic accuracy and size of neural anatomy, as articulated by the “selection trade-offs hypothesis,” is a possibility. Our explorative evidence enables and encourages broader investigation of how variable mimic accuracy impacts the neuroanatomy in ant mimics as a direct test of the “selection trade-offs hypothesis.”

J. Kelly, M. B., Penna-Gonçalves, V., Willmott, N. J., McLean, D. J., Black, J. R., Wolff, J. O., & Herberstein, M. E. (2024). Small Brains: Body Shape Constrains Tissue Allocation to the Central Nervous System in Ant-Mimicking Spiders. Journal of Comparative Neurology, 532(11), e25680. https://doi.org/10.1002/cne.25680