A new species of the mygalomorph spider genus Euagrus Ausserer (Araneae: Euagridae) from central Mexico and new records of E. gus Coyle from Tlaxcala

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  A new species of the mygalomorph spider genus Euagrus Ausserer (Araneae: Euagridae) from central Mexico and new records of E. gus Coyle from Tlaxcala Abstract  A new species of the spider genus Euagrus Ausserer, 1875 from temperate pine-oak forests in the states of Tlaxcala and Hidalgo, Mexico is described: E. pulque sp. nov. The description of the new species is based on male and female adult specimens. Additionally, Euagrus gus Coyle, 1988 is recorded for the very first time in the state of Tlaxcala. These species have sympatric distributions in La Malinche National Park, Tlaxcala. With this description, the diversity of the genus increases to 23 species, with Mexico harboring the highest diversity with 17 described species.  Valdez-Mondragón, A., Salinas-Velasco, H. V. & Bueno-Villegas, J. (2026). A new species of the mygalomorph spider genus Euagrus Ausserer (Araneae: Euagridae) from central Mexico and new records of E. gus Coyle from Tlaxcala. Zootaxa 5810 (...

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