Living underground: first record of myrmecophily in a species of tarantula (Mygalomorphae: Theraphosidae: Catumiri Guadanucci, 2004)

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  Living underground: first record of myrmecophily in a species of tarantula (Mygalomorphae: Theraphosidae: Catumiri Guadanucci, 2004) Abstract Myrmecophily is widespread among arthropods but remains poorly documented in spiders, particularly in Mygalomorphae. Tarantulas (Theraphosidae) have not previously been shown to form true myrmecophilous associations, with existing records limited to anecdotal observations. Here, we provide the first robust evidence of myrmecophily in a tarantula, based on combined field and experimental data. Fieldwork in the Ñacuñán Biosphere Reserve (Monte Desert, Argentina) revealed that individuals of a species of Catumiri Guadanucci 2004 inhabit nests of the leaf-cutting ant Acromyrmex lobicornis Emery 1887. Of 45 excavated nests, 16 (35.5%) contained spiders, with a total of 69 individuals recorded. The presence of multiple developmental stages, including early instars cohabiting with adult females, indicates that reproduction and early development ...

Troglomorphic trends of palpigrades in the Eukoenenia mirabilis-berlesei group, and discovery of a new cave-dwelling species from Spain (Palpigradi, Eukoeneniidae)

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Troglomorphic trends of palpigrades in the Eukoenenia mirabilis-berlesei group, and discovery of a new cave-dwelling species from Spain (Palpigradi, Eukoeneniidae)

Abstract

The arachnid order Palpigradi remains poorly studied, particularly with respect to patterns of morphological adaptation to subterranean environments. Subterranean adaptation in palpigrades and comparison with endogean species has been documented scarcely. In this study, Eukoenenia serrana sp. nov. is described as a new species in the E. mirabilis-berlesei group from the cave Sima del Pla de Llomes in eastern Spain. The new species exhibits pronounced troglomorphic features, including large body size and strong elongation of appendicular elements, particularly leg I, while retaining diagnostic characters of the group like the single lateral prosomal organ. We explored the morphological differentiation between endogean and hypogean species in the E. mirabilis-berlesei group, a lineage traditionally regarded as endogean and only marginally associated with caves. An analysis of elongation patterns, with an emphasis on the palp and legs, showed clear differences between species from different habitats using a set of linear measurements and derived ratios related to body and their appendages size. Hypogean species consistently show marked elongation of tibia I, basitarsus IV, and combined tarsus–tibia lengths, whereas changes in overall body characters are more moderate. In contrast, the basitarsus IV/tibia IV ratio remains largely unchanged, indicating proportional elongation of these segments. Highly cave-adapted species in this group retained a single blade in the lateral organ, suggesting that sensory and appendicular traits may evolve independently. The results reveal a mosaic pattern of subterranean adaptation within the E. mirabilis-berlesei group and by extension in palpigrades.

Barranco P, Sánchez-Camacho FJ, Mayoral J (2026) Troglomorphic trends of palpigrades in the Eukoenenia mirabilis-berlesei group, and discovery of a new cave-dwelling species from Spain (Palpigradi, Eukoeneniidae). Subterranean Biology 57: 117-138. https://doi.org/10.3897/subtbiol.57.202620