Endecous (Ramalhoecous) spelaeus, Carvalho & Ferreira, 2025

Carvalho, Pedro Henrique Mendes & Ferreira, Rodrigo Lopes, 2025, No need to jump in the darkness: A new troglobitic species of Endecous Saussure, 1878 (Orthoptera: Grylloidea: Phalangopsidae) from the Brazilian Semiarid region, Zootaxa 5642 (4), pp. 317-330 : 327

Is E. (Ramalhoecous) spelaeus sp. nov. a troglobitic species?

E. (R.) spelaeus sp. nov. presents elongated legs relative to body length, reduced compound eyes, and a lighter integument coloration compared to other species of the genus Endecous . These features are commonly associated with organisms strictly adapted to cave environments ( Christiansen 1962; Desutter-Grandcolas 1997a, 1997b; Howarth & Moldovan 2018). In addition, E. (R.) spelaeus sp. nov. exhibits slow walking behavior and an apparent inability (or at least a reduced tendency) to jump. Such behavioral traits are also typical of subterranean-adapted species ( Lavoie et al. 2007; Howarth & Moldovan 2018). Based on this combination of morphological and behavioral traits, we propose that E. (R.) spelaeus sp. nov. is a troglobitic species. However, further surveys in the epigean environment surrounding the Gruta Boca da Lapa cave are necessary to confirm this hypothesis. Furthermore, we suggest that the reduction in the number and size of subapical spurs on the hind legs may represent a troglomorphic trait. We propose two possible explanations for this hypothesis, both of which warrant further investigation to confirm or refute their validity:

1. Reduction of subapical spurs as a consequence of diminished jumping ability: E. (R.) spelaeus sp. nov. exhibits underdeveloped hind femora compared to other Endecous species, which may reflect a reduction in the musculature responsible for jumping. As this species rarely, if ever, engages in jumping, the associated muscles are likely used less frequently. This muscular reduction may, in turn, impair the species’ ability to perform kicking, an agonistic behavior commonly employed by crickets during territorial disputes and competition for resources ( Adamo & Hoy 1995; Briffa 2008; Fianco et al. 2018; Lobregat et al. 2019). With reduced reliance on hind-leg combat, the subapical spurs may have been secondarily lost due to the disappearance of their primary functional role.

2. Reduction of subapical spurs as a consequence of low population density: The very limited number of E. (R.) spelaeus sp. nov. individuals observed within the Gruta Boca da Lapa cave suggests a low population density. This rarity likely reduces the frequency of agonistic encounters, thereby diminishing the selective pressure to maintain structures involved in intraspecific combat. As a result, the loss of subapical spurs may be attributed to their reduced functional relevance in such interactions.

The reduction of spines on locomotor appendages has been documented in troglobitic Cixiidae planthoppers from the genera Ferricixius Hoch & Ferreira, 2012 ( F. urieli Santos, Hoch & Ferreira, 2023 ; F. michaeli Santos, Hoch & Ferreira, 2023 ; F. davidi Hoch & Ferreira, 2012 ; F. goliathi Santos, Hoch & Ferreira, 2023 ) and Solonaima Kirkaldy, 1906 ( S. baylissa Hoch & Howarth, 1989 ) ( Hoch & Howarth 1989, Santos et al. 2023). Although the spines (apical teeth) on the hind tarsomeres of planthoppers likely serve different functions from the subapical spurs located on the dorsal surface of the hind tibiae in phalangopsid crickets, the repeated reduction of such projections in troglobitic species across distinct taxonomic groups suggests a broader evolutionary trend of structural regression associated with life in subterranean environments.