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. 2019 Oct 23;14(10):e0223828.
doi: 10.1371/journal.pone.0223828. eCollection 2019.

A relictual troglomorphic harvestman discovered in a volcanic cave of western Argentina: Otilioleptes marcelae, new genus, new species, and Otilioleptidae, new family (Arachnida, Opiliones, Gonyleptoidea)

Luis E Acosta  1   2
Affiliations

A relictual troglomorphic harvestman discovered in a volcanic cave of western Argentina: Otilioleptes marcelae, new genus, new species, and Otilioleptidae, new family (Arachnida, Opiliones, Gonyleptoidea)

Luis E Acosta. PLoS One. .

Abstract

The troglomorphic harvestman Otilioleptes marcelae gen. nov., sp. nov. from the basaltic cave Doña Otilia, Payunia region, Mendoza Province, Argentina, is described. Its systematic affinities were studied through cladistic and Bayesian analyses that included representatives of Gonyleptoidea; it was determined to represent a new monotypic family, Otilioleptidae fam. nov., occupying a basal position within the clade Laminata. This species shows accentuated troglomorphic traits, typical for troglobitic harvestmen: elongated appendages, depigmentation, reduction of eyes and fading of scutal sulci. Additionally, it almost lacks sexual dimorphism, the distal portion of coxa IV is not completely fused to the stigmatic segment, and penis morphology is remarkably divergent with other Laminata; these features cannot be attributed to cave adaptation and may reflect early lineage divergence. Otilioleptes marcelae is the first troglobitic gonyleptoid known from a lava tube. The xeric environments around the cave (Patagonian ecoregion) and the paleoenvironmental history of the area suggest the relictual character of O. marcelae. Scattered evidence supports a long time evolutionary scenario and a presumable relationship with the Chilean opiliofauna (especially with genus Osornogyndes). A comparative overview of all known troglobitic gonyleptoids is provided. The urgent need to protect this new species and its unique cave environment is emphasized.

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Conflict of interest statement

The author has declared that no competing interests exist.

Figures

Fig 1
Fig 1. Otilioleptes marcelae gen. nov., sp. nov. Paratype male (FML-OPIL 00218), dorsal view.
Photo: Abel Pérez-González.
Fig 2
Fig 2. Cladistic relationships of Gonyleptoidea and placement of Otiloleptes marcelae gen. nov., sp. nov.
Single most parsimonious tree obtained with implied weights (IW), k = 6 (Ci: 0.30, Ri: 0.59, tree length: 510 steps). Number above each branch indicates Bremer support; below, values of bootstrap, jackknife and symmetric resample (B-J-SR). Grid (‘Navajo rug’) beside a clade summarizes whether it is retrieved (grey cell) or not (white cell) in selected treatments (k = 1, 3, 6, 9, 12, 15, B, J, SR resamplings of the k = 6 tree). In red: sector of K&V [25] hypothesis where Otilioleptes is incorporated (basal in Laminata).
Fig 3
Fig 3. Otilioleptes marcelae gen. nov., sp. nov., holotype male (FML-OPIL 00211), habitus.
A: Dorsal view. B: Ventral view. C: Lateral view. D: Detail of ocular mound and frontal hump, lateral view. Scale bars: 1 mm.
Fig 4
Fig 4. Otilioleptes marcelae gen. nov., sp. nov., holotype male (FML-OPIL 00211), appendages.
A-B, right pedipalp, A: retrolateral view; B: prolateral view. C-F: right tarsi of legs, retrolateral view (basal tarsomeres indicated as “b”), C. Tarsus I; D. Tarsus II; E. Tarsus III; F. Tarsus IV. Scale bars: 1 mm.
Fig 5
Fig 5. Otilioleptes marcelae gen. nov., sp. nov., holotype male (FML-OPIL 00211), distal end of penis.
A. Lateral view (slightly rotated dorsad to reveal the vps), B. Dorsal view. Scale bar: 0.1 mm.
Fig 6
Fig 6. Osornogyndes tumifrons Maury, 1993, paratype male (MACN 9117), habitus.
A. Dorsal view; B. Ventral view. Photos: Willians Porto.
Fig 7
Fig 7. Osornogyndes tumifrons Maury, 1993, paratype male (MACN 9117), distal end of penis.
A. Lateral view; B. Dorsal view. Scale bar: 0.1 mm.
Fig 8
Fig 8. Location of Doña Otilia cave in the Payunia region (Mendoza Province, Argentina).
The site is indicated as (1). Other caves in the area with records of Gonyleptidae: (2) Caverna de Las Brujas; (3) Caverna de Chorriaca and Caverna Aguada de la Mula, Neuquén Province. Light-blue dots: records of Osornogyndes tumifrons Maury, 1993 in Osorno Province, Chile. Ecoregions (following [59]): Patagonian Steppe (PS, white outline) and Valdivian Temperate Forests (VTF, shaded). Inset: position of Mendoza Province (grey) and the type locality (dot) in South America.
Fig 9
Fig 9. Epigean landscape in the Payunia, around Doña Otilia cave.
Plant cover shows the characteristic pulvinate shrubs on sandy soil; the Sierras de Palauco are on the background.
Fig 10
Fig 10. Plan view map of Doña Otilia cave.
Transverse sections of the passage are displayed at the same scale. Q2: the humid sector; cw: crawlway passages. Arrow indicates the approximate location of Fig 11A and the collecting site of Otilioleptes marcelae. Redrawn from a 1973 survey made by C.A.E. (Centro Argentino de Espeleología).
Fig 11
Fig 11. Hypogean environment in Doña Otilia cave.
A: General view in the 2Q section of the cave (at about 350 m from the entrance); large roots can be observed hanging on the left side. B: Detail of speleothems and roots of epigean plants emerging through fissures on the ceiling and the walls.
See this image and copyright information in PMC

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