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Research Article
A new subterranean species of Entomoculia Croissandeau, 1891 from the Canary Islands, Spain (Coleoptera, Staphylinidae, Leptotyphlinae)
expand article infoCarles Hernando, Heriberto López§
‡ Natural Sciences Museum of Barcelona, Barcelona, Spain
§ Island Ecology and Evolution Research Group, Instituto de Productos Naturales y Agrobiología, La Laguna, Spain
Open Access

Abstract

The genus Entomoculia Croissandeau, 1891, is the only representative of the subfamily Leptotyphlinae present in the Canary Islands and is composed by only two species: E. (Stenotyphlus) canariensis Outerelo, 1982, from La Gomera and E. (Stenotyphlus) lauricola Outerelo & Hernández, 1989, from Tenerife, both found in deep soil (= endogean) habitats. In this paper, we describe Entomoculia (Stenotyphlus) vulcanica sp. nov., the third Canarian species of the genus, which is reported for the first time from Gran Canaria and has been found in the mesovoid shallow substratum “MSS”. This new species has some of the characteristics that are specific to Canarian species of the genus Entomoculia, such as the lack of a denticle or spiniform process on the male metatrochanters. However, it is a remarkable species as it is the only known species of the genus with a tridentate labrum, as the labrum is monodentate in the species so far known from Canary Islands and bidentate in non-Canary species. We provide a key to Canarian species and illustrations of the habitus and the primary and secondary sexual characters of the male. We also describe the sampling techniques used and provide detailed information on habitat characteristics and associated arthropod fauna.

Key Words

endemics, islands, Macaronesia, new species, rove beetles, taxonomy

Introduction

The staphylinid genus Entomoculia Croissandeau, 1891 includes exclusively anophtalmic and wingless endogean beetles, represented by 135 species and subspecies organised in two subgenera: the nominotypical E. (Entomoculia) and E. (Stenotyphlus) Coiffait, 1955. Its species are distributed in the western Palearctic: western Mediterranean Europe (Spain, France and Italy), the Maghreb (Tunisia, Algeria and Morocco) and the Canary Islands (Outerelo 1980, 1982; Outerelo and Hernández 1989; Hernando 2013, 2015, 2022; Schülke and Smetana 2015; Assing 2018). In the Canary Islands, Entomoculia includes two endemic species: Entomoculia (Stenotyphlus) canariensis Outerelo, 1982 (= E. (S.) viti Outerelo, 1980) from La Gomera and Entomoculia (Stenotyphlus) lauricola Outerelo & Hernández, 1989 from Tenerife (Machado and Oromí 2000; Oromí et al. 2004), both species being characterised by having a monodentate labrum and male metatrochanter lacking denticle or spiniform process, unlike the non-Canarian species with a bidentate labrum and male metatrochanter with a denticle or spiniform process. This article is the result of studies carried out on Gran Canaria regarding the biodiversity of invertebrates from the mesovoid shallow substratum (henceforth referred as MSS; see Juberthie et al. (1980); Culver and Pipan (2010)). Some individuals of Entomoculia belonging to a new species were found, which are characterised by being the only known species of the genus with a tridentate labrum and which we describe here. The discovery of this Entomoculia in this underground substratum probably shows that species of this genus inhabit the continuum represented by endogean and hypogean environments, as do other beetle genera that include species living in both types of habitats (García et al. 2021).

Material and methods

Specimens of a new species were collected using special permanent pitfall traps according to López and Oromí (2010), installed in the MSS of Gran Canaria (Canary Islands). Four traps were set in the type locality in 2006, baited with blue cheese or liver and surveyed each four months until 2023. After this sampling time, we collected four specimens of a new species of Entomoculia on whose examination this study is based.

The aedeagus was dissected from the abdomen of a specimen previously softened in boiling water for 5 minutes. After examination, genitalia were mounted on plastic transparent cards in dimethyl hydantoin formaldehyde resin (DMHF) and pinned beneath the specimen. All images were taken using a Canon EOS 50D digital camera attached to a Zeiss Axiostar plus compound microscope. Serial images were stacked with Helicon Focus 8.2.3 software. Measurements were taken with a linear ocular micrometer and given in millimetres. The label data are reproduced verbatim; within the label data, a slash “/” indicates line breaks.

Type material of the new species is deposited in the following collections:

CHC Personal collection of C. Hernando, Badalona, Catalonia, Spain.

IPNA Institute of Natural Products and Agrobiology (IPNA-CSIC), La Laguna, Tenerife, Canary Islands, Spain.

Results

Entomoculia (Stenotyphlus) vulcanicasp. nov.

Figs 1–6

Type locality

Caldera de Los Marteles, MSS, UTM 28R 448100/3092038, Gran Canaria, Canary Islands, Spain.

Type material

Holotype ♂ CANARY ISLANDS: “GRAN CANARIA / Caldera de Los Marteles MSS-2 / UTM 28R 448100/3092038 / 22-05-2021, H. López leg.” (IPNA). Paratypes 1 ♀: “GRAN CANARIA / Caldera de Los Marteles MSS-1 / UTM 28R 448100/3092038 / 07-12-2009, H. López leg.” (CHC); 1 ♂: “GRAN CANARIA / Los Majaletes MSS-2 / UTM 28R 450511/3091134 / 26-12-2010. H. López leg.” (CHC); 1 ♂: “GRAN CANARIA / Caldera de Los Marteles MSS-1 / UTM 28R 448100/3092038 / 26-03-2016, H. López leg.” (IPNA).

Description

Male. Habitus as in Fig. 1. Body length: 1.7 mm. Colour: entirely depigmented (reddish-brown). Apterous and anophthalmous. Labrum tridentate (Fig. 2). Antennae with ten antennomeres (Fig. 1). Metatrochanter unarmed, without denticles or spiniform process. Morphology of aedeagus characteristic, sternal plate long and narrow, with the external margin serrated, endophallus with two accessory pieces: one dorsal, forked at apical end and another central and stiletto-shaped.

Head elongated, slightly wider than the pronotum, almost parallel-sided, with punctation widely scattered over whole surface, neck well marked, entirely covered by an elongated polygonal reticulation and with two longitudinal series of small setal pores on both sides of the neck (Fig. 1). Labrum tridentate with two small lateral denticles and protruding median denticle, bearing eight long setae (Fig. 2). Antennae with antennomeres markedly setulate (especially the last one) progressively increasing in size from the third antennomere onwards, ending with the last very thickened (Fig. 1).

Pronotum as long as wide and widest at anterior angles, subparallel-sided; anterior and posterior margins almost straight and anterior and posterior angles rounded; surface covered with small, scattered punctation, with very short setae (Fig. 1).

Elytra small and strongly narrowed at base; distinctly narrower than pronotum and subparallel (Fig. 1); surface covered by punctation similar to that on pronotum and by an isodiametric polygonal microsculpture.

Abdomen tergites with polygonal reticulation and widely scattered punctation; the first visible tergite is trapezoidal and the second to fifth tergites quadrangular; tergite VIII posterior margin regularly projected into a point at middle (Fig. 3). Sternite VIII symmetrical, posterior margin with small median excision bearing two distinct blunt protuberances on both sides (Fig. 4).

Legs with the metatrochanter unarmed, without denticles or spiniform process.

Aedeagus. Sternal plate long and narrow, with the external margin serrate (Figs 5a, 6a); endophallus with two accessory pieces (i.e. copulatory pieces sensu Coiffait (1959)): one dorsal, forked at the apical end (Figs 5c, 6c) and other central and stiletto-shaped (Figs 5b, 6b).

Figures 1–6. 

Entomoculia (Stenotyphlus) vulcanica sp. nov. 1. Habitus in dorsal view; 2. Labrum in dorsal view; 3. Male tergite VII; 4. Male sternite VIII; 5. Aedeagus in right lateral view; 6. Aedeagus in left lateral view; a) Sternal plate; b) Dorsal accessory piece; c) Central accessory piece.

Female. General appearance as the male, except for unmodified sternite VIII.

Differential diagnosis

Entomoculia vulcanica sp. nov. is very similar, at least in one of the characters of the external morphology, to the two species known from the Canary Islands: E. canariensis from the Island of La Gomera and E. lauricola from the Island of Tenerife. This character is the metatrochanter of the male, without denticle or spiniform process; however, E. vulcanica sp. nov. is separated from both, besides the morphology of the aedeagus and sternite VIII clearly different, by having the labrum tridentate (Fig. 2), with only one denticle in the other two Canarian species. The new species differs completely from all non-Canarian species of the genus, as these have the labrum with two denticles and the metatrochanter of the male armed with a denticle or spiniform process. For illustrations of the aedeagus, male sternite VIII and labrum of E. canariensis and E. lauricola, see Outerelo (1980) and Outerelo and Hernández (1989).

Distribution

So far, only two nearby collecting sites are known around the Caldera de los Marteles in the north-eastern sector of the Island, also called Neocanaria in geological terms, which has a higher diversity of subterranean species compared to the rest of the Island or Paleocanaria (Naranjo et al. 2020).

Bionomics

This new species has been collected in the central east region of the Island of Gran Canaria, in two nearby localities showing slight geological and floristic differences. The locality described in labels as “Caldera de Los Marteles” is, in fact, a pyroclastic cinder cone near the volcanic caldera, comprised of 1–6 cm lapilli, volcanic bombs, and slag (up to 70 cm) (Figs 9, 10). In turn, Los Majaletes is located at a lower altitude and is geologically characterised by stacks of massive basalt flows up to 2–3 m thick with interspersed scoriaceous layers that must function as a deep MSS. The vegetation at Caldera de Los Marteles is dominated by a pine woodland of Pinus canariensis C. Sm., with clearings occupied by shrubby vegetation with Adenocarpus foliolosus (Aiton) DC., Chamaecytisus proliferus (L. f.) Link, Euphorbia regis-jubae J. Gay, Micromeria benthamii Webb & Berthel. and Teline microphylla (DC.) P. E. Gibbs & Dingwall (Fig. 7). At Los Majaletes, the pines are absent, the vegetation being dominated by the same assembly of bushes (Fig. 8).

Figures 7–10. 

Habitat of Entomoculia (Stenotyphlus) vulcanica sp. nov. 7. Appearance of the vegetation in Caldera de Los Marteles; 8. Appearance of vegetation at Los Majaletes; 9. Terrain of cinder cone excavated in road construction near Caldera de Los Marteles, showing the presence of an MSS; 10. Detail of pyroclastic deposit that forms the MSS in the same cinder cone.

The model of a subterranean trap, used to study the biodiversity of the MSS at these two localities, has led us to discover a rich underground invertebrate community of many different taxonomical groups. Most of this fauna are epigean species non-adapted to subterranean life, which penetrate through the fissures of the soil until reaching the MSS, attracted by the bait in the traps or because the environmental conditions of this habitat are suitable for part of their life cycle. However, what is really striking about the MSS of these two localities is the amount of differently adapted subterranean species that we have collected there over the years, using this model of trap. Together with this new species of Entomoculia, we have collected the pseudoscorpion Occidenchthonius beieri Zaragoza, 2017; the spiders Agraecina canariensis Wunderlich, 1992, Walckenaeria subterranea Wunderlich, 2011 and undescribed blind species of the genera Dysdera Latreille, 1804 and Macarophaeus Wunderlich, 2011; a new species of blind opilion, the millipede Dolichoiulus oromii Enghoff, 2012; the cockroach Symploce microphthalma Izquierdo & Medina, 1992; together with new blind species of the beetle genera Lymnastis Motschulsky, 1862 (Carabidae), Euconnus Thomson, 1859, Domene Fauvel, 1872 (Staphylinidae) and Oromia Alonso-Zarazaga, 1987 (Curculionidae).

Etymology

The specific name refers to the presence of this new species on a volcanic island.

Discussion

For the moment, all the Canarian species of the genus Entomoculia are characterised by lacking a denticle or spiniform process on the metatrochanter of the male and by having a different number of denticles on the labrum (one or three), compared to non-Canarian species of the genus; with the metatrochanter of the male armed with a denticle or spiniform process and with the labrum bidentate. Due to these morphological peculiarities, Outerelo and Hernández (1989) considered that the Canarian species of Entomoculia could be included in a new subgenus or even in a genus that presents a series of characters shared with the genera Entomoculia and Mesotyphlus Coiffait, 1957, although it could be that this is only a distinct group of species belonging to the genus Entomoculia that are found exclusively in the Canary Islands. Further molecular data and morphological studies of the Canarian species of Entomoculia will probably provide the necessary data to establish their correct taxonomic position.

Key to the species of the genus Entomoculia from the Canary Islands

1 Labrum bidentate; male metatrochanter with a strong denticle or spiniform process non-Canary species
Labrum monodentate or tridentate, male metatrochanter lacking denticle or spiniform process 2
2 Labrum monodentate; aedeagus with external margin of sternal plate smooth 3
Labrum tridentate; aedeagus with external margin of sternal plate serrate E. (S.) vulcanica sp. nov.
3 Sternal plate in lateral view, very broad and falciform, endophallus with accessory pieces shorter than the sternal plate E. (S.) canariensis Outerelo, 1982
Sternal plate in lateral view narrow and slender, endophallus with accessory pieces of the same length as the sternal plate E. (S.) lauricola Outerelo & Hernández, 1989

Acknowledgements

We thank Daniel Suárez and Helena Morales for their help with sampling and the two reviewers whose comments and suggestions helped to improve the text. Guido Jones revised the English of the manuscript. Specimens of the new species were collected during field studies supported by the Cabildo de Gran Canaria, which kindly granted collecting permits.

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