The first stygobiont species of Coleoptera from Portugal, with a molecular phylogeny of the Siettitia group of genera (Dytiscidae, Hydroporinae, Hydroporini, Siettitiina) Author Ribera, Ignacio Author Reboleira, Ana Sofia P. S. text ZooKeys 2019 813 21 38 http://dx.doi.org/10.3897/zookeys.813.29765 journal article http://dx.doi.org/10.3897/zookeys.813.29765 1313-2970-813-21 Iberoporus pluto sp. n. Figures 2, 3, 4, 6 Type locality. Portugal, Penela, Gruta Soprador do Carvalho ( 39°59'N , 8°23'W ) (Fig. 6). Type material. Holotype female (NHMD) Portugal, Penela, Gruta Soprador do Carvalho, ASPS Reboleira leg., 24.X.2014, with red holotype label and DNA voucher label "IBE-AN151" . Diagnosis . A blind and depigmented species of Iberoporus , larger and wider than the other subterranean species of the genus, with a cordiform pronotum without lateral stria, less prominent constriction between pronotum and elytra and with a more transverse pronotum. Appendages longer and more slender, especially antennae and pro- and mesotibiae. Male unknown. Description. Body length 2.8 mm, maximum width 1.1 mm. Habitus: Body elongate, strongly parallel-sided (including pronotum and head) (Fig. 2), flattened in lateral view (Fig. 3a); in dorsal view lateral outline with a slight discontinuity between posterior angles of pronotum and base of elytra. Body and appendages uniformly pale orange (cuticle appears translucent after DNA extraction due to digestion of soft tissue). Figure 2. Habitus of Iberoporus pluto sp. n., dorsal view (holotype, after DNA extraction). Scale bar: 1 mm. Figure 3. Iberoporus pluto sp. n., holotype. a Lateral view (scale bar, 1 mm) b Detail of the sensory setae of pronotum and elytra (both previous to DNA extraction). Head (Fig. 2): Wide, anterior margin almost perfectly semicircular, deeply encased in pronotum, with two lateral dark scars in place of eyes; surface smooth, with very sparse small shallow punctures, surface weakly micro-reticulated, stronger on margins, glabrous. Antennae with ovoid pedicel, distal antennomeres conical, more elongate. Pronotum (Figs 2, 3): Cordiform, margins sinuated, anterior part slightly wider than head, posterior part narrower than head and base of elytra; anterior margin more or less straight (except angles), angles strongly acute; posterior margin sinuated, angles acute; sides without rim, anterior margin with transverse depression with irregular row of large punctures; posterior margin with some sparse large punctures very loosely forming a row. Pronotum without sublateral stria on each side, with only a slight depression and very irregular row of larger punctures. Surface smooth, with fine shallow punctures denser on disk, with very fine microreticulation, stronger near margins, cells not contiguous; centre of disc with small longitudinal rectangular mark. Pronotum with long lateral sensorial setae (Fig. 3b). Elytra (Figs 2, 3): almost parallel-sided on basal 2/3, apical third regularly acuminate. Sides of elytra with weak rim, not visible from above. In lateral view margin of elytra almost straight, only very weakly ascending to humeral angle in anterior quarter; epipleuron not visible until shoulders. Surface with same structure as on pronotum, with very sparse larger punctures; larger punctures forming very loose and irregular lines on elytra; more distinct near to suture and on disk. With long sensorial setae on margins (Fig. 3b). Without traces of hind wings. Ventral surface (Fig. 4): Uniformly pale, colour similar to dorsal surface. Prosternal process lanceolate, apex acuminate; not reaching anteromedial metaventral process. Epipleuron becoming narrower short before mid-length, without oblique carina near shoulder. Metepisternum more or less triangular in shape. Metacoxal lines obsolete; joint hind margin of metacoxal processes incised; lobes of processes rounded. Figure 4. Iberoporus pluto sp. n., holotype, ventral view (previous to DNA extraction). Legs (Figs 2-4): long and slender, especially posterior legs. Metafemora very thin, not enlarged, regularly curved; without natatorial setae. Etymology. From "Πλούτων" (Ploutōn), the ruler of the underworld in the Greek mythology. Name in apposition. Notes on the habitat. Soprador do Carvalho is a cave with approximately 4 km of horizontal development (Fig. 7). It is the largest cave of the so-called Dueca Speleologi cal System, located in the north-eastern part of the Sico karst area in central Portugal ( Neves et al. 2005 ). The subterranean stream feeds the spring of the Dueca River, a contributor to the Mondego River. The substrate of the river is mostly composed of clasts and gravel, with large clay deposits on the margins. The specimen was found in the bottom of a clay pound connected to the margin of the subterranean stream. Other invertebrate stygobionts are found in this stream, such as a new species of the asellid genus Proasellus and of the amphipod genus Pseudoniphargus , and unidentified copepods ( Reboleira 2012 ). In the terrestrial compartment of the cave, several cave-adapted species are known: the pseudoscorpion Occidenchthonius duecensis Zaragoza & Reboleira, 2018; the millipede Scutogona minor Enghoff & Reboleira, 2013; the woodlice Trichoniscoides sicoensis Reboleira & Taiti, 2015 (which has an amphibian behaviour and can be collected inside the stream totally submerged) and Porcellio cavernicolus Vandel, 1946; and the dipluran Podocampa cf. fragiloides Silvestri, 1932 ( Enghoff and Reboleira 2013 , Reboleira et al. 2015 , Zaragoza and Reboleira 2018 ). Over recent years, the cave is being explored for tourism. This may represent a major threat, as tourists constantly trample the bottom of the subterranean stream where the new species was found. Remarks. Iberoporus pluto sp. n. is most similar in its external morphology to I. cermenius . Both share a similar shape of the head, a cordiform pronotum without lateral stria, and similar general appearance (Figs 2, 5a). In the absence of males of I. pluto sp. n. (and in addition to the genetic differences), both species can be easily separated by the body shape, larger and wider in I. pluto sp. n., and with a less prominent constriction between pronotum and elytra (clearly visible in I. cermenius ) and with a more transverse pronotum. The appendages of I. pluto sp. n. are also longer and more slender, especially the antennae and the pro- and mesotibiae (Figs 2, 5a). Iberoporus cermenius has also well-defined parasutural rows on the elytra formed by large punctures, which are absent in I. pluto sp. n. Figure 5. Habitus of the species of Iberoporus . a I. cermenius (modified from Millan et al. 2014) b I. agnus comb. n. c I. argaensis comb. n. (both modified from Fery 2016 ). Figure 6. Distribution map of the Iberian species of Rhithrodytes and Iberoporus . Key: red star, I. pluto sp. n.; blue diamond, I. cermenius ; filled purple circle, I. argaensis comb. n.; empty purple circle, I. agnus comb. n.; black circles, R. bimaculatus (data from Millan et al. 2014). Figure 7. Soprador do Carvalho Cave, type locality of Iberoporus pluto sp. n.