Trechus (Trechus) messoulii, Casale, 2011

Casale, Achille, 2011, Two new subterranean, microphthalmous trechine beetles from the Mediterranean area, and a synonymic note (Coleoptera: Carabidae, Trechini), Contributions to Natural History 16, pp. 1-16 : 8-14

Trechus (Trechus) messoulii sp. nov.

Type locality: Morocco, Rif (Taza): Toghobeit cave.

Type material:

Holotype ♂ with the following data: " Maroc, Rif, Gr. Toghobeit , 25–30.VII. 1999 leg. M. Messouli " ( CCa).

Diagnostic features

A small-medium sized (TL: 4.25 mm), glabrous, depigmented, microphthalmous trechine species ( Fig. 4 ), with the character states of the genus Trechus CLAIRVILLE, 1806 of the fulvus species group in the sense of Jeannel (1927), Casale (1983), Ortuño (2008), Reboleira & al. (2010), and in the widest sense that will be discussed in Conclusions.

Colour dark yellow reddish. Pronotum markedly transverse, widened in front, with lateral sides regularly curved, slightly constricted and sinuate towards hind angles, which are obtuse. Elytra elongate-ovate, widened in the apical third, depressed, with humeral angles rounded. Chaetotaxy as in Fig. 4 . Male genitalia as in Fig. 5 .

Close to some North African species attributed to the genus Antoinella JEANNEL, 1937 , in the sense of Casale (1982), Mateu & Comas (2006) and Mateu & Escolà (2006), from which it is recognized by several different morphological features (see: Relationships).

Description

General features as in Fig. 4 . Small-medium sized: TL: 4.25 mm; L: 4.50 mm. Colour uniformly dark yellow reddish. Dorsal surface moderately shiny; transversal cuticular microlines evident on frons and pronotum, scarcely visible as polygonal meshes on elytral intervals.

Head robust, stout, with frontal furrows markedly impressed, angulate in the anterior third; frons convex; supraorbital setiferous punctures inserted on ranges slightly convergent backwards; eyes very small, as long as 1/5 of genae, flat, oblique and whitish, with slightly distinguishable ommatidia, pigmented only at margins; genae regularly curved, slightly convex; neck wide, neck constriction moderate; labrum slightly emarginate at the anterior side; mentum tooth slightly scooped-out distally; antennae relatively long, exceeding backwards the level of the fourth humeral setiferous puncture.

Pronotum markedly transverse (PL/PW: 0.74), widened in front; disc convex; sides regularly curved, slightly constricted and shortly sinuate towards hind angles, which are obtuse; marginal furrows narrow and shallow; anterior margin almost straight, front angles effaced; base slightly oblique at sides, not beaded; basal foveae deep; basal area densely wrinkled.

Elytra elongate-ovate (EL/EW 1.47), widened in the apical third, depressed, with humeral angles rounded, widened at the apical third, much wider than prothorax; disc depressed; lateral furrows wide and deep; striae all complete and visible, moderately impressed, punctate; apical striola curved and connected with apex of stria 5; intervals flat; apical carina slightly prominent. Chaetotaxy as in Fig. 4 : three setiferous discal punctures (two discal on stria 3, one pre-apical on apex of interval 3); umbilicate pores 5 and 6 very close to each other; apical and angulo-apical punctures present, forming with the preapical puncture an apical triangle.

Legs long, slender; femora robust, thickened; protibiae dilated, very shallowly grooved on the external side, and sparsely pubescent at apex; protarsi in the male each with two basal tarsomeres dilated and denticulate inwards.

Male genitalia as in Fig. 5 . Median lobe of aedeagus elongate (1.05 mm long, measured from apex to the posterior margin of basal bulb, basal carina excluded), slender, slightly thickened in the middle, markedly narrowed and curved on the dorsal side at apex, with apical lamina asymmetrical widened and ventrally hooked in lateral aspect; basal bulb with big, rounded sagittal carina, not extended on the ventral side of the bulb. Endophallus with complex structure: in left lateral view, it shows a dorsal group of scales that covers a sclerotized piece of subtriangular form; in the inner part, it shows a second sclerotized piece, covered with scarcely sclerotized scales, elongate, narrowed and bent distally. Parameres robust, asymmetrical; left paramere with an elongate, ventral basal lobe on the ventral side (as is typical in Antoinella species : see below), with five apical setae; right paramere shorter, with three apical setae.

Female genitalia: unknown.

Specific epithet

I wish to dedicate this interesting new species to Dr. Mohamed Messouli, active speleologist in Marrakesh, who sampled the holotype specimen several years ago, during an expedition with the Spéléo Club of Blois ( France), and through our friend Lucien C. Genest offered it to me for study.

Geographical distribution and habitat

The male holotype of this new species was sampled in the cave Toghobeit ( Northern Morocco, Rif Massif , Taza , near Chaouen or Chefchaouen ). This subterranean system is so far one of the deepest caves of the African continent: located at 1700 m of altitude, its actual depth is - 732 m, and the development reaches 3050 m (after: "Inventaire Spéléologique du Maroc", 1981: DC 5, Kef Toghobeit). The only examined individual was collected in the "salle Renner" at - 120 m depth, but a second individual (not available at the moment) was collected in the "salle du bivouac" and entrusted to L. C. Genest (Messouli, personal communication).

Relationships

Trechus messoulii sp. nov., for both its external features and peculiar characters of male genitalia – in particular, the structure of copulatory pieces in endophallus (a sclerotized piece of triangular shape, a second elongate piece, and some groups of sclerotized scales) – is close to some Trechus species of the fulvus species group in the sense of Reboleira & al. (2010) (in particular, for the widened and hooked apical lamina of the median lobe of the aedeagus, it recalls T. arribasi JEANNE, 1988 , endemic to the Northern Iberian peninsula).

But it is mostly related to Algerian species ( Jeannel, 1927; Casale, 1983; Ortuño, 2008) and several subterranean North African species of the Rif massif ( Morocco) currently treated as Antoinella JEANNEL, 1937 (Casale, 1982; Mateu & Comas, 2006; Mateu & Escolà, 2006). In particular, it seems to be close to A. iblanensis MATEU & ESCOLà, 2006 , and A. fadriquei MATEU & ESCOLà, 2006 . It is, however, markedly distinct by the smaller size (5.8–5.9 mm in A. iblanensis and A. fadriquei , respectively, about 4.5 mm in T. messoulii sp. nov.), and the shape of the median lobe of the aedeagus, which in T. messoulii sp. nov. is slender and elongate as in A. iblanensis , but shows an apical lamina similar to that of A. fadriquei , more curved dorsally and more obtusely truncate.

In this case, the combination of both morphological features and biogeographical considerations allows the following remarks:

1. From the taxonomical point of view, the so-called genus Antoinella JEANNEL, 1937, appears as a paraphyletic unit, without any relationships with the genus Duvalius . This datum is evident from both morphological features, as already supposed by Jeannel (1937) in the original description of the genus, and supported by Casale (1982, 1983); furthermore, it has been confirmed by a recent molecular phylogeny ( Faille & al. 2010). Therefore, either it will be demonstrated that Trechus is a polyphyletic unit, and in this case the T. fulvus species group should merit the genus rank (named Antoinella ), or the latter is a simple lineage within this group, and an objective junior synonym of Trechus (in the widest sense).

2. The only current distinctive character between Antoinella and Trechus of the fulvus species group, i.e. protibiae pubescent in Antoinella (as in Duvalius species ), and glabrous in Trechus , is not a constant diagnostic feature: Reboleira & al. (2010) for instance, who have just described T. tatai from Portugal, specified that it has "conspicuously hairy (including the protibiae)" legs. Furthermore, the structure of the median lobe of aedeagus, endophallus, and asymmetrical parameres (the left one with an elongate, ventral basal lobe on the ventral side) is absolutely the same both in Antoinella species and in some Algerian Trechus of the fulvus species group, as illustrated by Jeannel (1927) and Casale (1983).

3. Finally Ortuño (2008) and Reboleira & al. (2010), in their excellent contributions, exhaustively showed that the T. fulvus species group, in its wide distribution along North Africa, the Iberian Peninsula and, thanks to the wide distribution of T. fulvus , also along the Atlantic coast of northern Europe ( Jeannel 1927), is heterogeneous, and includes at least two lineages.

In this context, it is evident that the so-called Antoinella species , with the martinezi -lineage (sensu Ortuño & Arillo 2005; Ortuño 2008), form a typical subterranean lineage within the Trechus fulvus species group, which has survived in the south-western Mediterranean region. The present distribution of extant species suggests a Betic-Rifean origin (see also Ortuño 2008: fig. 4), with strong biogeographical coherence: a well known case in entomological literature. Another interesting fact is the surprising speciosity of this group in the Rif massif: in fact every cave, so far, revealed a separate species markedly distinct from its relatives, all with markedly reduced eyes, depigmented integument, and other troglomorphic features.

In conclusion, the following new synonymy is proposed:

Antoinella JEANNEL, 1937 (type species: Duvalius groubei ANTOINE, 1935 ) junior synonym of Trechus CLAIRVILLE, 1806 (type species: Carabus rubens FABRICIUS sensu CLAIRVILLE, 1806 = Carabus quadristriatus SCHRANK, 1781 )

A separate question is the validity and rank of Irinea MATEU & COMAS, 2006 , described as subgenus of Antoinella . The type species, A. (I.) aurouxi MATEU & COMAS, 2006 , shows marked distinctive features: in particular, only one basal tarsomere is dilated in fore tarsi of males, median lobe of aedeagus without basal sagittal carina – typically present in all " Antoinella " species and Trechus of the fulvus species group – and endophallus of simple structure, with only one small copulatory piece.

Nevertheless, these characters are not unique and peculiar to Irinea , but present in several species attributed to Trechus in the current (and widest) sense. In a contribution dedicated to the Ethiopian Trechus species , Ortuño & Novoa (in press) discuss the sexual dimorphism in species of this genus, and stress that the occurrence of a single dilated articulation on the protarsus in males is present in the Nearctic subgenus Microtrechus JEANNEL, 1927 , in Trechus (Atlantotrechus) cautus WOLLASTON, 1854 , from Madeira and in some Ethiopian species (Ortuño, personal communication; Pawlowski 2003). Furthermore, it must be recalled that recently Vigna Taglianti & Magrini (2009) described the subgenus Minitrechus for Trechus gypaeti , new species from Ethiopia, in which only one basal tarsomere is dilated in fore tarsi of males. Therefore, given that the apomorphy of a single dilated tarsomere in males appears sporadically in Trechus belonging to different lineages and in different areas, this character seems not a valid characteristic able to distinguish just one group within Trechus in the widest sense (Ortuño & Novoa, in press; Ortuño, personal communication).

Therefore taxonomic position, validity, and phylogenetic relationships of Irinea merit further investigation.

Figures

Fig. 4: Trechus (Trechus) messoulii sp. nov., male holotype, habitus, dorsal aspect.

Fig. 5: Trechus (Trechus) messoulii sp. nov., male holotype, aedeagus in left lateral aspect (a) and in dorsal aspect (b).