Trechus (Abyssinotus) apertus Schmidt, 2024

Schmidt, Joachim & Merene, Yeshitla, 2024, Trechus species from Mt. Choke of northern Ethiopia related to T. niloticus (Quéinnec & Ollivier) with notable male genital morphology (Carabidae: Trechini), Zootaxa 5492 (3), pp. 343-355 : 344-346

Trechus (Abyssinotus) apertus Schmidt , sp. n.

Fig. 1

Type material. Holotype: ♂, with label data: Ethiopia, Amhara, W-slope Mt.Choke , 3370 m, 23.II.2019, 10°38’07”N 37°45’51”E, leg. D. Hauth, J. Schmidt, Yeshitla M., Yitbarek, W. ( CSCHM) . Paratypes: 8 ♂♂, 7 ♀♀, with same data as holotype ( CSCHM) . 4 ♂♂, 5 ♀♀, W-slope Mt. Choke , 3450 m, 22.II.2019, 10°38’09”N 37°46’06”E, leg. D. Hauth, J. Schmidt, Yeshitla M., Yitbarek, W. ( NHMAA, CAF, CSCHM) .

Etymology. The species’ epithet refers to the extraordinary wide dorsal opening of the aedeagal median lobe which is a morphological peculiarity of the new species.

Description. Body length: 2.5–2.8 mm.

Proportions (n = 12): PW/HW = 1.35–1.44 (Ø = 1.41); PW/PL = 1.37–1.45 (Ø = 1.40); PW/PBW = 1.18–1.22 (Ø = 1.20); PBW/PAW = 1.18–1.24 (Ø = 1.21); EW/PW = 1.38–1.46 (Ø = 1.43); EL/EW = 1.24–1.30 (Ø = 1.27).

Colour: Head, pronotum and elytra blackish brown; mandibles, palps, antennal base and legs yellowish brown; antennae slightly darkened beginning from second antennomere; in most specimens 2 nd maxillary palpomere somewhat darkened; elytral apical margin very narrowly yellowish.

Microsculpture: Sculpticells on frons and supraorbital area large, moderately impressed, almost isodiametric; sculpticells on clypeus very finely impressed, slightly transverse. Sculpticells on pronotal disc smaller and finer impressed than on head disc, slightly transverse. Elytra with large and deeply impressed, almost isodiametric sculpticells throughout.

Head: Moderately robust. Mandibles short, with right mandible tridentate where all teeth are almost the same length, without diastema, without recognizable separation of premolar and retinaculum ( Fig. 1B ); tooth of left mandible with two blunt cusps ( Fig. 1C ). Penultimate labial palpomere with three setae ( Fig. 1F ). Labrum with apical margin moderately emarginate, with six setae near apical margin ( Fig. 1D ). Clypeus each side with two setae. Compound eyes rather small, slightly convex; tempora about ¾ of length of eyes, markedly convex, distinctly wrinkled to the neck. Dorsal surface of head with supraorbital area and frons markedly convex, and with supraorbital furrows deeply impressed, evenly curved. Two supraorbital setae and one suborbital seta each side. Tempora distinctly pubescent. Antennae short, with second antennomere about as long as scape, and with third antennomere shorter than second.

Pronotum: Large and transverse, sub-discoidal, broadest slightly before middle, with base distinctly broader than apex; disc moderately convex. Anterior margin slightly concave (almost straight in middle), with anterior angles slightly protruded anteriorly, rounded; basal margin convex, with laterobasal angles markedly shifted anteriorly; lateral margin almost evenly rounded throughout; laterobasal angles very obtuse, indistinct ( Fig. 1A ). Marginal gutter narrow, slightly widened near laterobasal angle, extending towards laterobasal foveae. Median longitudinal impression very finely incised, disappearing near apex; anterior and posterior transverse impressions indistinct, smooth; laterobasal foveae small, moderately deep, smooth. Lateral and laterobasal setae present, with the former situated at the end of anterior pronotal third.

Pro- and mesepisternum: Glabrous and smooth.

Pterothorax: Elytra short, ovate, with disc convex, in dorsal view broadest in middle, humerus rounded but distinct, subapical sinuation indistinct, apex rounded. Striae 1–3 and anterior portion of stria 8 slightly impressed, punctate, external striae finer, 6–7 sometimes indistinct, stria 8 distinctly deepened before apex; parascutellar stria very short, deep, isolated. Recurrent preapical stria short, deep, with outer curvature directed towards the fifth stria. Parascutellar seta present; three discal setae located in the 3rd interval, adjoined to the 3rd stria ( Fig. 1A ): anterior seta located near the end of the anterior elytral 7th; middle seta located anterior of elytral middle, near the end of elytral 3/7; posterior seta (= subapical seta) located about 1/8 of elytral length from elytral apex; seta of the recurrent stria isolated, removed from this stria by distance of the diameter of the pore ( Fig. 1A ). Number and positions of the setae of the marginal umbilicate series typical of Trechus s. l. ( Fig. 1A ). Metepisternum very short, glabrous and smooth, with outer margin about as long as anterior margin.

Legs: Moderately short and robust. Protibia dilated towards apex, straight on external margin, its dorsal surface with very flat longitudinal groove without micro-setae on anterior surface. Two basal protarsomeres of males dilated and dentoid at the inner apical border ( Fig. 1C ).

Male genitalia: EL/AL= 2.00–2.23 (Ø = 2.11; n = 8). Aedeagal median lobe robust, in lateral view markedly bent in basal third, almost straight towards apex, with ventral margin slightly convex in middle, ventrally bent towards apex, the latter with a small upwardly bent hook ( Fig. 1G ); in dorsal view broad in basal half, sinusoidal, narrowed from middle to apex ( Fig. 1H ). Dorsal surface of median lobe not sclerotized apart from the basal quarter of the basal bulb near the basal opening which is slightly sclerotized; sagittal aileron absent. Endophallus symmetrical in dorsal view, without distinct copulatory pieces, densely covered by rows of tiny scales along dorsal side of the inactive internal sac from its base to apex, and with a complex folding structure and large sclerotized scales near base of internal sac. Parameres similar in size and shape, moderately short, each with three or four apical setae.

Differential diagnosis. Trechus apertus sp. n. is distinguished from all previously described Trechus (s. l.) species of Ethiopia, by the aedeagal median lobe ostium which extends basally across three quarters of the basal bulb. Not any Ethiopian Trechina species was known so far that has a dorsal opening that includes parts of the basal bulb. In external characters, the new species differs additionally from all the small to medium-sized trechine species from Mt. Choke as follows: from Trechus abyssinicus (Quéinnec & Ollivier) , T. afroalpinus (Quéinnec & Ollivier) , T. amharicus Ortuño & Novoa and T. lobeliae (Quéinnec & Ollivier) in two basal protarsomeres dilated in males (one in all the latter species), from T. amharicus additionally in the presence of the middle seta of the elytral discal series (absent in T. amharicus ), from T. lobeliae additionally in the smaller body size and the almost completely rounded pronotal laterobasal angles (rectangular in T. lobelia ), and from T. abyssinicus , T. afroalpinus , T. igori sp. n., T. kniphofia sp. n., T. reebae (Quéinnec & Ollivier) and T. yitbareki sp. n. in the more deeply impressed and distinctly punctate elytral striae (finely impressed and smooth or indistinctly punctate in all the latter species). In habitus, T. apertus sp. n. is very similar to T. niloticus Quéinnec & Ollivier which was described from the western crater rim of Mt. Choke. However, in T. niloticus the dorsal opening of the aedeagal median lobe do not reach the basal bulb (see Quéinnec et al. 2021: Fig. 26B, C). In addition, in T. niloticus , the median lobe is more elongated, with ventral margin straight in middle (convex in T. apertus sp. n.), its apical lamella is much longer, markedly bent ventrally (short and slightly bent ventrally in T. apertus sp. n.), the parameres are slenderer.

Distribution. Endemic to Mt. Choke in northern Ethiopia. The new species was only found near the top of a mountain ridge that extends from the crater rim to the west ( Fig. 4 ).

Habitat preferences. All specimens of T. apertus sp. n. were sifted from the humus-rich soil under dense vegetation alongside a small brook. The brook has its source near the top of the mountain ridge and flows to the north, at an elevation of 3370–3450 m. No specimens were found on the pastures and in the bushland which bordered the brook. Based on these collecting circumstances, the new species can be considered hygrophilic and cold-adapted. As potentially natural vegetation, a moist afromontane forest would have formed at the site where the new species was found, but here it has given way to a cultivated steppe.

Figures

FIGURE 1. Trechus (Abyssinotus) apertus Schmidt, sp. n., holotype (Fig. 1A) and details of paratypes (Fig. 1B–H). A, habitus; the white circles point to the insertions of the supraorbital setae, pronotal lateral setae, parascutellar seta, elytral discal setae, and setae of the umbilicate series. B, right mandible, ventral aspect. C, left mandible, ventral aspect. D, labrum, dorsal aspect. E, left maxilla. F, left labial palpus and ligula, dorsal aspect; the arrows point to the three setae inserting on the penultimate palpomere. G, aedeagus, left lateral view. H, aedeagus, dorsal view.

FIGURE 4. Topographic map of Mt. Choke (highest point marked by a white triangle), showing sampling localities of six Trechus (Abyssinotus) species of the niloticus group (white circles; the numbers refer to the different species). 1, T. apertus Schmidt, sp. n. 2, T. reebae (Quéinnec & Ollivier). 3, T. yitbareki Schmidt, sp. n. 4, T. kniphofia Schmidt, sp. n. 5, T. igori Schmidt, sp. n. 6, T. niloticus (Quéinnec & Ollivier). Sampling data of T. reebae and T. niloticus published by Quéinnec et al. (2021) are considered. Base map was downloaded from Topographic-map.com.