Bureschia serbica sp. nov. urn:lsid:zoobank.org:act: B31E6F2B-F012-42E3-BA7F-944FFFA983BC Figs 2–7 Diagnosis A blind, medium-sized troglobite species with a narrow body (maximum length: ♂ 7 mm, ♀ 7.2 mm). Antennula with elongated articles and reduced number of aesthetascs (3).Antenna with flagellum of nine articles, longer than article 5 by a third of article length. Maxilliped endopodite wide with enormously widened, distally truncate endite. Male pleopod 1 endopodite basal segment with a solid outer projection at its tip and flagelliform terminal segment with thick base; exopodite distally with wide outwardly curved, quadrangular protruding tip. Male pleopod 2 endopodite with stout basal article, three times as long as wide; distal article three times as long as basal one, tapering to a whip-like tip, grooved in the apical third. Uropod basis enlarged posteriorly, as long as endopodite; exopodite and endopodite subequal in length, inserted at the same level. Etymology The species is named after the country where it has been collected. Material examined Holotype SERBIA • ♂; Stara Planina Mt, Bela, Suva dupka Cave; 28 Oct. 2017; M. Petković leg.; ZZDBE 1143/1. Paratypes SERBIA • 11 ♂♂, 7 ♀♀, 3 juvs; same collection data as for holotype; ZZDBE 1143/2. Description Holotype male BODY. 6.8 mm long, colorless, smooth, outline as in Fig. 2A. CEPHALON (Fig. 2A). With suprantennal line medially blunt; lateral lobes short and narrow, quadrangular, longer than wide. PEREONITES (Fig. 2A). Posterior margin of pereonites 1–3 convex, 4–7 progressively concave. PLEON (Fig. 2A). Slightly convex; pleonites 3–5 with slightly developed epimera. PLEOTELSON (Fig. 2A). With a wide triangular distal part and rounded apex. ANTENNULA (Fig. 2B). With elongated basal article; second article narrow, elongated, somewhat shorter than basal article; third article narrow, as long as second article, with three short aesthetascs and a spine on its tip. ANTENNA (Fig. 2C). Moderately elongated; article 3 twice as long as broad; article 4 3.5 times as long as broad; article 5 shorter than flagellum; flagellum with 9 articles. MANDIBLES. Right mandible (Fig. 3B) with two penicils; pars incisiva elongated, ending with two flat teeth; lacinia mobilis bottle-shaped distally with sparse small thorns; pars molaris elongated with one penicil. Left mandible (Fig. 3A) with three penicils; pars incisiva lateralis and pars incisiva medialis elongated with 3-4 short teeth on their tops; pars molaris oval in shape with one penicil. MAXILLA 1. Outer endite (Fig. 4A) with 10 elongated teeth, outer 4 stronger than others, 2 inner slightly shorter than others; three elongated pectinate seta distally; inner endite (Fig. 4B) with three penicils, terminal one with a broad base, densely setose, almost as long as proximal one. MAXILLA 2 (Figs 4C, 5). Outer lobe significantly reduced, with 3 rod-like setae on its tip and a row of sparse tiny elongated setae on outer margin; terminally, both sides of inner lobe with brush-like surfaces – dense rows of curled setae (Fig. 5), more elongated on its terminal and outer edge. MAXILLIPED (Fig. 4D). With strongly widened endite. Endite distally truncate, with large and wide penicil near medial margin and a row of long setae on its distal margin. Latero-distal margin slightly protruding, distally truncate with a row of setae terminally; outer margin protruding in its basal half; palp on medial edge with four pronounced lobi with setae. PEREOPODS. Pereopods 1–2 similar in shape; 3–7 progressively longer, similar in shape. Pereopod 1 (Fig. 6A) merus longer than carpus; ventral surfaces of carpus, merus and propodus covered with small pointed scales. On pereopod 2, such scales are smaller than on pereopod 1, sparsely covering ventral surface of propodus only. Other legs without such pointed scales. Pereopod 7 (Fig. 6B) merus shorter than carpus, propodus longer than carpus. Water conducting structures on pereopods 6 and 7 missing. Elongated dactylar seta (usually developed in Trichoniscidae) does not exceed top of unguis on all pereopods. GENITAL PAPILLA (Fig. 7A). Conical, elongated in apical part. PLEOPOD 1 (Fig. 7B). Endopodite basal segment skittle-shaped with a solid outer projection at its tip and a long flagelliform terminal segment with a thick base; outer projection as long as wide. Exopodite wide, with a fringe of short setae on medial margin; distally with wide, outwardly curved, quadrangular protruding tip. PLEOPOD 2 (Fig. 7C). Endopodite biarticulated; basal article stout, three times as long as wide; distal article elongated, three times as long as basal one, tapering to a whip-like tip, grooved in apical third; Exopodite wide, oval, with slightly bent distal margin and with a fringe of short setae on its outer margin. PLEOPODS 3–5 (Fig. 6C–E). Vascularized endopodites, triangular in shape, with an enlarged basal part. Exopodites 3 and 4 tetragonal, exopodite 5 triangular; with a fringe of setae on their distal, medial and outer margins and sparse setae covering their outer surfaces. UROPOD (Fig. 2A). Basis dilated posteriorly; exopodite and endopodite subequal in length, conical, inserted at same level and with a tuft of several short setae at apex. Females Differ from males only in the structure of pleopods 1 and 2. Remarks The new species is also amphibious, but it differs partially from the nominal B. bulgarica in its way of life. The new species has adapted to amphibious life in running groundwater as opposed to the nominal one in subterranean lakes and ponds. It is readily distinguishable from the nominal one by the structure of the antennula, antenna, mouthparts, pereopods and male pleopods. We compared specimens of the new species with specimens of B. bulgarica from Lakatnik and with Verhoeff’s original description. The antennula third article of B. serbica sp. nov. is shorter than the basal article and has three short aesthetascs, vs longer with 6 aesthetascs in the nominal species. Antenna flagellum is shorter in the new species. Pars incisiva of both mandibles are more elongated in the new species than the in nominal one. The maxilla 1 inner endite is with a longer terminal penicil in B. serbica. The maxilliped endopodite latero-distal margin is somewhat narrower than in the nominal species. Pereopod articles of the new species are stubbier compared with the same in B. bulgarica. Those differences are mostly connected with the different ways of life. The male pleopod 1 exopodite is stubbier than in B. bulgarica, with a wider outer projection at its tip. The male pleopod 2 endopodite basal article is short, one-third the length of the terminal one, compared to the same in B. bulgarica where it is half of the length of the terminal one. The new species is also smaller than the nominal one. In Suva dupka cave, we watched a specimen that entered a small shallow stream that descended the rock slope at about 35º, moving against a strong water current and raising a wave of water in front of it. We assume that we observed the specimen in its regular activities (feeding) and not that it entered the stream disturbed by our presence. Another finding place of this species (noted by Matija Petković) is probably a small cave in Bela village with a stream flowing out of it. Specimens were noted in subterranean running water in the cave. Unfortunately, we have had no opportunity to examine specimens from that population for this study, but the closeness to the type locality and the same way of life suggest their conspecificity.

Published as part of Karaman, Ivo & Horvatović, Mladen, 2022, A new amphibious species of the subterranean genus Bureschia Verhoeff, 1926 (Isopoda: Oniscidea: Trichoniscidae) from Serbia, pp. 145-159 in European Journal of Taxonomy 847 (1) on pages 148-155, DOI: 10.5852/ejt.2022.847.1989, http://zenodo.org/record/7400273