Alpioniscus stochi Taiti & Argano

Taiti, Stefano, Argano, Roberto, Marcia, Paolo, Scarpa, Fabio, Sanna, Daria & Casu, Marco, 2018, The genus Alpioniscus Racovitza, 1908 in Sardinia: taxonomy and natural history (Isopoda, Oniscidea, Trichoniscidae), ZooKeys 801, pp. 229-263 : 229

Alpioniscus stochi Taiti & Argano sp. n. Figs 12, 13, 14, 18, 19

Material examined.

Prov. Ogliastra: Holotype: ♂ (MZUF 9833), Grotta Su Palu, c.n. 1988 Sa/OG, 40°10'38.23"N, 9°33'50.53"E, 185 m, Codula Ilune, Urzulei, 1.V.2009, leg. F. Stoch and G. Tomasin. Paratypes: 3 ♂♂, 4 ♀♀ (MZUF 9833), same data as holotype; 4 ♂♂, 5 ♀♀ (MZUF 9834), same locality, 18.IX.2010, leg. G. Tomasin.

Description.

Maximum length: ♂ and ♀, 4.5 mm. Colourless body, pleon slightly narrower than pereon (Fig. 12A). Dorsal surface smooth with some scattered scale-setae as in Fig. 12B. Some gland pores on lateral margins of pleonites 4 and 5, telson and on dorsal surface of uropodal protopod and exopod (Fig. 12F). Cephalon (Fig. 12 C–E) with suprantennal line V-shaped; antennal lobes quadrangular. Eyes absent. Posterior margins of pereonite 1-4 straight, of pereonites 5-7 progressively more concave (Fig. 12A). Pleonites 3-5 with very short posterior points (Fig. 12F). Distal part of telson with concave sides and very broadly rounded apex (Fig. 12F). Antennula (Fig. 12G) with distal article narrow and bearing two apical aesthetascs. Antenna (Fig. 12H) with fifth article as long as flagellum; flagellum of five to seven articles. Mandibles with two penicils in the right (Fig. 13A) and three penicils in the left (Fig. 13B). Outer branch of maxillula with 5 + 6 teeth, apically entire, three or four of the outer group strongly bent inwards, two slender stalks, one setose; inner branch with three long penicils (Fig. 13C). Maxilla with setose apex (Fig. 13D). Maxilliped (Fig. 13E) endite quadrangular with a setose distal margin and a distinct subapical short penicil on medial margin; palp narrow and bent in medial direction, three tufts of setae on medial margin and one apically, basal article with a single seta; basis distally enlarged with a triangular lobe on outer margin. Pereopods with setose dactylar seta (Fig. 14A). Pereopod 7 (Fig. 14B) basis with a groove covered with scales on rostral surface (water conducting system). Uropod (Fig. 12F) with protopod not grooved on outer margin; endopod slightly shorter than exopod, exopod and endopod inserted at the same level.

Male. Pereopod 1-4 (Fig. 14A) with carpus and merus bearing numerous short scales on sternal margin. Pereopod 7 (Fig. 14B) ischium with straight sternal margin covered with short setae; merus with scales on sternal margin, carpus enlarged proximally. Genital papilla (Fig. 14C) with a rounded tip. Pleopod 1 (Fig. 14C) exopod triangular with narrow posterior point; endopod narrow with almost parallel sides, armed with an apical seta. Pleopod 2 (Fig. 14D) exopod subovoidal, with no apical seta; endopod with first article nearly twice as long as second, strong terminal seta ending with thinner seta. Pleopods 3-5 exopods (Fig. 14 E–G) quadrangular with no apical seta.

Etymology.

The new species is named after our colleague and friend Dr. Fabio Stoch, who greatly contributed to the knowledge of Italian stygobiotic fauna and collected part of the material.

Remarks.

The specimens were collected under stones on the bottom of a subterranean stream in the Grotta Su Palu, in the eastern part of the karstic area of Supramonte. Alpioniscus stochi sp. n. is similar to A. kuehni in having a thin third article of the antennula bearing a small number of aesthetascs, and the maxilliped with a quadrangular endite and a narrow palp bent medially. It is readily distinguishable from A. kuehni by the smaller size (4.5 mm vs. 12.0 mm of the latter), narrower body shape, shorter and more thickset antenna with smaller number of flagellar articles, uropods with shorter branches, the presence of a water conducting system on pereopod 7 ischium, a more thickset merus of the male pereopod 7, a stouter male pleopod 2 endopod, and no apical seta on the exopod of the male pleopods 2-5.