Alpioniscus sideralis 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 sideralis Taiti & Argano sp. n. Figs 15, 16, 17, 18, 19

Alpioniscus n. sp.; Bessone et al. 2013: 325, fig. 11; 2016: 218, fig. 8.

Material examined.

Prov. Nuoro: Holotype: ♂ (MZUF 9835), Grotta Su Bentu, c.n. 105 Sa/NU, 40°15'18.23"N, 9°29'6.52"E, Lanaittu, Oliena, 21.IX.2013, leg. Astronauts. Paratypes: 1 ♂, 1 ♀ (MZUF 9836), same data as holotype; 1 ♂, 3 ♀♀ (MZUF 9836), same locality, 11-14.IX.2012, leg. P. Marcia and Astronauts; 1 ♂, 2 ♀♀ (MZUF 9837), same locality, 6.I.2013, leg. P. Marcia; 2 ♂♂, 1 ♀ (MZUF 9838), Grotta Sas Venas, c.n. 3064 Sa/NU, 40°07'32.33"N, 9°26'27.04"E, Orgosolo, VI.2013, leg. P. Marcia; 3 ♀♀ (MZUF 9839), Grotta Piggio de Janas, c.n. 3236 Sa/NU, 40°08'32.70"N, 9°27'18.60"E, Tauledda, Codula del Flumineddu, Orgosolo, 28.X.2012, leg. C. Corongiu. Prov. Ogliastra: 2 ♂♂, 1 ♀ (MZUF 9840), Grotta Lovettecannas, c.n. 2642 Sa/OG, 40°08'33.72"N, 9°34'35.35"E, Baunei, 5.I.2013, leg. L. Sanna; 7 ♂♂, 7 ♀♀ (MZUF 9841), same locality, 1.IV.2013, leg. P. Marcia; 1 ♂ (MZUF 9842), Grotta Su Palu, c.n. 1988 Sa/OG, 40°10'38.23"N, 9°33'50.53"E, 185 m, Codula Ilune, Urzulei, 8.XII.2012, leg. P. Marcia; 5 ♂♂, 9 ♀♀ (MZUF 9843), Grotta Istirzili, c.n. 50 Sa/OG, 40°04'49.50"N, 9°37'13.40"E, Baunei, 12.V.2013, leg. C. Onnis.

Description.

Maximum length: ♂, 7 mm; ♀, 7.5 mm. Body colourless, ovoidal, with pleon narrower than pereon (Fig. 15A). Dorsal surface smooth with some scattered scale-setae as in Fig. 15B. Some gland pores on lateral margins of pleonites 4 and 5 and on uropodal protopods (Fig. 15E). Cephalon (Fig. 15C, D) with suprantennal line sinuous; antennal lobes quadrangular. Eyes absent. Posterior margin of pereonite 1-3 straight, of pereonites 4-7 progressively more concave (Fig. 15A). Pleonites 3-5 with very short posterior points (Fig. 15E). Distal part of telson with slightly concave sides and truncate apex (Fig. 15E). Antennula (Fig. 15F) with distal article narrow and bearing two apical and three subapical aesthetascs. Antenna (Fig. 15G) with fifth article of peduncle shorter than flagellum; flagellum of 10-11 articles with couple of aesthetascs on second and third article. Mandibles with one penicil in the right (Fig. 16A) and three penicils in the left (Fig. 16B). Outer branch of maxillula with 5 + 6 teeth, apically entire, and two slender setose stalks; inner branch with three penicils increasing in length from distal to proximal (Fig. 16C). Maxilla with setose and bilobed apex, inner lobe very small (Fig. 16D). Maxilliped (Fig. 16E) endite quadrangular with setose distal margin and distinct subapical penicil on medial margin; palp narrow and bent in medial direction, with three tufts of setae on medial margin, tuft at apex and single seta on outer margin, basal article with two setae; basis distally enlarged with a rounded lobe on outer margin. Pereopods with bifid setose dactylar seta (Fig. 17A). Pereopod 7 (Fig. 17B) basis with water conducting system. Uropod (Fig. 15E) with protopod not grooved on outer margin; endopod distinctly shorter than exopod, exopod inserted slightly distally to endopod.

Male. Pereopod 1-4 (Fig. 17A) with ischium, carpus and merus bearing numerous short scales on sternal margin. Pereopod 7 (Fig. 17B) ischium with straight sternal margin covered with short setae; merus with triangular lobe at base of sternal margin, more or less protruding according to size; carpus enlarged proximally. Genital papilla (Fig. 17C) with a rounded tip. Pleopod 1 (Fig. 17C) exopod triangular with long narrow distal point slightly bent outwards; endopod narrow with almost parallel sides and proximally enlarged, armed with an apical plumose seta. Pleopod 2 (Fig. 17D) exopod subovoidal with no apical plumose seta; endopod with first article nearly twice as long as second, a strong terminal bifid seta. Pleopods 3-5 exopods (Fig. 17E-G) ovoidal with a long plumose apical seta.

Etymology.

Latin: sideralis meaning of or with respect to the distant stars. The name refers to the international team of astronauts, taking part in training courses (ESA CAVES) in Sardinia organized by the European Space Agency, who first collected this new species.

Remarks.

The species occurs in subterranean freshwater ponds and streams in the karstic areas of Supramonte. It is closely related to the other two Sardinian stygobiotic species of Alpioniscus ( A. kuehni and A. stochi sp. n.). It is readily distinguishable from A. kuehni by the smaller size (7.7 mm vs 12 mm), narrower body shape, shorter and more thickset antenna with smaller number of flagellar articles, presence on pereopod 7 ischium of a water conducting system, male pereopod 7 carpus shorter with more enlarged proximal part, male pleopod 1 exopod with narrower distal part, endopod shorter than exopod, male pleopod 2 exopod without setose apical seta. Alpioniscus sideralis differs from A. stochi in its larger size (7.5 mm vs. 4.5 mm of the latter), antennula with a group of subapical aesthetascs, more numerous flagellar articles of the antenna (10-11 vs. 5-7), maxillipedal basis with a rounded instead of triangular lobe on outer margin, uropods with longer exopod and endopod, male pereopod 7 with thinner merus and carpus, merus with a distinct lobe on sternal margin.