Soteriscus gibbosus, Taiti & Rossano, 2015

Taiti, Stefano & Rossano, Claudia, 2015, Terrestrial isopods from the Oued Laou basin, north-eastern Morocco (Crustacea: Oniscidea), with descriptions of two new genera and seven new species, Journal of Natural History 49 (33), pp. 2067-2138 : 2099-2103

Soteriscus gibbosus sp. nov.

( Figures 18–20)

Material examined

Holotype: ♂, St. 14, Phillyrea wood, leg. S. Taiti, 27 April 2004 ( MZUF 9504 ) . Paratypes: 3 ♂♂, 11 ♀♀, same data as holotype ( MZUF 9504 ) ; 1 ♂, 6 ♀♀, same locality, leg. S. Taiti and C. Rossano, 27 September 2005 ( MZUF 9505 ) ; 1 ♀, St. 10, leg. S. Taiti and C. Rossano, 26 April 2004 ( MZUF 9506 ) ; 1♀, St. 12, leg. C. Rossano, 26 April 2004 ( MZUF 9507 ) ; 1 ♀, St. 20, under stones along path to waterfall, leg. S. Taiti and C. Rossano, 2 May 2004 ( MZUF 9508 ) .

Description

Maximum length: ♂, 11 mm; ♀, 15 mm. Body outline as in Figure 18A. Brown colour with numerous yellowish muscle spots; a round pale spot at the base of pereon epimera in the frontal half of the segment; an elongated pale spot in the middle of pereonites and second or third to fifth pleonite; males darker than females. Back smooth with some scattered pointed scale-setae ( Figure 18B); a distinct sulcus marginalis at the sides of pereon epimera with numerous gland pores along its whole length ( Figure 18G); numerous gland pores scattered on the whole dorsal surface of the body; noduli laterales clearly visible, more or less at the same distance from the lateral margin of the pereonites, b/c and d/c co-ordinates as in Figure 18C. Cephalon ( Figure 18D– F) with no suprantennal line, frontal line straight; very small lateral lobes bent downwards and not protruding frontwards; eye with about 25 ommatidia. Pereonites 1–3 with posterior margin regularly convex; pereonite 4 with posterior margin straight; pereonites 5–7 with posterior corners pointing backwards. Pleonites 3–5 with distinct but short posterior points ( Figure 18H). Telson triangular with distinctly concave sides ( Figure 18H). Antennule ( Figure 18I) with first article longer than second and third; third article with a tuft of elongated aesthetascs at apex. Antenna ( Figure 19A) reaching back the posterior margin of pereonite 3; fifth article of peduncle slightly curved, as long as flagellum; first flagellar article about 1.6 as long as second. Mandibles ( Figure 19B, C) with molar penicil dichotomized and a line of several free penicils. Maxillule outer branch with 4 + 6 teeth (3 slightly cleft); inner branch with a distinct posterior point and two long and thin penicils ( Figure 19D). Maxilla ( Figure 19E) bilobate with setose apex, inner lobe quadrangular, much smaller than outer one; two long setae on the margin between the two lobes. Maxilliped ( Figure 19F) endite with two small triangular setae on distal margin and no penicil; first article of palp with two strong setae. Pleopod 1 and 2 exopods with monospiracular covered lungs. Uropod ( Figure 18H) with a triangular depression on protopodal outer margin; exopod almost twice as long as endopod; endopod proximally inserted.

Male: Carpus of pereopod 1 ( Figure 20A) to 3 with a brush of pointed setae increasing in length distally. Pereopod 7 ( Figure 20B) ischium with straight sternal margin and a longitudinal depression in the middle of the rostral surface; merus with a distinct hump on the posterior half of tergal margin. Pleopod 1 ( Figure 20C) exopod with large medial lobe about twice as long as wide, with largely rounded apex bearing a line of short setae; endopod with distal part with almost parallel sides and a tuft of short setae at apex. Pleopod 2 ( Figure 20D) endopod slightly longer than exopod. Pleopod 3–5 exopods as in Figure 20E– G.

Etymology

From the Latin ‘ gibbosus ’ = having a hump. The name refers to the male pereopod 7 merus which shows a distinct hump on the posterior half of tergal margin.

Remarks

At present the genus Soteriscus includes 15 species from Atlantic islands (Madeira Archipelago, Canary Islands and Cape Verde), northern Morocco, northern Algeria and southern Spain ( Schmalfuss 2003). Three species have been recorded in northeastern Africa ( Vandel 1956b, 1958 a, 1960b): S. gaditanus , S. virescens ( Budde-Lund, 1885) and S. fuscovariegatus ( Lucas, 1849) . Of these species, only S. gaditanus was recorded from the Rif region ( Vandel 1956b, 1958a; Achouri et al. 2008a, 2008c), but this species has not been collected by us. Re-examination of the material identified as S. gaditanus from the Rif region is necessary to confirm its occurrence.

Soteriscus gibbosus differs from all the other species in the genus in having a distinct hump on the male pereopod 7 merus. In having the male pleopod 1 exopod with a large medial lobe, the news species shows affinities with S. gaditanus and S. fuscovariegatus , but in both these two species the medial lobe is distinctly more slender. It also differs from the former in having a broadly rounded instead of triangular apical part of the medial lobe of the male pleopod 1 exopod (see Figure 2B in Vandel 1956b), and in the thicker and shorter uropodal exopods (see Figure 2A in Vandel 1956b); from the latter in having shorter frontal lateral lobes and longer and more slender uropodal exopods (see Figure 3A, B in Vandel 1956b).