Trichoniscus microphthalmus, 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 : 2070-2073

Trichoniscus microphthalmus sp. nov.

( Figures 1 and 2 )

Material examined

Holotype: ♂, St. 8, leg. S. Taiti and C. Rossano, 28 September 2005 ( MZUF 9453 ) . Paratypes: 25 ♂♂, 75 ♀♀, same data as holotype ( MZUF 9453 ) ; 3 ♂♂, 5 ♀♀ same locality and collectors, 28 April 2004 ( MZUF 9454 ) .

Description

Maximum length: ♂, 2.0 mm; ♀, 2.5 mm. Body colourless, ovoidal, with pleon narrower than pereon ( Figure 1A ). Back almost smooth covered with numerous cordiform scale-setae ( Figure 1B ). Cephalon ( Figure 1C ) with suprantennal line bent downwards; antennal lobes rounded, distinctly visible in dorsal view; eye reduced, visible as one to three small dots of dark pigment. Distal part of telson with concave sides and truncate apex ( Figure 1D ). Antennule ( Figure 1E ) of three articles; distal article longer than second, bearing three aesthetascs on apical margin. Antenna ( Figure 1F ) fifth article as long as flagellum; flagellum of three articles with one row of five aesthetascs on second article. Mandibles with one penicil in the right ( Figure 1G ) and two penicils in the left ( Figure 1H ). Outer branch of maxillule with 5 + 5 teeth, apically entire, and three slender stalks; inner branch with three penicils ( Figure 2A ). Maxilla with setose and bilobate apex, inner lobe smaller ( Figure 2B ). Maxilliped endite narrow, with a large apical penicil ( Figure 2C ). Pereopods with an ungual seta and a large, bifid and setose dactylar seta ( Figure 2D, 2E ). Uropod ( Figure 1D ) with protopod not grooved on outer margin; endopod slightly shorter than exopod, inserted at the same level.

Male: Pereopods 1–4 ( Figure 2D ) with carpus and merus bearing numerous short scales on sternal margin. Pereopod 7 ( Figure 2E ) ischium with straight sternal margin. Pleopod 1 ( Figure 2F ) exopod with straight medial margin and sinuous outer margin; endopod of two articles, distal article tapering to a point, apical part shagreened. Pleopod 2 ( Figure 2G ) exopod subrectangular with distal margin slightly convex; endopod of two articles, distal article styliform, about three times as long as basal one.

Etymology

From the Greek ‘mikrós’ = small + ‘ophthalmós’ = eye. The name refers to the reduced eye visible as one to three small dots of dark pigment.

Remarks

The genus Trichoniscus was previously known in Morocco only for the widespread species T. pygmaeus Sars, 1899 (Vandel 1959) . A second species, Trichoniscus solisensis Vandel, 1959 , from a cave near Safi, western Morocco, has been proved to belong to the genus Adoniscus Vandel, 1955c (Olibrinidae) ( Taiti and Ferrara 2004). In Algeria four species of Trichoniscus are known: T. gachassini ( Giard, 1899) , T. fragilis Racovitza, 1908 , T. provisorius Racovitza, 1908 , and T. peyerimhoffi Vandel, 1955a ( Schmalfuss 2003) . Another species of Trichoniscus ( T. gordoni Vandel, 1955a ) is known from several caves in southern Spain and Gibraltar ( Vandel 1955a). The new species T. microphthalmus is readily distinguishable from all these species by the male pereopods 1–4 with sternal margin of carpus and merus bearing a fringe of scales, and by the shape of the male pleopod 1 exopod.

Figures

Figure 1. Trichoniscus microphthalmus sp. nov. from St. 8, paratype ♀: (A) adult specimen, dorsal view; (B) dorsal scale-seta; (C) cephalon, frontal view; (D) pleonite 5, telson and left uropod; (E) antennule; (F) antenna; (G) right mandible; (H) left mandible.

Figure 2. Trichoniscus microphthalmus sp. nov. from St. 8, paratype ♀: (A) maxillule; (B) maxilla; (C) maxilliped. Paratype ♂: (D) pereopod 1; (E) pereopod 7; (F) pleopod 1; (G) pleopod 2.