Trichorhina crassisetae, 2011

Souza, L. A., Araújo, J. P. & Campos-Filho, I. S., 2011, The genus Trichorhina Budde-Lund in Brazil, with description of seven new species (Isopoda, Oniscidea, Platyarthridae), Iheringia, Série Zoologia 101 (32), pp. 239-261 : 244-247

Trichorhina crassisetae sp. nov

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( Figs 2 ; 25–43 )

Type material. Holotype ♂, BRAZIL, Mato Grosso do Sul: Três Lagoas ( Sucuriú river, Corredeira Chupão ), in the forest along the river, in the leaf mold, VI.1964, without collector ( MNRJ 4113 ). Paratypes: 8♂, 8♀, same data as holotype ( MNRJ 4114 ).

Diagnosis. Pigmentation of body dark brown. Eyes with eight black ommatidia. Peduncle of antenna with conspicuous bristles. Exite of maxillulae with four teeth in the outer group, one very small. Pereopod Iof malewith setaebifurcated in carpus. Endopodof pleopod Iof male with row of small setae in inner border. Measurements. Male, length: 3.18 mm, width: 1.19 mm; female, length: 2.52 mm, width: 1.06 mm.

Description. Pigmentation of body dark brown; lighter in head (with small dark brown spots) ( Fig. 25 ), antennae, sides of pereon and of pleon and uropods. Eyes black with eight ommatidia. Pereonite Iwith anterior margins reaching the eyes. Cephalic lateral lobes small, shorter than median lobe which has rounded apex and straight sides ( Fig. 26 ). Eyes with eight ommatidia. Pleon outline continuous with pereon; pleonites III–V with well developed epimera. Pereon, pleon and telson covered with fan-shaped scale-setae ( Fig. 27 ). In the posterior margins of pereonites, scalesetae large and wide intercalate with small and narrow, and in the lateral margins small. Fan-shaped scale-setae more or less rounded and with four shafted frame. Nodulilaterales withfeaturelessbase. Pereonite VII with only one nodulus lateralis on each side. Position of noduli laterales as illustrated ( Fig. 2 ). Distal joint of antennula with five aesthetascs ( Fig. 28 ). Antenna ( Fig. 29 ) stretched reaches posterior margin of pereonite II. Second joint of antennal peduncle without dorsal keel nor crest in outer border. Second joint of antennal flagellum without groove. Left mandible ( Fig. 30 ) without rods between molar and incisory processes. Six penicils in molar process of left mandibles ( Fig. 30 ), right four ( Fig. 31 ). Outer group of exite of maxillulae with four teeth, one much smaller. Inner group of exite of maxillulaewith four teeth: two bifid ( Fig. 32 ). Maxilla with inner lobe narrower than outer lobe. Sensilla on the inner lobe ( Fig. 33 ). Endite of maxilliped without small teeth in outer distal border, and with inner distal border smooth ( Fig. 34 ). Pleopods without respiratory areas.

Male. Pereopod I ( Fig. 35 ) with bifurcate setae in carpus, contrasting to that of female ( Fig. 37 ); pereopod VII ( Fig. 36 ) without prominent sexual dimorphism, compared to that of female ( Fig. 38 ). Pleopod Iwith exopod subrectangular ( Fig. 39 ); endopod with a row of small setae parallel to the inner border ( Fig. 40 ). Pleopod II with triangular exopod ( Fig. 41 ); endopod with distal half slender ( Fig. 42 ). Pleopod Vwith exopod subrectangular ( Fig. 43 ).

Remarks. Trichorhina crassisetae sp. nov. is distinguished from species with eight to twelve ommatidia as follows: from T. amazonica Souza-Kury, 1997 by 1) molar process of left mandible with six penicils (four in T. amazonica ); 2) maxillulae with eight teeth, two bifid (in T. amazonica seven, two bifid). From T. atlasi by 1) absence of frontal line (frontal line very thin in T. atlasi ); 2) sexual dimorphism in pereopod I of male: carpus with remarkable bifurcate setae (males without particular features, see VANDEL 1959:101, for T. atlasi ); 3) pleonites three to five with well developed points (blunt in T. atlasi ). From T. kribensis Ferrara & Schmalfuss, 1983 by 1) antenna without aesthetascs; 2) exite of maxillulae with eight teeth, two bifid (nine undivided in T. kribensis ); 3) pereopod VII of male without dimorphism. From T. marianii Arcangeli, 1930 by 1) tegument smooth (granulous in T. marianii ); 2) sexual dimorphism in pereopod Iof male: carpus with bifurcate setae (sexual dimorphism only in length and width of merus and carpus in T. marianii ). From T. pubescens (Dollfus, 1893) by 1) antenna with joints II–V of peduncle without inferior groove; 2) exite of maxillulae with eight teeth, of which two bifid (all teeth undivided in T. pubescens ). Promptly distinguishable from all other species of the genus by eyes with eight ommatidia.

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Etymology. From Latin crassus = thick + seta = bristle, due to the stout bristles in antenna.

Figures

Figs 1–7. Ratio b/c and d/c of noduli laterales on pereonites I–VII: 1, Trichorhina biumbonata sp. nov.; 2, Trichorhina crassisetae sp. nov.; 3, Trichorhina lenkoi sp. nov.; 4, Trichorhina myrmecophila sp. nov.; 5, Trichorhina orensis sp. nov.; 6, Trichorhina sexdens sp. nov.; 7, Trichorhina tropidocerata sp. nov.

Figs. 25–34. Trichorhina crassisetae sp. nov. Female, habitus: 25, dorsal; 26, lateral; 27, cephalothorax, frontal view. Male: 28, antennula; 29, antenna; 30, left mandible; 31, right mandible; 32, exite of maxillula; 33, maxilla; 34, maxilliped. Scale bars: Figs 25–26, 1 mm; Fig. 27, 0.5 mm; Figs 28–34, 0.1 mm.

Figs. 35–43. Trichorhina crassisetae sp. nov. Male: 35, pereopod I; 36, pereopod VII. Female: 37, pereopod I; 38, pereopod VII. Scale bars: Figs 35–38, 0.1 mm; arrowed details, 0.01 mm; 39, exopod of pleopod I; 40, endopod of pleopod I; 41, exopod of pleopod II; 42, endopod of pleopod II; 43, exopod of pleopod V. Scale bars: Figs 39–43, 0.1 mm; arrowed details, 0.01 mm