Trichorhina sexdens, Souza & Araújo & Campos-Filho, 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 : 252-255

Trichorhina sexdens sp. nov.

( Figs 6 , 95–107 )

Type material. Holotype ♂, BRAZIL, São Paulo: Ilha dos Búzios , 16.X to 04.XI.1963, K. Lenko col. ( MNRJ 4121 ). Paratypes: 3♂, 6♀, same data as holotype ( MNRJ 4122 ).

Diagnosis. Body brown. Eyes with four dark brown ommatidia. Molar process of mandibles with one penicil. Exite of maxillulae with six simple teeth. Measurements. Male, length: 2.13 mm, width: 0.65 mm; female, length: 2.13 mm, width: 0.71 mm.

Description. Body brown, with small dark brown spots in head. Eyes dark brown with four ommatidia. Head narrowed in the anterior half and not sunken in pereonite I. Cephalic lateral lobes very small, shorter than the median lobe, which has rounded apex ( Figs 95, 96 ). Body surface with plates. Pereon, pleon and telson covered with fan-shaped scale-setae. Noduli laterales with simple base. Each side of pereonite VII with one nodulus lateralis. Position of nodulilaterales as illustrated ( Fig. 6 ). Second joint of antennal peduncle without crest in outer border and without keel in dorsal side. Second joint of antennal flagellum entire ( Fig. 97 ). Left mandible ( Fig. 98 ) without rods between molar and incisory processes. Number of penicils in molar process of left mandibles one ( Fig. 98 ), right one. Outer group of exiteof maxillulae with three teeth. Inner group of exite of maxillulae with three undivided teeth ( Fig. 99 ). Endite of maxilliped ( Fig. 100 ) with two small teeth in distal outer border, and one small tooth in distal inner border. Pleopods without respiratory areas.

Male. Pereopods I ( Fig. 101 ) and VII ( Fig. 102 ) without sexual dimorphism. Pleopod Iwith subrectangular exopod ( Fig. 103 ); endopod with distal half slightly turned to the outside and apex armed with a short row of scale-setae parallel to the inner border ( Fig. 104 ). Pleopod II with triangular exopod ( Fig. 106 ); endopod with distal half slender ( Fig. 105 ). Pleopod V with subtriangular exopod with five large bristles ( Fig. 107 ).

Remarks. Trichorhina sexdens sp. nov. is distinguished from other species with four to five ommatidia as follows: from T. acuta by 1) exiteof maxillulae with six undivided teeth (in T. acuta seven, with two bifid); 2) endite of maxilliped with two teeth in inner distal border and one tooth in outer distal border (without teeth in outer distal border in T. acuta ). From T. barbouri by 1) tegument smooth (granulous in T. barbouri ); 2) second joint of antennal flagellum without groove. From T. hospes by 1) exite of maxillulae with six undivided teeth (in T. hospes nine, with two bifid); 2) endite of maxilliped with two teeth in inner distal border and one tooth in outer distal border. From T. paraensis by 1) eyes with dark brown ommatidia (light brown in T. paraensis ); 2) exite of maxillulae with six undivided teeth (in T. paraensis eight, two bifid). From T. silvestrii by 1) absence of rods between molar and incisory processes of left mandible; 2) molar process of mandible with one penicil (three in T. silvestrii ); 3) exite of maxillulae with six undivided teeth (in T. silvestrii eight, of which two bifid). From T. vandeli by 1) molar process of mandibles with one penicil (many in T. vandeli ); 2) exite of maxillulae with six undivided teeth (in T. vandeli eight, of which two bifid); 3) exopod Iof male subrectangular (subtriangular in T. vandeli ). From T. biumbonata sp. nov., T. lenkoi sp. nov., T. myrmecophila sp. nov. and T. orensis sp. nov. mainly by the eyes with four ommatidia (five in these species).

The species with three ommatidia [e.g. T. triocellata Ferrara & Taiti, 1985 and T. squamata (Verhoeff, 1933) ] have eyes with a conspicuous triangular conformation of ommatidia.

Etymology. Species name originates from Latin, meaning six teeth, due to dentition of maxillular exite.

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. 95–100. Trichorhina sexdens sp. nov., male: 95, cephalothorax and four first pereonites, dorsal view; 96, cephalothorax, frontal view; 97, antenna; 98, left mandible; 99, exite of maxillula; 100, maxilliped. Scale bars: Fig. 95, 1 mm; Fig. 96, 0.5 mm; Figs 97–100, 0.1 mm

Figs. 101–107. Trichorhina sexdens sp. nov., male: 101, pereopod I; 102, pereopod VII; 103, exopod of pleopod I; 104, endopod of pleopod I; 105, endopod of pleopod II; 106, exopod of pleopod II; 107, exopod of pleopod V. Scale bars: Figs 101–107, 0.1 mm.