Benthana cairensis, Sokolowicz & Araujo & Boelter, 2008

Sokolowicz, Carolina C., Araujo, Paula B. & Boelter, Juliana F., 2008, A new species of Benthana (Crustacea: Isopoda: Philosciidae) from southern Brazil, Revista Brasileira de Zoologia 25 (2), pp. 314-318 : 315-318

Benthana cairensis sp. nov.

Figs 1-28

Material. Holotype: male, BRAZIL, Rio Grande do Sul: Taquara (29°46’S, 50°50’W, Sítio Cairé , in leaf litter), 25.IV.2004 ( MNRJ 20574 ) . Paratypes: same locality as holotype, 1 male and 1 female, 26.II.2007 ( MZUSP 17362 ) and 5 males and 5 females, 26.II.2007 ( UFRGS 4399 ) , 5 males and 5 females, 19.III.2007 ( UFRGS 4421 ) and 5 males and 5 females, 23.III.2007 ( UFRGS 4422 ) ; Sapiranga (29°37’52”S, 51°00’34”W), 8 males, 7 females, 29.XII.2001 ( UFRGS 4471 ) .

Diagnosis. Eye with 22-25 ommatidia, antennula with 15+2 aesthetascs; antenna, when extended posteriorly, reaches anterior margin of the fifth pereionite; lateral endite of maxillula with 4+6 setae, five of inner set pectinate, proximal teeth with 5+1 denticles. Male exopod of pleopod 1 elongated (sensu ARAUJO & LOPES 2003), with lobe on inner lateral margin; bearing up to 6 setae on outer lateral margin. Exopods and endopods of uropods inserting at different levels.

Description. Maximum cephalothorax width: male 1.70 mm, female 2.60 mm. Maximum length: male 9.7 mm, female 11.5 mm. Body color chestnut, with unpigmented regions along pereion; unpigmented spots on anterior region of each coxal plate; elongated unpigmented lines on median longitudinal part of the pereionites ( Fig. 1 ). Antenna articles 1-5 with few small areas without pigmentation; flagellum uniformly chestnut colored. Pleonites 1-2 with three unpigmented spots, pleonites 3-5 with elongated spots with fine lateral projections without pigmentation on median longitudinal line. Pleotelson with same pattern of pleonites 3-5. Uropods uniformly pigmented. Pereiopods partially pigmented. Pereion with smooth and bright tegument bearing setae on all pereionites. Noduli laterales ( Figs 15 and 16 ) with d/c coordinates showing a maximum on pereionite 4. Pleon narrows abruptly in relation to pereion; neopleura well-developed on segments 3-5. Pleotelson triangular with slightly concave lateral margins, and with rounded apex, reaching more than halfway down the protopodite of uropods. Cephalothorax with eyes having 22-25 ommatidia. Antennula with coniform distal article with five rounds of three aesthetascs each and two apical aesthetascs ( Fig. 2 ). Antenna, when extended posteriorly, reaches anterior margin of fifth pereionite. Antenna article 5 and flagellum approximately same length. Second flagellar article smallest, apical organ about onethird the size of distal article ( Fig. 3 ). Mandibles: right mandible with two penicils on incisor process and tuft of at least 10 plumose setae on molar ( Fig. 4 ); left mandible with three penicils on incisor process and tuft of at least 10 plumose setae on molar ( Fig. 5 ). Maxillula: lateral endite with 4+6 setae, five of inner set pectinate, proximal teeth with 5+1 denticles ( Fig. 6 ), medial endite with two apical penicils; ( Fig. 7 ). Maxilla: external lobe with sinuous posterior margin and internal mar- gin with three long and fine setae ( Fig. 8 ). Maxilliped: endite with long and short seta; two short teeth on the distal external margin, with three small protuberances. Apex of palp with tuft of short fine setae ( Fig. 9 ). Pereiopods: with tricorns on all articles, antenna-groming brush of the carpus and dentate carpal seta present on pereiopod 1 ( Fig. 27 ). Uropod: insertion of endopod and exopod at different levels, endopod extending to half of exopod ( Fig. 1 ). Sexual differentiation: pereiopods 1-4 of male with rows of bifid setae, particularly on merus and carpus, missing in female; ischium and merus of all pereiopods of male of sub-equal length. In males, ischium of pereiopod 7 robust with setae approximately in the middle; in females, ischium with setae on distal third ( Figs 17-26 ). Pleopods: in males, elongated exopod of pleopod 1 (z:y ratio = 3.1, excluding the lobe), with subapical dentiform expansion and lobe on inner lateral margin and up to six setae on outer lateral margin ( Fig. 10 ), endopod with five fine pical spines ( Fig. 11 ). Pleopod 2 with exopod distally elongated carrying setae on external margin, endopod tapered on distal third ( Figs 12 and 13 ). Pleopod 5 exopod with up to approximately nine setae on external lateral margin ( Fig. 14 ).

Etymology. The specific name refers to a location, Sítio Cairé, at which the species was found, in Taquara, Rio Grande do Sul, Brazil.

Remarks. Benthana cairensis sp. nov. has 5+1 denticles in the proximal teeth of the lateral endite in the maxillula, while the other 19 species have at least 6+1denticles. The new species does have characteristics found in other congeneric species, such as: the lobe on the inner lateral margin on the male exopod of pleopod 1 and setae on the opposite margin, five pectinate teeth on the lateral endite of the maxillula, insertion of the endopod and exopod at different levels, and male sexual dimorphism on pereiopods 1-3(4).

Three species of the genus have a lobe on male pleopod 1 exopod: 1) B. serrana , lacks setae on the pleopod 1 exopod and has 20 ommatidia (22-25 on the sp. nov.); 2) B. taeniata , also lacks setae on pleopod 1 exopod, has endopod and exopod insertions of the uropod at the same level, sexual dimorphism of males only in the first pereiopod and 17 to 19 ommatidia; and 3) B. olfersii has all of the characteristics for B. cairensis sp. nov. except that the sexual dimorphism of males is restricted to the pereiopods 1-3, and, uniquely, a lobe with six setae on the internal margin of the proximal extremity of the merus on pereiopod 7 ( Fig. 28 ).

In a review of Benthana , sexual dimorphism was described on the exopodites of the uropods, which are longer in males than in females ( LEMOS DE CASTRO 1958b). In B. olfersii studied here, one male and one female of similar size were examined and had this same dimorphism and so this species should be included in the subgenus Benthanoscia , in which dimorphism on male exopodites is an autapomorphy ( LEISTIKOW & ARAUJO 2006). Therefore, by lacking this dimorphism (autapomorphy), the new species is not included in the subgenus Benthanoscia .

Benthana cairensis sp. nov. is commonly abundant in leaf litter and under fallen tree branches of Araucaria angustifolia (Bert.) O. Ktze. , the only native conifer in Brazil. While classified as runners following SCHMALFUSS (1984), this species is also capable of thanatosis.

Figures

Figures 1-16. Benthana cairensis sp. nov. Male: (1) dorsal view; (2) antennula; (3) antenna; (4) right mandible; (5) left mandible; (6) lateral endite of maxillula; medial endite of maxillula; (8) maxilla; (9) maxilliped; (10) pleopod 1 exopod, (11) pleopod 1 endopod, with detail of five small spines; (12) pleopod 2 exopod; (13) pleopod 2 endopod; (14) pleopod 5 exopod; (15-16) co-ordinates b/c and d/c of the noduli laterales. Scales: 1.0 mm.

Figures 17-28. Benthana cairensis sp. nov.: (17) male pereiopod 1; (18) male pereiopod 2; (19) male pereiopod 3; (20) male pereiopod 4; (21) male pereiopod 7; (22) female pereiopod 1; (23) female pereiopod 2; (24) female pereiopod 3; (25) female pereiopod 4; (26) female pereiopod 7; (27) male pereiopod 1 carpus; B. olfersii: (28) male pereiopod 7 merus; arrow indicates unique lobe with 6 setae. Scales: (17-26) 500 µm; (27) 100 µm; (28) 200 µm.