A new Brazilian species of Isotomiella (Collembola: Isotomidae), with notes on I. bidentata Delamare Deboutteville, 1950 and I. amazonica Oliveira & Deharveng, 1990 Author Mendonça, Maria Cleide De Author Abrantes, Eduardo Assis text Zootaxa 2007 1652 41 48 journal article 10.5281/zenodo.179786 f2eda0c6-5d07-49ba-a560-55d396d65901 1175-5326 179786 Isotomiella bidentata Delamare Deboutteville, 1950 Figs 12–23 Isotomiella bidentata Delamare Deboutteville, 1950 : 66 , Barra 1968 : 95 Redescription. Length: 0,43-0,60 mm . Habitus typical of the genus. Tegument of the body slightly granulated with visible pseudopores and big craters, measuring two to three times the diameter of a normal seta socket, more dense on abdominal segments IV-VI; dorsal chaetotaxy of the body as in figure 12. Antennae subequal to the head diagonal, ratio antennae: head = 1: 1,09. Cephalic setae ordinary and subequal, except the anterior and posterior ones which are a little longer. Antennal segment IV with one microsensillum protected by a longer and curved seta; 6 dorso-lateral subcylindrical sensilla; one seta longer and curved setae next to s6 sensillum; with 5–6 supplementary sensilla, one thicker dorso-medial, two very thin on dorso-external region and 2–3 also very thin on dorso-internal region. Antennal segment III with about 24 setae, sensory organ with two cylindrical microsensilla, laterally protected by s1 and s4 sensilla, and more laterally the s5 sensillum, longer and curved than the others ( Fig. 13 ). Antennal segment II with about 24 setae, one latero-external thicker sensillum, 2–4 microsetae: one dorsal, one ventral and sometimes with 1+1 lateral. Antennal segment I with 12–16 setae, two unequal sensilla and two microsetae, one ventral and one dorsal ( Fig. 14 ). Labrum with simple setae, without spiniform ones. Maxillary outer lobe with three sublobal setae. Thoracic segment II with 6+6 to 8+8 smooth axial seta; 1+1 lateral macroseta; 3+3 unequal lateral sensilla measuring respectively 13 µm, 7 µm and 10 µm ( Fig. 15 ). Thoracic segment III with 5+5 to 7+7 smooth axial setae; 1+1 lateral macroseta; 2+2 unequal sensilla measuring 12 µm and 4 µm. Abdominal segment I with 2+2 smooth axial setae, 1+1 ciliated, 1+1 lateral macroseta and 1+1 microsensillum (3 µm) ( Fig. 16 ). Abdominal segment II with 2+2 smooth axial setae, 1+1 ciliated, 1+1 lateral macroseta and 1+1 lateral sensillum about 15 µm long ( Fig. 17 ). Abdominal segment III with 2+2 ciliated axial setae, 4+4 ciliated macrosetae, 3+3 anterior and 1+1 posterior, 1+1 ventral sensillum (11 µm). Abdominal segment IV with 3+3 ciliated axial setae; 4+4 ciliated macrosetae, 3+3 anterior and 1+1 posterior, 1+1 lateral sensillum (10 µm). Abdominal segment V-VI with 3+3 macrosetae, 2+2 anterior slightly ciliated and 1+1 posterior smooth; 1+1 thin lateral sensillum ( spl ) about 10 µm long and 1+1 ventral sensillum ( sv ) about 16 µm long; unpaired setae a0 , m0 , p0 , smooth, unequal and measuring respectively 4 µm, 20 µm and 10 µm ( Fig. 18 ). Legs covered with ordinary setae, excepting two thick spines (6–8 µm) in the metathoracic tibiotarsus. Unguis untoothed, unguiculus lanceolated ( Fig. 19 ). Ventral tube with 3–4+3–4 distal, 2+2 posterior and 1+1 posterior setae ( Fig. 20 ). Tenaculum with 4+4 teeth and one seta on corpus. Furcal subcoxae: anterior with 4– 9 setae (including 1–3 ciliated), posterior with 5–6 setae (including 3–4 ciliated). Manubrium with 22 posterior setae( Fig. 21 ), 1+1 anterior-distal and 1+1 lateral setae ( Fig. 22 ). Dens with 12–20 anterior setae, the most distal longer, and five posterior setae ( Fig. 22 ). Mucro bidentated, the apical tooth bigger than the anteapical. ( Fig. 23 ). Ratio manubrium: dens: mucro = 8,2: 17: 1. Material examined : Brazil : Rio de Janeiro State: Rio de Janeiro City, Parque Nacional da Tijuca, Floresta da Tijuca: four specimens on slide nº 866 CM/ MNRJ , 23.ix.1999 ; three specimens on slide nº 925 CM/ MNRJ , 29.xi.1999 ; four specimens on slide nº 978 CM/ MNRJ , 23.ii.2000 ; 12 specimens on slide nº 991 CM/ MNRJ , 23.ii.2000 ; 20 specimens on slide nº 1033 CM/ MNRJ , 26.iv.2000 ; five specimens on slide nº 1040 CM/ MNRJ , 26.iv.2000 ; 6 specimens on slide nº 1051 CM/ MNRJ , 23.v.2000 ; four specimens on slide nº 1063 CM/ MNRJ , 23.v.2000 ; five specimens on slide nº 1070 CM/ MNRJ , 23.v.2000 , two specimens on slide nº 1674 CM/ MNRJ , 08.iii.2007 ; two specimens on slide nº 1675 CM/ MNRJ , 08.iii.2007 ; M. C. de Mendonça, coll. FIGURES 12–18. Isotomiella bidentata Delamare Deboutteville, 1950: 12 , tergite chaetotaxy in dorso-lateral view; 13, dorsal view of antennal segments III–IV; 14, ventral view of antennal segment I; 15, lateral sensilla of thoracic segment II; 16, lateral sensilla of thoracic segment III and abdominal segment I; 17, lateral sensilla of abdominal segment II; 18, dorsal view of abdominal segment VI. Remarks. Isotomiella bidentata was originally described by Delamare Deboutteville (1950) in the African material collected in Ivory Coast . This species was later redescribed by Barra (1968) , based on two specimens from the Delamare Deboutteville collection, probably from the same African region. The specimens of I. bidentata collected in the “Floresta da Tijuca” agree with both descriptions mentioned above in most characters. However, previous description does not refer to the general chaetotaxy of the segments, antenna or cover sensilla, which are considered to be very important taxonomical characters. There are also some differences between the Brazilian and the African specimens of I. bidentata . The Brazilian examined specimens have 12–19 anterior setae on dens, while the African ones, redescribed by Barra (1968) , have less than 10 setae. The antennal segment IV supplementary sensilla are given by Barra (1968: Fig. 2 ) . In the specimens studied here, they occur as one thicker dorso-medial, 2–3 thinner latero-external and two thinner dorso-internal, almost inconspicuous. The typical spl sensilla of the Isotomiella genus were not observed by Barra either, probably due to their thin aspect which is hard to observe. In the Brazilian specimens, spl sensilla are present but a little bit thicker than the surrounding ordinary setae. Comparisons between I. bidentata and the other “ delamarei ” group species reveal their similarity with I. nummulifer and I. spinifer , both from the Amazon, described by Oliveira & Deharveng (1990), although they only share two metathoracic tibiotarsus spines and mucro bidentated.