Isotomiella barrana, Mendonça, Maria Cleide De & Abrantes, Eduardo Assis, 2007

Mendonça, Maria Cleide De & Abrantes, Eduardo Assis, 2007, A new Brazilian species of Isotomiella (Collembola: Isotomidae), with notes on I. bidentata Delamare Deboutteville, 1950 and I. amazonica Oliveira & Deharveng, 1990, Zootaxa 1652, pp. 41-48 : 41-44

Isotomiella barrana sp.nov.

Figs 1–11

Description. Body length: 0,42 to 0,45 mm. Habitus subcylindrical, typical of the genus. Without pigment. Tegument of the body slightly granulated without craters. Dorsal chaetotaxy of the body as in Fig. 1 and sensillary cover as in Fig. 2 . Pseudopores visible on some tergites.

Antennae longer than the head diagonal, ratio antennae: head = 1: 0,81. Antennal segment IV with 1 microsensillum protected by a curved setae; 6 broad subcylindrical and subequal sensilla (5 µm); 5–6 supplementary sensilla, three more thick dorso-external and 2–3 very thin, dorso-internal ( Fig. 3 ). Antennal segment III with 20–22 setae; sensory organ with two cylindrical microsensilla, laterally protected by two long, thin and subcylindrical sensilla, and one below, short and curved microsensillum. Antennal segment II with 16–17 subequal setae and one basal dorsal microseta ( Fig. 4 ). Antennal segment I with about 12 setae, two ventral and unequal sensilla and one dorso-basal microseta. Ratio of the antennal segment I: II: III: IV = 1: 1,5: 1,7: 2,1.

Head without eyes and postantennal organ; cephalic setae subequal, the anterior and posterior little longer (15 µm) ( Fig. 1 ). Labrum with small and thin setae, without spiniform ones. Maxillary outer lobe with three sublobal hairs.

Thoracic segment II with 3+3 smooth axial setae, 1+1 ciliated lateral macroseta (24 µm), 3+3 small subequal lateral sensilla (5 µm); thoracic segment III with 3+3 smooth axial setae, 1+1 ciliated dorso-lateral macrosetae (25 µm), 2+2 lateral sensilla (4–5 µm).

Abdominal segment I with 2+2 smooth axial setae, between 1+1 dorsal ciliated seta and 1+1 lateral ciliated macrosetae (25 µm); abdominal segment II with 2+2 smooth axial setae, 2+2 dorsal ciliated ordinary setae and 1+1 lateral ciliated macrosetae (20 µm); abdominal segment III with 2+2 smooth axial setae, 1+1 ciliated seta, 2+2 dorso-lateral macrosetae (25 µm), 1+1 (sv) ventral sensillum (3 µm); abdominal segment IV with 2+2 smooth axial setae, 4+4 ciliated macrosetae (25 µm), being 1+1 dorsal, 2+2 dorso-lateral and 1+1 postero-lateral, 3+3 (sp) posterior sensilla (7-9 µm); abdominal segments V–VI fused, with 6+6 ciliated macrosetae (32 µm) and several ciliated setae, unpaired setae a0 smooth (10 µm), m0 ciliated (20 µm) and p0 smooth (10 µm), 1+1 cylindrical and tough lateral sensillum (spl) measuring 10 µm, 3+3 (sa, spi, spe) small dorso-lateral sensilla (9 µm), 1+1 thin and small ventral sensilla (4 µm).

Legs with ordinary setae, one lateral longer than the proximal seta; unguis untoothed (11-12 µm); unguiculus lanceolated about half size of unguis ( Fig. 5 ). Ventral tube with 1+1 anterior, 1+1 posterior and 3+3 apical setae ( Fig. 6 ). Tenaculum with 4+4 teeth and one seta on corpus ( Fig. 7 ). Furcal subcoxa anterior with two ciliated and two smooth setae; posterior with three ciliated and one smooth setae ( Fig. 8 ). Manubrium with 20-22 dorsal setae ( Fig. 9 ), 1+1 ventral distal and 1+1 lateral setae ( Fig. 10 ). Dens with 6 posterior and 16 anterior setae, with one distal longer than the others ( Fig. 10 ). Mucro very small, tridentated, with two basal teeth symmetrical ( Fig. 11 ). Ratio manubrium: dens: mucro = 10: 19,5: 1.

Type locality. Floresta da Tijuca, Parque Nacional da Tijuca, Rio de Janeiro City, Rio de Janeiro State, Brazil. Found in forest litter and soil.ção3

Type material. Brazil: Rio de Janeiro State: Rio de Janeiro City, Parque Nacional da Tijuca; holotype: female on slide n° 1675 CM/ MNRJ, 08.iii.2007. M. C. de Mendonça coll.; 10 paratypes on slide nº 864 CM/ MNRJ, 23.ix.1999; five paratypes on slide nº 897 CM/ MNRJ, 25.x.1999; 8 paratypes on slide nº 982 CM/ MNRJ, 23.ii.2000; four paratypes on slide nº 997 CM/ MNRJ, 23.ii.2000; 15 paratypes on slide nº 1029 CM/ MNRJ, 26.iv.2000; two paratypes on slide nº 1045 CM/ MNRJ, 26.iv.2000; 6 paratypes on slide nº 1067 CM/ MNRJ, 23.v.2000; four paratypes on slide nº 1109 CM/ MNRJ, 26.vii.2000; 13 paratypes on slide nº 1675 CM/ MNRJ, 8.iii.2007; Brazil, Rio de Janeiro State, Maricá City, Restinga de Maricá, one paratype on slide Nº 1266 CM/ MNRJ, 28.i.2003; one paratype on slide Nº 1268 CM/ MNRJ, 28.i.2003; two paratypes on slide Nº 1274 CM/ MNRJ, 28.i.2003; one paratype on slide Nº 1275 CM/ MNRJ, 28.i.2003; E. A. Abrantes coll.; Brazil, Rio de Janeiro State, Mangaratiba City, Restinga da Marambaia, 12 paratypes on slide n° 1645 CM/ MNRJ, 24.i.2007, E. A. Abrantes coll.

Discussion. Isotomiella barrana sp. nov. was collected from soil and litter of the Atlantic rainforest and from the preserved area sand dunes of two distant and different “restingas”. In the first locality, Maricá, the specimens were found in herbaceous vegetation (Manilkara subsericea, Guapira obtusata, Allagoptera arenaria ) and in the second one, Marambaia, in leaf cover of Allagoptera arenaria (Arecaceae) . Isotomiella barrana sp. nov. is morphologically close to I. sodwana Barra, 1997 , also from the littoral zone of South Africa. Both show the same reduced chaetotaxy of the body, number of manubrial and dental setae and number of anterior and posterior furcal subcoxa setae. According to the original I. sodwana description ( Barra 1997), the mucro is small and bidentated, sometimes thickened on the internal side. However, in I. barrana sp. nov. there are, undoubtedly, three invariable mucronal teeth. In all the studied specimens the antennal segment IV shows three supplementary thick sensilla on the externo-dorsal region and 2–3 very thin sensilla, almost undistinguished, on the internal side, whereas I. sodwana possess four sensilla on the dorsal region and three supplementary ones on the latero-internal region. The sensillary chaetotaxy of the body shows 3+3 posterior sensilla on abdominal segment IV in I. barrana sp. nov., versus 2+ 2 in I. sodwana . In the new species, the ventral tube always has 3+3 distal setae, 1+1 anterior and 1+1 posterior setae, contrary to the 3+3 distal, 2+2 anterior and 2+2 posterior setae of I. sodwana . The anterior and posterior furcal subcoxae have 4+4 setae in both species, respectively. However, in I. barrana sp. nov., two setae are smooth and two are ciliated in the anterior; one is smooth and three are ciliated in the posterior, differently from all smooth setae in I. sodwana . In relation to the African species, it is very difficult to assure the gender in the studied adults, but it was possible to verify two females with slightly visible genital opening.

Etymology. This species is cordially dedicated to Dr. Jean Barra, from Louis Pasteur University in Strasbourg ( France).

Figures

FIGURES 1 – 5. Isotomiella barrana sp. nov.: 1, dorsal chaetotaxy of tergites; 2, lateral sensillary chaetotaxy of tergites; 3, dorsal view of antennal segment IV; 4, dorsal view of antennal segments II – III; 5, leg III.

FIGURES 6 – 11. Isotomiella barrana sp. nov.: 6, ventral tube; 7, tenaculum; 8, furcal subcoxa; 9, posterior view of the manubrium; 10, anterior view of the manubrium and dens; 11, apical part of the dens and mucro.