Psammisotoma restingae, Abrantes, Eduardo Assis & Mendonça, Maria Cleide De, 2009

Abrantes, Eduardo Assis & Mendonça, Maria Cleide De, 2009, A new species of Psammisotoma Greenslade and Deharveng (Collembola: Isotomidae) from Brazil, Zootaxa 2295, pp. 25-30 : 28-30

Psammisotoma restingae sp. nov.

(Figures 1–17)

Type material. HOLOTYPE female: Brazil, State of Rio de Janeiro, Maricá City, Restinga de Maricá, beach sand in halophic psammophilous vegetation, 31.vii.2003, collection number CM/ MNRJ 1354. PARATYPES: 10 females and 2 males, same data as holotype. 17 juveniles, same locality as holotype, 25.vi.2003, CM/ MNRJ 1320. Deposited in the Museu Nacional, Universidade Federal do Rio de Janeiro.

Description. Size: 0.65–0.95 mm. Colour light grey with ventral side paler. Cuticle consisting of primary triangular granules linked together in hexagonal rings. Antennae longer than head diagonal, ratio antennae:head diagonal = 1.6:1.0. Ant. IV with several setae, approximately 7 poorly differentiated sensilla, sub-apical organ minute, protected by one curved seta (Fig. 1). Ant. III approximately 70 setae and one basolateral microseta, sensory organ composed of 2 broad sensilla (6 µm), located in deep open groove (Fig. 14), surrounded by one microsensillum and 5–6 sensilla poorly differentiated from proximal seta (Fig. 2). Ant. II with normally 58 setae, 2–3 dorsolateral sensilla very thin and three basal microsetae, one dorsal, one lateral and one ventral (Fig. 2). Ant. I with normally 30 setae, two ventral sensilla, very thin of different sizes, and five basal microsetae, three dorsal and two ventral (Fig. 3). Ratio of antennal segments, I:II:III:IV=1:1.8:2.5:3.1.

Head. Eyes 6+6 on dark patches. Postantennal organ (PAO) elliptical (21 µm), not constricted, surrounded by 4–5 guard setae, length about twice the diameter of nearest eye (Fig. 4). Labral setal formula 4/5,5,4; anterior two rows inserted in papilla (Fig. 5). Maxillary palp trifurcate, with 4 sublobal hairs (Fig. 6). Head of maxilla complex, with 3 teeth and 6 lamellae; lam. 1 apically expanded bearing 3 regular rows of fine ciliation; lam. 2 and 3 with marginal ciliations; lam. 4 and 5 smaller and capitulum with marginal ciliations; lam. 6 strong, fan like, with long marginal ciliations. Labial palp with 5 papillae and outer labial process short (9 µm), the same size as the labial palp E (Fig. 7). Labium with 5 basomedial setae; ventral side of head with 5+5 or 6+6 postlabial setae along ventral line.

Body chaetotaxy. Setae on body short, fine, and numerous, polychaetotic type, glands in the setal base not seen (Fig. 8). Abdominal segment IV with two pairs of trichobothria, the anterior (45 µm) longer than the posterior (18 µm). Tergal sensillary formula 66/656550 (accp), 32/10000 (al), anterosubmedial sensilla as 1+1 on abdominal IV and 1+1 anterior sensilla on abdominal V (Fig. 9).

Appendage. Unguis (20 µm in leg III) with two asymmetrical lateral teeth; empodial appendage with lamellae but without apical seta (Figs. 10, 15). Tibiotarsi I–III with ordinary setae (normally 27, 33, 44 respectively); Tibiotarsus II with one modified seta (17 µm) mediodistally on dorsal side (Fig. 16). Ventral tube (40 µm) with 4+4 lateral distal, 3+3 anterior and 2+2 posterior setae. Retinaculum with 4+4 teeth and one setae on corpus. Anterior and posterior parts of furcal subcoxa respectively with normally 36+36 and 13+13 setae. Manubrium anteriorly with normally 44 setae, lateral line with 8+8 setae and 2+2 distal spine-like setae. Dens long and crenulated, with 4–5 internal basal spine-like setae, normally 65 anterior and 11 posterior setae (Fig. 11); the juveniles specimens show a reduced chaetotaxy on the manubrium and dens (Fig. 12). Mucro small with 3 asymmetrical teeth (Fig. 17). Ratio of length of manubrium:dens:mucro as 10,2: 28,5: 1.

Genital plate. Female with 2+2 outer setae and 9+ 9 in peripheral area. Male with 5+5 outer setae and 8+ 8 in peripheral area.

Etymology. The new species is named after the typical Brazilian Atlantic ecosystem.

Remarks. Psammisotoma restingae sp. nov. resembles P. kingae in several characters: habitus, sensory organ of antennal segment III, number of eyes, furcal chaetotaxy and mucro. However, it differs from P. kingae in body size, being markedly smaller and in the tergal sensillary pattern. The claw of P. restingae sp. nov. also possesses two lateral asymmetrical teeth, and the outer labial process is short and does not exceed the labial palp E. The differentiating characters are given in the Table 1 .

In the same samples we found several juveniles specimens of P. restingae sp. nov. similar to the adults in several aspects: the same outer labium process, eyes, post antennal organ, sensillary formula, modified setae on tibiotarsus II and claw. Several differences observed in these intermediary forms such as the smaller body size (0,55mm: 0,57mm), few and sparse setae on the tergites, absence of setae on the tenaculum corpus, much reduced chaetotaxy on the manubrium, dens with small number of setae and only one pair of spine-like setae on the internal margin, could be attributed to different ontogenetic stages.

PLATE 3 (Figures 13–17). Psammisotoma restingae sp.nov. Scanning electron micrographs. 13, Habitus; 14, Sensory organ of antennal segment III; 15, Claw; 16, Detail of modified seta on tibiotarsus II; 17, Mucro.

Maxillary palp trifurcated, trifurcated trifurcated??

4 sublobal hairs 4 sublobal hairs 3 sublobal hairs

1 basal seta 1 basal seta without basal seta

Outer labial process short long short??

Tables

TABLE 1. Comparison diagnostic characters of Psammisotoma restingae with the four other species known in the genus

Characteristic	restingae sp.nov.	kingae Greenslade & dispar Christiansen & mariagalanteae Deharveng, 1986 Bellinger, 1988 Thibaud, 1993	galapagoensis Thibaud, Najt & Jaquemart, 1994
Body length (mm)	0.65–0.95	1.6–2.2 maximum 1.5 0.45–0.66	0.6–0.9
Colour	light grey	dark grey speckles Th. grey blue-violet II–III; paler posteriorly	grey-bluish