Odontella rapoporti, Arbea & Palacios-Vargas, 2020

Arbea, Javier I. & Palacios-Vargas, José G., 2020, A new species of Odontella from Tierra del Fuego and notes on Afrodontella Deharveng, 1981 (Collembola: Odontellidae), Zootaxa 4808 (3), pp. 526-538 : 527-530

Odontella rapoporti sp. nov.

Figs. 1–19 , Tables 1−3

Type locality. Argentina, Tierra del Fuego Province, near Rio Grande city (53º 36’ S 68º 04’ W) .

Type material. Holotype female, 2 female and 3 juvenile paratypes, Tierra del Fuego Province, near Rio Grande city, Argentina, dense Chiliotrichum scrub, with Festuca gracillima and Chiliotrichum diffusum , leg. S.M. Bonaventura and V. Mascitti, February 2001. Holotype and paratypes deposited in MNCN.

Other material: Argentina, Tierra del Fuego, Ushuaia (54°48’ S, 68°18’ W), Lengal forest (Notophagus pumilio), ex soil, leg. A. Salazar, November 2005, 7 females, 4 males, 2 juveniles, deposited in the collection of the second author, Facultad de Ciencias , UNAM .

Etymology. We have the honor of dedicating the new species to the late Professor Eduardo Hugo Rapoport, the eminent Argentinean ecologist and taxonomist in Collembola.

Description. Holotype female length 0.62 mm, paratype female length 0.59–0.67 mm. Colour in alcohol spotted pale bluish, ocular plate blue-black. Body integument strongly granulated. Central granulated area on head between d3 and d5 chaetae as in Fig. 4 , Th. II tergite granulation between a1 and p1 chaetae as in Fig. 5 , Abd. V–VI tergite granulation as in Fig. 6 .

Antennae 0.7−0.8 of head length. Ant. I, II and III with 7, 10−11 and 18 ordinary chaetae, respectively. AIIIO consisting of two small rounded internal sensory rods and two long, bent, guard sensilla, with ventral ms present ( Figs. 11, 12a ). Ant. IV dorso-distally with small ovoid organite and a short ms; five subcylindrical, bent, subequal sensilla (S2, S3, S6, S7 and S8), an extra S9 sensilla present in one specimen ( Fig. 11 ); very long ventro-subapical blunt chaeta (v); 14−15 long, slender, more or less blunt dorsal mou-chaetae; 10−11 short, pointed chaetae (includ- ing dorsal chaeta i), and 15−16 ventral, short, blunt chaetae. Ant. IV apex with a domed integumentary swelling. Apical exertile vesicle absent. With eversible sac between Ant. III and IV ( Figs 11, 12 ).

Ocelli 5+5. PAO 1.8−1.9× longer than ocellus B, of amoeboid shape with (3)4−5 lobes ( Figs. 3, 7 ). Buccal cone rather short. Maxillae without lamellae; fulcrum with PEP 1.8–2 times shorter than PIP; mandibles reduced ( Fig. 10 ). Labrum very difficult to observe; labral chaetotaxy 4,4,2; two prelabral chaetae. Labium (per half) with five papillate chaetae (two of which are longer) and three short chaetae (A, B, C) on labial palp; four chaetae on submentum: F as macrochaeta, G and f as mesochaetae and E as microchaeta; 6 or 7 chaetae on mentum (a, b, c, d, e, and e’) ( Fig. 9 ). Perilabial area with 4+4 chaetae (a1–4); chaeta a3 longer than a1 and a2, a4 shorter. With 3+3 postlabial subequal chaetae (a1, m1, p1) ( Fig. 9 ).

Dorsal chaetotaxy as in Fig. 1 and Table 1. Dorsally, ordinary body chaetae subequal, smooth and pointed, longer on Abd. V and VI than on Th. I−Abd. IV. Formula of s-chaetae per half tergum: 0,2,2/1,1,1,1,1; position from Th. II to Abd. V: m6+p4, m6+p4/p5, p5, p5, p5, p3. Ms present on Th. II and III. Head without chaeta a0, with chaetae sd2 and c1−4. Th. I with 4+4 chaetae; Th. II and III with 14+14 chaetae, m1, m4, m5 and m6(s) present. Abd. I–III with 11+11 chaetae (a5 absent); Abd. IV with 15+15 chaetae (m3−5 chaetae present, m1 absent); Abd. V with 4+4 chaetae between s-chaetae (a1−2, p1−2). Anal spines absent.

Ventral abdominal chaetotaxy as in Fig. 2 . Th. I−III without chaetae. Ventral tube with 3+3 apical and 1+1 lat- eral chaetae. Abd. II with 4+4 chaetae; Abd. III with 9+9 chaetae. Furcula well developed with 5(4) identical chaetae on each dens; mucro reduced, unilobed, 5−6 times shorter than dens ( Figs. 15−16 ). Manubrium with 17−18+17−18 posterior chaetae. Retinaculum with 3+3 teeth. Genital plate with ca. 10 chaetae in females and ca. 14 chaetae in males ( Fig. 8 ). Each anal valve with three hr−chaetae.

Tibiotarsi I, II and III with 18, 18 and 17 pointed chaetae (11+7, 11+7 and 11+6), respectively; without chaetae M on all legs, tibiotarsus III also lacking chaeta B6 ( Figs. 13, 14 ). Subcoxa 1, subcoxa 2, coxa, trochanter and femur with 1/2/2; 0/3/3; 3/4/5; 6/6−7/6; 13/12−13/12 chaetae on legs I, II and III, respectively. Claws without teeth. Empodial appendage absent.

Variations. Despite the relative low number of material, five notable types of variation were detected within it. The bulk of the type material has 5+5 chaetae on the dentes, except one female that has 4+5 chaetae; most of specimens from Ushuaia have 5+5 dental chaetae, whereas some have 4−5, or even 3 chaetae on the dens ( Figs 16−17 ). One female from Ushuaia has 5+5 chaetae on Th. I tergite (4+4 chaetae in other specimens). One female from Ushuaia has 6 sensilla on Ant. IV, with S9 ( Fig. 10 ) (absent in other specimens, Fig 11 ). Two specimens from Ushuaia have 3+4 vesicles in the PAO ( Fig. 7 ). One retinaculum possesses 4+3 teeth.

Description of juvenile specimens. In Figs. 18−19 and Table 2 are represented the chaetotaxy in juvenile spec- imens. Body length (without antennae) 0.45−0.49 mm. PAO is similar to that of adults. Sensory complex on Ant. IV consisting of one (S7) to four (S2, S3, S6, S7) sensilla. Head and body chaetotaxy less developed than in adult ( Figs. 18 and 19 ). Head dorsal, Th. I and Abd. V-VI tergites as in adults; Th. II and III tergites with 11+11 chaetae (a4, a5 and m4 absent); Abd. I–III tergites with 9+9 chaetae (a6 and p4 absent); Abd. IV tergite with 13+13 chaetae (m5 and p4 absent); head ventral with 2+2 postlabial chaetae (m1 absent); ventral tube without lateral chaetae; Abd. II and III sternites with 3+3 and 4+4 chaetae, respectively.

Discussion. The new species belongs to Deharveng’s (1981) lobata group without ventral sensorial file on Ant. IV, without spines on anterior border of labium and without anal spines, and with ventro-apical vesicle on dens and mucro reduced. According to the number of dental chaetae, sensilla on Ant. IV and dorsal chaetotaxy the new species is most similar to Odontella lobata ; they differ in the number of tibiotarsal chaetae. For the latter character, the new species is close to O. setosa ; but they differ by other characters (Ant. IV sensilla, chaetae on dens… see Table 3).

The monotypic genus Afrodontella is related to the new species by the furcula structure: reduced mucro and dens with a large ventro-apical vesicle. This has led us to redescribe the type species of this genus, A. septemlobata , in order to establish the differences and similarities between Afrodontella and the species of the Odontella lobata group. Main differences between O. rapoporti sp. nov. and these species are summarized in Table 3.

Figures

FIGURES 1–8. Odontella rapoporti sp. nov.: 1, dorsal chaetotaxy; 2, ventral abdominal chaetotaxy; 3, PAO and ocelli; 4, central area of head between d1 and d5 chaetae; 5, central area of Abd. II tergite between a1 and p1 chaetae; 6, Abd. V and VI tergites; 7, PAO; 8, male genital plate. Scales: 0.1 mm (1,2), 0.02 mm (3,4,5,6,7), 0.05 mm (8).

FIGURES 9–17. Odontella rapoporti sp. nov.: 9, labial and perilabial chaetotaxy; 10, maxilla and mandible; 11, antennal chae- totaxy; 12, Ant. III and IV dorsally (12a) and ventrally (12b); 13, Tibiotarsus and claw II; 14, Tibiotarsus and claw III dorsally (14a) and ventrally (14b); 15, typical dens and mucro; 16–17, dens and mucro of two specimens from Ushuaia. Scales: 0.02 mm.

FIGURES 18–19. Odontella rapoporti sp. nov., juvenile specimen: 18, dorsal chaetotaxy; 19, ventral chaetotaxy. Scale: 0.1 mm.