Isotomodes tyrrhenicus, Fanciulli, Pietro Paolo, Dallai, Romano & Meneguz, Marco, 2015

Fanciulli, Pietro Paolo, Dallai, Romano & Meneguz, Marco, 2015, A new littoral interstitial species of the genus Isotomodes (Collembola, Isotomidae) from Italy, Zootaxa 3931 (2), pp. 293-297 : 293-297

Isotomodes tyrrhenicus sp. nov.

Figs 1–3 , Tab. 1

Type locality. Specimens of the new species were collected in the littoral sand dune of the regional park of S. Rossore (Tuscany) (43°47’12.5’’N, 10°16’09.7’’).

Type material. Holotype (female) and 10 paratypes (7 females and 3 males). All types deposited in the Collembola collection of the Department of Life Sciences, University of Siena.

Description. Length of holotype and paratypes about 0.6-0.7 mm. Eyes and body pigment absent, cuticle granulation fine and regularly distributed. Antennae longer than the cephalic diagonal (A/d = 1.2). Ant. I with 12 setae, one dorsal microseta and two ventral sensilla of different length ( Fig. 1A ); Ant. II with 14 setae, three basal microsetae and one ventral sensillum ( Fig. 1A ). Ant. III with 20-23 setae; Ant. III sensory organ formed by two globular sensilla placed in two cuticular pits, two curved and subcylindrical guard sensilla and one ventrolateral thinner sensillum ( Fig. 1A ). Ant. IV with about 15 subcylindrical dorsal sensilla and several ordinary setae ( Fig. 1A , 3B ); subapical organite and microsensillum present ( Fig. 1B ). Basomedial field (submentum) with 4 +4 setae, basolateral field (mentum) with 5 setae ( Fig. 1F ). Labial palp with four papillae (A, B, D, E) with 1, 2, 2, 2 guard setae respectively. Lateral process of labial palp thicker, similar to basal papilla with a blunt roundish apex ( Fig. 1H ). Labrum with 3/4,4,4 setae ( Fig. 3C ). PAO elliptical, slightly narrower than the base of the antenna with six posterior setae ( Fig. 1C , 3E ). Tibiotarsi I, II and III with 21, 21 and 21–22 acuminate setae respectively (Fig. 2E). Claw without internal teeth, empodium lanceolate half as long as the claw. Head with 5+5 setae along the ventral line (Fig. 2C); thoracic sternites I, II and III with 2, 2 and 4 setae (Fig. 2C) FIGURES 2A–F. Isotomodes tyrrhenicus sp. nov.: A, dorsal chaetotaxy; B, distribution of macrosetae (M), accp sensilla (accessory to the p row), lateral sensilla (al) and microsensilla (ms); C, ventral chaetotaxy; D, chaetotaxy of the head showing the five unequal dorsomedial setae (eg. A0); E, chaetotaxy of leg III; F, chaetotaxy of abdominal segmants IV–VI.

VT with 5 + 5 distal setae and 2 +2 proximal setae ( Fig. 1G , 3D ). Furca well developed, manubrium longer than dens with 10-11 +10-11 posterior setae; dens with 2 posterior setae of different lengths and 4 anterior setae; mucro bidentate ( Fig. 1E , 3A ). Retinaculum with 3 teeth and one seta on the body. Female genital opening with 2+2 setae on anterior and 1+1 on posterior valve, male genital opening as shown in Fig. 1D . Dorsal and ventral body chaetotaxy as in Fig. 2 A and 2C; head with five unequal dorsomedial setae including A0 (Fig. 2D). Axial dorsal chaetotaxy of the thorax and abdomen as follows: 7,6 / 4,4,5. Dorsal macrochaetotaxy: 1,1 / 3,3,3,2+2; sensillar chaetotaxy (accp): 1,1 / 2,2,2,1. Lateral sensilla: 3,2 / 0 0 0 0 (Fig. 2B). Abd. V + VI with one ventro lateral sensillum close to the setae P5 and P6 (Fig. 2F). There are 10 setae between the macrosetae S1 and 2 between macrosetae S2. 5 microsetae m present. The posterior row of setae on the abdominal segment IV includes 25 setae between lateral accp sensilla, one of them unequal (P0) and the others as 5 thick setae (P1, P3, P5, P6, P10) and 7 thin setae (P2, P4, P7, P8, P9, P11, P12) (Fig. 2F). Abd. tergite V with 4 +4 thin setae (one of them longer than the others), 2 long dorsal macrosetae and 1 +1 microsensilla. Chaetotaxy of abdominal segment VI consists of some spine-like and slightly barbulate setae (P0, P1, P3, P4) while the others are long, thin and smooth setae (P2, P5 and P6).

Remarks. The new species is closely related to Isotomodes alavensis Simón, Luciáñez, Ruiz & Martin, 1994 from which it can be separated by the different number of setae on the ventral tube (4+ 4 in I. alavensis against 5+ 5 in I. thyrrenicus sp. nov.). Further differences are in the type of setae on the VI abdominal tergites (P4 spine-like and slightly barbulate in I. thyrrenicus sp. nov., ordinary seta in I. alavensis ); moreover I. thyrrenicus sp. nov. has P12 on Abd. IV while it is absent in I. alavensis . Others 5 species of Isotomodes have 5+5 distal setae on the ventral tube as I. thyrrenicus sp. nov. but they can be distinguished by the different chaetotaxy of dens ( Tab. 1 ): I. thyrrenicus sp. nov. (dens anterior setae= 4; posterior= 2), I. gisini Gama, 1963 (ant.= 2; post.= 2), I. maroccanus Stach, 1947 (ant.= 1; post.= 2), I. productus ( Axelson, 1906) (ant.= 1; post.= 2), I. sexsetosus Gama, 1963 (ant.= 6; post.=2) and I. sotoensis Simon et al 1994 (ant.= 5; post.=2).

Etymology. The name of the new species refers to the Tyrrhenian Sea that is just in front of the beach in which it was found.

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Figures

FIGURES 1 A – H. Isotomodes tyrrhenicus sp. nov.: A, antenna dorsal view: B, apex of Ant. IV showing the organite and the microsensillum; C, postantennal organ; D, male genital opening; E, furca; F, basomedial (submentum) and basolateral (mentum) fields; G, ventral tube; H, labial palp (A, B, D, E = labial papillae).

FIGURES 3 A – E. Isotomodes tyrrhenicus sp. nov., scanning electron microscopy: A, dens and mucro; B, antennal segment IV dorsal view; C, labrum; D, ventral tube; E, postantennal organ.

Tables

TABLE 1. Characters comparison between I. thyrrenicus sp. nov. and some closely related species. * SSLM = smooth spin like macroseta, BSLM = barbulated spin like macrosetae; ** a = spiniform slightly barbulate; b = ordinary setae.

Species	number of laterodistal setae on VT	number of setae on posterior margin of PAO	number of anterior setae on dens	presence/ absence of p12 seta on Abd. IV	presence/absence and shape of macroseta on Abd. V*	Shape of P setae on Abd. VI**
I. thyrrenicus sp. nov.	5+5	6	4	present	1+1 SSLM	a=P0,P1,P3,P4; b=P2,P5,P6
I. alavensis	4+4	6-7	4	absent	1+1 SSLM	a=P0,P1,P3; b=P2,P4,P5,P6
I. gisini	5+5	5	2	absent	0+0	b=P0,P1,P2,P3,P4,P5,P6
I. marroccanus	5+5	6	1	present	0+0	b=P0,P1,P2,P3,P4,P5,P6
I. productus	5+5	7	1	present	1+1 SSLM	b=P0,P1,P2,P3,P4,P5,P6
I. sexsetosus	5+5	6	6	absent	0+0	b=P0,P1,P2,P3,P4,P5,P6
I. sotoensis	5+5	6-7	5	absent	1+1 BSLM	a=P1,P3; b P0,P2,P4,P5,P6
References