Hypogastrura pizzoci, Fanciulli, Pietro Paolo & Dallai, Romano, 2008

Fanciulli, Pietro Paolo & Dallai, Romano, 2008, Three new species of Collembola from north-east Italy, Zootaxa 1701, pp. 15-28 : 16-19

Hypogastrura pizzoci sp. nov.

Material examined. Type material. Holotype (female) and 9 paratypes (4 females; 5 males) collected in the Cansiglio forest along the road heading toward the top of Mt. Pizzoc, 12.xi.1976. Samples consisted of soil and mosses from a meadow near a pond. Holotype and paratypes are conserved in the collembolan collection of the Department of Evolutionary Biology of the University of Siena.

Description. Body length 0,9–1,0 mm. Body colour dark grey. Tegumental granulation fine; usually ten granules between setae p1 on abdominal tergum V (Fig. 19). Ocular plate with 8+8 ocelli (Figs 9, 20D); post antennal organ consisting of four lobes ( Figs 20 D–E). Antennal segment IV with simple apical vesicle, 4–5 thickened sensilla sometimes similar to setae ( Fig. 8 ), and a microsensillum ( Fig. 20 A); subapical organite not well visible. Antennal organ III with two long and two short sensilla ( Figs 7 , 20 B); microsensillum present ( Fig. 20 C). Antennal segment I, II and III with 7, 13 and 18 setae, respectively ( Fig. 6 ).

Dorsal chaetotaxy of head and body made of short and smooth setae and macrosetae as in Fig. 1 ; ventral chaetotaxy of the head as in Fig. 2 , labium with 6+6 setae. Labial palp with 6 proximal setae, labial papillae A, B, C, D and E with 1, 4, 0, 3 and 6 guard setae, respectively ( Fig. 4 ). Chaetotaxy of the labrum with 5,5,4 setae and four roundish papillae (Fig. 18); maxillary outer lobe with one basal seta and two sublobal hairs (Fig. 18). Maxillary head as in Fig. 3 , with lamellae 1 slightly longer than the maxillary teeth; apical part of lamellae 1 without marginal filaments; mandible with four apical teeth ( Fig. 5 ).

Thoracic tergum I with 3+3 setae, seta m2 present on thoracic tergum II and absent in thoracic tergum III. Seta p2 on abdominal tergum V absent. Ventral part of thorax without setae. Ventral tube with 4+4 setae (Fig. 15), retinaculum with 3+3 teeth (Fig. 11). Male and female genital opening as in Fig. 13 and Fig. 14, respectively. Furca well developed, dens with 6 setae (Fig. 16); mucro lengthened with large lateral lamellae that fold and overlap dorsally (Figs 17, 20F). Ratio dens:mucro = 3:1. Anal spine relatively short positioned on papillae of the same size (Fig. 10).

Tibiotarsi I, II, III with 19, 19, 18 setae respectively, each one with 1 clavate tenent hair (Fig. 12). Claw with inner tooth at 50–55% of the inner ridge; empodial appendage showing a large basal lamella with apical filament nearly reaching the apex of the claw. Subcoxae I, II, III bearing 1, 3, 3 setae, respectively.

Etymology. The species name is derived by the type locality, Mt. Pizzoc.

Discussion. Hypogastrura pizzoci sp. nov. is characterized by a combination of characters that makes it difficult its placement in any of the groups of species proposed by Thibaud et al. (2004). The H. viatica and H. sahlbergi groups have some characters in common with the new species. However the species included in the first group have more than one clavate tenent hairs on the tibiotarsi while Hypogastrura pizzoci sp. nov. shows only one hair on each tibiotarsus. The species belonging to the second group have the retinacle with 4+4 teeth rather than 3+3 as in H. pizzoci sp. nov. According to the taxonomic key proposed by Thibaud et al. (2004) the new species is similar to Hypogastrura ramia Lee & Choe, 1979 , from Korea; but it differs from this species for other features, such as the different shape of the foot complex. In H. ramia the internal tooth is positioned at ¾ of the internal lamella while in H. pizzoci sp. nov. is almost at half of its length. Both species have well developed basal lamella, but in H. ramia the filament is half as long as the internal lamella of the claw, while it is longer in H. pizzoci sp. nov., where it reaches the apex of the claw. Also, the ratio dens:mucro is different: 4: 1 in H. ramia , 3: 1 in H. pizzoci sp. nov. Both species have six setae on the posterior side of the dens but, according to the original description, in H. ramia all setae are of the same size while in the new species the basal seta is clearly longer than the others. Several others species have 6 setae on the posterior side of the dens; among these, the most closely related to the new species is H. boldorii Denis 1931 . It has a similar shape and distribution of setae on the dens and also the same ratio dens:mucro (3:1), however the number of clavate tenent hairs on the tibiotarsi is clearly different: 2, 3, 4 in H. boldorii 1, 1, 1 in H. pizzoci sp. nov. Another species similar to H. pizzoci sp. nov. is H. capitata Cassagnau & Delamare, 1955 ; however the new species can be distinguished for the different size of PAO, that is smaller than in H. capitata , the different ratio FIGURES 9–19. Hypogastrura pizzoci sp. nov.: 9, ocular plate; 10, anal spine; 11, retinacle; 12, foot complex III; 13, male genital opening; 14, female genital opening; 15, chaetotaxy of the ventral tube; 16, furca; 17, mucro; 18, chaetotaxy of labrum and maxillary outer lobe; 19, granules between setae p1 on abdominal tergum five.

dens:mucro (5,4: 1 in H. capitata , 3: 1 in H. pizzoci sp. nov.) and the presence of long and slightly knobbed psetae on the abdomen of H. capitata that are absent in the new species. Also H. fuentei Denis, 1930 , endemic from Spain (see also Jordana et al. 1997) is similar to the new species. They share some common characters such as the ratio dens:mucro (3:1), the retinacle with 3+3 teeth and the ventral tube with 4+4 setae; however they differ each other for the different number of setae on the dens (7 in H. fuentei ; 6 in H. pizzoci sp. nov.) and the shape of the tenent hairs on the tibiotarsi that are clavate in H. pizzoci sp. nov., but pointed in H. fuentei .

Figures

FIGURE 20. Scanning electron microscopy of Hypogastrura pizzoci sp. nov.: A, microsensillum on antennal segment IV; B, sensilla of antennal organ III; C, microsensillum of antennal segment III; D, ocular plate and postantennal organ (PAO); E, higher magnification of PAO; F, mucro.

FIGURES 1 – 8. Hypogastrura pizzoci sp. nov.: 1, habitus and dorsal chaetotaxy; 2, chaetotaxy of labium; 3, head of maxillae; 4, labial palp; 5, mandible; 6, chaetotaxy of antennal segment I, II and III; 7, Antennal organ III; 8, chaetotaxy of antennal segment IV.