Ballistura rossi Soto-Adames & Giordano

Soto-Adames, Felipe N. & Giordano, Rosanna, 2011, New species of springtails in the Proisotoma genus complex from Vermont and New York, USA with descriptive notes on Ballistura alpa Christiansen & Bellinger 1980 (Hexapoda, Collembola, Isotomidae)., ZooKeys 147, pp. 19-37 : 21-24

Ballistura rossi Soto-Adames & Giordano sp. n.

Material Examined.

Holotype– Female, locality U, slide mounted. Paratypes– locality U, 15 on slides, 3 in alcohol.

Type Locality.

USA,Vermont, Chittenden Co., South Burlington, University of Vermont Constructed Wetland, N 44.45869 W 73.18936.

Etymology.

The new species is dedicated to Ross Bell in celebration of his contributions to our understanding of the entomological fauna of Vermont.

Description.

Length to 0.5 mm. Live individuals black, alcohol preserved specimens (Fig. 1) purple, with pigment more or less uniformly distributed throughout head, body and antennae, legs and manubrium purplish brown. Ant. 4 without basal microsensilla, with 8-9 well developed thin-walled sensilla, and 2-3 additional poorly developed sensilla distributed along distal 2/3 of segment; subapical sense organ with 1 differentiated microsensilla and 1 microrod in a pit. Ant. 3 with 0-1 basal microsensilla; sense organ with 2 clubbed sensilla and 2 differentiated guard sensilla; 1 lateral sensilla present. Ant. 2 with 2 basal microsensilla and 1 distal sensilla. Ant. 1 with 2 basal microsensilla, and 1 whorl of hairs comprising 11 acuminate setae and 2 sensilla. Eyes 8+8, H slightly smaller or subequal to C (Fig. 2), with 3 interocellar setae; PAO circular to elliptical, about 1-1.7X diameter of eye B, and 3 associated setae. Prelabral and labral chaetotaxy 2/554; distal labral margin smooth. Papilla of outer maxillary lobe bifurcate, sublobal plate with 2 appendages. Maxilla with lamella 1 narrow, su rpassing tip of capitulum and ciliate only along external margins. Labial palps with a full complement of papillae and 3 proximal setae; papillae E with blunt lateral process and 6 guard setae, e7 absent; labial triangle with 5 anterior and 4 posterior setae; distribution of postlabial setae in columns I, C, E and L as 3,3,1,3/4 (Fig. 3). Body dorsally covered by smooth hairs; some hairs on the pre-posterior row reaching base of setae on posterior row; tergal macrochaetae undifferentiated; thorax without ventral setae. Axial setae on Th. 2-Abd. 3 as 5-6,4//3,3,3; Th. 3 with 14-16 setae on posterior row; microsensillar and sensillar formulae 10//101 and 33//22224, respectively (Figs. 5-6); antero-lateral sensilla on Th. 2 anterior to microsensilla, lateral sensilla on Th. 2-3 anterior to medial sensilla; medial thoracic sensilla inserted on preposterior row of setae, abdominal sensilla inserted just anterior or on posterior row of setae; lateral sensilla on Abd. 5 similar to medial sensilla (Fig. 6). Proximal and medial subcoxae on legs 1-3 with 1,1; 1,5; 3,5-6 setae. Lateral valve of Abd. 6 with 1 hr seta (Fig. 4). Tibiotarsi on legs 1-3 with 20, 20, 22 setae, respectively; tibiotarsal whorl B with B4/5 (Fig. 7); only male seen apparently in reproductive quiescent instar, without modified metatibiotarsal setae; legs 1-3 with 1, 2, 2 clearly capitate tenent hairs (Fig. 11). Unguis and unguiculus toothless, unguiculus lanceolate or acuminate. Ventral tube with 4+4 apical and 1+1 posterior setae. Tenaculum with 3+3 teeth and 1 seta. Anterior and posterior furcal subcoxae with 8-11 and 4-5 setae, respectively. Proportion manubrium/dens/mucro as 3/2/1. Manubrium with 13 dorsal and 0 ventral setae (Fig. 10). Dens weakly tuberculate, with 11 (12) dorsal (Fig. 9-10) and 5 (4/6) ventral setae (Fig. 8, 10). Mucro bidentate, with a pronounced basal membrane (Figs. 12-13).

Remarks.

Following Potapov (2001), Ballistura rossi sp. n. is most similar to Ballistura hankoi (Stach), 1929 from which it can be distinguished (Table 1) by the number of dorsal manubrial setae (13 in rossei, 20 in hankoi), number of setae around the PAO (3 in rossei, 2 in hankoi), and number of dorsal setae on dens (11-12 in rossi, 10 in hankoi). Ballistura tuberculata (Stach), 1947 (if this is really different from Ballistura hankoi ) can be separated from Ballistura rossi by the same characters of the furcula and PAO as Ballistura hankoi , and by coloration (pale blue-grey in tuberculata, dark purple in rossi), size (largest individual of rossi is 0.5 mm whereas tuberculata reaches 0.9 mm) and, possibly, shape of the basal membrane of the mucro (wider at middle in rossi, wider on basal half in tuberculata). Other chaetotaxic characters may distinguish these three species, but practically nothing has been published about the chaetotaxy Ballistura hankoi or Ballistura tuberculata ( Potapov 2001).

Christiansen and Bellinger (1998) reported Ballistura tuberculata from Indiana and Nova Scotia, but whereas the relatively large size of those individuals (up to 0.8 mm) support the determinationas tuberculata, the relative size of the OPA and shape of the mucronal membrane suggest similarities to hankoi. The specimens from Vermont fit the general description provided by Christiansen and Bellinger (1998) for Ballistura tuberculata , except for the larger number of dorsal setae on the dens and the smaller size of the Vermont specimens (Table 1).

Ballistura rossi sp. n. appears to be unique among Ballistura sp. in having 2 instead of 3 appendages in the sublobal plate of the outer maxillary lobe. However, this character has been reported in relatively few of the species currently placed in Ballistura and further information is needed to determine how unique the condition in Ballistura rossi sp. n. is.