Simopelta anomma, Fernandes, Itanna O., Souza, Jorge L. P., Fernández, Fernando, Delabie, Jacques H. C. & Schultz, Ted R., 2015

Fernandes, Itanna O., Souza, Jorge L. P., Fernández, Fernando, Delabie, Jacques H. C. & Schultz, Ted R., 2015, A new species of Simopelta (Hymenoptera: Formicidae: Ponerinae) from Brazil and Costa Rica, Zootaxa 3956 (2), pp. 295-300 : 297-299

Simopelta anomma sp. nov.

( Figures 1–3 )

Type material. Holotype worker: BRAZIL, Rondônia, Rio Madeira (módulo da Ilha do Búfalo), 09°08’18”S, 64°29’22”W, km 2, subparcela 200, 19.i.2014, leg. A. H. C. Oliveira, pin labeled USNMENT00923312 ( INPA). One paratype: same data as the holotype, but pin labeled USNMENT00923313 ( MZSP).

Additional material. COSTA RICA, 1 worker, Cordillera Volcanica Central, La Selva Biological Station (Conservation International's TEAM Project), 10°24’35”N, 84°02’21”W, 160 m elevation, 26.vii.2006, Winkler sample, pin labeled INB0003695155, AMI–2–W–088–08, leg. M. Marcos, H. Gilberth & C. Felix ( INBio).

Diagnosis (worker). Eyes absent; antennal club 3–segmented; midtibiae covered by short, golden, stout setae; arolia reduced and translucent; ventral petiolar process rounded; body yellow.

Measurements, workers (n=2): HL: 0.464–0.480; HW: 0.400–0.416; SL: 0.288–0.320; WL: 0.672–0.720; PW: 0.264–0.288; NH: 0.168–0.192; NL: 0.168–0.192; GL: 0.840–0.984; TL: 2.160–2.360.

Description. Head rectangular, sides almost straight and parallel with one another, occipital corners rounded. Mandibles subtriangular with acute basal tooth, two closely spaced apical teeth, and no teeth or denticles between basal and apical teeth; eyes absent; antennae with 12 segments; antennal scapes not extending beyond posterior cephalic margin; antennae with distinct 3-segmented club; last funicular segment as long as the preceding three together; frontal lobes elevated by a narrow and deep furrow; clypeus triangular, elevated in the middle, with a sharp and almost cylindrical median spine. Pronotum as long as the propodeum; laterocervical plate inflated; promesonotal groove well marked. Metanotal groove deep dorsally and well marked laterally; katepisternum and anepisternum not separated by a suture. Propodeum in dorsal view subrectangular with posterior superior corners slightly rounded; in lateral view, propodeal spiracles round, large, almost reaching the dorsal surface. Petiole in lateral view as long as high, subquadrate, with subparallel anterior and posterior sides; ventral petiolar process rounded. Gaster with constriction between abdominal segment III and IV; coxae, femurs, and tibiae robust; arolia reduced and translucent.

Body predominantly yellow. Mandibles and legs smooth and shiny. Head and antennae finely punctulate and shiny. Mesosoma finely punctulate and shining laterally.

Body covered with fine, short, golden hairs, most abundant on the dorsal surface; middle area of clypeus and mandibles along the masticatory border with long, subdecumbent, golden hairs; sparse golden hairs on the coxae, trochanters, and femurs; pectinate spur present on the legs; tibiae on the forelegs and hindlegs covered by thick, short, golden hairs on the ventral surface; tibiae on the middle legs with abundant, golden, stout setae on all surfaces; tarsus covered by short, golden, stout setae, more abundant on the ventral surface.

Etymology of the species name. Greek origin: an= without and omma =eyes, due the absence of eyes.

Distribution. Costa Rica, La Selva Biological Station (Cordillera Volcanica Central); Brazil (Rondônia, Ilha do Búfalo–Rio Madeira).

Discussion. The combination of eyes absent, yellow coloration, a distinct 3-segmented antennal club, and midtibia covered by short, golden, stout setae has so far never been documented in a species of Simopelta . As a result, we modify Schmidt and Shattuck's (2014) generic diagnosis as follows: subtriangular mandibles; raised clypeal rostrum; eyes small or absent, when present often consisting of only a single enlarged ommatidium; metapleural gland orifice with a posterior U-shaped lip; usually an absence of stout traction setae on the middle and hind legs (present in S. anomma ); and usually with prominent arolia (highly reduced in S. anomma ).

The form of the clypeus, mesosoma, petiole, and the gastral constriction in S. anomma are similar to those in S. pergandei , but eyes are present in the latter species. Simopelta minima (Brandão) is also similar to S. anomma in total length (TL: 2.08–2.40) and presence of the clypeal spine, but, again, differs by the presence of eyes, as well as in its 4-segmented antennal club; lack of short, golden, stout setae on the midtibia; triangular anteroventral petiolar process; finer sculpture; and darker color. Simopelta anomma is apparently a member of the curvata species complex created by Mackay and Mackay (2008) due to the presence of an elongate spine on the median border of the clypeus and the total length less than 4mm.

The robust forecoxa, lack of eyes, and clubbed (3-segmented) antennae of S. anomma all suggest that the species is subterranean. Most cryptobiotic ponerines have at least moderately clubbed antennae, which may facilitate movement and prey detection in lightless conditions ( Schmidt & Shattuck 2014). The legs are often short and stocky, and are sometimes armed with stout setae to facilitate traction in soil or wood (present in Centromyrmex , Feroponera , Promyopias , and most Cryptopone species) ( Schmidt & Shattuck 2014). According to Schmidt and Shattuck (2014), cryptobiotic ponerines are typically small-bodied, extremely so in many Cryptopone , Dolioponera , Hypoponera , and Ponera species. The eyes are typically greatly reduced in size or even entirely absent (including in Boloponera , Centromyrmex , Dolioponera , Feroponera , Promyopias , and some Cryptopone and Hypoponera species). Although these characteristics strongly suggest that S. anomma may be mostly or entirely subterranean, the fact that the three known specimens were collected by Winkler leaf-litter sifting suggests that it may occasionally forage above ground in the leaf litter.

The area where the workers were sampled in Rondônia ( Ilha do Búfalo, Rio Madeira, km 2–subparcela 200) is part of a conservation monitoring project supported by the Santo Antônio Energia Hydroelectric Plant. At the time when the ants were collected, the water level of the Madeira River had risen 19 m above the maximum limit for the first time in four years of monitoring. Due to the elevation of the river water, the groundwater was also climbing, perhaps forcing normally subterranean species to the surface (Fernandes et al. in press). Following the elevation of the river water no additional specimens of S. anomma were encountered.

Virtually nothing is known about the life histories, population structures, or reproductive biologies of most rare ant species ( Brandão et al. 2008). Rare species may have low population densities at the localities in which they are collected for a variety of reasons. They may be rare immigrants from a nearby source locality in which they are more populous, e.g., rare epigaeic foragers of a mostly subterranean species; they may be temporarily rare due to fluctuations in population size; or they may represent remnants of a declining population or the first individuals of an increasing population ( Longino & Colwell 1997). The rarity of this species and S. jeckylli (reported below) is perhaps explained by inadequate sampling of their microhabitat. Winkler extraction or other common sampling techniques (see Bestelmeyer et al. 2000) may be inadequate for sampling some cryptobiotic ant assemblages, including subterranean species. The discovery of the S. anomma emphasizes the need for increased exploration of subterranean ant diversity.

Figures

FIGURES 1 – 3. Holotype of Simopelta anomma sp. nov.. in full – face, lateral, and dorsal view.