A new species of Furculanurida is described and illustrated. Furculanurida bistribus sp. nov. differs from other species of the genus by the presence of three eyes, three setae on the dens, and the white and purple coloration pattern. A key for identification of the world species of the genus is included.

Island, Luquillo Experimental Forest, subtropical forest, taxonomy

In Puerto Rico, most studies of arthropod community dynamics have been done in the Luquillo Mountains. Designated as a US Experimental Forest in 1956, it became part of the International Network of Biosphere Reserves in 1976 (González and Barberena 2018; Quiñones et al. 2018; Richardson 1999). Four easily distinguishable forest types are dominated by an assortment of distinctive tree species. The Tabonuco forest (Dacryodes excelsa Vahl) occupies areas below 600 m, in the mid-elevation zone. Palo Colorado forest (Cyrilla racemiflora L.) occurs in areas above the cloud condensation level from 600 to 900 m a.s.l. The Elfin forest (dominant tree Tabebuia rigida Urban), with stunted vegetation and waterlogged anoxic soils, is located only on the highest peaks above 900 m. Palm forests (Prestoea montana (R. Grah.) Nichols) occur at all elevations, predominantly on windward slopes, in wet gullies, and in stream valleys (Gould et al. 2006). These forests represent subtropical wet and subtropical rain forest life zones in Puerto Rico (Ewel and Whitmore 1973).

In most studies of litter and soil fauna in the Luquillo Experimental Forests (hereafter LEF), Collembola are an important group because of their numerical dominance, combined with their key responses to changes in disturbance, altitude, and vegetation type (Schowalter and Ganio 1999; Schowalter et al. 2003; Richardson et al. 2005; Richardson et al. 2010; Schowalter et al. 2014). In Puerto Rico, Collembola are well known in comparison to other groups of soil arthropods. However, not all Collembola species from LEF have been identified.

In a recent survey between 2014 and 2015, we identified 16 families (sensu Deharveng 2004; Soto-Adames et al. 2008; Bellinger et al. 1996–2019), 37 genera, and probably 60 species, of which 15 are new. As a result of this survey, the inventory of Collembola in the LEF increased to 44 genera and 70 species. The purpose of this paper is to describe a new species of Furculanurida Massoud, 1967, a genus not previously reported from Puerto Rico.

The genus Furculanurida was created to relocate Micranurida africana Massoud, 1963 because of the development of its furcula (Massoud 1967). The main characters of this genus have been discussed previously (Palacios-Vargas and Gao 2009; Queiroz and Fernandes 2011; Zon et al. 2014, Neves et al., 2019), and some species are dubiously placed within Furculanurida (Table 1). To date, the genus has 16 nominal species distributed in the Neotropical, Ethiopian, and Nearctic regions, with seven, six, and one described species, respectively. Reported in the Neotropical Region are F. arawakensis Thibaud & Massoud, 1983 from the Lesser Antilles; F. guatemalensis Palacios-Vargas & Gao, 2009 and F. septemoculata Palacios-Vargas & Gao, 2009 from Guatemala; F. nessimiani Fernandes & Mendonça 2002, F. belemensis Arlé & Rufino, 1976, F. goeldiana Arlé & Rufino, 1976, and F. tropicalia Queiroz & Fernandes, 2011 from Brazil; and F. longisensillata Najt, Thibaud & Weiner, 1990 from French Guiana.

Initially, the genus Furculanurida was established using the combination of the following characters: postantennal organ (PAO) present, eyes absent, maxilla styliform, and furcula present (Massoud 1967). According to Queiroz and Fernandes (2011) species of the genus have Ant IV with a trilobed apical bulb, dorsolateral microsensillum present or absent, 4–7 sensilla, and long ordinary setae; PAO circular or elliptical with 4–22 vesicles; eyes from zero to eight per side; mandible with 2–10 teeth; maxilla styliform with two fused lamellae; tenent hair on tibiotarsi acuminated; ventral tube with 3 or 4 setae on each side; tenaculum with 2 or 3 teeth on each ramus; furcula complete, with well-developed dens and mucro; dens with 5 or 6 setae on each side; mucro separated from dens and with two tapering lamellae, sensilla on body always long. However, the more recently described Furculanurida species include specimens without the full development of the furcula (Zon et al. 2014). Zon et al. concluded that Furculanurida can only be separated from Pseudachorutes Tullberg, 1871 by a conditional combination of characters, i.e., “eyes less than 8+8, or, when 8+8, microchaeta ms absent on Ant. IV”. Similarly, differences with Stachorutes Dallai, 1973 would be “mucrodens complete, or, if mucro absent, ms absent on Ant. IV” (Zon et al. 2014: 496). Therefore, these genera need an extensive revision to clarify the morphological differences between them.

Furculanurida bistribus sp. nov. is placed in Furculanurida because many of its characters are similar with those of the other species of that genus, and it matches the current genus diagnosis: apical bulb trilobed, long setae present on Ant IV, maxilla styliform, furcula fully developed, and ordinary setae on the body short but sensory setae long (Queiroz and Fernandes 2011). Although the presence of one tooth on the unguis is observed in most Furculanurida, there are two exceptions where the unguis is toothless: F. africana and the new species described here. In any case, the inner tooth on the claw is usually considered as a specific, not a generic character (Zon et al. 2014). The antennal chaetotaxy is also useful to characterize the genus; the new species has antennal characters of Furculanurida: apical vesicle trilobed, microsensillum absent, and presence of six S-sensilla and long setae on Ant IV (Queiroz and Fernandes 2011). The low number of dental setae is a character shared with Hypanurida perplexa Salmon, 1956, but the position of this species is controversial because of the reduction of the furcula (Queiroz and Fernandes 2011).

Although morphological characters, including furcal reduction, appear similar between some Furculanurida (including F. bistribus sp. nov.) and Stachorutes (Zon et al. 2014), the geographic separation of the two genera is remarkable. The genus Furculanurida was established for three sub-Saharan African neanurids: Micranurida africana, Kenyura furculata Salmon,1956, and Hypanurida perplexa (see Massoud 1967). Subsequently, other species were described or included in Furculanurida from the Lesser Antilles, Guatemala, Brazil, French Guiana, Tanzania, Morocco, Nepal, and Ivory Coast (Queiroz and Fernandes 2011; Zon et al. 2014). The genus, thus, conforms to a general Gondwanan distribution, with a few exceptions, like Furculanurida langdoni which is found in North America. In contrast, Stachorutes exhibits mostly an Holarctic distribution, with species known from China, France, Poland, Russia, Slovakia, Spain, and North America, except for a single species from Africa (Tanzania) (Simon-Benito et al. 2005; Fanciulli et al. 2017).

According to Queiroz and Zeppelini (2017), there are key diagnostic characters that define two groups of Pseudachorutinae in the Neotropics, which are chaetotaxy of antennae, head, thorax, and tibiotarsi. Furculanurida bistribus sp. nov. exhibits many similarities with Arlesia group of genera. In the antennal chaetotaxy, the only difference was the absence of S10 sensu Queiroz and Zeppelini (2017). Regarding head and thorax chaetotaxy, the main characters are similar, i.e. the absence of setae c2 and c3 and the presence of p1, p2 and p3 on head, the presence of only 2+2 setae on Th I, and one posterior setae displaced laterally on Th II and III. In consequence, this description reinforces the need for a revision of Furculanurida, as not only F. bistribus sp. nov. but possibly other species of Furculanurida might present characters that fit the pattern displayed by the Arlesia-group of genera sensu Queiroz and Zeppelini (2017).

Despite the differences of the new species with the most recent genus diagnosis of Furculanurida (Queiroz and Fernandes 2011), we place F. bistribus sp. nov. in this genus because of the fully developed furcula in this species (Fig. 11) and its distribution, despite the number of setae on the dens. Inclusion of the new species in this genus thereby enlarges the generic diagnosis to include species with 3–6 setae on the dens. The characters that place the new species close to Stachorutes are of uncertain generic value and need more studies (Bernard 2007; Zon et al. 2014, Neves et al. 2019).

Furculanurida bistribus sp. nov. has this unique combination of characters: six sensilla on Ant IV, 3+3 eyes, three setae in the dens, and the absence of an internal tooth on the unguis, combined with its color pattern. Members of Furculanurida have between zero and eight eyes per side; F. bistribus sp. nov. has 3+3 eyes, though some specimens of F. arawakensis may have this number (usually 4+4 eyes). All the described species have a fully developed furcula, but more dental chaetae than the new species. Leaving aside the unique characters of F. bistribus sp. nov., it is more similar to F. arawakensis from which it differs by the presence of four teeth on mandibles (versus seven), less dental chaetae (3 versus 6), and the absence of tooth on unguis. The differences between all the species of the genus are summarized in Table 2.

This research was supported by Grant DEB 1239764 and 1546686 from the US National Science Foundation to the Institute for Tropical Ecosystem Studies, University of Puerto Rico, and to the International Institute of Tropical Forestry (IITF) USDA Forest Service, as part of the Luquillo Long-Term Ecological Research Program. The US Forest Service (Department of Agriculture) Research and Development Unit and the University of Puerto Rico provided additional support. We also thank to María M. Rivera (IITF) who helped with fieldwork and Edward Quigley assisted with the digitization of the figures.