Type species.

Troglobius coprophagus Palacios-Vargas & Wilson, 1990

Diagnosis.

Habitus as Entomobryomorpha, eyeless, without pigment. Body with ciliated chaetae and hyaline ovoid scales. Mesothorax and metathorax not humped or bent. Ant. IV not subdivided. Labial chaetotaxy with chaetae: M1, M2, R, E and L1 present, L2 absent. Head bearing two pairs of trichobothria. Mucro elongate, four times as long, or more, than its greatest width, with many serrations along one or both dorsal lamellae. Dens without spines, anterior side covered with scales. A couple of large scale, about the same size as mucro, present on apex of anterior surface of dens. Posterior side of dens with, at least, three rows of chaetae and scales. Some (or most) scales, or thick chaetae, of internal row deeply fringed. In other rows only some distal chaetae modified. Unguis and unguiculus with winged teeth.

Remarks.

The original description places the genus in the family Paronellidae Börner, 1913. Soto-Adames et al. (2008) define the subfamilies Paronellinae and Cyphoderinae as follows:

Separation between Paronellinae and Cyphoderinae is based on the presence of fringed dental scales in the latter and their absence in the former. All cyphoderines are eyeless, whereas the majority of paronellines have eyes. In addition, all cyphoderines have scales, whereas many paronellines lack these scales.

The morphology of the dental scales, the absence of eyes, the shape of mucro and the presence of large scales at the tip of dens, about the same size as mucro, indicate that the genus Troglobius belongs to the subfamily Cyphoderinae (with 128 species distributed among 13 genera of blind Collembola) instead of Paronellinae (with 384 species in 27 genera) as proposed by Bellinger et al. (2013).

In the new proposed diagnosis for the genus, we conclude that the labial chaeta “R” is present, normal shaped, and variable in size, while chaeta L2 is always absent. An additional lateroventral trichobothria, close to the basis of antennae is present in each side of head, this feature is also seen in Cyphoderus, another genus of Cyphoderinae. The genus Troglobius can be differentiated from other Cyphoderinae by the shape of the mucro, which has, at least one lamella serrated.

Type locality.

Brazil, Minas Gerais, Itabirito, Várzea do Lopes. Cave VL29/30, 20°20'05"S, 43°56'18"W. Aphotic zone on water film over the substrate and organic matter, 8 individuals collected.

Holotype. Slide mounted in Hoyer’s solution. Deposited at “Coleção de Referência de Fauna de Solo da Paraíba – Universidade Estadual da Paraíba” (CRFS/UEPB), #2766. Várzea do Lopes, Itabirito, MG, Brazil. Cave VL29/30. 02-06/x/2011. Leg. Speleology team of Carste consultants.

Paratypes. One paratype deposited at Laboratorio de Ecología y Sistemática de Microartrópodos - UNAM (slide #2837 donated from CRFS/UEPB). Várzea do Lopes, Itabitito, MG, Brazil. Cave VL 29/30. Andrade Col. 03-20/XI/2007.

One paratype deposited at Muzeu Nacional – Universidade Federal do Rio de Janeiro - MN/UFRJ (slide #2765 donated from CRFS/UEPB) Várzea do Lopes, Itabitito, MG, Brazil. Cave VL 29/30. 03/IV/2012. Other two paratypes at CRFS/UEPB, under numbers #2838 and 3098, from the same locality as the holotype.

Description.

Habitus of entomobryomorphs (Fig. 1). Length (n = 4) 2.3 mm in average (1.9-2.7 mm). Color pearly white. Body with smooth and ciliated chaetae of different sizes, oval scales hyaline, trichobothria long and ciliated.

Ratio head:antenna 1:2.5, ratio antenna:body length 1:1.9. Ant. I-II with scales. Ratio of Ant. I-IV as 1: 2.6; 2.5; 3.7. Apex of Ant. II with three candle-shaped sensilla, two close to each other and a third laterally displaced (Fig. 2). Apical sensory organ of Ant. III with two candle-shaped sensilla, apical guard chaetae thicker than others. Ant. IV undivided, with rows of chaetae and sensilla or finely ciliated microchaetae, without apical bulb.

Eyes and pigment absent, head with two pairs of trichobothria (Fig. 3A), chaetae Ps5 and Pa5 ciliated. Pre-labral and labral chaetae formula 4/5, 5, 4; all chaetae smooth. Labial triangle with anterior row (A1-5) smooth. All labial triangle chaetae smooth, labial seta R well developed, L2 absent (Fig. 4).

Legs with ciliated setae. Coxa of leg I with one chaeta. Metatrochanteral organ with 21 chaetae forming a “V” and 13 additional short chaetae (Fig. 5). Tenent hairs acuminate, shorter than ventral lamella of unguis (Fig. 6-8); ratio unguis: tenent hair = 1: 0.65. All unguis with two inner basal winged teeth of different sizes; one median inner tooth and one very small tooth at the base of the outer lamella. All unguiculi with well-developed outer lamella and normal sized inner lamella (Figs 6–8).

Abd II with two trichobothria, Abd III-IV with three trichobothria each; Abd. IV with 4+4 lenticular organs on posterior margin (Fig. 9). Posterior surface of ventral tube with 2 long macrochaetae, scales on proximal end, 10 proximal pairs of ciliated chaetae and 11 distal pairs of small smooth chaetae; anterior face with only 2 pairs of ciliated macrochaeta (Fig. 10).

Furcula with scales and ciliated chaetae; mucro, dens and manubrium ratio 1.0:3.8;4.2. The distal end of dens with a pair of large scales, about the same size of mucro (Fig. 11). Dens without spines, normal scales on anterior side, internal row of posterior face with 21 fringed scales (Fig. 12A), median row with one fringed scale (Fig. 13A). Other rows with finely ciliated chaetae in irregular pattern. Mucro elongated, bearing 10–15 teeth on outer lamella, inner lamella smooth with one tooth at the tip.

Etymology.

The name of the new species Troglobius ferroicus sp. n. comes from Latin ferrum (iron) and Greek oikos (house). This makes allusion to the iron caves where the new species was found.

Distribution.

Good’s biogeographic zone 27, northeastern and central Brazil (Good 1974, Culik and Zeppelini 2003). The climate is defined by dry winters and wet summers, with average temperatures of 18 °C during winter and 22 °C in summer.

Habitat.

Troglobius ferroicus sp. n. is found in small (less than 100 m deep) iron-caves, dwelling on water film over the rocks and organic debris in the aphotic zone. The species was found in a single cave, and it is likely to be a troglobite which lives in the in the Mesovoid Shallow Substratum (MSS) (Juberthie et al. 1980) and the adjacent cave.

Conservation status.

This cave is placed in a mining area with iron ores, which represents a putative threat to the species if the cave and surrounding environments, including the MSS, are not preserved. The species was included in the recent evaluation of the Brazilian Fauna Red List, and must be published in the next issue of the Brazilian Red List as Critically endangered (CR).

Remarks.

Troglobius ferroicus sp. n. is the largest species in the genus, adults are 2.3 mm long in average (2-2.8 mm), while other species are about 1.5 mm long (Table 1). It has the longest antennae and ratio of head:antennae (Table 1). Ungual internal unpaired teeth are lacking in Troglobius coprophagus, there are two teeth in Troglobius brasiliensis and a single tooth in Troglobius ferroicus sp. n. Mucronal serration is different in Troglobius brasiliensis, where both edges are serrated, in Troglobius coprophagus and Troglobius ferroicus sp. n. the inner edge is smooth. One important diagnostic feature to differentiate the species is the relative size of mucro and dens, the ratio mucro/dens in Troglobius ferroicus sp. n. is 1:4.0, in Troglobius brasiliensis is 1:3.0 and Troglobius coprophagus 1:2.5. Number and shape of the dental scales can, also, easily differentiate the species (Figs 12–13). Chaeta m2 on Abd. I is lacking in Troglobius ferroicus sp. n., and present in the other two species, and chaeta T1 on Abd. IV is present in Troglobius ferroicus sp. n., but absent in the other two species.

Finally, Troglobius coprophagus was found in La grotte d’Andrafiabe (25°C and 100% of humidity) in  Ankarana, which is a small limestome massif in the extreme North of Madagascar. Troglobius brasiliensis was found in Cave Limoeiro at Pará, North Brazil and Gruta dos Paiva at Sao Paulo, Southeastern Brazil, both in limestone massifs.  The new species Troglobius ferroicus sp. n. was found in one iron cave in the state of Minas Gerais, with very different climate and environmental conditions.