Dicranocentrus dolosus, Bellini & Greenslade & Baquero & Jordana & Souza, 2022

Bellini, Bruno Cavalcante, Greenslade, Penelope, Baquero, Enrique, Jordana, Rafael & Souza, Paolla Gabryelle Cavalcante De, 2022, A synthesis of the current knowledge on the Australian Orchesellidae (Collembola, Entomobryoidea), Zootaxa 5115 (2), pp. 221-257 : 224-231

publication ID	https://doi.org/ 10.11646/zootaxa.5115.2.3
publication LSID	lsid:zoobank.org:pub:52305F19-9185-448D-AE5C-AE90353C7460
DOI	https://doi.org/10.5281/zenodo.6352292
persistent identifier	https://treatment.plazi.org/id/B14287AA-FF94-7051-3E83-B315FC1BF8AB
treatment provided by	Plazi
scientific name	Dicranocentrus dolosus
status	sp. nov.

Treatment

Dicranocentrus dolosus View in CoL sp. nov. Bellini, Greenslade & Souza

Figs 2–8 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6 View FIGURE 7 View FIGURE 8 , Table 1 View TABLE 1

Type material. Holotype female in slide ( MVMA), with one specimen from the type series of Falcomurus pulukokos : Australia, Cocos and Keeling Islands, West Island (12°09’S 96°49’E), v–vi.2005, leaf litter light trap near the beach, A. Yen coll. GoogleMaps Paratypes three females in slides ( MVMA), one in the same slide of the holotype, the other two in a second slide, with another specimen from the type series of Falcomurus pulukokos , same data of holotype GoogleMaps .

Diagnosis. Four needle-like labral papillae present. Dorsal head with M3, S0, S2, Pa2–3e, Pm3, Pp2–3, Pp5, Pe2–3 mac, A1, M4, and Ps series as mic (sundanensis group sensu Mari-Mutt 1979), with 3 interocular mes. Labial papilla E lateral process short and finger-shaped, not reaching the papilla apex. Labial basomedian field with 0–3 posterior ciliate chaetae internal to e, labium unscaled. Ventral head postlabial chaetatoxy with anterior chaetae smooth and posterior ciliate, including the basal chaeta. Th. II to Abd. IV formula of central mac as: 12,9|3,2,2,3; Abd. V with four sens. Trochanteral organ with about 20 chaetae. Tibiotarsi without smooth chaetae with the exception of the distal one on tibiotarsus III. Tenent hairs clearly capitate; unguis with two unpaired internal teeth; unguiculus (empodium) lanceolate, postero-external lamella smooth (toothless). Ventral tube (collophore) anterior face with one distal mac plus 10–12 ciliate chaetae, lateral flap with about 19–20 smooth chaetae, with the exception of 0–1 small ciliate chaeta. Manubrium without smooth chaetae, dental lobe with a regular ciliate chaeta, dens without spines, mucro posterior tooth shorter than the distal one.

Description. Habitus typical of the genus ( Fig. 2 View FIGURE 2 ). Body length (body + trunk) of holotype = 1.54 mm; range of type series length = 1.35–1.99 mm. Colour pattern unknown. Coarsely ciliate scales present on Ant. I–II, head (dorsally and ventrally), dorsal trunk, legs (all segments), ventral manubrium and ventral dens; ventral tube unscaled.

Head ( Figs 3–4 View FIGURE 3 View FIGURE 4 ): Antennal ratio Ant. Ia–IV | head of holotype = 1: 6.5: 1.5: 8:?: 29.5 | 20.5; antennal ratio of type series = 1: 5–6.7: 1.5–2: 6.7–8: 15: 21–29.5 | 14–20.5. Ant. IV with a ventral, almost apical, bifurcated pin projection, dorsally with 1–3 swollen subapical sens ( Fig. 3A View FIGURE 3 ). Ant. III sense organ with two slightly swollen sensory rods, guard sensilla not seen, with one swollen extra sens on the dorsal side ( Fig. 3B View FIGURE 3 ). Ant. IIb apically with two swollen sensory rods, similar to the Ant. III sense organ; Ant. IIb and Ib with one and three ventral smooth acuminate chaetae, respectively ( Figs 3C–D View FIGURE 3 ). All four labral papillae present and subequal, needle-shaped ( Fig. 3E View FIGURE 3 ); Labral formula with four (a1–2), five (m0–2), five (p0–2) smooth chaetae, p0–2 longer than the others, a chaetae slender, prelabral chaetae larger than the labral ones ( Fig. 3F View FIGURE 3 ). Eyepatches lenses A–F subequal, G–H smaller than the others, with three interocular mes ( Fig. 3G View FIGURE 3 ). Head dorsal chaetotaxy with antennal (An) row with 7–8 mac, anterior (A) row with five (A0, A2–3, A5–6), medial (M) row with three (M1–3), sutural (S) row with eight (S0–6), post-occipital anterior (Pa) row with four (Pa2–3e, Pa5), post-occipital medial (Pm) row with one (Pm3), post-occipital posterior (Pp) row with three (Pp2–3, Pp5), and post-occipital external (Pe) row with two (Pe2–3) mac, respectively; further details are represented in Fig. 3G View FIGURE 3 . Labium with six papillae (H, A–E), with 2, 0, 5, 0, 4, 5 guard chaetae respectively, papilla E lateral process (l.p.) short and finger-shaped, not reaching the papilla apex ( Fig. 4A View FIGURE 4 ); five proximal chaetae subequal in size (an1–3, p2–p3) ( Fig. 4A View FIGURE 4 ). Labial basomedial (submentum or labial triangle) and basolateral (mentum) fields with chaetae a1–5, e, l1–2 smooth, a5 reduced, l2 larger than l1, 3–6 posterior chaetae internal to e (m field, including m1–2 and r with unclear positions), with 0–3 of them ciliate, labium unscaled ( Fig. 4B View FIGURE 4 ). Maxillary outer lobe basal chaeta acuminate, slender and rough, subequal to the apical one; sublobal plate with four chaeta-like appendages, lateral one slightly reduced ( Fig. 4C View FIGURE 4 ). Post-labial chaetotaxy complex, with the anterior chaetae smooth (including the post-labial quadrangle and the transversal row just above the labium) and posterior chaetae ciliate, including the basal chaeta ( Fig. 4D View FIGURE 4 ).

Trunk dorsal chaetotaxy ( Figs 5–6 View FIGURE 5 View FIGURE 6 ): Th. II, excluding the anterior collar, with one anterior (a5), four medial (m1–2, m4–4i), and seven posterior (p1–5) mac ( Fig. 5A View FIGURE 5 ). Th. III with eight anterior (a1–7), two medial (m6ai, m7), and three posterior (p1–3) mac ( Fig. 5B View FIGURE 5 ). Abd. I with three medial (m2–4) mac ( Fig. 5C View FIGURE 5 ). Abd. II with three medial (m3–3e, m5) mac ( Fig. 5D View FIGURE 5 ). Abd. III with one anterior (a3), two medial (m3 and pm6), and one posterior (p6) mac ( Fig. 6A View FIGURE 6 ). Abd. IV with three central (A3, B3, and Be2?) and eight lateral (D3, E2–4, F1–2, Fe5, and a posterior one without clear homology) mac, as sens lost, but possibly near A3, ps sens near T7, plus at least six central long sens (possibly many more) ( Fig. 6B View FIGURE 6 ). Abd. V with two anterior (a6–6e?), four medial (m2–3, m5–5a), six posterior (p1, p3–5, ap6, pp6), one postero-posterior (p5pe) plus one mac without clear homology near m3; with four sens (as, acc.p3–5) ( Fig. 6C View FIGURE 6 ); further details are represented in Figs 5–6 View FIGURE 5 View FIGURE 6 . Ratio Abd. III: IV of holotype = 1: 1.45.

Trunk appendages ( Fig. 7 View FIGURE 7 ): Trochanteral organ with about 20 spine-like smooth chaetae ( Fig. 7A View FIGURE 7 ). Tibiotarsi without smooth chaetae, with the exception of the distal one on tibiotarsus III. Tenent hairs smooth and capitate, two small pretarsal chaetae present, empodial complex III ratio of smooth chaeta: tenent hair: unguiculus: unguis as 1: 1.4: 1.1: 2; unguis with a single short dorsal tooth, lateral teeth reduced, almost imperceptible, internally with two paired proximal teeth, one unpaired median tooth, similar in size to the paired basal teeth, and one distal minute tooth; unguiculus lanceolate with all lamellae smooth and toothless ( Fig. 7B View FIGURE 7 ). Ventral tube anterior face with one distal ciliate mac plus 10–12 ciliate chaetae, the two more proximal weakly ciliate, almost smooth ( Fig. 7C View FIGURE 7 ); posterior face unclear; lateral flap with about 19–20 smooth chaetae, one of them also as a ciliate chaeta ( Fig. 7D View FIGURE 7 ). Tenaculum corpus with a single rough chaeta, each ramus with four teeth. Manubrium without smooth chaetae; manubrial plate with about seven ciliate chaetae, pseudopores not seen; manubrium ventro-apical region with one ciliate chaeta. Proximal dorsal dens (dental lobe) with a single regular chaeta, not remarkably different in size or shape from other dental surrounding chaetae; dens without spines or smooth chaetae; mucro apical tooth larger than the basal one, mucronal spine present, reaching the apex of the basal tooth ( Fig. 7E View FIGURE 7 ).

Etymology. The new species was named “ dolosus ” (from Latin = deceitful) due to its similarity with D. inermodentes ( Uchida, 1944) , which led us to firstly identify it mistakenly as the former species.

Distribution and habitat. The new species was collected from Cocos and Keeling West Island ( Fig. 8 View FIGURE 8 ), from sandy beaches in the upper intertidal zone, along with F. pulukokos Bellini, Souza & Greenslade, 2021 .

Remarks. The new species is remarkably similar to D. inermodentes , and was firstly identified as this species. They share a very similar dorsal head and trunk macrochaetotaxy, labral papillae, labial lateral process and empodial complex morphology, the absence of smooth chaetae on tibiotarsi (other than the distal one on the tibiotarsus III) and manubrium, and the absence of dental spines (see Mari-Mutt 1979, 1981). However, the new species differs from D. inermodentes by: dorsal head Pa5 mac present (vs. absent); labial basomedian field with 0–3 posterior ciliate chaetae internal to e (vs. 5–7); posterior post-labial chaetae ciliate (vs. smooth); unguis with an apical tooth (vs. absent); and dental lobe with a regular ciliate chaeta (vs. with a long plumose chaeta) ( Mari-Mutt 1979, 1981).

As noted by Mari-Mutt (1979, p. 67), D. inermodentes is quite similar to D. indicus . In this sense, the new species differs from D. indicus especially by: Th. II with two mac on m1–2 complex (vs. three), two on m4 complex (vs. none) and seven posterior mac (vs. eight); unguis with an apical tooth (vs. absent); and dental lobe with a regular ciliate chaeta (vs. with a thick blunt mac) (see Yosii 1966; Mari-Mutt 1979). Further comparisons of the cited species are presented in Table 1 View TABLE 1 .

We revised four specimens of Dicranocentrus sp. from Christmas Island, about 980 km distant from Cocos and Keeling. Such specimens were quite similar in dorsal chaetotaxy to D. dolosus sp. nov., but differed at least in manubrium and tibiotarsi with smooth chaetae. At least two specimens were also devoid of the mucronal spine, similarly to D. indicus ( Yosii, 1966) . Unfortunately the specimens were in bad condition and we could not study further aspects of the morphology to confirm their identity or described them as a new species. Nevertheless, we record the presence of the genus in Christmas Island for the first time.