Lepidocyrtus thoracicus Mateos, 2023

Mateos, Eduardo, Zhang, Bing & Álvarez-Presas, Marta, 2023, New species of Lepidocyrtus (Collembola, Entomobryidae) from Italy with a discussion of characters defining European Lepidocyrtus lignorum-group, Zootaxa 5270 (2), pp. 306-324 : 312-320

Lepidocyrtus thoracicus Mateos sp. nov.

Figs 3–25

urn:lsid:zoobank.org:act:B3DF5C60-D0AC-4611-804C-5789C76C137D

Type material. Holotype: Female on slide code CRBA-102730, Padevena, Veneto ( Italy), 920 m above sea level, lat/long coordinates N46.04116 E11.84655, collected using a modified leaf blower functioning as an aspirator (diameter of opening 14 cm), 04.v.2015, leg. B. Zhang. Paratypes: 18 specimens on slides (5 female, 2 juvenile and 11 without visible sexual plate) and 11 specimens preserved in absolute alcohol, same data as holotype. Four paratypes prepared on slides were previously used in the molecular analyses . Holotype and paratype female slide code CRBA-102731 saved in the collection of the Centre de Recursos de Biodiversitat Animal , Faculty of Biology, University of Barcelona (http://www.crba.ub.edu); other paratypes kept in the E. Mateos’ collection (lot LP386 ) .

Diagnosis. With dark blue pigment on Abd.II–III, lateral dot on Abd.IV, and coxae I–II. Th.II slightly projecting over the head. Ant.I–III, legs, ventral tube, and posterior region of manubrium with scales. Labial chaetotaxy M1M2REL1L2, R shortened. Dorsal cephalic and body macrochaetae formula A0[A2a]A2A3Pa5/10/0101+3. Abd.IV without chaeta s. Unguiculus truncate and with finely serrated outer margin.

Molecular diagnosis. This species includes all populations that cluster with Cox2 and EF sequences of the individuals LP386-1 to LP386-5 ( Table 1), with significant support in an adequate molecular delimitation model.

Etymology. The species name refers to the presence of a pair of dorsal macrochaetae on mesothorax.

Description. Holotype body length (without head nor furca) 1.1 mm, paratypes 1.0– 1.3 mm. Body color pattern ( Fig. 3 ) with dark blue pigment on Abd.II–III, lateral dot on Abd.IV, and coxae I–II; Ant.II-IV slightly pigmented; densely black pigmented ocular areas. Mesothorax slightly projected over the head.

HEAD. Eyes 8+8; eyes A to F subequal, G and H slightly smaller, ratio F/G and C/H ≈ 1.6 ( Fig. 4 ).

Dorsal cephalic macrochaetae A0, A2, A3, Pa5, with pair of smaller supplementary macrochaetae A2a between A0 and A2; maximum number of macrochaetae An on head 11+11. Interocular chaetotaxy with s, t, p ciliated chaetae and 2–3 scales ( Fig. 4 ).

Clypeus ( Fig. 5 ) with three prefrontal chaetae (1 pf0 and 2 pf1), four facial chaetae (f), and four lateral chaetae (2 L1 and 2 L2), all these chaetae ciliated.

Labrum ( Fig. 5 ) with prelabral and labral chaetae in typical number 4/554, prelabral chaetae ciliated, first and second rows of labral chaetae smooth, lateral chetae of apical row curved and pointed ( Fig. 6-A ), medial chaetae bifurcated ( Fig. 6-B, C ); labral intrusion as an inverted U; four rounded labral papillae with 1–3 small spines.

Maxillary palp outer lobe ( Fig. 7 ) with smooth apical appendage and basal chaeta, sublobal plate with three smooth appendages and a minute distal process.

Labial and postlabial chaetotaxy as in Fig. 8 ; with five smooth proximal chaetae at base of labial palp; labial anterior row with five smooth chaetae (a1–a5); posterior row formula M1M2REL1L2 all ciliate; chaeta R shortest, ratio M2/R = 2–2.3; postlabial chaetaxy with all chaetae ciliated, row I (along ventral cephalic groove) with four chaetae. Lateral process of outer labial papilla ( Fig. 9 ) finger-shape, slightly curved, not reaching apex of papilla.

BODY. Dorsal body macrochaetae formula 10/0101+3 (macrochaetae p3 on Th.II, m3 on Abd.II, and Sm+B4, B5, B6 on Abd.IV). Dorsal chaetotaxy of Th.II–III as in Figs 10–11 . Th.II with 2 lateral S-chaetae (al and ms) and with one macrochaetae (p3) in dorsal position. Th.III with a lateral sensillum (al) close to several ciliated chaetae. Chaetotaxy of Abd.I–III as in Figs 12–14 .Abd.I with a lateral S-microchaeta (ms) external to a6. Abd.II macrochaeta m3 1.2 times longer than macrochaeta m5. Abd. III chaeta mi absent, with chaeta d3 between macrochaetae pm6 and p6, and with S-chaetae as and ms. All chaetae associated with the trichobothria on Abd.II–III strongly ciliate ( Fig. 15 ). Chaetotaxy of Abd.IV as in Figs 16–19 ; macrochaetae Sm, B4, B5, B6, D3, De3, E2, E3, E4, F1, F2, F3 with large socket ( Fig. 17-A ); macrochaetae T6, T7, D2, E1, E4p, E4p2, Fe4, Fe5, F3p, F3p2, r3 longer or shorter but always with socket of minor diameter ( Fig. 17-B,C ); macrochaeta F2 inserted above macrochaeta E3; the ratio of distances between macrochaetae Sm–B4 / B4–B6 as 0.7–0.8; ratio of distances between macrochaetae B4–B5 / B5–B6 as 1.0–1.3; accessory chaeta s associated with trichobothrium T2 absent; chaetae a, D1, m, pe and pi associated with trichobothria T2 and T4 strongly cilate ( Fig. 19 ); sens chaetotaxy composed of three anterior dorsomedial elongate S-chaetae, and short chaetae as and ps.; posterior margin with 6+6 smooth mesochaetae; lateral region and BP4 without pseudopori. Dorsal chaetotaxy of Abd.V ( Fig. 20 ) with S-chaetae as, acc.p4 and acc.p5.

APPENDAGES. Antennal segments I–III with scales on all faces. Ratio antenna:cephalic diagonal ≈ 1.6 (head diagonal measured from cervical edge to apex of mouth part); ratio Ant.I:II:III:IV as 1:1.9:1.6:2.8. Proximal margin of Ant.I dorsally with three microchaetae arranged in triangle (Ant.I-organ); ventro-distal membranous margin of Ant.I with a short curved S-chaeta. Ant.III organ composed of two subcilindrical and curved sensory rods. Ant.IV without apical bulb.

All legs segments with scales. V-shaped trochanteral organ ( Fig. 21 ) formed by a maximum of 12 smooth straight chaetae. Unguis ( Fig. 22 ) with basal pair of teeth at 47% from base of inner edge and with two inner unpaired teeth at 65% and 84% from base of inner edge, respectively; apical inner tooth minute and sometimes difficult to see; one external tooth and a pair of lateral teeth also present. Unguiculus truncate with finely serrated outer margin. Tenent hair spatulate, smooth and a little longer than claw (ratio TH/claw ≈ 1.1); ratio of supra-empodial chaeta (smooth chaeta on tibiotarsus III opposite to tenent hair) / unguiculus ≈ 1.3.

Ventral tube with 5+5 ciliated chaetae on anterior side ( Fig. 23 ) and 8+8 ciliated chaetae on posterior side; scales present on anterior and posterior sides; lateral flaps with a maximum of 17 laterodistal chaetae (7–10 ciliated and 7 smooth).

Manubrium with scales on anterior and posterior surfaces, with 2+2 ciliated apical chaetae on anterior side. Ratio manubrium:dens:mucro as 15:17:1. Manubrial plate ( Fig. 24 ) with two pseudopores, three inner chaetae, and a maximum of six outer chaetae. Dental tubercle absent. Mucro with two subequal teeth, basal spine smooth (without spinelet).

PSEUDOPORES. Pseudopores distribution on dorsal and ventral regions of head, body, and appendages as in Figs 25-A, B .

Ecology and distribution. All specimens were collected from grass in a small grassland surrounded by forests. The only known locality is the type locality in Italy.

Discussion. Apart from the presence of one macrochaeta on Th.II, all the other morphological characters of the Lepidocyrtus thoracicus sp. nov., as well as the molecular analyses, indicate that it belongs to the Lepidocyrtus lignorum -group (sensu Mateos 2011). The presence of a dorsal macrocheata in Th.II is a character not found so far in any species of the L. lignorum -group, and it represents an excellent diagnostic character to differentiate the new species within the group. It should be noted that in the Lepidocyrtus species described so far, when they have a mesothoracic macrochaeta, it is always p3. In the European fauna, this mesothoracic macrochaeta is present in all species of the lusitanicus -group and lanuginosus -group (see Mateos et al. 2021). Out of Europe, the only species in which the presence of the mesothoracic p3 macrochaeta has been described are L. vireticulus Mari Mutt, 1986 and L. diminutus Mari Mutt, 1986 , both from Puerto Rico. Molecular analyzes place the new species as a sister group to L. pulchellus Denis, 1926 . Morphologically, both species are very similar, and the new species differs from L. pulchellus by the presence of the mesothoracic macrochaeta p3, the color pattern, and slightly smaller body size. Molecularly both species are clearly differentiated ( Fig. 2 ). Within the L. lignorum -group, four species have truncated unguiculus, L. peisonis Traser & Christian, 1992 , L. pulchellus , L. ruber , and L. uzeli Rusek, 1985 (see Mateos 2020); the presence of the mesothoracic macrochaeta p3 and the color pattern clearly differentiate the new species from all of them.

Figures

FIGURE 2. Phylogenetic tree inferred using the Cox2 dataset with ML. Numbers at nodes correspond to UFB values, showing only values> 75%. Vertical bars to the right of the phylogeny correspond to the three molecular species delimitation results (ASAP, ABGD and mPTP from left to right). Scale bar shows number of substitutions per site.

FIGURE 3. Lepidocyrtus thoracicus sp. nov.: Habitus lateral (A) and dorsal (B). Specimen in alcohol.

FIGURE 4. Lepidocyrtus thoracicus sp. nov.: Dorsal head chaetotaxy (left side). Broad circles––long ciliated macrochaetae, small circles––short ciliated macrochaetae.

FIGURES 5–9. Lepidocyrtus thoracicus sp. nov.: 5, clypeal and labral chaetotaxy; 6, chaetae morphology of the apical row of the labrum, the two lateral chaetae have pointed apex (A) and the two central chaetae have bifurcate apex with two possible morphologies (B, C); 7, maxillary palp; 8, labial and postlabial chaetotaxy, p.c.—proximal chaetae of labial palp. 9, outer labial papilla.

FIGURES 10–11. Lepidocyrtus thoracicus sp. nov. dorsal chaetotaxy (left side): 10, Th.II; 11, Th.III. Empty circles––ciliated chaetae, black circle––ciliated macrochaeta, crossed circles––pseudopores.

FIGURES 12–14. Lepidocyrtus thoracicus sp. nov. dorsal chaetotaxy (left side): 12, Abd.I; 13, Abd.II; 14, Abd.III. Black circles––ciliated macrochaetae, crossed circles––pseudopores.

FIGURE 15. Lepidocyrtus thoracicus sp. nov.: Abd.III dorsolateral chaetotaxy photograph (A) and drawing (B). Black circles– –ciliated macrochaetae.

FIGURES 16–17. Lepidocyrtus thoracicus sp. nov.: 16, Abd.IV photograph showing trichobothria (T2 and T4), dorsal macrochaetae (Sm, B4, B5 and B6) and dorsolateral macrochaetae (D3, De3, E2, E3, E4, F1, F2 and F3); 17, broad ciliated macrochaeta (A), long thin ciliated macrochaeta (B) and short thin ciliated macrochaeta (C).

FIGURES18–20. Lepidocyrtusthoracicus sp. nov.: 18,Abd.IVchaetotaxy (left side), broadblackcircles––ciliatedmacrochaetae with large socket, small black circles––ciliated macrochaetae with small socket; 19, Abd.IV trichobothrial complex; 20, Abd.V chaetotaxy (left side), black circles––ciliated chaetae with length proportional to diameter socket.

FIGURES 21–24. Lepidocyrtus thoracicus sp. nov.: 21, trochanteral organ; 22, third leg unguis and unguiculus; 23, anterior face of ventral tube (left side); 24, manubrial plate (left side), circles––ciliated chaetae with length proportional to diameter socket, crossed circles––pseudopores.

FIGURE 25. Lepidocyrtus thoracicus sp. nov.: Pseudopores distribution on dorsal (A) and ventral (B) surfaces.