Megalothorax anterolenis, Schneider & Minor & D’Haese, 2023

Schneider, Clément, Minor, Maria A. & D’Haese, Cyrille A., 2023, A new group of species of the genus Megalothorax (Collembola, Neelidae) with Gondwanan distribution, and introducing an open interactive identification key of Megalothorax species, Zootaxa 5228 (2), pp. 101-121 : 104-107

publication ID	https://doi.org/ 10.11646/zootaxa.5228.2.1
publication LSID	lsid:zoobank.org:pub:07D486F0-D44C-4F4B-B625-557442893DF2
DOI	https://doi.org/10.5281/zenodo.7532175
persistent identifier	https://treatment.plazi.org/id/01379830-FFFE-507E-E0E9-0BF7BD9DD419
treatment provided by	Plazi
scientific name	Megalothorax anterolenis
status	sp. nov.

Treatment

Megalothorax anterolenis View in CoL sp. nov.

Figs. 1–3 View FIGURE 1 View FIGURE 2 View FIGURE 3 , 8A–D View FIGURE 8 .

Material examined. Holotype. Female on slide ( CSCOL _104), Chile, X Región de Los Lagos, Llanquihue, Parque Nacional Alerce Andino , 2011.xi.23, 41.5838°S, 72.5698°W, dwelling among epiphytic plants on a living tree, sample CHL002. GoogleMaps

Paratypes. Four females on a single slide ( CSCOL _105), same data as the holotype GoogleMaps ; two females and two males on two slides ( CSCOL _111, 113), same data as the holotype GoogleMaps but sampled on another tree: 41.5836°S, 72.5692°W, sample CHL004.

Other material. One female, one juvenile on two slides ( CSCOL _190, 191), Chile, X Región de Los Lagos, Llanquihue, Parque Nacional Alerce Andino , 2011.xi.24, 41.5882°S, 72.5808°W, among mosses on dead wood, sample CHL015. One female on slide ( CSCOL _125), Chile, X Región de Los Lagos, Llanquihue, Parque Nacional Alerce Andino, 2011.xi.26, 41.5787°S, 72.5599°W, among mosses and epiphytic plants naturally fallen from the host tree, sample CHL028. Three females on slide ( CSCOL _213, 214, 221), Chile, Región de Aysén, Sendero Laguna Los Pumas, 2011.xii.04, 44.2354°S, 72.5195°W, among mosses growing on the base of a tree, sample CHL218. All material collected by C. Schneider. GoogleMaps

Material deposit. The holotype and two paratypes ( CSCOL _104, CSCOL _111) will be deposited at the Museo Nacional de Historia Natural de Chile, Santiago, Chile . Four paratypes ( CSCOL _105) will be deposited at the Muséum National d’Histoire Naturelle, Paris , France . Rest of the material will be deposited at the Senckenberg Museum für Naturkunde, Görlitz, Germany.

Obtained molecular data and genbank accession number. One specimen from sample CHL002 (same a holotype): 28S rDNA: OP942371 View Materials (808bp). One specimen from sample CHL004, COI: OP933760 View Materials (658bp), 16S rDNA: OP942368 View Materials (454bp), 28S rDNA: OP942372 View Materials (808bp). One specimen from sample CHL218, COI: OP933759 View Materials (658bp), 16S rDNA: OP942369 View Materials (468bp), 28S rDNA: OP942373 View Materials (784bp). Vouchers could not be recovered.

Diagnosis. Colour varying from whitish to red (in 96% ethanol), labrum a1 chaetae ordinary with acuminate tip, maxillary palp with an internal bifurcate hair, basomedian and basolateral fields of labium each with 1 + 1 chaetae, secondary granulation limited to the abdominal I–IV tergites, s-chaetae s3 present on the abdomen, tenaculum with 3 + 3 teeth, posterior lamellae of the mucro moderately enlarged and finely serrated.

Description. General aspect. Habitus and segmentation typical of the genus. Length from labrum to anus: up to 450µm. Specimens whitish to red (in 96% ethanol). All typical chaetal types of the genus are accounted for, without any remarkable development.

Integument. The ordinary secondary granulation is limited to the posterior half of the trunk (roughly corresponding to the abdominal region), absent on the head, the thoracic region and Abd. VI ( Fig. 1A View FIGURE 1 ). Anteriorly on the abdomen, dorso-median line also without secondary granulation until the terminal secondary granule T (same as in Fig. 9A View FIGURE 9 ). Primary granulation pattern distinctly visible dorsally on the head and the thorax: primary grains stronger and hexagons surface larger than on the secondary granulated part of the abdomen (same as in Fig. 9A View FIGURE 9 ). On the clypeal area, a speckled pattern of hexagons with enlarged primary grain yielding superficial resemblance to ordinary secondary granulation (same as in Fig. 9B View FIGURE 9 ).

Integumentary channels moderately developed on the head ( Fig. 1B, C View FIGURE 1 ). On each side of the head, the basal channel splits successively. At each split, the external branch is always terminal (never splitting). The first external branch extending to the antero-dorsal region of the head, then up to four branches extending to the latero-posterior part of the head. Finally, the two most posterior branches reaching the dorso-posterior part of the head. Channels connection with linea ventralis from circular (mostly observed, Fig. 1C View FIGURE 1 ) to almost crossed (seen in one specimen, Fig. 1D View FIGURE 1 ). Channels absent on trunk.

Sensory fields and wax rods. Ordinary distribution of sensory fields and wax rods secretory crypts: 2 + 2 wrc on head, 12 + 12 wrc on body; including the ones associated with the 6 + 6 sensory fields ( Fig. 1A, B View FIGURE 1 ). Sensory fields include the swollen inner chaetae in the usual distribution (from sf1–6: 0, 1, 3, 2, 2, 1). The swollen inner chaetae are all short and flame-shaped, some with a tendency toward the T-shape ( Fig. 1A View FIGURE 1 ). Level of separation of wrc5 and 6 from sf5 cannot be quantified with the amount of secondary granules (non applicable).

Head chaetotaxy. Postero-dorsal chaetae without remarkable thickening, only subtly stronger than antero-dorsal chaetae ( Fig. 1B View FIGURE 1 ). Number of chaetae: 12 + 12 in the postero-dorsal region, 8 + 8 and 2 unpaired in the antero-dorsal region, 2 + 2 in the antero-lateral region ( Fig. 1B View FIGURE 1 , 8A View FIGURE 8 ). Ventrally, 3 + 3 chaetae in the sub-labial region ( Fig. 1C View FIGURE 1 , 8B View FIGURE 8 ). Diagram of head chaetotaxy provided in Fig. 8A, B View FIGURE 8 .

Labium. Basomedian fields of labium with 1 + 1 chaetae, basolateral fields of labium with 1 + 1 chaetae on a small papilla ( Fig. 1C View FIGURE 1 ). Labial palps ordinary.

Labrum. Chaetae a1 and a2 thicker than chaetae m0-2; a1 shorter than a2; m0-2 smooth; a1 and a2 acuminate, with inward curvature, each with one external, basal tooth ( Fig. 2A, B View FIGURE 2 ). A median, very fine tooth can sometimes be perceived on a2 ( Fig. 2B View FIGURE 2 ). Labral anterior process apparently as in M. minimus , with a continued transversal crest separating a1-2 from m0-2. Ridge of the labrum with at least two small teeth ( Fig. 2B View FIGURE 2 ).

Other mouthparts. Oral fold with 2 + 2 chaetae ( Fig. 1B View FIGURE 1 ). Maxilla outer lobe with two chaetae (apical and basal) and with a strong bifurcate hair in subapical internal position ( Figs 1B View FIGURE 1 , 2C View FIGURE 2 ). Sub-lobal plate without hair, but with a small lobe near the anterior ridge ( Fig. 2C View FIGURE 2 ). Mandibula with the ordinary asymmetry: one strong basal tooth on the left mandibula ( Fig. 2D View FIGURE 2 ), missing on the other side. Maxilla with a well developed apical lamella ( Fig. 2E View FIGURE 2 ).

Antenna. Ant. I with one chaeta ( Fig. 2F View FIGURE 2 ). Ant. II with four chaetae, the anterior one stronger than the three others ( Fig. 2F View FIGURE 2 ). Ant. III with eight chaetae and five S-chaetae including S1–S4 from the sensory organ and Sb4; S2 and S3 small but clearly protruding from the cupule; without perceptible ornamentation in light microscopy ( Fig. 2F, G View FIGURE 2 ). Ant. IV with five chaetae (X present) and 11 S-chaetae (Sb1–3, Sb5, Sa1–5, Sx and Sy); Sa2 is notably enlarged in regard to the others common S-chaetae Sa and Sb (as in Fig. 8C View FIGURE 8 ); apical and subapical rods (a, sa) present ( Fig. 2F, G View FIGURE 2 ). Diagram of antennal chaetotaxy provided in Fig. 8C View FIGURE 8 .

Thoracic tergites. Th. II with 12 + 12 ordinary chaetae, 1 + 1 s-chaetae s1 and three τ-chaetae (only the bases of τ-chaetae could be perceived using light microscopy); chaetae a5, a6 present and chaeta a7 missing; the laterodorsal τ-chaeta is far from chaeta p4, in the lateral direction ( Fig. 1A View FIGURE 1 ). Th. III with 10 + 10 ordinary chaetae, 6 + 6 wrc, 4 + 4 τ-chaetae and 2 + 2 pseudopores (ps); a5 sensibly bigger than a6, wrc 2 distant from p4 ( Fig. 1A View FIGURE 1 ). Diagram of chaetotaxy provided in Fig. 8D View FIGURE 8 .

Abd. I–V tergites. With 22 + 22 ordinary chaetae, 2 + 2 globular s-chaetae (s 2, s 3) s3 notably smaller than s2, 2 + 2 τ-chaetae, 1 + 1 pseudopores and 2 + 2 wrc; chaetae ζ1 and η4 present ( Fig. 1A View FIGURE 1 ).

Abd. VI. Tergite with 4 + 4 and 1 unpaired chaetae. Each anal valves with one small chaeta. Sternite with 10 + 10 chaetae ( Fig. 2 H View FIGURE 2 ).

Genital plate. Ordinary: female with 2 + 2 chaetae ( Fig. 2 H View FIGURE 2 ). Males present, but the genital plate could not be studied in detail.

Abd. IV sternites. With 2 + 2 usual neosminthuroid chaetae, usually with 2 + 2 ordinary chaetae and 1 + 1 small lobes but anomalous asymmetry observed in one specimen ( Fig. 2 H View FIGURE 2 ).

Abdominal appendages. Manubrium with 2 + 2 posterior chaetae ( Fig. 2 H View FIGURE 2 ). Dens ordinary: basal part of dens with 1 + 1 posterior chaetae, apical part of dens with 1 + 1 posterior chaetae and 7 + 7 small spines ( Fig. 2 H, I View FIGURE 2 ). Mucro elliptical, with moderately wide lamellae, with a dozen of teeth on each posterior lamellae ( Fig. 2 J View FIGURE 2 ). Ventral tube with 2 + 2 apical chaetae, retinaculum with 3 + 3 teeth.

Legs. Chaetal composition on each legs subcoxa 1, 2, coxa, trochanter, femur and tibiotarsus: Leg I, 1, 0, 1, 2, 8, 12 chaeta(e) ( Fig. 3A View FIGURE 3 ); leg II, 1, 1, 1, 3, 8, 12 chaeta(e) ( Fig. 3B View FIGURE 3 ); leg III, 2, 1, 1, 4, 8, 10 chaeta(e) ( Fig. 3C View FIGURE 3 ). Claws ordinary, as in Fig. 3A, C View FIGURE 3 ., with short external basal lamellae.

Differential diagnosis. Megalothorax anterolenis sp. nov. shares some uncommon chaetotaxic similarities with M. granulosus : only 1 + 1 chaetae on the basomedian field of labium, and presence of chaetae a5 and a6 on Th. II and chaetae ζ1 and η4 on the abdomen. However M. anterolenis sp. nov. and M. granulosus are clearly distinct on many aspects, such as the shape of the connection of the head integumentary channels (circular vs crossed), the secondary granulation (ordinary vs coarse), the antennal chaetotaxy and the mucro lamellae (toothed vs smooth). In general, the repartition of the secondary granulation clearly distinguish Megalothorax anterolenis sp. nov. from any species of the incertus and minimus -group (absent on head and anterior part of trunk vs full dorsal coverage).

Name etymology. Combination of the Latin anterior and lçnis (smooth).