Megalothorax anterolenis Schneider & Minor & D'Haese 2023, sp. nov.
Creators: name: Schneider, Clément
name: Minor, Maria A.
name: D'Haese, Cyrille A.
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Collembola
Neelipleona
Neelidae
Megalothorax
Megalothorax anterolenis

description: Megalothorax anterolenis sp. nov.
Figs. 1–3, 8A–D.
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.
Paratypes. Four females on a single slide (CSCOL _105), same data as the holotype; two females and two males on two slides (CSCOL _111, 113), same data as the holotype 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.
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 (808bp). One specimen from sample CHL004, COI: OP933760 (658bp), 16S rDNA: OP942368 (454bp), 28S rDNA: OP942372 (808bp). One specimen from sample CHL218, COI: OP933759 (658bp), 16S rDNA: OP942369 (468bp), 28S rDNA: OP942373 (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). Anteriorly on the abdomen, dorso-median line also without secondary granulation until the terminal secondary granule T (same as in Fig. 9A). 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). 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).
Integumentary channels moderately developed on the head (Fig. 1B, C). 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) to almost crossed (seen in one specimen, Fig. 1D). 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). 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). 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). 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, 8A). Ventrally, 3 + 3 chaetae in the sub-labial region (Fig. 1C, 8B). Diagram of head chaetotaxy provided in Fig. 8A, B.
Labium. Basomedian fields of labium with 1 + 1 chaetae, basolateral fields of labium with 1 + 1 chaetae on a small papilla (Fig. 1C). 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). A median, very fine tooth can sometimes be perceived on a2 (Fig. 2B). 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).
Other mouthparts. Oral fold with 2 + 2 chaetae (Fig. 1B). Maxilla outer lobe with two chaetae (apical and basal) and with a strong bifurcate hair in subapical internal position (Figs 1B, 2C). Sub-lobal plate without hair, but with a small lobe near the anterior ridge (Fig. 2C). Mandibula with the ordinary asymmetry: one strong basal tooth on the left mandibula (Fig. 2D), missing on the other side. Maxilla with a well developed apical lamella (Fig. 2E).
Antenna. Ant. I with one chaeta (Fig. 2F). Ant. II with four chaetae, the anterior one stronger than the three others (Fig. 2F). 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). 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); apical and subapical rods (a, sa) present (Fig. 2F, G). Diagram of antennal chaetotaxy provided in Fig. 8C.
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). 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). Diagram of chaetotaxy provided in Fig. 8D.
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).
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).
Genital plate. Ordinary: female with 2 + 2 chaetae (Fig. 2 H). 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).
Abdominal appendages. Manubrium with 2 + 2 posterior chaetae (Fig. 2 H). 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). Mucro elliptical, with moderately wide lamellae, with a dozen of teeth on each posterior lamellae (Fig. 2 J). 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); leg II, 1, 1, 1, 3, 8, 12 chaeta(e) (Fig. 3B); leg III, 2, 1, 1, 4, 8, 10 chaeta(e) (Fig. 3C). Claws ordinary, as in Fig. 3A, C., 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).
description: Published as part of 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, pp. 101-121 in Zootaxa 5228 (2) on pages 104-107, DOI: 10.11646/zootaxa.5228.2.1, http://zenodo.org/record/7532173