Megalothorax zealanterolenis

Ecology. The new species was found in soil and litter of montane southern beech forests in the subalpine zone (ca. 1000 – 1100 m above sea level) of Mt Arthur (1795 m) in the Kahurangi National Park, Nelson-Tasman region of the South Island of New Zealand. The Mt Arthur sites vegetation is dominated by montane forests of southern beech, mostly mountain beech Fuscospora cliffortioides (Hook. f.) Heenan & Smissen, some red beech Fuscospora fusca (Hook. f.) Heenan & Smissen and silver beech Lophozonia menziesii (Hook. f.) Heenan & Smissen, small shrubs and mosses. The soils in sampled plots were cold (7 – 8 deg Celsius) and wet (21 – 44 % volumetric moisture content) in January (mid-summer). The new species was widespread in samples from Mt. Arthur and locally found in high abundance (mean density 2,800 ind. m- 2, max 10,800 ind. m- 2). The new species may be geographically restricted, as it was not observed in subalpine beech forests of two other mountains sampled in the same region.

Description. General aspect. Habitus and segmentation typical of the genus. Length from labrum to anus: up to 400 µm. Specimens whitish (in 96 % ethanol). All typical chaetal types of the genus are accounted for, without any remarkable development. Integument. Secondary granulation restricted to the dorsal part of the abdominal area except Abd. VI, similarly to M. anterolenis sp. nov. Head channels connection with linea ventralis circular, integumentary channels not precisely analysed, apparently limited to the dorsal part of the head. Sensory fields and wax rods. Same observation as in M. anterolenis. sp. nov., see Fig. 6 A, B. Head chaetotaxy. Postero-dorsal chaetae without remarkable thickening, stronger than antero-dorsal chaetae. Number of chaetae: 12 + 12 in the postero-dorsal region, 9 + 9 and 2 unpaired in the antero-dorsal region, 2 + 2 in the antero-lateral region (Fig. 6 B). Ventrally, 3 + 3 chaetae in the sub-labial region (Fig. 8 B). Labium. Basomedian fields of labium with 1 + 1 chaetae, basolateral fields of labium with 1 + 1 chaetae on a small papilla. Labial palps ordinary. Labrum. Same observations as in M. tasmanterolenis. Other mouthparts. Same observations as in M. tasmanterolenis, left mandibula figured in Fig. 6 C. Antenna. Ant. I with one chaeta. Ant. II with four chaetae, the anterior one much stronger than the three others (Fig. 6 D). Ant. III with 10 chaetae, and five S-chaetae including S 1 – S 4 from the sensory organ and Sb 4; S 2 and S 3 small but clearly protruding from the cupule; without perceptible ornamentation in light microscopy; S 1 and S 4 appeared well contrasted with perceptible ornamentation rings. Ant. IV with five chaetae (X present), and 11 Schaetae (Sb 1 – 3, Sb 5, Sa 1 - 5, Sx and Sy; Sa 2 notably enlarged and with a clearer appearance than the others common S-chaetae (Sa and Sb); 2 apical and subapical rods (a, sa) present (Fig. 6 D). Thoracic and abdominal tergites. As in Fig. 6 A, same observations as in M. anterolenis sp. nov., but with schaetae s 3 absent and s-chaetae s 2 elongated. Pseudopores not studied, 3 + 3 τ-chaetae could be seen (the others to be considered not studied). Abd. VI. Ordinary, with nine chaetae on tergites, a small chaetae on each anal valves. Sternites chaetotaxy not studied. Genital plate. Female with 2 + 2 chaetae, male not studied. Abd. IV sternites. With 2 + 2 usual neosminthuroid chaetae and 2 + 2 ordinary chaetae, the external chaetae much shorter than the internal ones (Fig. 7 A). Abdominal appendages. Manubrium with 2 + 2 posterior chaetae. 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. Apex of the five anterior spines tapering to a filament. Mucro elliptical, with wide lamellae; five to seven teeth on the external posterior lamella, internal posterior lamella smooth and waved, sometimes with weak teeth (Figs 7 H – J, 9 E). Ventral tube with 2 + 2 apical chaetae, retinaculum with 4 + 4 teeth. Legs. Chaetal composition on legs (subcoxa 1, 2, coxa, trochanter, femur and tibiotarsus): leg I, 1, 0, 1 (at least), 2, 8, 12 chaeta (e); leg II, 1, 1, 1, 3, 8, 12 chaeta (e); leg III, 2, 1, 1, 4, 8, 10 chaeta (e). Claws ordinary, as in Fig. 7 E, F, G.; with basal lamellae la and lp short.

Figs 6, 7, 8 A, B, 9 E

Diagnosis. Whitish in ethanol, labrum a 1 chaetae with bifurcate 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, on the abdomen s-chaetae s 2 elongated and tubular, s 3 absent, tenaculum with 4 + 4 teeth, posterior lamellae of the mucro moderately enlarged, internal lamella serrated, external lamella smooth and waved or with weak teeth.

Differential diagnosis. Most similar to M. tasmanterolenis sp. nov., the two species can be distinguished from the shape of s-chaetae s 2 on the abdomen. Name etymology. Derived from the name of M. anterolenis sp. nov. combined with the country of discovery (New Zealand).

Material examined. For all following material, name of locality, date of collection and name of collector: New Zealand, South Island, Nelson-Tasman region, Kahurangi National Park, Mt Arthur summit track, 27 January 2017, collected by M. Minor. Holotype. Female on slide (CSCOL _ 1327), 41.1967 ° S, 172.7312 ° E, 1096 m a. s. l., southern beech forest (mostly Fuscospora cliffortioides (Hook. f.) with some Lophozonia menziesii (Hook. f.), in soil with litter and moss Hypnum cupressiforme Hedw., sample MtAb _ T 1 - 1. Paratypes. Four females and one male on three slides (CSCOL _ 1326, 1328, 1329), same data as the holotype, sample MtAb _ T 1 - 1. Other material. One female on slide CSCOL _ 1330, 41.1966 ° S, 172.7315 ° E, 1091 m a. s. l., southern beech forest (F. cliffortioides), in soil with litter, sample MtAb _ T 1 - 4. A juvenile on slide CSCOL _ 1331, 41.1965 ° S, 172.7319 ° E, 1082 m a. s. l., southern beech forest (mostly F. cliffortioides with some F. fusca), in soil with litter, sample MtAb _ T 1 - 5. A female on slide CSCOL _ 1332, 41.1962 ° S, 172.7322 ° E, 1084 m a. s. l., southern beech forest (mostly F. cliffortioides with some F. fusca), in soil with litter, sample MtAb _ T 1 - 6. Three juveniles, three males, one female and one adult (sex indet.) on eight slides CSCOL _ 1333 – 1340, 41.1923 ° S, 172.7354 ° E, 1066 m a. s. l., southern beech forest (F. cliffortioides with some L. menziesii), in soil with litter, sample MtAb _ T 2 - 1. Four juveniles, two females on three slides CSCOL _ 1341 – 1343, 41.1923 ° S, 172.7354 ° E, 1066 m a. s. l., southern beech forest (F. cliffortioides with some L. menziesii), in soil with litter under liverwort Bazzania involuta (Mont.) Trevis., sample MtAb _ T 2 - 2. Two females on a slide CSCOL _ 1345, 41.1920 ° S, 172.7359 ° E, 1077 m a. s. l., southern beech forest (F. cliffortioides with some L. menziesii), in soil with litter, sample MtAb _ T 2 - 5. Two females on two slides CSCOL _ 1346, 1347, 41.1901 ° S, 172.7397 ° E, 1018 m a. s. l., mixed southern beech forest (F. cliffortioides with some Fuscospora fusca (Hook. f.) and L. menziesii), in soil with litter, sample MtAb _ T 3 - 1. One female on slide CSCOL _ 1348, 41.1901 ° S, 172.7397 ° E, 1018 m a. s. l., mixed southern beech forest (F. cliffortioides with some F. fusca and L. menziesii), in soil and litter with moss Dicranoloma robustum (Hook. f. & Wilson) Paris, sample MtAb _ T 3 - 2. One female on slide CSCOL _ 1349, 41.1902 ° S, 172.7399 ° E, 1024 m a. s. l., mixed southern beech forest (F. cliffortioides with some F. fusca), in soil and litter with moss D. robustum, sample MtAb _ T 3 - 3. Two juveniles, one adult (sex indet.) on three slides (CSCOL _ 1350 – 1352), 41.1902 ° S, 172.7400 ° E, 1025 m a. s. l., southern beech forest (F. cliffortioides with some F. fusca), in soil and litter with moss D. robustum, sample MtAb _ T 3 - 4. One male, one female on two slides (CSCOL _ 1353, 1354), 41.1903 ° S, 172.7409 ° E, 1013 m a. s. l., mixed southern beech forest (F. cliffortioides with some F. fusca and L. menziesii), in soil and litter with moss Ptychomnion aciculare (Brid.) Mitt., sample MtAb _ T 3 - 6. Material deposit. The holotype (CSCOL _ 1327) and two paratypes (a female and a male, CSCOL _ 1328, CSCOL _ 1329) will be deposited at the Museum of New Zealand Te Papa Tongarewa, Wellington, New Zealand. Three female paratypes (CSCOL _ 1326) will be deposited at the Senckenberg Museum für Naturkunde, Görlitz, Germany.