Yuukianura deharvengi, Smolis, Adrian, 2017

Smolis, Adrian, 2017, Contribution to the knowledge of Neanurinae of Vietnam with description of three new species (Collembola, Neanuridae), ZooKeys 688, pp. 15-33 : 15-16

Yuukianura deharvengi sp. n. Figs 16-24, 25-29; Table 3

Type material.

Holotype: male on slide: Vietnam, Do son near Haiphong, marine littoral zone, by hand, 12.IV.1997, leg. R.J.Pomorski (housed in DIBEC). Paratypes: 2 females on slides, same data as holotype (DIBEC and MNHN).

Etymology.

The species is named in honour of Prof. Louis Deharveng, for his important contribution to the knowledge on Collembola .

Diagnosis. Habitus typical of the genus Yuukianura . Dorsal tubercles present but poorly developed. 3+3 small eyes. Color of body alive yellow. Mandible with five teeth. Ventral lamella of maxilla with 20-25 cilia. Head with chaetae A, B, C, D and E, chaeta O absent. Tubercle Oc with three chaetae on head. Tubercles Di on Th. II and III with 3 chaetae. Abd. V with 2+2 tubercles. Abd. V with 3+3 chaetae Di. Claw with small inner tooth. Tibiotarsi with chaetae B4 and B5 short and pointed.

Description.

General (Figs 16, 27, 29). Body length (without antennae): 1.60 to 1.70 mm (holotype: 1.65 mm). Habitus elongate, narrow, parallel-sided and slightly dorsoventrally flattened. Cuticular granulations fine, tubercles inconspicuous or poorly developed, without visible subcuticular reticulations. Color yellow alive and white in alcohol. 3+3 small black eyes (Figs 16, 27), anterior ocelli outside tubercle Oc.

Chaetal morphology (Figs 16, 29). Dorsal ordinary chaetae of four types: Ml, Mc, me and mi. Macrochaetae Ml long, moderately thickened, straight, narrowly sheathed, feebly scaled and rounded apically. Macrochaetae Mc morphologically similar to long macrochaetae, but shorter. Mesochaetae similar to ventral chaetae, thin, minutely scaled and pointed. Microchaetae similar to mesochaetae, but apparently short. S-chaetae of tergites thin, smooth and equal or slightly shorter than closest Ml.

Antennae (Figs 17-20, Tab. 3b). Typical of the genus. S-chaetae of Ant. IV of medium length and moderately thickened. Ant. IV with one additional s-chaeta mou (Fig. 19). Apical vesicle not elevated and multilobed (Figs 17, 18). Sensillum sgd migrated distally. Sensillum sgv short and straight (Fig. 20).

Mouthparts (Figs 21-26). Buccal cone relatively short, wide and truncated, with labral sclerifications non-ogival (Fig. 26), labral formula: 0/2,2. Labium as in Fig. 25, papillae x present and relatively large. Maxilla well developed with 2 teeth and 2 lamellae, inner ventral lamella dagger-like and not fringed, outer ventral lamella fringed with 20-25 cilia arranged in 2-3 rows (Figs 21, 22). Mandible thick with five teeth, four apical and one strong basal, and one ventral lamella with 7-9 cilia in one row (Figs 23, 24).

Dorsal chaetotaxy and tubercles (Figs 16, 29; Tab. 3a, c). Chaetotaxy and arrangement of tubercles of head as in Fig. 16 and Tab. 3a. Chaeta O present. Tuberle Oc with three chaetae. Chaetotaxy of Th. and Abd. as in Figs 16, 29 and Tab. 3c. Abd. IV with 3 chetae Di. Abd. V with 2+2 tubercles, tubercles Di not fused to (De+Dl).

Ventral chaetotaxy (Tab. 3c). On head, groups Vea, Vem and Vep with 4, 3, 4 chaetae respectively. Group Vi on head with 6 chaetae. On Abd.IV, furca rudimentary without microchaetae. On Abd.V, chaeta Vl present. Male without modified chaetae.

Legs (Fig. 28, Tab. 3c). Claw with small internal tooth. On tibiotarsi, chaeta M absent and chaetae B4 and B5 short and pointed (Fig. 28).

Remarks.

Taxonomy of the genus Yuukianura is controversial and problematic mostly due to insufficient descriptions of some species ( Deharveng et al. 2017). The majority of species live in littoral zones of streams and seashore of many Pacific regions, from Russian Far East to Hawaiian Island and North Australia. Yuukianura deharvengi sp. n. seems to be most similar to Y. halophila Yosii, 1955, found in the Nakanoshima Island belonging to the Ryukyu Archipelago (Southern Japan). They differ in a few subtle but distinctive and important features: shape of maxilla (in deharvengi with one ciliated lamella, in halophila lamellae without cilia), size of eyes (in deharvengi small, with diameter not longer than twice of diameter of closest granules; in halophila large, with diameter at least three times longer than diameter of closest granules), number of chaetae Di on Abd. IV (in deharvengi 3 chaetae, in halophila 2 chaetae), number of tubercles on Abd. V (in deharvengi 2+2, in halophila 1+1 tubercles), and position and size of inner tooth on claw (in deharvengi small and situated in one third of inner edge, in halophila large and in half of inner edge).