Isotoma koreana, Park, 2018

Park, Kyung-Hwa, 2018, Redescription of Isotoma grana Lee, Kim & Kim, 1993 and description of a new species of Isotoma Bourlet, 1839 (Collembola: Isotomidae) from Korea, Zootaxa 4450 (4), pp. 473-480 : 474-475

Isotoma koreana sp. nov.

( Figures 1–21 )

Type material. Holotype: female on slide, KOREA: Jejudo Island: 508m alt., Mulyeongari oreum N33˚21′51″, E126˚41′26″, Sumang-ri, Namwon-eup , Seogwipo-si , collected from fallen leaves of broad-leaf bamboo at the foot of the Parasite volcano, 20–XI–2009, leg. Kyung-Hwa Park . Paratypes: 3 females and 2 males on slides, the same data as holotype . 1 female and 1 male on slides, KOREA: Shinhapri N 36˚08′19″, E126˚33′16″, Seocheon-gun , Chungcheongnam-do Province; collected from fallen leaves of oak trees, 19–III–2010, leg. Kyung-Hwa Park .

Holotype is deposited in the National Institute of Biological Resources ( NIBR), Incheon, Republic of Korea . Paratypes are deposited in NIBR and the Insect Collection , Department of Biology Education , Chonbuk National University, Jeonju, Korea ( ICCU) .

Description. Body length up to 2.6 mm. Habitus as for the genus. Abd. V and VI separate. Colour of body greyish yellow in alcohol ( Fig. 1 ); Antenna blue; Head with front transverse band connecting eye-spots and medial patch in a posterior position ( Figs 1, 2 ). Th. II–Abd. II with distinct narrow longitudinal middorsal dark stripe; Lateral sides of Th. II–III with longitudinal stripes; All segments with narrow transverse band along the posterior edge, especially thicker on Abd. II, III and IV; Abd. III and IV, sometimes even Abd. II, with irregular transverse bands on mid dorsally.

Furca pale.

Head. Eye patch black, with 8 ocelli on each side ( Fig. 4 ), G and H smaller. PAO small, roundish, shorter than 1/2 diameter of nearest ocellus. All antennal segments with many hair-like sensilla. Ant. I with 2–4 short ventral sensilla and 3–6 ventrolateral sensilla ( Figs 5, 6 ). Ant. II with a curved, thickened lateroapical sensillum and several hair-like sensilla in ventral and dorsal sides ( Figs 7–10 ). Ant. III organ normal, surrounded by several short blunt sensilla and thin hair-like sensilla ( Fig. 11 ). Ant. IV without apical bulb, with simple or bifurcate subapical pin-chaeta ( Fig. 12 ) and short rod-shaped subapical organite in a pit ( Fig. 13 ). Labrum 4/554, with four apical folds, lateral folds much larger than median pair. Frontoclypeal area with 15 chaetae. Maxilla with 6 short lamellae covered with denticles, lamella 1 not passing tip of capitulum. Maxillary palp bifurcate with 4 sublobal chaetae ( Fig. 14 ). Labium with 4 proximal and 7–11 basomedian chaetae, and guards; guard e7 present.

Body chaetotaxy. Ordinary chaetae varying lengths and thickness abundant. Macrochaetae long and moderately serrated. Macrochaetae on Abd. I–VI as 3,3,3,3,5,4 ( Fig. 3 ; short simple chaetae omitted from the drawing). Median macrochaetae on Abd. V are more than 5 times of length of inner claw III. Mesochaetae on Th. II–Abd. I often hardly distinguished from macrochaetae in large specimens. Unpaired central chaeta on dorsal side of Abd. VI (m0) short simple chaeta. Sensillary chaetotaxy of Th. II–Abd. IV as 66/5556, including 11/111 spinelike microsensilla. All posterior chaetae on anal valves smooth.

Appendages. Unguis simple, with 1 pair of lateral teeth and 2 inner teeth. Unguiculus with one corner tooth ( Figs 15, 16 ). Tita with spine-like serrated chaetae along inner edge, stronger on leg III; without clavate hairs, tenant hairs pointed; apical whorl has 8 chaetae. Ventral tube with 16–23 anterior and 25–39 laterodistal chaetae on each side, 32–40 posterior chaetae ( Fig. 18 ). Retinaculum with 4+4 teeth and 18–28 chaetae ( Fig. 20 ). Furcula long and tapering, reaching ventral tube. Manubrium with 3–6+3–6 strong, spine-like smooth chaetae in ventroapical position ( Fig. 19 ). Manubrial thickening simple. Dorsal manubrial macrochaeta A shorter than B. Dens long and continuously narrowing, on posterior side with many crenulations. Posterior side of dens with few chaetae, two of which in the basal part are larger ( Fig. 17 ). Mucro tridentate ( Fig. 21 ).

Etymology. The name of the new species refers to Korea, the country of the type locality.

Remarks. The new species Isotoma koreana sp. nov. belongs to the species group as it has simple manubrial thickening, and two inner teeth on unguis and one corner tooth on unguiculus. This new species is allied to Isotoma pinnata by having middorsal longitudinal line on body and much smaller PAO than nearest ommatidia ( Yosii, 1939, 1963; Lim & Park, 2013). However, it can be easily distinguished from the latter by the body pattern (strong central stripe in I. pinnata vs. fine central stripe in I. koreana sp. nov.) and the structure of apical spines on manubrium (serrated in I. pinnata vs. smooth in I. koreana sp. nov.). Morphologically it is near I. iranica Arbea & Kahrarian (2015) , but it can be easily separated from it by its simple (in I. koreana sp. nov.) vs. bispinose (in I. iranica ) manubrial thickening and the chaetotaxy. An indentification key to the Sino-Japanese species of Isotoma is provided here.

Figures

FIGURES 1–6. Isotoma koreana sp. nov.: 1, habitus (photo); 2, habitus (drawing); 3, dorsal chaetotaxy of Th. II–Abd. VI (large circles indicate meso- or macrochaetae, small circles indicate common setae but short simple chaetae omitted from the drawing); 4, eye-field and PAO; 5, Ant. I (ventral); 6, Ant. I (dorsal). Scale bar 1000 µm (Fig. 2), 100 µm (Figs 3–6).

FIGURES 7–14. Isotoma koreana sp. nov.: 7, Ant. II (dorsal); 8, Ant. II (dorsal sensilla); 9, Ant. II (ventral); 10, Ant. II (ventral sensilla); 11, Ant. III (dorsal); 12, Tip of Ant. IV (ventral); 13, Tip of Ant. IV (dorsal); 14, maxillary palp. Scale bar 100 µm (Figs 7–13), 50 µm (Fig. 14).

FIGURES 15–21. Isotoma koreana sp. nov.: 15, first leg (lateral); 16, second leg (ventral); 17, dens; 18, ventral tube; 19, apical setae on manubrium (ventral; drawn left side); 20, retinaculum; 21, mucro. Scale bar 100 µm (Figs 15–17), 50 µm (Figs 18, 20), 25 µm (Figs 19, 21).