Blasconura triangulum, Kasai & Hayasaka & Sawahata, 2022

Kasai, Hiro, Hayasaka, Daisuke & Sawahata, Takuo, 2022, First report of the genera Paralobella and Blasconura (Collembola: Neanuridae Neanurinae) from Japan with the description of three new species, Zootaxa 5168 (3), pp. 332-349 : 338-343

Blasconura triangulum sp. nov.

[Japanese name: sankaku-niseamime-ibotobimushi]

Figures 12–24 , Table 2

Type material. Holotype: female, Japan, Okinawa, Miyako-jima (alt. 39 m, 24°48'38"N 125°18'48"E), 24-XII- 2021, Hiro Kasai leg. ( NMNS, NSMT-Ap 596) . Paratypes: 2 females ( NMNS, NSMT-Ap 600–601) , 3 males ( NMNS, NSMT-Ap 597–599) and 2 juveniles ( NMNS, NSMT-Ap 602–603), same data as holotype .

Diagnosis. 2+2 unpigmented eyes on head. Body color light red alive and white in alcohol. Dorsal tubercles well developed, with tertiary granulation. Tubercle Fr fused to An, forming an Af tubercle. 2 tubercles Di very close to each other, but not fused. Labrum chaetotaxy as 0/ 2, 2. Mandible with three teeth. Maxilla consists of 2 styliform lamellae.Ant. I and II with 7 and 11 chaetae respectively. Cephalic chaeta O absent. Cephalic tubercles Dl, L, and So fused with 15 chaetae. Chaetae formula of tubercle Di on Th. I–Abd. V as 1, 3, 3/2, 2, 2, 2, 3. Length of chaeta Di 1 in Abd. V 146–163 µm. Tibiotarsi I–III with 19, 19, and 18 chaetae respectively. Unguis without an inner tooth.

Description. Body length: 1.33–1.79 mm in adults. Color: Light red alive ( Fig. 12 ) and white in alcohol. Eyes: 2+2, unpigmented. All dorsal tubercles well developed with tertiary granulation ( Figs 12–13 ). Ordinary chaetae of five types: Ml, Mc, Mcc, me, and mi. Macrochaetae Ml relatively long, thickened, and barbulated ( Fig. 16 ); some lateral and ventral chaetae weakly acuminate, and slightly serrated. Macrochaetae Mc morphologically similar to long macrochaetae, but much shorter. Macrochaetae Mcc shorter than Mc, slightly barbulated, apically pointed. Mesochaetae and microchaetae similar to ventral chaetae: thin, smooth, and pointed. S–chaetae of tergites thin, smooth.

Antennal morphology and chaetotaxy ( Figs 14–15 and Table 2c ). Antenna 4-segmented. Ratio of antennal segments as I: II: III + IV = 1: 1: 1.8. Ant. I with 2 Ml and 5 me. Ant. II with 2 Ml, 1 Mc (me), and 8 me. Antennal macrochaetae located in subcuticular reticulation areas ( Fig. 14 ). Ant. III dorsally fused to Ant. IV. AOIII consists of 2 short rods, exposed in separate pits. Guard chaeta sgd positioned near the 2 rods ( Fig. 14 ). Apical bulb trilobed.

Mouthparts. Labrum chaetotaxy 0/2, 2 ( Fig. 19 ). Labium with 4 basal, 3 distal, and 4 lateral chaetae, papillae x absent ( Fig. 20 ). Mandible with 3 teeth ( Fig. 17 ). Maxilla styliform, maxillary head consisting of 2 lamellae ( Fig. 18 ).

Cephalic tubercles and chaetotaxy ( Figs 13 , 21, 24 , and Table 2a, 2b ). Tubercle Fr fused to An across the midline, forming an Af tubercle, not fused to Cl ( Figs 13 , 21 ). The anterior margin area (between chaetae C) of tubercle Af slightly or deeply hollow ( Fig. 21 ). Tubercles Dl, L, and So fused. 2 tubercles Di very close to each other, but not fused. Macrochaeta length in adults (n = 6): chaeta F 86 µm (63–86 µm), chaeta B 98 µm (92–122 μm), chaeta A 82 µm (62–93 μm), chaeta Ocm 115 μm (99–133 μm), chaeta Ocp 76 μm (33–76 μm), chaeta Di1 95 μm (76–113 µm), chaeta De1 107 μm (88–121 µm), lateral Ml 97–134 µm (96–151 µm), and lateral Mc 41 µm. Lateral chaeta Mc basically me. On the ventral side of head, group Vi with 6+6 chaetae, and groups Vea, Vem, and Vep with 5, 3, and 4 chaetae respectively ( Fig. 24 ).

Body tubercles and chaetotaxy ( Figs 13 , 22 and Table 2d ). Tubercle L on Abd. I-IV shifts backward or to the ventral side.Abd. V with 6 tubercles, De and Dl fused, and L situated on the ventral side. Weakly cryptopygy. Length of chaeta Di1 on Abd. V in adults (n = 6) 163 µm (146–163µm) ( Fig. 16 ). Ventral chaetotaxy of Abd. I–VI ( Fig. 22 ). Chaeta L2 on Abd. V smooth (sometimes weakly serrated) and apically pointed ( Fig. 22 ). VT with 4+4 chaetae. Furcular remnant with 4 chaetae. Genital plate with 10–27 and 43–57 chaetae in females and males respectively.

Legs ( Fig. 23 and Table 2d ). Tibiotarsi I–III respectively with 19, 19, 18 chaetae, chaetae M present. Unguis without inner tooth and tenent hair ( Fig. 23 ).

Etymology. The species epithet “triangulum” is used here to mean “triangle” and is in reference to the tubercle Af triangle form.

Ecology. The new species is a resident of fallen branches on the floor of secondary forests dominated by Pinus luchuensis .

Remarks. Nine species of the genus Blasconura have been reported till date, mainly from South and Southeast Asia ( Bedos&Deharveng2000).Six of these species have tubercleAf on head,and the other three species have tubercle An separated from Fr. Blasconura triangulum sp. nov. is the seventh species, with a tubercle Af. B. triangulum sp. nov. is most similar to B. batai Bedos & Deharveng, 2000 and B. hirtella ( Börner, 1906) . Resemblance is observed in terms of absent cephalic chaeta O, cephalic tubercle Oc with 3 chaetae, macrochaeta barbulated, tubercle Di of Th. I with 1 chaeta, and tubercle Di of Abd. I–IV with 2 chaetae. However, these species can be distinguished by the following characteristic features: inner tooth on the claw (in B. triangulum sp. nov. absent, in batai and hirtella present), distance between 2 tubercles Di on head (in B. triangulum sp. nov. very close, in batai and hirtella distinctly separate), chaetae formula of tubercle Di on Th. I–Abd. V (in B. triangulum sp. nov. and hirtella 1, 3, 3/2, 2, 2, 2, 3, in batai 1, 2, 2/2, 2, 2, 2, 2), number of chaetae of tubercle (De+Dl) on Abd. V (in B. triangulum sp. nov. 4+s, in batai 3+s, in hirtella 6+s), and number of chaetae on the ventral tube (in B. triangulum sp. nov. and batai 4+4, in hirtella 3+3). For morphological characteristics of B. hirtella, Yosii (1976) can be referred.

d) Postcephalic chaetotaxy.

Figures

FIGURES 12. Live specimen of Blasconura triangulum sp. nov.

FIGURES 13–18. Blasconura triangulum sp. nov. 13, dorsal tubercles and chaetotaxy; 14, dorsal chaetotaxy of Ant. I–IV; 15, ventral chaetotaxy of Ant. I–IV; 16, chaeta Di1 of abd. V; 17, mandible; 18, maxilla.

FIGURES 19–24. Blasconura triangulum sp. nov. 19, labrum; 20, labium; 21, Dorsal tubercles and chaetotaxy of central area on head; 22, ventral side of abdomen; 23, chaetotaxy of tibiotarsus III and unguis; 24, ventral chaetotaxy on head.

Tables

TABLE 2. Chaetotaxy of Blasconura triangulum sp. nov.

a) Cephalic chaetotaxy––dorsal side.
Tubercle	Number of chaetae	Types of chaetae	Names of chaetae
Cl	4	Mc	F
		me	G
An+Fr	10	Ml	B
		Mc	A
		me or mi (or Mcc)	E
		mi	C, D
Oc	3	Ml	Ocm
		Mc or Mcc	Ocp
		mi	Oca
Di	1	Ml or Mc	Di1
De	3	Ml	De1
		me or mi	De2, De3
Dl+L+So	15	3Ml+Mc+me (Mc)+8me+2mi	uncertain
b) Cephalic chaetotaxy––ventral side.
Group		Number of chaetae
Vi		6
Vea		5
Vem		3
Vep		4
Labium		11, 0x
c) Chaetotaxy of antennae.
Segment, Group	Number of chaetae Segment, Group		Number of chaetae adult
I	2Ml+5me	IV	or, 8 S, i, 12 mou, 6 brs, 2 iv
II	2Ml+Mcc(me)+8me
III	5 sensilla AOIII
ve	5	ap	8 bs, 5 miA
vc	4	ca	2 bs, 3 miA
vi	4	cm	3 bs, 1 miA
d	5	cp	8 miA, 1 brs