Crossodonthina leodeus sp. nov.

[Japanese name: Shishigami-aka-ibotobimushi]

Figs 1C, 1H, 3–5; Tables 2–5

Material examined. Holotype: female, collected at Kamamamine Park, Shimozato, Hirara, Miyako Island, Okinawa, Ryukyu Archipelago, Japan (24.7982°N, 125.2753°E, elevation 28 m) on 10 May 2023 by Ohira, A., Nakamori, T. and Takaesu, R. Deposited in the National Museum of Nature and Science, Tsukuba, Japan (NSMT-Ap 717).

Paratypes: 2 males, 7 females, collected at Kamamamine Park, Shimozato, Hirara, Miyako Island, Okinawa, Ryukyu Archipelago, Japan (24.7982°N, 125.2753°E, elevation 28 m) on 10 May 2023 by Ohira, A., Nakamori, T. and Takaesu, R. Deposited in the National Museum of Nature and Science, Tsukuba, Japan (NSMT-Ap 718–726; INSD accession numbers LC857141 – LC857143 for COI gene) .

Other materials examined. Four males and five females, collected at Kamamamine Park, Shimozato, Hirara, Miyako Island, Okinawa, Ryukyu Archipelago, Japan (24.7982°N, 125.2753°E, elevation 28 m) on 10 May 2023 by Ohira, A., Nakamori, T. and Takaesu, R . Two males and six females, collected at Kamamamine Park, Miyako Island, Okinawa, Ryukyu Archipelago, Japan (24.7982°N, 125.2753°E, elevation 28 m) on 24 April 2024 by Nakamori, T .

Diagnosis. Eyes 3+3, black. Cephalic chaeta O present. The sgd displaced apically, close to i on Ant. IV. Mandible head consisting of 6 rami and 3 basal teeth. Maxilla head consisting of 3 stylets. Labrum granulated, chaetal formula 2/2, 2. Labium with 10 chaetae and 2 x. Head Oc with 3 chaetae. Lateral sensilla present on tubercles Dl on Th. II and III, and on L on Abd. I–IV.

Description. Body length about 1.5–2.2 mm. Colour red in living specimen (Fig. 1C) and white in alcohol. Eyes 3+3, black (Fig. 3B). Postantennal organ absent. Antennae shorter than head. Ant. III and IV dorsally fused (Fig. 4A). Ant. I and II with 9 and 11 chaetae, respectively. Ant. III organ with 5 sensory chaetae, including sgd, sgv, ms and 2 finger-like rods in separate pits. The sgd displaced apically, close to i. Ant. IV with trilobed apical bulb, dorsal chaetotaxy with 8S and i (Fig. 4A). Mandible head consisting of 6 rami and 3 basal teeth (Fig. 4D): five rami of flagellum (Fig. 4D): the largest one (ramus 1) twice as long as the smaller two (rami 3 and 4), with simple (rarely bifurcated) cilia; medium one (ramus 2) slightly longer than the smaller two (rami 3 and 4), with simple (rarely bifurcated) cilia; 2 smaller ones (rami 3 and 4) multiply branched; the smallest one (ramus 5) with simple and bifurcated cilia; basal ramus (ramus 6) as fringed lamella. Medial tooth much smaller than the other two. Maxilla head consisting of 3 stylets: inner one with 2 minute apical teeth, middle one fringed, outer one needle-shaped (Fig. 4E). Labrum granulated, chaetal formula 0/2, 2 (Fig. 4B). Boundary between labrum and prelabral area not distinct. Labium with 10 chaetae and 2 x (Fig. 4C).

Cephalic tubercles and chaetotaxy. Cephalic area with 12 separate tubercles. Chaetotaxy of dorsal head as in Fig. 3B. Tubercle Cl with 4 chaetae, An with 4 chaetae, Fr with 3 chaetae (O-chaeta present), Oc with 3 chaetae, Di with 2 chaetae, De with 2 chaetae, area between De and L with 1–2 microchaetae and Dl+L+So with 11–16 chaetae (Fig. 3B, Table 2). Ventral chaetotaxy of the head as in Fig. 3A and Table 3.

Body tubercles and chaetotaxy. Th. I–Abd. VI without unpaired tubercles. Tubercles Di on Th. I and II not distinct. Tubercles Di on Th. III and Abd. I–V distinct. Th. I with 3+3 tubercles (Di, De, Dl). Th. II–Abd. IV with 4+4 tubercles, respectively (Di, De, Dl, L). Abd. V dorsally with 2+2 tubercles (Di, De+Dl); tubercle L ventrally situated (Fig. 3B). Abd. VI with 1+1 tubercles. Body dorso-lateral chaetotaxy as in Fig. 3B and Table 4. Sensory chaetae on the body acuminate, long and smooth; macrochaetae slightly serrated (Fig. 5). Formula of s and ms on half terga of Th. II–Abd. V as 2+ms, 2/2, 2, 2, 2, 1. Tubercles De with s on Th. II–Abd. IV. Each tubercle De+Dl on Abd. V with 1 sensory chaeta. Lateral sensilla present on tubercles Dl on Th. II–III and on L on Abd. I–IV. Ventral chaetotaxy of Abd. I–Abd. VI as in Fig. 3C.

Appendages. Chaetotaxy of legs, ventral tube and furcular remnant as in Table 5. Tibiotarsi I–III with 19, 19 and 18 chaetae, respectively. Unguis with 1 inner tooth, unguiculus absent (Fig. 4F). Ventral tube with 4+4 chaetae. Furcula absent. Furcular remnant with 3 chaetae. Genital plate with 16–42 chaetae (male: 18–26; female: 16–42). Each ventral anal valve with 14–15 Ve chaetae and 3 hr microchaetae. Dorsal anal valve with 3 hr microchaetae (Fig. 3C).

Etymology. The name leodeus, as a Latin noun, is derived from the Latin nouns leo (lion) and deus (god). The species was named after the Shisa, Okinawan guardian lions. Shisa are regarded as traditional amulets and guardian deities in Okinawa Prefecture. The park where they were collected has a huge Shisa monument, so the name was derived from the guardian deity.

Ecology. This species was found in leaf litter in forests. The species emitted light when stimulated (Fig. 1H).

DNA barcoding. The p -distances for the COI gene within Crossodonthina leodeus sp. nov. (3 sampled individuals) were 0.000. No COI gene sequences with>93% identity to the new species were found in the GenBank or BOLD databases. The p -distances of the COI gene between C. leodeus sp. nov. and other congeneric species, i.e., C. elegans (LC857144 – LC857146; present study), C. laterisensillata (LC612526 – LC612528; Ohira et al. 2023), Crossodonthina nipponica Yosii, 1954 (LC715144 – LC715145; Ohira et al. 2023), collected from their respective type localities, were 11.7%–11.8%, 8.2%–8.9% and 19.6%, respectively. In addition, the p -distance between C. leodeus sp. nov. and an undescribed Crossodonthina species collected from Okinawa Island (LC760484 – LC760485; Ohira et al. 2023) was 17.3%.

Remarks. Crossodonthina leodeus sp. nov. is similar to Crossodonthina tridentiens Yue & Yin, 1999 in having well-defined tubercles and De tubercles fused to Dl tubercles on Abd. V, but the new species can be distinguished from the latter by having additional sensory chaetae on tubercles L of Abd. I–IV and 6 rami on the mandible (no additional sensory chaetae on tubercles L of Abd. I–IV and 4 rami on the mandible in C. tridentiens). Crossodonthina leodeus sp. nov. is also similar to C. laterisensillata from Iriomote Island and Crossodonthina tiantongshana Xiong, Chen & Yin, 2005 in mouthpart structures and in tergal sensory chaeta formula. However, it differs from C. laterisensillata by having chaetae Di2 on Abd. IV as microchaetae (mesochaetae in C. laterisensillata). Furthermore, the new species is genetically distinct from C. laterisensillata, with a p -distance of 8.2%–8.9% in the COI gene. Crossodonthina leodeus sp. nov. also differs from C. tiantongshana by having an unguis with an inner tooth without basal denticules and 3-branched maxillae consisting of 1 bidentate, 1 fringed and 1 needle-shaped stylet, while C. tiantongshana has an unguis with an inner tooth, with 1–3 tiny basal denticules and 4-branched maxillae consisting of 1 tridentate, 1 fringed and 2 needle-shaped stylets (Luo & Chen 2010).

A non-luminous congeneric species currently under taxonomic examination has been collected from Okinawa ( Crossodonthina sp. of Ohira et al. 2023; voucher specimen numbers, NSMT-Ap 628–629; INSD accession numbers of DNA barcodes, LC760484 – LC760485).This species resembles C. nipponica in lacking additional sensory chaetae on tubercles L of Abd. I–IV. This information was not provided in the previous study and is presented here. In contrast, the species described here possesses additional sensory chaetae on tubercles L of Abd. I–IV, distinguishing it from both C. nipponica and the Okinawan species of Crossodonthina .