Bleptus michinokuensis Tojo et Miyairi 2021, sp. nov.
Creators: name: Tojo, Koji
name: Miyairi, Ken
name: Kato, Yuto
name: Sakano, Ayana
name: Suzuki, Tomoya
Publisher: name: Zenodo
Year: 2021
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Ephemeroptera
Heptageniidae
Bleptus
Bleptus michinokuensis

description: Bleptus michinokuensis Tojo et Miyairi sp. nov.
[Japanese name: Obinashi-obi-kagerou]
Descriptions. Male adult (Figs. 3, 4A, 5, 7 vs. 6)
Measurements (N=14): Body 11−15 mm (antennae, cerci omitted); antenna 0.9−1.1 mm; cerci 25−31 mm; fore wings 11−15 mm. Head: Head capsule broadly yellow, area between three ocelli black; compound eyes black, clearly divided transversely into upper part with large facets and lower part with small facets; ocelli black, with translucent apical area (Figs. 3, 4A, 5B, 7A). Antennae milky white, unicolorous; scape and pedicel short (scape: pedicel = about 1:3); flagellum conspicuously long, moderately tapered distally, about 4.5 times as long as scape + pedicel (Figs. 3, 4A, 7A). Mouthparts extremely minute. Thorax: Thorax broadly yellow, with tergum brownish yellow; dark brownish line on lateral side (base of fore, middle and hind legs) (Figs. 3, 4A, 5 A−B). Fore wings hyaline with light yellowish transparent frontal border, hind wings small and hyaline; all veins brownish (Figs. 3, 4A, 5 A−B). Proximal half (coxa, trochanter and femur) of fore, middle and hind legs light yellow, apical half (tibia, tarsi and pretarsus) brownish. Fore legs elongated as long as body length (Figs. 3, 4A, 5B); femur and tibia long, about 8−9 times length of coxa + trochanter; tarsus five-segmented, much longer, about 1.2−1.3 times length of femur or tibia (Fig. 7 D−G); 1st tarsomere not fused to tibia; middle and hind legs about 2/3 length of fore legs, tarsus five segmented not fused to tibia (Fig. 7 D−G); pretarsus of all legs with paired claws of different shape (Fig. 7 D−G). Abdomen: Abdomen broadly light yellow, posterior margin of each segment dark brownish (Figs. 3, 4A, 5 A−B). Genital forceps brownish, five segmented (Fig. 5 B−D). Penis lobes long, about 1/3 length of genital forceps (Fig. 5D). Cerci dark brownish, about twice length of body (Figs. 3, 4A, 5B–C). Caudal filament completely degenerated (Figs. 3, 4A, 5 B−D).
Female adult (Fig. 4B). Measurements (N=6): Body 16−20 mm (antennae, cerci omitted); antenna 0.9−1.2 mm; cerci 25−29 mm; fore wings 16−18 mm. Head: Head capsule broadly yellow, area between three ocelli black; compound eyes black, somewhat smaller than those of males, not transversely divided (all facets’ size equal); color pattern of compound eyes and ocelli similar to those of males (Fig. 4B). Antennal structure and color pattern similar to those of males (Fig. 4B). Mouthparts extremely minute. Thorax: Thorax broadly brownish yellow, with dark brownish line on lateral side (base of fore, middle and hind legs) (Fig. 4B). Structure and color pattern of wings similar to those of males (Fig. 4B). Fore legs much shorter than those of males. Five segmented tarsomeres visible but not fused to tibia as in middle and hind legs of males. Structure of middle and hind legs similar to those of males. Color patterns of all of legs similar to those of males (Fig. 4B). Abdomen: Abdomen much thicker than that of males. Color pattern of abdomen slightly darker brownish yellow than males; posterior margin of each segment dark brownish (Fig. 4B). Sterna 7 and 9 posteriorly elongated, elongations of both sterna roundish. Structure and color pattern of cerci similar to those of males, although somewhat shorter in length (Fig. 4B). Caudal filament completely degenerated as in that of male (Fig. 4B).
Mature (ultimate instar) nymph (Figs. 8−12). Measurements (N=9): Body 15−20 mm (antennae, cerci omitted); antenna 0.9−1.1 mm; cerci 12−18 mm. Head: Head broadly brown with light brownish spots on front of ocelli; compound eyes brownish black with many sensory hairs in gap between individual facets (Figs. 8, 9G, H); ocelli translucent, with black basal area (Fig. 8). Antennae brownish; scape and pedicel short (scape: pedicel = 1:2); flagellum conspicuously long, moderately tapered distally, about 4−5 times as long as scape + pedicel (Fig. 9B–D). Labrum width subequal to length, fan-shaped and slightly swollen antero-medially; anterior-lateral margin with dense comparatively long setae (Fig. 9A, E, F, I, J). Inner and outer incisors of mandibles equal in length, inside ridges of inner and outer incisors each with row of thorn teeth (Fig. 10A, B, D, E); surface of molar parts of mandibles denticulate chitinous structure with many bundles of setae-like projections (Fig. 10 A−C, F). Maxillary endite pointed, undifferentiated into lacinia and galea parts; maxillary endite with row of numerous hairs of various lengths; maxillary palps long and two segmented; tip of maxillary palps with dense curled comb-shaped bristles (Fig. 11). Anterior margin of labial glossa and paraglossa with numerous setae; labial palps large and strong, two segmented, with numerous setae and rows of comb-shaped bristles (Fig. 12 A−D). Hypopharyngeal lingua egg-shaped, without hairs; superlinguae rounded with dense marginal setae (Fig. 12 E−H). Thorax: Tergum broadly brown with light brownish spots (Fig. 8). Mesonotum yellowish brown with black wing buds (Fig. 8). Metanotum yellowish brown, with minute black wing pads. Thoracic sterna milky white. All legs brown with light brownish spots (Fig. 8). Tarsal claws denticulate, blackish brown, and 1/3 as long as tarsi. Abdomen: Terga broadly brown with light brownish spots; sterna uniformly milky white. Median spines on posterior margins of terga 1 to 9 (Fig. 8C). Terga 1 to 7 with spines comparatively large and sharp. Gills on segments 1 to 7, each with dorsal leaf-like lamellae and ventral filaments; lamella of gill 1 very much smaller than those of other segments; only filamentous portion apparent. Cerci long, about same length as body (Fig. 8), light brown without rows of hairs. Caudal filament completely degenerated (Fig. 8).
Egg (Figs. 13−14). Egg pale yellowish translucent, ellipsoidal, about 130 µm long and about 80 µm wide; chorion about 2 µm thick, smooth surface structure (Figs. 13A vs. 14A). Adhesive layer or gelatinous layer very thin, about 0.1−0.2 µm thick. Chorion with some micropyles on equator; micropyle (micropylar opening, s. str.) about 1.0 µm in diameter, with large sperm guide structure about 10 µm in diameter (Figs. 13B vs. 14B).
Etymology. ‘Michinoku’ is the historic name of the Tohoku District of Japan, almost perfectly matching the distributional range of this new Bleptus mayfly. This name is also often still used today as a favored name of this area. The Japanese common name, “Obinashi-obi-kagerou,” means that there is no black line pattern on the forewings.
Distribution. This new species of mayfly was collected from riverhead locations in the seepage zone of a small branch of the ‘Tachiya-zawa-gawa’ River located amongst the northern foothills of Mt. Gassan (Type locality: Shonai-machi Town, Yamagata Prefecture, Honshu, Japan; locality No. 14). In addition to this type locality collection site, many specimens of this new mayfly species were also collected from some other sites surrounding the type locality amongst the foothills of Mt. Gassan (Table 1, Fig. 1).
Although we have been able to collect only nymphs (i.e., we could not confirm their adult form and characteristics), some specimens collected from other areas of the Tohoku District (i.e., from Aomori, Iwate, Akita, Miyagi, Yamagata and Fukushima Prefectures; Table 1, Fig. 1) and the northernmost parts of Niigata Prefecture belonged to the same genetic clade (according to their mtDNA COI, 16S rRNA and nDNA ITS2 gene sequences) as the specimens from Mt. Gassan (type locality), and some specimens collected from sites around Mt. Gassan. Detailed data of their genetic relationships are discussed later in the section titled ‘ Phylogenetic relationships’. Thus, this new mayfly species seems to have a comparatively wide distribution in the Tohoku District and northernmost parts of Niigata Prefecture.
Materials examined. The holotype (male adult), allotype (female adult) and paratype (nymph), were preserved with 70% ethanol and deposited in the collections of the Natural History Museum and Institute, Chiba (CBM-ZI 151242−151244).
Holotype: Male adult (imago), a small freshwater branch of the ‘Tachiya-zawa-gawa’ River located amongst the northern foothills of Mt. Gassan; Shonai-machi Town, Yamagata Prefecture, Honshu, Japan (locality No. 14); collection on 24-VI-2010 (fixation on 25-VI-2010); K. Tojo, T. Suzuki and A. Kume leg., CMB-ZI 151242. Allotype: One female adult (imago) with eggs; same data as holotype for locality and collectors; collection on 24-VI- 2010 (emergence and molt to adult on 4-VII- 2010 in laboratory; fixation on 5-VII-2010; CMB-ZI 151243. Paratype: One ultimate instar nymph; same as holotype for locality and collectors; collection on 24-VI-2010; fixation on 30-VI-2010; CMB-ZI 151244. Other materials: Two male adults, two female adults and two nymphs (same data as holotype for locality and collectors) were preserved with 70% ethanol and deposited in the collections of the Shinshu University Museam. Other materials were deposited in the private collection of the corresponding author (KT).
description: Published as part of Tojo, Koji, Miyairi, Ken, Kato, Yuto, Sakano, Ayana & Suzuki, Tomoya, 2021, A description of the second species of the genus Bleptus Eaton, 1885 (Ephemeroptera: Heptageniidae) from Japan, and phylogenetic relationships of two Bleptus mayflies inferred from mitochondrial and nuclear gene sequences, pp. 333-360 in Zootaxa 4974 (2) on pages 342-346, DOI: 10.11646/zootaxa.4974.2.5, http://zenodo.org/record/4775688