Notacanthurus baei, Braasch, Dietrich & Boonsoong, Boonsatien, 2009

Braasch, Dietrich & Boonsoong, Boonsatien, 2009, A new Notacanthurus Tshernova, 1974 and a new Rhithrogena Eaton, 1881 (subgenus Tumungula Zhou & Peters, 2004) from Thailand (Heptageniidae, Ephemeroptera), Zootaxa 2166, pp. 33-44 : 34-38

Notacanthurus baei sp.n.

Description. Mature larva, male: Body length 7.95 mm, length of caudal filaments 8.97 mm (female larva: body length 7.47 mm, length of caudal filaments 12.4 mm).

Head: Head subquadrate, brown, with irregular pale yellow (Fig. 1). markings; anterior and lateral margins round; posterior margin nearly straight; head width 2.4 mm, head length 1.7 mm, HI (1.4); eyes black, antennae brown. Labrum (Fig. 2) ca. 0.5x width of head, dorsally with dense hairlike setae, anteriorly convex and laterally tapering and slightly curved. Mandibles (Figs. 3–4) each with scattered setae along molar area; incisor moderately developed; dense hairlike setae on anterolateral margin. Maxillae (Fig. 5) with 19–21 comb-like setae on crown, with scattered hairlike setae on ventral surface; outer margin of maxillary palp segment 2 and 3 with long hairlike setal field; terminal segment of maxillary palp with dense hairlike setae. Hypopharynx (Fig. 6) with lingua convex at apex; superlinguae each with lateral arm developed, laterally with row of dense hairlike setae. Labium (Fig. 7) with U-shaped separation of glossae; glossae subquadrangular; paraglossae slightly expanded laterally; apical segment of each palp acutely pointed, dorsal surface with dense row of setae.

PLATE I. FIGURE 1. 1, Dorsal habitus of Notacanthurus baei sp. n.

Thorax: Thorax brown with scattered dark brown markings around basal wingpads; pronotum slightly smaller than head (Fig. 1), pronotum width 2.3 mm, smaller than head width. Legs: Forefemora (Fig. 8) light yellow, with median dark brown spots, scattered short simple stout setae on dorsal surfaces (Fig. 9), with row of long hair-like setae along posterior margins; claws (0.15 mm length) with basal tooth and 3 (rarely 2) subapical denticles (Fig. 10). Mid legs and hind legs similar to forelegs in colour and setation; foretibiae with weakly developed hair-like setae; mid tibiae and hind tibiae with dense hairlike setal field along outer margin.

PLATE II. FIGURE 2–7. Larva of Notacanthurus baei sp. n. 2, Labrum, dorsal view (left) and ventral view (right). 3, Left mandible, dorsal view. 4, Right mandible, dorsal view. 5, Left maxilla, ventral view. 6, Hypopharynx, dorsal view (left) and ventral view (right). 7, Labium, dorsal view (left) and ventral view (right).

Abdomen: Terga brown, with distinct oblique markings; terga I-IX each with single prominent median spine (Figs. 1, 11, 12), with row of short spiny bristles on posterior margin (Fig. 12). Sterna pale yellow; posterior end of sternum 10 with notch (Fig. 13), in mature specimens sometimes with prospective median dark stripe. Gills with both lamellae and fibrilliform portion on abdominal segments I–VI (Figs.15–16); gill VII (Fig. 17) with only lamellae; lamellae of gills I knife-shaped (Fig. 15); lamellae of gills II–VI each oval anteriorly; gills V–VI each with arrowlike accessory lobe (Fig. 16); lamellae of gill VII narrower lanceolate, with fine hair-like marginal setae (Fig. 17). Genitals: Prospective penis (Fig. 14) from last segment has an Electrogena -like shape with narrow, apically rounded lobes and median pair of titillators. Cerci about 1.3x length of body, each

segment with whorls of minute bristles and without interfacing setae (Fig. 18).

Imagines and subimagines: Unknown.

Etymology: Species name is given in honour of Prof. Yeon Jae Bae, Korea.

Diagnosis: Differing from genuine Notacanthurus , the new male larva matches that of Electrogena in having a simple, apical penis bulb (Fig. 14) with distally paired portions as wide as proximal integral portion provided with titillators medially. In contrast to Notacanthurus , it bears denticles on the claws; the hind margin of the head is nearly straight. With Notacanthurus it shares the head proportions, the longitudinal median ridge with posterior spines on terga I – IX as well as the colouration pattern of terga, the crossbar on the dorsal surface of the femur medially and the microstructure as chagrination of terga surface. Gill set differs from that of Notacanthurus by having the first gill knife-shaped, gills II – VI moderately lanceolate and gill VII narrower lanceolate (Fig. 17). Mouthparts differ from Notacanthurus in having the labrum more tapered and with longer decurved wings and mandibles with shorter stocky shafts.

PLATE III. FIGURE 8–18. Larva of Notacanthurus baei sp. n. 8, Foreleg, right, dorsal view. 9, Foreleg, setae on middle section of anterior face, dorsal view. 10, Foreleg, tarsal claw, dorsal view (right). 11, Abdomen, posterior segments, left lateral view. 12, Abdominal tergum VI, posterior margin. 13, Abdominal sterna, posterior end, ventral view. 14, Penis of mature male nymph, ventral. 15, Gill I, ventral view (right). 16, Gill V, ventral view (right). 17, Gill VII, ventral view (right). 18, Setae on cercus.

Discussion: The new species conspicuously resembles those in the genus Notacanthurus in having sharp spinal tubercles on most median terga, chagrination of terga, similar abdominal colour pattern, HI of 1.4, and a broad middle-femur cross band. In contrast to Notacanthurus that has a bilobate head of the penis lobes, the penis of the new species exhibits an Electrogena -like shape with apically rounded lobes. Deviating from Palearctic Notacanthurus of which claws have only a single subapical tooth, the new species bears also subapical denticles (Fig. 10). Considering all these respects, the new species points out affinities to genera Electrogena as well as to Notacanthurus . A further species apparently of the same generic origin and identified as Notacanthurus has been collected recently by Zhou (personal communication, 2004) in southern China and is being prepared by him for publication. Comparatively, the specimens of Southeast Asian new species are of smaller size, 8.0-9.0 mm, than most genuine Notacanthurus from Middle Asia (12.5 – 14.0 mm), Himalaya (10.0 – 14.0 mm), Korea ( Bae 1997: 9.4 mm, not full-grown). Counting all collection sites of species in northern Thailand, it seems that N. baei n. sp. inhabits smaller streams and spring brooks. Unfortunately, rearing of species was not possible because local people are very active in collecting and hunting for food at the river, even in the night, so that undisturbed working with appropriate devices was impossible. In the near future, recognition of larval stages by use of circumstantial evidence should be attempted based on longer experiences with fauna composition of the area by rearing at suitable habitats.

Material examined. HOLOTYPE: mature larva, male, THAILAND, North, Mae Hong Son Province, Soppong/Pangmapa, mouth of small tributary into Nam Lang river, 19°34.447ˏ N, 98°18.727ˏ E, altitude 605 m, 21-V-05, DB, in 70% alcohol; PARATYPES: 2 larvae, same locality and same date as holotype. 3 larvae, North Thailand, Mae Hong Son Province, Nam Rhin, small stream below waterfall, 19°28’N, 98°17’E, altitude 829 m, 11-IV-03, DB; 2 mature larvae, Thailand, Mae Hong Son Province, Pai river catchment, small brook, 19°16’N, 98°29’, altitude 835 m, DB; 2 larvae, North Thailand, Mae Hong Son Province, Soppong, River Nam Lang, 19°32’N, 98°14’E, 03-25.IV-03, DB; 4 larvae, North Thailand, Mae Hong Son Province, tributary system of Nam Lang River, upper reaches, near village Nam Rhin, 15 km NE Soppong, below a waterfall, 19°28’N, 98°17’, altitude 829 m, 11-IV-03, DB; 12 larvae, North Thailand, Mae Hong Son Province, Mae Hung near border to Myanmar, small stream, upper course, 19°41’, 98°10’E, altitude 764 m, 23-II-04, DB; 1 larva, North Thailand, Chiang Mai Province, Doi Inthanon National Park, small stream near Headquarters, 18°31’33.35’’N, 98°29’57.20’’E, altitude 1690 m, 20-V-05, DB; 1 larva, North Thailand, Chiang Mai Province, Doi Suthep National Park, tributary of Ping River; 18°48’20.05’’N, 98°55’17.01’’E, altitude 844 m, 19-IV-03, DB; 6 larvae, North Thailand, Chiangmai Province, right affluent of large Mae Nam Ping river, coming from Doi Suthep National Park, 18°49’N, 98°55’, 19-IV-03, DB.

Types deposition: HOLOTYPE: mature larva, male PARATYPES: 2 mature larvae, in ZMKU; some larvae in DBP, SMF Eph and MNHU.