Megabranchiella longusa Phlai-ngam & Tungpairojwong, 2022

Phlai-ngam, Sirikamon, Boonsoong, Boonsatien, Gattolliat, Jean-Luc & Tungpairojwong, Nisarat, 2022, Megabranchiella gen. nov., a new mayfly genus (Ephemeroptera, Baetidae) from Thailand with description of two new species, ZooKeys 1125, pp. 1-31 : 1

publication ID	https://dx.doi.org/10.3897/zookeys.1125.90802
publication LSID	lsid:zoobank.org:pub:F4ACDB4D-5BC1-415C-B098-5D494A15263A
persistent identifier	https://treatment.plazi.org/id/65816410-4304-459F-85AF-5C372989F48A
taxon LSID	lsid:zoobank.org:act:65816410-4304-459F-85AF-5C372989F48A
treatment provided by	ZooKeys by Pensoft
scientific name	Megabranchiella longusa Phlai-ngam & Tungpairojwong
status	sp. nov.

Treatment

Megabranchiella longusa Phlai-ngam & Tungpairojwong sp. nov.

Holotype.

One male larva on slide and SEM stubs (KKU-AIC), Thailand, Chiang Mai, Chom Thong district, Ban Luang, Siribhum waterfall, 18°32'50.02N, 98°30'49.79E, 1,359 m, 11.03.2021, B. Boonsoong and C. Sutthinun leg.

Paratype.

One larva in alcohol (ZMKU), same data as holotype.

Other materials.

One larva in alcohol (MZL), Thailand, Nan, Bo Kluea district, Kluea district Tai , Sapan River , 19°09'19.09N, 101°10'12.96E, 995 m, B. Boonsoong and C. Suttinun leg. GoogleMaps

Description.

Coloration (Fig. 9A-B View Figure 9 ). Head dorsally brownish, darker brown along frontal suture. Thorax dorsally brown; pronotum with dark brown pattern medially, mesonotum with longitudinally darker brown pattern medially. Abdomen light brown with dark brown pattern; tergites I-VIII brownish, with darker brown marks laterally to posterior margin, tergites II-III with a paired of pale dots medially, tergites IV-VIII with distinct paired of pale, oblique streak, and with a pale, longitudinal pattern medially, tergites IX-X paler than other tergites, with the same pattern as tergites IV-VIII; abdomen ventrally light brown (Fig. 9C View Figure 9 ). Legs light brown; dorsal, ventral, and apical femur margins dark brown; claws distally dark brown. Caudal filaments brownish.

Body (Fig. 9 View Figure 9 ). Ventrally flattened (Fig. 9C View Figure 9 ), body length 3.5 mm, covered with scattered long, hair-like setae.

Head (Fig. 9B View Figure 9 ). Lateral view rounded, head width ca. 1.2 × as long as head length.

Antenna. Ca. 2 × as long as head length (Fig. 9B View Figure 9 ); scape without process, subequal in width and length, slightly shorter than pedicel, pedicel ca. 2 × as long as width, scape and pedicel almost bare, without scales bases, covered with scattered long, fine setae; flagellum covered with scattered long, fine setae.

Labrum (Fig. 10A View Figure 10 ). Broadly rounded; wider than long, width ca. 1.17 × as long as length; dorsal surface with submarginal row composed of one long, point, simple seta medially plus three long, point, simple setae anterolaterally, dorsal surface with scattered simple, hairlike setae; distal margin with anteromedian notch shallow. Ventrally with submarginal row of setae composed of lateral and anterolateral long, feathered setae and medial long, pectinate setae; ventral surface with five short, spine-like setae near lateral and anterolateral margin.

Right mandible (Fig. 10B View Figure 10 ). Canine (Fig. 10C View Figure 10 ) with 4 + 4 apically rounded denticles, largely fused outer and inner incisors; inner margin of inner incisor with small denticulation; prostheca robust (Fig. 10D View Figure 10 ), apically with small denticles and comb-shaped structure; mola between mola and prostheca smooth, without setae; mola with well-developed denticulation; apex of mola with tuft of spines like setae.

Left mandible (Fig. 10E View Figure 10 ). Canine (Fig. 10F View Figure 10 ) with 4 + 4 apically rounded denticles, largely fused outer and inner incisors; inner margin of inner incisor with small denticulation; prostheca robust, apically with small denticles and comb-shaped structure (Fig. 10G View Figure 10 ); mola between mola and prostheca smooth, without setae; mola with reduced denticulation, molar area with numerous small, round teeth, apex of mola with tuft of spines like setae.

Maxilla (Fig. 10H View Figure 10 ). Short and compact; galea-lacinia (Fig. 10I View Figure 10 ) with long, robust, simple setae under crown; inner dorsal row of setae with denti-setae; distal denti-seta tooth-like, middle denti-seta (Fig. 10J View Figure 10 ) slender, bifid and pectinate; proximal denti-seta slender, pectinate; inner ventral row of six robust, simple setae; medially with one seta and four simple setae. Maxillary palp 2-segmented, with scattered small, blunt setae; distal segment with distinct, small tip at apex.

Labium (Fig. 10K View Figure 10 ). Short and compact; glossa basally broad, narrower toward apex, slightly shorter than paraglossa; inner margin with medium, pointed, simple setae; apex with four long, robust, pectinate setae. Paraglossa sub-rectangular, broader than glossa, apically curved inward, apical margin with three rows of long, robust, apically pectinate setae (Fig. 10L View Figure 10 ), ventrally with 2-3 long, spine-like setae near inner margin, with an arch of 4-5 long, simple setae on outer margin. Labial palp 3-segmented, segment I rectangular and broad, covered with scattered fine, setae and several micropores; segment II with small distolateral expansion, with a few scattered, simple setae and a row of setae reduced to two large, blunt, robust, simple setae near distal margin; segment III rounded, covered with long, robust, simple setae.

Hypopharynx (Fig. 10M View Figure 10 ). Lingua subequal to superlingua, apically rounded, with apical tuft of fine, short simple setae; superlingua with distal margin rounded, with fine, short simple setae along margin.

Thorax. Hindwing pads (Fig. 13A View Figure 13 ). Highly reduced.

Forelegs (Fig. 12A View Figure 12 ). Ratio of foreleg segments 0.68: 0.59: 0.25. Femur (Fig. 13B View Figure 13 ). Length ca. 3 × maximum width. Dorsal margin of femur (Figs 11A View Figure 11 , 13C-D View Figure 13 ) with a row of 18-20 long, robust, apically pointed, laterally pectinated setae; short stout, lanceolate, laterally pectinate setae and scattered fine hair-like setae along dorsal and ventral margins; femora patch present; surface with scattered tiny spines anteromedially (Fig. 13E View Figure 13 ); dense long, fine, small apically blunt, hair-like setae present; dorsal margin of tibia with a row of long, apically pointed, pectinate setae; several short stout, lanceolate, laterally pectinate setae and scattered short, apically pointed, hair-like setae along dorsal and ventral margins, patella-tibial suture present; tarsus dorsally with a row of fine, simple setae; ventral margin with a row of fine, simple setae; surface covered with scattered fine hair-like setae. Tarsal claw (Fig. 12B View Figure 12 ) with one row of about 16 denticles increasing in length toward apex, subapical setae absent. Midlegs and hindlegs. As forelegs.

Abdomen (Fig. 11B View Figure 11 ). Tergites. Posterior margin smooth, posterior marginal spines extremely reduced to absent (Figs 11C View Figure 11 , 12C View Figure 12 , 13F View Figure 13 ), tergal surface with scattered fine, hair-like setae and scattered long translucent scales distally; abdominal sternites without posterior marginal spines, sternal surface with loose scattered, fine, hair-like setae.

Gills (Fig. 12D View Figure 12 ). Seven pairs of gills present on abdominal tergites I-VII, slender and elongated; gills I (Fig. 11D View Figure 11 ) enlarged to covered abdominal sternites II-V, oriented ventrally, relatively elongated shape with length approximately 2.5 × of width, medially part broad, tracheation extending from main trunk and outer margin, gill margin smooth, surface and gill margin without long, fine hair-like setae; gills II-VII oriented dorsolaterally, slightly oval and slender with length approximately 3.3 × of width, gill margin smooth, surface and gill margin covered with scattered long, fine hair-like setae.

Gonostyli bud (Fig. 11E View Figure 11 ). Acentrella -type, three-segmented, segment I very short, 0.3 × of segment II length, segment III relatively short and broad, rounded at apex.

Paraproct (Fig. 12E View Figure 12 ). Margin smooth without marginal spines and without prolongation at posterior margin, surface without scale bases, with micropores and fine, stout, simple setae and scattered fine, hair-like setae, and with a patch of notch scales.

Caudal filaments. Cerci 0.4 × of body length, inner margin of cerci with very thin, long setae; median filament 0.5 × of cerci length, lateral margins with very thin, long setae.

Winged stage.

Unknown.

Etymology.

The name of the species “longusa” refers to the outline of abdominal gill I which is elongate- shaped.

Distribution.

Northern part of Thailand (Chiang Mai and Nan Provinces) (Fig. 15 View Figure 15 ).

Ecological notes.

The larvae were collected in Siribhum waterfall (Fig. 14D View Figure 14 ) and headwater stream (Sapan River River) (Fig. 14E View Figure 14 ). The sampling sites were located at high altitudes of 995-1,360 m a.s.l. in forest areas on mountains in the northern part of Thailand. The waterfall was in the upper stream of the Ping River, and the substrate types were dominated by boulders, cobbles, pebbles, gravel, and a sand bottom. The stream was in the Sapan River and located near the resort which can be disturbed by touristic attractions. The larvae were found on the surface and underside of cobbles in fast-flowing water (Fig. 14F View Figure 14 ).