Megabranchiella scutulata 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/9DBB55FF-E63C-4DDA-9235-D825D0A0C08E
taxon LSID	lsid:zoobank.org:act:9DBB55FF-E63C-4DDA-9235-D825D0A0C08E
treatment provided by	ZooKeys by Pensoft
scientific name	Megabranchiella scutulata Phlai-ngam & Tungpairojwong
status	sp. nov.

Treatment

Megabranchiella scutulata Phlai-ngam & Tungpairojwong sp. nov.

Materials examined.

Holotype. Thailand, One male larva on slide (KKU-AIC), Chiang Mai, Mae On district, Mae Kampong , The Royal Project of Teen Tok , 18°52'01.65N, 99°19'20.83E, 779 m, 21.12.2020, S. Phlai-ngam leg. GoogleMaps

Paratypes. One larva on slide (KKU-AIC), same data as holotype GoogleMaps ; 21 larvae in alcohol, same data as holotype GoogleMaps ; Four larvae in alcohol (MZL), same data as holotype GoogleMaps .

Other materials.

Two larvae in alcohol (ZMKU), Thailand, Chiang Rai, Muang district, Pong Phra Baht waterfall, 20°00'39.60N, 99°48'14.47E, 476 m, B. Boonsoong and C. Sutthinun leg. GoogleMaps

Description.

Coloration (Figs 1 View Figure 1 - 2 View Figure 2 ). Head dorsally yellow to brownish, with a darker brown pattern between ocelli. Thorax dorsally brown; pronotum with dark brown pattern laterodorsally, mesonotum with longitudinally dark brown pattern medially. Abdomen dorsally brownish; tergite I light brown; tergites I-VIII brown with reddish brown pattern posterolaterally, tergites IV and V slightly lighter; tergites IX and X light brown with or without pale markings. Head and thorax ventrally light brown to yellow; abdomen ventrally light brown; sternites I-V light brown; sternites V-X medium to dark brown (Fig. 3 View Figure 3 ). Legs light brown; dorsal, ventral, and apical femur margins dark brown; claws distally dark brown. Caudal filaments brownish.

Body (Fig. 4 View Figure 4 ). Relatively short and ventrally flattened (Fig. 4B View Figure 4 ), body length 3.6 mm, covered with scattered long, hair-like setae.

Head (Fig. 4B View Figure 4 ). Lateral view rounded, head width ca. 1.5 × as long as head length.

Antenna. ca. 2 × as long as head length (Fig. 4B View Figure 4 ); scape without process, subequal in width and length, pedicel length, ca. 2 × as long as width, scape and pedicel almost bare, without scales bases and spines, covered with scattered long fine setae; flagellum covered with scattered long fine setae in each segment.

Labrum (Fig. 5A View Figure 5 ). Broadly rounded; wider than long, width ca. 1.75 × as long as length; dorsal surface with submarginal row composed of one long, point, simple seta medially plus three medium, simple setae anterolaterally, dorsal surface with scattered simple, hairlike setae; distal margin with shallow anteromedian notch. Ventrally with submarginal row of setae composed of lateral and anterolateral long, feathered setae and medial long, pectinate setae; ventral surface with six short, spine-like setae near lateral and anterolateral margin.

Right mandible (Fig. 5B View Figure 5 ). Canine with 4 + 4 apically rounded denticles (Fig. 5C View Figure 5 ), largely fused outer and inner incisors, inner margin of inner incisor with small denticulation; prostheca robust (Fig. 5D View Figure 5 ), apically with small denticles and comb-shaped structure; margin between mola and prostheca smooth, without setae; mola with well-developed denticulation; apex of mola with tuft of spines like setae.

Left mandible (Fig. 5E View Figure 5 ). Canine with 4 + 3 apically rounded denticles (Fig. 5F View Figure 5 ), largely fused outer and inner incisors, outer and inner incisors separated by a small, rounded tooth; prostheca robust (Fig. 5G View Figure 5 ), apically with small denticles and comb-shaped structure; margin between mola and prostheca smooth, without setae; mola with reduced denticulation, apex of mola with tuft of spines like setae.

Maxilla (Fig. 5H View Figure 5 ). Short and compact; galea-lacinia (Fig. 5I View Figure 5 ) with long, robust, simple seta under crown; inner dorsal row of setae with three denti-setae, distal denti-seta tooth-like, middle denti-seta slender, bifid and pectinate (Fig. 5J View Figure 5 ); proximal denti-seta slender, pectinate; inner ventral row of seven robust, simple setae; medially with one seta and four short to long, simple setae. Maxillary palp 2-segmented, with scattered small, blunt setae; distal segment with distinct, small tip at apex.

Labium (Fig. 5K View Figure 5 ). Glossa basally broad, narrower toward apex, slightly shorter than paraglossa; inner margin with medium, pointed, simple setae; apex with four long, robust, pectinate setae; basal area with fine scattered setae. Paraglossa sub-rectangular, broader than glossa, apically curved inward, apical margin with three rows of long, robust, apically pectinate setae (Fig. 5L View Figure 5 ), ventrally with 4-5 long, spine-like setae near inner margin, with an arch of 4-5 long, simple setae on outer margin; basal area with a single medium seta. 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 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. 5M View Figure 5 ). Lingua subequal to superlingua, apically rounded, with apical tuft of fine, simple setae; superlingua with distal margin slightly incurved, margin covered with fine simple setae.

Thorax. Hindwing pads (Fig. 8A View Figure 8 ). Highly reduced.

Forelegs (Fig. 7A View Figure 7 ). Ratio of foreleg segments 0.58: 0.48: 0.22. Femur. Length ca. 2.5 × maximum width. Dorsal margin of femur (Figs 6A View Figure 6 , 8B-C View Figure 8 ) with a row of 11-13 long, robust, apically rounded, simple setae; short stout, lanceolate, laterally pectinate setae and scattered fine hair-like setae along dorsal and ventral margins (Fig. 8D View Figure 8 ); femora patch present; surface with scattered tiny spines anteromedially (Fig. 8E View Figure 8 ); scattered long translucent scales present; dorsal margin of tibia with a row of long, simple setae; several short stout, lanceolate, laterally pectinate setae and scattered hair-like setae along dorsal and ventral margins, patella-tibial suture present; tarsus dorsally with a row of fine, spine-like, simple setae, ventral margin bare or with a row of fine, spine-like, simple setae, surface covered with scattered fine hair-like setae; tarsal claw (Fig. 7B View Figure 7 ) with one row of about 12 denticles increasing in length toward apex, subapical setae absent. Midlegs and hindlegs. As forelegs.

Abdomen (Fig. 6B View Figure 6 ). Tergites. Posterior margin smooth, posterior marginal spines extremely reduced to absent, tergal surface with scattered stout, fine, hair-like setae and scattered long translucent scales distally (Figs 6C View Figure 6 , 7C View Figure 7 , 8F View Figure 8 ); abdominal sternites without posterior marginal spines; sternal surface with loose scattered fine, hair-like setae.

Gills (Fig. 7D View Figure 7 ). Seven pairs of gills present on abdominal tergites I-VII; gills I (Fig. 6D View Figure 6 ) enlarged to covered abdominal sternites II-V, ventrally oriented, relatively rhombus shape, length approximately 1.4 × of width, medially part broad, tracheation extending from main trunk to outer margin, gill margin smooth, surface and gill margin without long, fine hair-like setae; gills II-VII oriented dorsolaterally, slightly oval length approximately 2.1 × of width, gill margin smooth, surface and gill margin covered with scattered long, fine hair-like setae.

Gonostyli bud (Fig. 6E View Figure 6 ). 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. 7E View Figure 7 ). 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 stages.

Unknown

Etymology.

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

Distribution.

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

Ecological notes.

The larvae were collected in headwater stream (Mae Kampong River) (Fig. 14A View Figure 14 ) and Pong Phra Baht waterfall (Fig. 14B View Figure 14 ). The sampling sites were located with altitudes of 475-780 m a.s.l. Both stream and waterfall were situated in forest areas with relatively complete canopy cover on mountains in the northern part of Thailand. The stream was in The Royal Project of Teen Tok area which has some human disturbances resulting from touristic attractions and resorts. The substrates were dominated by 50% cobbles, 20% pebble, 20% boulders, 10% gravels respectively with sand bottom. The waterfall was located upstream. The larvae were found on the surface of cobbles in fast-flowing water (Fig. 14C View Figure 14 ).