Procerobaetis totuspinosus Suttinun, Kaltenbach & Boonsoong sp. nov. Figures 1, 2, 3, 4, 5, 6, 7

Materials examined.

Holotype. 1 larva on slide, deposited in ZMKU, Thailand, Chiang Mai, Mae Chaem district, Mae Chaem wadeable river, 18°30'45.3"N, 98°21'23.8"E, 475 m, 16.02.2020, B. Boonsoong leg.

Paratypes. 1 larva on slide, deposited in ZMKU, same data as holotype; 1 larva in alcohol, GBIFCH00673237, deposited in MZL, same data as holotype .

Other materials.

6 larvae in alcohol, deposited in ZMKU, same data as holotype . 2 larvae in alcohol, deposited in ZMKU, 1 larva in alcohol, GBIFCH00673238, deposited in MZL, Thailand, Chiang Mai, Mae Rim district, Mae Sa stream, 18°54'39.1"N, 98°55'33.6"E, 355 m, 15.02.2020, B. Boonsoong leg.

Description.

Larva (Figs 1 - 7). Body length 4.5-4.6 mm.

Colouration (Fig. 7). Head, thorax and abdomen dorsally brown, head and thorax with bright, median, dorsal suture. Head, thorax and abdomen ventrally light brown. Legs whitish. Caudal filaments whitish.

Head. Antenna (Figs 2A, 6A, B) approximately 3-4 × as long as head length; flagellum with lanceolate spines at apex of each segment, longer at inner lateral margin, increasing in length distally in segment VII-XI and decreasing thereafter.

Labrum (Fig. 1A). Rectangular, length 0.6 × maximum width. Distal margin with medial emargination and a small process. Dorsally with many long, stout, simple setae scattered over area, erratically distributed, not arranged in an arc. Ventrally with a marginal row composed of five lateral long, feathered setae and ten anterolateral medial long, bifid, pectinate setae; ventral surface with ca five short, spine-like setae near lateral and anterolateral margins, increasing in length distally.

Right mandible (Fig. 1B, C). Outer and inner sets of denticles with 4 + 1 + 3 denticles. Prostheca stout, arched, shorter than half of canines. Margin between prostheca and mola straight, with a row of medium, stout setae. Setae at apex of mola present.

Left mandible (Fig. 1D, E). Outer and inner sets of denticles with 4 + 3 denticles. Prostheca stout, apically broad, reduced comb-shaped structure. Subtriangular process long and slender, above level of area between prostheca and mola. Denticles of mola apically constricted. Setae at apex of mola absent.

Both mandibles with lateral margins almost straight. Basal half with fine, simple setae scattered over dorsal surface.

Hypopharynx (Fig. 1F). Lingua equal to superlingua, longer than broad, with medial tuft of long, stout setae. Superlingua distally almost straight, lateral margin rounded, with fine, long, simple setae along laterodistal margin.

Maxilla (Fig. 1G). Galea-lacinia with two simple, robust apical setae under crown. Medially with one pectinate, spine-like seta and a row of five long, simple setae increasing in length. Maxillary palp 1.8 × as long as length of galea-lacinia with segment I shorter than galea-lacinia; palp segment II 0.5 × length of segment I, palp segment III 1.4 × length of segment II; setae on maxillary palp fine, simple, scattered over surface of segments I, II and III; apex of last segment rounded.

Labium (Fig. 1H). Glossae basally broad, narrowing toward apex, shorter than paraglossae; inner margin with eight spine-like setae; apex with two long and one medium, robust, pectinate setae; outer margin with six spine-like setae, increasing in length distally; ventral surface with medium, fine, simple, scattered setae. Paraglossae subrectangular, apically curved inward; apex rounded, with two rows of long, robust, simple setae; ventrally two medium, simple setae in anteromedial area; dorsally with a row of four or five long, spine-like setae near inner margin. Labial palp with segment I 0.85 × length of segments II and III combined, ventrally scattered with short, fine, simple setae; segment II with very small distomedial expansion, ventrally with scattered short, fine, simple setae, dorsally with a row of four long, spine-like setae; segment III subquadrangular, apex rounded, ventral surface with an arc of five stout, spine-like setae on anteromedially, covered with short spine-like, simple setae and short, fine, simple setae. Mentum distally scattered with fine, simple setae.

Thorax. Foreleg (Figs 3A, 4). Ratio of foreleg segments 1.4:1.0:0.9:0.3. Femur. Length 3.7-4.1 × maximum width; dorsal margin with a row of six curved, spine-like setae; length of setae 0.23 × maximum width of femur; apex rounded, with one pair of spine-like setae (Fig. 4A); many stout, lanceolate, laterally pectinate setae scattered along ventral margin (Fig. 4B); femoral patch absent. Tibia. Dorsal margin with a row of fine, simple setae; ventral margin with a row of curved, laterally pectinate, spine-like setae, on apex three longer, laterally pectinate, spine-like setae; anterior surface scattered with stout, lanceolate, laterally pectinate setae; patellotibial suture present on basal 1/3 area. Tarsus. Dorsal margin with a row of fine, simple setae (Fig. 4C); ventral margin with a row of curved, laterally pectinate, spine-like setae, on proximal area with some curved, laterally pectinate, spine-like setae (Fig. 4C), not arranged in a row; tarsal claw (Fig. 4D) elongate, slender, apically pointed, with one row of six or seven larger denticles and many minute denticles, ventral margin at apex straight, with many stripes.

Middle leg (Fig. 3B). As foreleg, but dorsal margin of femur slightly concave.

Hind leg (Fig. 3C). As foreleg, but dorsal margin of femur slightly concave.

Abdomen. Tergites (Fig. 5). Surface with scattered scales, U-shaped scale bases and micropores. Posterior margin of tergites I-V bare, tergites VI-VIII with triangular spines, tergite IX (Fig. 5B) with triangular spines absent in middle part.

Gills (Fig. 2B-H). Present on segments I-VII; elongate with very long, extended points; margin with very small denticles intercalating fine, simple setae; tracheae limited to main trunk. Gill I (Fig. 2B) as long as length of segments II and III combined, gill II (Fig. 2C) as long as length of segments III and 2/3 of IV combined, gill III (Fig. 2D) as long as length of segments IV and V combined, gill IV (Fig. 2E) as long as length of segments V and VI combined, gill V (Fig. 2F) as long as length of segments VI and VII combined, gill VI (Fig. 2G) as long as length of segments VII and VIII combined, gill VII (Fig. 2H) as long as length of segments VIII-X combined.

Paraproct (Figs 2I, 6C). Posterior margin with nine or ten stout spines; surface scattered with scales and U-shaped scale bases; posterolateral extension (cercotractor) with nine medium, blunt, marginal spines.

Caudal filaments (Fig. 6D). Cerci ca 0.4 × body length, median caudal filament ca 0.8 × length of cerci.

Diagnostic characters.

Larva. The main diagnostic characters are: i) the posterior margin of tergites VI-VIII entirely with triangular spines; ii) the maxillary palp is shorter than in other species, with segment I shorter than galea-lacinia; and iii) all gills present extended points as in P. freitagi, while in P. leptobranchius and P. petersorum only gills I and II are apically strongly produced.

Winged stages.

Unknown.

Etymology.

Procerobaetis totuspinosus sp. nov. is a combination of totus (derived from the Latin word meaning entire, whole, complete) and spina (meaning spine), in reference to the remarkable complete row of triangular spines at the posterior margin of tergites VI-VIII.

Distribution.

Chiang Mai province

Biological aspects.

The specimens were collected in a stream and a wadeable river (Fig. 8) at a range of altitudes (355-475 m a.s.l.). Mae Sa stream is located mostly in residential areas with a partly closed canopy; the substrate was dominated by pebble and gravel, with few patches of leaf litter or dead wood (Fig. 8A). Mae Chaem wadeable river is kind of the submontane type, bordered by farmland and residential areas; its substrate was dominated by sand (Fig. 8B). The larvae of the new species were found in the littoral zone, which was characterised by submerged wood, a sand and gravel bottom (Fig. 8C), and vegetation and roots along the riverbank (Fig. 8D).

Molecular analysis.

The Kimura 2-parameter (K2P) analysis revealed interspecific distances (COI) between the new species and the other species of 20-23%. In addition, the interspecific genetic distances of known Procerobaetis species varied between13-20% (Table 2).