Labiobaetis ancoralis, Shi, Weifang & Tong, Xiaoli, 2014

Shi, Weifang & Tong, Xiaoli, 2014, The genus Labiobaetis (Ephemeroptera: Baetidae) in China, with description of a new species, Zootaxa 3815 (3), pp. 397-408 : 398-399

Labiobaetis ancoralis n. sp.

( Figs. 1–15 )

Specimens examined. Holotype (in ethanol): 1 mature nymph, CHINA, Guangdong Province: Shixing County, Mashi (25.03°N, 114.15°E), 16-iii-2012, coll. Shi Weifang; Paratypes (in ethanol): Hunan Province, Dong’an County, Wujiaqiao Town, Wujiahe River, 26 nymphs, 27-i-2002, and 11 nymphs, the same locality but collected on 4-v-2002, coll. Wang Wenli; Guangdong Province: 13 nymphs, Qingyuan City, Yangshan, Chengjia Forest, 13- vii-1996, coll. Tong Xiaoli; 1 nymph, Wuhua County, Shuanghua Town, near Junying Hydropower Station (23.75°N, 115.85°E, alt. 241m), 14-xi-2011, coll. Zhong Huimin; 2 nymphs on slides and 8 nymphs, same data as holotype; 4 nymphs on slides and 6 nymphs, Nanxiong City, Wujing Town, Huoshaoqiao (25.26°N, 114.60°E, alt. 155m), 16-iii-2012, coll. Shi Weifang, 14 nymphs, Nanxiong City, Wujing Town (24.85°N, 114.62°E), 16-iii- 2012, coll. Shi Weifang; 5 nymphs, Shixing County, Luoba Town, Luobahe River (24.85°N, 114.22°E), 16-iii- 2012, coll. Shi Weifang; 9 nymphs, Nanxiong City, Shuikou Town (25.15°N, 114.47°E), 17-iii-2012, coll. Zhong Huimin.

Description. Mature nymph. Body length 6.5mm, cerci 3.7 mm, terminal filament 2.7 mm.

Head. Coloration cream shaded with irregular brown markings on vertex and frons. Antennal scape and pedicel brown, flagellum pale yellow-brown; scape with a distinct lateral thumb-like lobe at distolateral margin ( Fig. 1 ). Labrum ( Fig. 7 ) rectangular, approximately 0.8 times as long as wide, anterior margin with a small median notch; dorsal surface with one medial spatulate seta and about 12 spatulate submarginal setae in contiguous row and serrated distally, fine and simple setae scattered medially; ventrally bordered with feathered setae along margin and a distomedial arc of fine setae. Left mandible ( Fig. 9 ) incisor with 4+3 fused denticles; prostheca robust apically with 7 blunt and 4 acute denticles; Right mandible ( Fig. 10 ) with 4+4 fused denticles, inner margin of incisor with a row of fine, simple bristles; prostheca robust, apically denticulate; plane of mandible between incisor base and molar region smooth. Hypopharynx ( Fig. 11 ): lingua with a median projection, covered with abundant setae. Maxillae with 4 – 5 long, acute basal setae submarginally near medial hump and a single short, robust hump seta on the base of the galealacinia; palpus 2-segmented, longer than galealacinia, scattered with fine setae, inner margin of apical segment with a pronounced excavation near apex ( Fig. 3 ). Labium ( Fig. 8 ): glossae slightly shorter than paraglossae, with a row of 5–6 acute, stout setae along the outer margin dorsally and 3 long, robust, blunt setae at the apex; paraglossae broadly flattered apically, more than 2 times as wide as glossae with three rows of distally pectinate setae ventrally, and 6–7 stout, acute setae along the inner margin dorsally. Labial palpus 3- segmented; 2nd segment with a large thumb-like distomedial lobe, a row of 3–4 long, acute, stout setae near outer margin dorsally, and numerous long, fine, simple setae scattered over surface ventrally.

Thorax. Thorax off-white with irregular brown patterns ( Fig. 12 ). Hind wing pads well developed ( Fig. 4 ). Forelegs ( Fig. 13 ) cream except for tibia with dark-brown shading proximately basal and distally in outer margin, tarsi shaded with dark-brown apically. Femur with rudimentary villopore, dorsally with a row of 10 robust, acute, simple setae and a pair of stout, simple subapical setae, ventrally with numerous scattered acute, stout setae; tibiae dorsally with a row of minute setae and fine setae, ventrally with pointed setae, longer and more abundant apically; tarsi dorsally with sparse long and fine setae, ventrally with a row of pointed, stout setae increasing in length toward apex; claw with a row of about 15 small teeth, without subapical setae.

Abdomen. Coloration yellowish except for terga II to IX each with a large anchor-shaped brown marking ( Figs. 14, 15 ). Tergal surfaces with numerous scattered small scale bases, posterior margin with triangular pointed spines, length slightly longer than width, and some long, fine setae interleaved the spines ( Fig. 5 ). Sterna off-white except for sterna II–IV with brown stripes laterally, and V–IX laterally and postero-angular shaded with irregular brown markings ( Fig. 14 ); sterna surfaces also with numerous scattered scale bases, posterior margin smooth except for sterna VII–IX medially with triangular spines length subequal to width. Gills asymmetric ovoid and present on abdominal segments I–VII, tracheae visible, surface with numerous pores; serrations of gill margin increasing in frequency toward distal margin of gills, and with fine, simple setae between serrations ( Fig. 6 ). Paraproct ( Fig. 2 ) with many pointed spines marginally increasing in length distally, and with many scale bases scattered over surfaces, postero-lateral extension with scales and blunt spines marginally. Caudal filaments brown basally and cream to light brown distally, but middle part of cerci and distal half of median caudal filament dark brown ( Fig. 14 ); median caudal filament approximately 3/4 length of cerci, inner margin of cerci and two sides of median caudal filament fringed with long bristles.

Imago. Unknown.

Distribution. China (Hunan, Guangdong).

Etymology. The specific epithet is from Latin “ ancoralis ”, meaning anchor, referring to the color pattern of abdominal terga II–IX, each with an anchor-shaped brown marking.

Remarks. Nymph of L. ancoralis n. sp. appears to be closely related to L. multus (Müller-Liebenau) from Malaysia and L. pulchellus (Müller-Liebenau & Hubbard) from Sri Lanka by sharing similar color pattern of abdomen, but it differs from them by having the following characteristics: (1) labrum with spatulate submarginal setae instead of simple setae; (2) terminal segment of maxillary palpus with a conspicuous deeply excavation near apex rather than a shallowly subapical concavity. This new species usually co-occurs with L. atrebatinus orientalis (Kluge) and is often syntopic, furthermore, the final instar nymphs of these two species occur synchronously in the same stream during the surveys. But unlike L. atrebatinus orientalis , the new species is seldom found in riffle habitat with cobble and gravel substrates and generally inhabit streams with silty and sandy substrate with slow current.

Figures

FIGURES 1 – 6. Labiobaetis ancoralis n. sp. 1, antennal scape and pedicle; 2, paraproct; 3, left maxillae; 4, metanotum and hind wing pads; 5, posterior margin of abdominal tergum V; 6, gill V.

FIGURES 7 – 15. Labiobaetis ancoralis n. sp. 7, dorsal view of labrum; 8, labium (left: ventral view; right: dorsal view); 9, left mandible; 10, right mandible; 11, hypopharynx; 12, pro and mesonotum; 13, foreleg; 14, color pattern of abdomen; 15, habitus of female nymph.