Pareuchiloglanis arcuatum, Dao & Li & Yang & Zhou, 2020

Dao, Wei, Li, Xu, Yang, Hong-Fu & Zhou, Wei, 2020, Pareuchiloglanis (Teleostei: Sisoridae) from the Pearl River, China with description of three new species, Journal of Fish Biology 96 (1), pp. 23-36 : 26-29

3.1 | Pareuchiloglanis arcuatum sp. nov., Figure 3a

Pareuchiloglanis longicauda : Chu, 1989: 291 – 292 (Fuyuan and Luoping in Yunnan Prov.); Chu et al., 1990: 203 – 204 (Luoping and Fuyuan in Yunnan Prov.). Chu & Mo, 1999: 165 – 166 (Fuyuan and Luoping in Yunnan Prov.).

3.1.1 | Holotype

SWFC 0105004, 140.9 mm L S; China: Yunnan Prov.: Qujing City.: Luopin Co.: Lubuge Town: Duoyi Village : Duoyi-he (24 45 0 45.12 00 N, 104 29 0 46.91 00 E); collected by Y.W. Zhou & X.F. Pan, 6 May 2001 .

3.1.2 | Paratypes

SWFC 0105005, 01015007 – 0105012, 7 ex., 91.9 – 131.5 mm L S; the other data is the same as the holotype; SWFC 0603008 – 0603010, 3 ex., 67.6 – 94.1 mm L S; China: Yunnan Prov.: Qujing City.: Luopin Co.: Lubuge Town : Duoyi Village : Duoyi-he (24 45 0 45.12 00 N, 104 29 0 46.91 00 E); collected by L.P. Zheng & F.L Li, 12 Mar. 2006 ; SWFC 0504101, 1 ex., 70.5 mm L S, China: Yunnan Prov.: Qujing City: Luopin Co.: Changdi Town : Changdi Village : Xijiuhan-he (25 02 0 3.54 00 N, 104 30 0 20.13 00 E); collected by L.P. Zheng, 13 Apr. 2005 ; SWFC 0603011, 1 ex., 106.0 mm L S, China: Yunnan Prov.: Qujing City.: Luopin Co.: Changdi Town : Changdi Village : Xijiuhan-he (25 02 0 03.54 00 N, 104 30 0 20.13 00 E); collected by L.P. Zheng & F.L. Li, 9 Mar. 2006 ; SWFC 1905001 – 1905015, 15 ex, 54.0 – 167.9 mm L S, China: Yunnan Prov.: Wenshan Pref.: Qiubei Co.: Wenliu Town : Geyang Village : Qingshui-jiang (24 09 0 46.59 00 N, 104 32 0 36.01 00 E); collected by W. Zhou & H.F. Yang, 24 May. 2019 .

3.1.3 | Diagnosis

Pareuchiloganis arcuatum sp. nov. is distinguished from the congeners of the large-gill-opening group with long caudal peduncle by the following combination of characters (Table 1): anal-fin ray i, 3½ (v. i, 4½ in P. longicauda ); tip of maxillary barbel pointed, elongating as a whisker shape and extending beyond the lower corner of the gill opening ( v. only reaching the lower corner of gill opening in P. salicesbarba sp. nov. and P. posteranalis sp. nov.); anal-fin origin located at about 2/5 of distance between pelvic-fin insertion and caudal-fin base ( v. midpoint between distance of pelvic-fin insertion and caudal-fin base in P. longicauda , P. posteranalis sp. nov. and P. salicesbarba sp. nov.); adipose-fin origin located at about 2/3 of the distance between pelvic-fin insertion and anal-fin origin ( v. about 3/4 of the distance between pelvic-fin insertion and anal-fin origin in P. longicauda ); the length of dorsal-fin base shorter than the longest branched dorsal-fin ray ( v. longer in P. longicauda and P. posteranalis sp. nov.); caudal-peduncle depth 14.1 – 17.8% of caudal-peduncle length (v. 26.2 – 26.3% in P. longicauda , 27.2-31.3% in P. posteranalis sp. nov. and 18.3 – 23.0% in P. salicesbarba sp. nov.).

3.1.4 | Description

Morphometric and meristic data are given in Tables 1 and 2. Dorsal-fin rays i, 5½; anal-fin rays i, 3½; pectoral-fin rays i, 14 – 15; pelvic-fin rays i, 5 – 6; branched caudal-fin rays 6 + 7; vertebra 21 + 16 = 37 (n = 3), 22 + 16 = 38 (n = 1).

Mouth wide, inferior, transverse. Anterior margin of premaxillary tooth patches exposed when mouth closed. Oral teeth coniform, embedded in skin, only tips exposed, in irregular rows. Premaxillary tooth patches broad, appear joined, with median indentation, sides not extending posteriorly. Gill opening extending to the base of first pectoral-fin element. Post-labial groove interrupted, ending at base of inner mandibular barbel. Lower lip connected to base of maxillary barbel by skin flap, without sulcus between them.

Head depressed, rostral margin rounded when viewed dorsally. Ventral surface of the head and abdominal region moderately broad and straight. Dorsal profile rising gradually from snout tip to dorsal-fin origin, then sloping slowly ventrally to caudal-peduncle base. Slightly compressed caudal-peduncle. Oral region and anterior part of abdomen with dense papillae, density gradually decreasing posteriorly. Eye small, almost round, subcutaneous, located on dorsal surface of head. Eye closer to dorsal-most extremity of gill opening than to tip of snout. Barbels flattened, in four pairs. Nasal barbel with small flap of thin skin fringing posterior margin, not reaching anterior margin of orbital. Maxillary barbel with thin flap of skin fringing posterior margin, tip pointed, elongating as a whisker shape and extending beyond the lower corner of the gill opening. Origin of inner mandibular barbel far from midline. Outer mandibular barbel originating posterolateral of inner mandibular barbel, not near pectoral-fin origin.

Dorsal-fin origin located at about the anterior 1/3 of the L S (predorsal length 28.4-35.8% of L S), without spine, outer margin straight; tip of dorsal-fin rays extending beyond vertical through pelvic-fin insertion when depressed. Adipose-fin base longer, its length 42.4 – 45.7% of postdorsal distance but shorter than predorsal length; its margin almost straight and adipose-fin base deeply incised posteriorly. Anal-fin origin located at about 2/5 of the distance between the pelvic-fin insertion and the caudal-fin base. Pectoral and pelvic fins enlarged, with broadly rounded margins; first element on each broadened, with regular striae on ventral surface. Pectoral fin not reaching pelvic-fin origin. Pelvic fin extending beyond anus. Anus located anterior about 1/3 of the distance between the pelvic-fin insertion and the anal-fin origin, near the pelvic-fin insertion. Caudal fin truncate. Skin smooth. Lateral line complete and midlateral.

3.1.5 | Coloration in life

Body green-yellow on dorsal surface, milk-white on venter. Pectoral and pelvic fins yellow-brown, with light yellow distal margins. Pair of light yellow spots on post-temporal region. A yellow papilionaceous patch at dorsal-fin origin, a yellow triangular or quadrate patch at end of dorsal-fin base. Adipose fin with light yellow distal margins and a yellow stripe on its origin. Patch on dorsal caudal-fin base connecting with patch at end of adipose-fin base. Caudal fin gray-black with light yellow distal margin.

3.1.6 | Distribution

Pareuchiloganis arcuatum sp. nov. is only known from the lower Nanpan-jiang in Yunnan, part of the main stream of the Xi-jiang in the Pearl River drainage (Figure 4).

3.1.7 | Habitat and ecology

Pareuchiloganis arcuatum sp. nov. feeds on aquatic insects. Specimens were exclusively captured in rocky riffles where the width of the riverbed is narrow and shallow, about 8 – 15 m wide and not more than 1 m deep. The water is clear and swift flowing. The substrate is entirely rock, primarily cobbles and pebbles. The steep places on both riverbanks are well covered by vegetation, while relatively flat banks are mostly farmland (Figure 5a).

3.1.8 | Etymology

From the Latin arcuatum , meaning bow-shaped, alluding to feature that its body bow-shaped from the lateral view.