Metahomaloptera longicauda , Jian Yang, Xiaoyong Chen & Junxing Yang, 2007

Jian Yang, Xiaoyong Chen & Junxing Yang, 2007, A new species of Metahomaloptera (Teleostei: Balitoridae) from China., Zootaxa 1526, pp. 63-68: 64-68

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Metahomaloptera longicauda

sp. nov.

Metahomaloptera longicauda  sp. nov.

(Fig. 1)

Type material. Holotype: KIZ 20060304, 41.9 mm SL, Chuanhedong village, Deze town , Zhanyi County, Yunnan Province, China; 25° 54' 9.4'' N, 103° 34' 49.5'' E; 2 Dec. 2006; J. Yang, B. Yang.GoogleMaps 

Paratypes: KIZ 20060305, 36.9 mm SL, 1 ex. Same data as holotypeGoogleMaps  , KIZ 20060306, 43.5 mm SL, 1 ex. Tuole village , Zhanyi County, Yunnan Province, China; 25° 41' 28.2'' N, 103° 33' 01.5'' E; 1 Dec. 2006; J Yang, B YangGoogleMaps  . KIZ 603672, 38.4 mm SL, 1 ex. Fumin , Yunnan Province, China. 

Diagnosis. Metahomaloptera longicauda  is distinguished from M. omeiensis omeiensis  in dorsal fin inserting before the middle of body (vs. dorsal fin inserting in the middle of body), having a longer pectoral fin (expending beyond the dorsal-fin origin vs. not), anal fin far from caudal-fin base (vs. anal fin reaching base of caudal fin), pelvic fin reaching or expending beyond anus (vs. pelvic fin far from anus), head narrow (head width 19.4-22.6% SL, vs. 22.7-30.2), pre-anal length 69.0-74.3% SL (vs. 80.7-87.4), having a longer (17.1-20.7% SL vs. 8.4-11.9) and more slender (caudal-peduncle depth 33.7-43.1% caudal-peduncle length vs. 62.7-87.6) caudal peduncle, eye small (eye diameter 14.6-16.6% HL vs. 16.7-23.9), mouth wide (mouth width 63.2-75.5% body width at pectoral-fin origin vs. 30.3-42.3). Metahomaloptera longicauda  can be further distinguished from M. omeiensis hangshuiensis  ZBK  in having fewer blackish blotches along the median dorsal line from occipital region to base of caudal (8-9 vs. 10-15), a longer pectoral fin (expending beyond the dorsal-fin origin vs. not), more lateral-line scale rows (66-78 vs. 59-63), fewer branched pectoral rays (11-15 vs. 16-18), fewer branched pelvic rays (10-12 vs. 13-15), a longer (17.1-20.7% SL vs. 7.1-10) and more slender (caudal peduncle depth 33.7-43.1% caudal peduncle length vs. 76.9-111.1) caudal peduncle.

Description. Biometric comparisons of M. longicauda  and M. omeiensis omeiensis  are presented in Table 1. Ventral view of head of M. longicauda  is presented in Figure 2. Body elongate and compressed; head longer than width at pectoral-fin origin. Snout spatulate and broad; snout longer than half of head, 3-4 times eye diameter. Numerous small white tubercles on dorsal surface of head. Anterior and posterior nostrils closely situated; anterior nostril in short tubular flap. Eye small, 1/6 of head length; eye diameter slightly shorter than gill opening. Interorbital width shorter than snout length and less than 1/2 of head length. Gill opening very small, crescent-shaped, and situated entirely above base of pectoral fin. Mouth inferior, wide, and crescentshaped; corner of mouth almost reaching pectoral-fin origin. Mouth with four pairs of barbels, rostral fold with four notches to accommodate rostral barbels, a fleshy lobe between two neighboring notches, and the inner fleshy lobe larger than the lateral two. Four rostral barbels of equal length. Fleshy lobe enlarged between rostral and maxillary barbels. Rostral fold and upper lip separated by shallow groove; upper lip with single row of papillae and continuous with lower lip at mouth corner. Maxillary barbels at corner of mouth; inner pair of barbels shorter and more slender than outer pair. Lower lip plain and thin. Jaws with sharp largely exposed horny edge. Lower jaw with radial ridges on surface.

Dorsal-fin origin located before middle of body with iii,8 rays. Dorsal-fin margin straight. Base of dorsal fin shorter than head length. Pectoral fin with 13 simple and 11-15 branched rays; fin expanded and inserted vertical of nostrils. Tip of pectoral fin overlapping anterior part of pelvic fin and extending beyond vertical origin of dorsal fin. Pelvic fin with 8-9 simple and 10-12 branched rays. Pelvic-fin origin anterior to vertical of dorsal-fin origin. Pelvic fins fused posteriorly; posterior edge reaching or extending beyond anus and far from anal fin. Expanded muscular band present above pelvic-fin base. Anal fin with ii,5 rays and far from caudal-fin base. Anus closer to anal-fin origin than to posterior edge of pelvic-fin base. Caudal fin shallowly emarginated; lower lobe slightly longer than upper lobe. Body covered with tiny cycloid scales. Lateral line complete, straight and with 66-78 scales.

Coloration. After fixed in 10% formalin and storage in 75% ethanol, body is dark grey. Median dorsal line with 8-9 blackish blotches from occipital region to base of caudal fin; 2-3 blotches anterior to dorsal-fin origin and 5-6 posterior to dorsal-fin origin. Dorsal-fin rays dark grey with two blackish bands. Caudal and anal fins with one wide vertical blackish band.

Distribution. Presently known from the Niulan Jiang River and the Pudu River (tributaries of the lower Jinsha River) (Fig. 3).

Habitat and ecology. In Tuole (Niulan Jiang River), the river is clear and fast flowing, 8-20 m wide, 0.5- 2 m deep, and with a pH 6.0. The river substrate is sand, cobbles and boulders. Metahomaloptera longicauda  was collected in the rapid water amongst boulders. Other fishes found in the same locality include Discogobio yunnanensis  (Cyprinidae), Abbottina rivularis  (Cyprinidae), Pseudorasbora parvus  (Cyprinidae), Beafortia szechuanensis  (Balitoridae), Sinogastromyzon dezeensis  ZBK  (Balitoridae), Triplophysa grahami  (Balitoridae), Schistura fasciolata  (Balitoridae) and Liobagrus marginatus  (Amblycipitidae). In Deze (downstream of Tuole,), the habitat is the same as that at Tuole, but more species coexist with M. longicauda  . Those include the species listed above and Carassius auratus auratus  (Cyprinidae), Pseudogyrincheilus procheilus  (Cyprinidae), Rhinogobius brunneus  (Gobiidae), Rhodeus ocellatus  ZBK  (Cyprinidae) and Paracobitis variegatus variegatus  (Balitoridae).

Etymology. A noun from the Latin longus, meaning long, and caudal, meaning the tail of an animal, in reference to the species having a longer caudal peduncle when compared with M. oemeiensis omeiensis  and M. oemeiensis hangshuiensis  ZBK  .

Discussion. To date, only one species containing two subspecies is considered valid in Metahomaloptera  ZBK  (Chen & Tang, 2000; Tang & Chen, 2000), viz. M. omeiensis omeiensis Chang, 1944  , M. omeiensis hangshuiensis Xie, Yang & Gong, 1984  ZBK  . The description of M. longicauda  raises the number of known species in the genus to two. The significantly longer caudal peduncle and wider mouth of M. longicauda  easily distinguishes it from M. omeiensis omeiensis  (Figs. 4, 5).

Metahomaloptera  ZBK  is restricted to the lower Jinsha River (the name the Yangtse River in Yunnan Province) and the upper Yangtse River (Sichuan, Shanxi and Hubei Province) (Fig. 3). The distribution of M. omeiensis hangshuiensis  ZBK  is desctibed by Chen & Tang (2000) as the Hanshui River. Chang (1944) indicated that the rudimentary nature of the gill-opening in Metahomaloptera  ZBK  must be of generic significance, and Metahomaloptera  ZBK  is obviously more specialized and advanced than Sinogastromyzon  ZBK  . Chen (1980) discussed the phylogenetic position of Metahomaloptera  ZBK  based on an osteological study, corroborated the hypothesis of Chang (1944) that Metahomaloptera  ZBK  is more specialized and advanced than Sinogastromyzon  ZBK  . Metahomloptera  ZBK  is adapted to fast-flowing streams, and many of the morphological features are adaptations to the special environment. Notable adaptations includes those of the mouth, pelvic fin, maxillary barbels and gill-opening, and the depressed body and head. These specialized characters are always used to distinguish genera and species. Their function and importance in phylogenetic analyses should be studied further.