Rhodeus flaviventris, Li & Arai & Liao, 2020

Li, Fan, Arai, Ryoichi & Liao, Te-Yu, 2020, Rhodeus flaviventris, a new bitterling (Teleostei: Cyprinidae: Acheilognathinae) from China, Zootaxa 4790 (2), pp. 329-340 : 330-334

Rhodeus flaviventris , new species

( Figs. 1–9 ; Table 1)

Holotype. SOU 1909001, male, 49.8 mm SL; the Le-An River , a tributary flowing into Poyang Lake in the Yangtze River basin, in Xitou Township, Wuyuan County, Jiangxi Province, China; 29 Sep. 2019.

Paratypes. SOU 1904001, male, 50.5 mm SL; SOU 1904002 , female, 44.9 mm SL; same locality as holotype; 2 Apr. 2019 . SOU 1508001–1508003, 3 males, 34.4–51.1 mm SL; SOU 1508004–1508006 , 3 females, 38.1–50.5 mm SL; same locality as holotype; 22 Aug. 2015. DOS 07249 – 07250, 2 males, 45.8–46.5 mm SL; DOS 07251– 07253 , 3 females, 37.4–45.2mm SL; SOU 1110001–1110002 , 2 males, 46.2–52.9 mm SL; SOU 1110003–1110005 , 3 females, 37.9–51.2 mm SL; NSMT-P 136702–136703 , 2 males, 45.9–46.2 mm SL; NSMT-P 136704–136705 , 2 females, 41.5–41.8 mm SL; same locality as holotype; 2 Oct. 2011 .

Non-type specimens. SOU 201804501, 4 males, 44.1–57.2 mm SL; same locality as holotype; 24 Apr. 2018 .

Diagnosis. Rhodeus flaviventris can be distinguished from all congeners by branched dorsal-fin rays 9 in mode; branched anal-fin rays 9 in mode; longitudinal scale series 33–34; pored scales 4–7; vertebrae 32–34; nuptial males with yellowish iris, yellow belly, orange central part of caudal fin, and reddish-orange stripes on dorsal and anal fins. Most similar to R. albomarginatus , but differed in color of belly of nuptial males (yellow vs. reddish-orange) and absence of white margin on dorsal and anal fins in nuptial males (vs. presence).

Description. Morphometric and meristic data of holotype and paratypes are shown in Table 1. Body compressed. Mouth small and subterminal, corner of mouth not extending to vertical of anterior margin of orbit. Barbels absent. Pearl organs on snout and area between nostril and eye in adult males, absent in females. A long ovipositor present in mature females, maximum length approximately 18–24 mm, including a rigid basal part of approximately 5–7 mm ( Fig.2 ).

Dorsal fin with 3 simple and 9 branched rays (rarely 10). Anal fin with 3 simple and 9 branched rays (rarely 10). First simple ray in dorsal and anal fins very small, hidden under skin. Longest simple ray of dorsal fin thick and stiff; width of basal portion about 2.5 times wider than that of first branched ray; longest simple dorsal-fin ray segmented from area corresponding to third branching point of first branched ray ( Fig. 3 ). Pectoral fin with 1 simple and 11–13 branched rays. Pelvic fin with 1 simple and 6–7 branched rays. Principal caudal rays 19, including branched rays 17 (9 + 8); dorsal procurrent rays 7–8, ventral procurrent rays 6–8.

Longitudinal scale series 33–34 (31–32 on body and 1–2 on caudal fin). Lateral line incomplete. Pored scales 4–7. Transverse scale rows 10–12. Predorsal scale rows 14–15. Circumpeduncular scales modally 14 (12–14).

Abdominal vertebrae modally 16 (15–17); caudal vertebrae modally 17 (16–18); total vertebrae modally 33 (32–34). Position of first dorsal-fin ray pterygiophore (D-PTG-1) = 10 (between 10th and 11th vertebrae, denoted as 10; range from 9 to 11). Position of first anal-fin ray pterygiophore (A-PTG-1) = 16 (range from 15 to 17) ( Fig. 4 ). Pharyngeal teeth in one row, formula 0,0,5-5,0,0, occlusal grooves relatively reduced ( Fig. 5 ). Gill rakers on external side of first gill arch 12–13.

Ripe eggs large and spindle-shaped, major axis approximately 3.1–3.7 mm, ratio of major axis to minor axis 1.8–2.1 (examined from eight clutches of eggs from different females) ( Fig. 6A ). Larvae with wing-like yolk sac projections ( Figs. 6B, 6C ).

Coloration in life. Nuptial coloration present in adult males during breeding season. Body with a blue blotch between 4th and 5th scales in lateral series, and a slender blue longitudinal stripe running from below dorsal fin and ending about two scales in front of caudal-fin base. Iris yellowish. Posterior head, belly, and posterior caudal peduncle yellow. Color of all fins slightly yellowish. Dorsal and anal fins margined with black, lined proximally by a reddish-orange band; central part of caudal fin orange ( Fig. 7A ). Yellow and orange color usually fades outside the breeding season.

Females with grayish body color, darker dorsally ( Fig. 7B ). Ovipositor mostly whitish or pinkish, posterior part slightly grayish ( Fig. 2 ).

In postlarvae, juveniles, and small adult females (usually less than 35 mm SL), a large black blotch on anterior part of dorsal fin. Dorsal fins of postlarvae and early juveniles margined with white. Anal fins of early juveniles margined with white ( Figs. 6D , 8 ).

Color in preservative. Ground color brownish, lighter towards belly. Dorsal-fin membrane grayish with low intensity of melanophores. Two transverse rows of light spots on dorsal and anal fin rays. A blackish blotch on anterior of flank, a slender blackish longitudinal stripe on posterior of flank, and a black margin on dorsal and anal fins in adult males, but nearly invisible in females ( Figs. 1A, 1B ).

Distribution and ecology. Known only from the Le-An River, a tributary flowing into the Poyang Lake in the Yangtze River basin, in Wuyuan County, Jiangxi Province, China ( Fig. 9 ). The type locality was a stream with mud and gravel mixed substrate. The water level varied from approximately 0.5 to 1.5 m. Rhodeus flaviventris mostly occurred in backwater areas of the stream about 10 meters wide. The main breeding season is spring, from April to June. It spawns several times during the spawning period and usually releases 8– 15 eggs in a single clutch. Host mussels unknown.

Etymology. The specific name, flaviventris , is derived from the Latin terms flavus, meaning yellow, and venter, meaning belly, a noun in apposition, alluding to the diagnostic yellow belly in the adult males. A suggested Chinese vernacular is 黄腹×M.

Figures

FIGURE 1. Rhodeus flaviventris, China: Jiangxi Province: Wuyuan County. A, SOU 1909001, holotype, 49.8 mm SL, male; B, SOU 1903002, paratype, 44.9 mm SL, female

FIGURE 2. Ovipositor of a mature female Rhodeus flaviventris (45.1 mm SL).

FIGURE 3. Rhodeus flaviventris, SOU 1508002, paratype, 48.7 mm SL, male. Simple and first branched rays of dorsal (A) and anal (B) fins.

FIGURE 4. Rhodeus flaviventris, SOU 1110001, paratype, 52.9 mm SL, male. Radiograph.

FIGURE 5. Pharyngeal teeth of Rhodeus flaviventris.

FIGURE 6. Eggs and larvae of Rhodeus flaviventris, incubated at a water temperature of 23 °C. A, unfertilized ripe eggs; B, larvae just after hatching; C, larvae 4 days after hatching; D, larva 16 days after hatching, 8.1 mm SL.

FIGURE 7. Rhodeus flaviventris during the breeding season. A, male; B, female. Specimens not preserved.

FIGURE 8. Juvenile Rhodeus flaviventris, 15.4 mm SL. Specimen not preserved.

FIGURE 9. Distribution of Rhodeus flaviventris, R. albomarginatus, R. nigrodorsalis, and R. shitaiensis in the lower Yangtze River basin, China. ★ Type locality of R. flaviventris; ▲ localities of R. albomarginatus; ● localities of R. nigrodorsalis; ◆ type locality of R. shitaiensis.