Rhinogobius sudoccidentalis, Li & Li & Shao & Fu & Zhou, 2024

Li, Lingzhen, Li, Chaoyang, Shao, Weihan, Fu, Suxing & Zhou, Chaowei, 2024, Two new species of freshwater goby (Teleostei, Gobiidae) from the Upper Youshui River, Chongqing, China, ZooKeys 1210, pp. 173-195 : 173-195

Rhinogobius sudoccidentalis sp. nov.

Table 2 , Figs 2 , 3 , 4 , 5 , 6 , 7

Type materials.

Holotype. China • 1 ♂; Chongqing City , Xiushan County; 28 ° 23 ' 23 " N, 108 ° 53 ' 16 " E; 1 July. 2023; Lingzhen Li & Chaoyang Li leg.; RS 20230001 .

Paratypes. China - Chongqing City • 7 ♂♂, 3 ♀♀; Xiushan County; 28 ° 23 ' 23 " N, 108 ° 53 ' 16 " E; 1 July. 2023; Lingzhen Li & Chaoyang Li leg.; RS 20230101 to 20230110 . • 4 ♂♂; Xiushan County; 28 ° 26 ' 17 " N, 108 ° 59 ' 12 " E; 1 July. 2023; Lingzhen Li & Chaoyang Li leg.; RS 20230111 to 20230114 . • 1 ♂, 1 ♀; Xiushan County; 28 ° 24 ' 51 " N, 109 ° 7 ' 13 " E; 3 July. 2023; Lingzhen Li & Chaoyang Li leg.; RS 20230115 , 20230116 . • 1 ♂, 2 ♀♀; Xiushan County; 28 ° 22 ' 30 " N, 108 ° 53 ' 18 " E; 4 July. 2023; Lingzhen Li & Chaoyang Li leg.; RS 20230118 , 20230120 . - Guizhou Province • 1 ♂; Tongren City ; 28 ° 8 ' 50 " N, 108 ° 59 ' 13 " E; 3 July. 2023; Lingzhen Li & Chaoyang Li leg.; RS 20230117 .

Diagnosis.

Rhinogobius sudoccidentalis can be distinguished from other species in the genus by the following characteristics: it possesses VI – VII rays in the first dorsal fin and I, 8–9 rays in the second dorsal fin. The longitudinal scale series typically consists of 22–24 scales (most commonly 23), while the transverse scale series typically comprises 7–8 scales (most commonly 8). The predorsal scale series is absent. The total number of vertebrae counts is 12 + 17 = 29. Additionally, it features a black line stripe beneath the eye that extends to the mandible. Morphometrics Reference Table 2 .

Description.

Fins: The fins display distinct features: the first dorsal fin typically bears VI rays (18) or VII rays (2), while the second dorsal fin exhibits either I, 8 rays (2) or I, 9 rays (18). The 3 rd or 4 th spine of the first dorsal fin is the longest and lacks filamentous. In males, the depressed first dorsal fin extends to the base of the 1 st or 2 nd branched ray of the second dorsal fin; in females, it reaches only the base of the second dorsal fin anteriorly. The anal fin has I, 6 rays (1) or I, 7 rays (19), originating at a vertical line between the 2 nd and 3 rd branched soft ray of the second dorsal fin. The pectoral fin typically has 14 rays (2) or 15 rays (18) and is broad. In males, the rear tip of the pectoral fin aligns parallel to the anus, a feature absent in females.

Scales: The body is covered with ctenoid scales, with enlarged mid-trunk scales. The anterior predorsal area lacks scales, while the posterior occipital region is adorned with cycloid scales. The belly is covered with small cycloid scales. The longitudinal scale series ranges from 22 to 24 (mode: 23), and the transverse scale series ranges from 7 to 8 (mode: 8). No scales are present in the predorsal area.

Head canals: Pores σ are located between the anterior and posterior nares. The anterior interorbital sections of oculoscapular canal are separated, featuring paired pore λ. A single pore κ is situated in the posterior region, with ω present near posterior edge of eyes. There is an absence of ω 1. The lateral section of anterior oculoscapular canal exhibits pores α and terminal pore ρ. The posterior oculoscapular canal ends with two terminal pores θ and τ. Preopercular canals are presented, featuring pores ε, γ, and δ.

Sensory papillae: Row a extends anteriorly to just before the middle of the eye. Row b is oblique and reaches forward to the posterior margin of the eyes. Rows c and d are longer, extending behind the orbit, with Row cp positioned between Rows c and d. Row f is paired. Opercular papillae include Rows ot, oi, and os, with oi nearly reaching ot.

Vertebrae: The total vertebrae count is 12 + 17 = 29 (N = 5), with a (P – V) pattern of 3 / II II I I 0 / 9 (N = 5).

Coloration of preserved specimens: In males, the head and body of R. sudoccidentalis exhibit a yellowish-brown color. There are paired brown stripes on the snout converging at the tip, while the cheeks and opercle are adorned with small black spots. A black stripe extends from under the eye to the mandible. The ventral side displays dens coverage of small black spots. The membrane of the first dorsal fin is gray, the second dorsal fin has a transparent membrane with dense black mottling, and the anal fin exhibits a black membrane. The pectoral fin is transparent. In females, the head and body are yellowish, with a single black diagonal line below each eye. Irregular black patches are present on the ventral side, and both the dorsal and anal fins are transparent.

Color in life: In males, the head and body of the R. sudoccidentalis are creamy white. There are paired reddish-brown stripes on the snout meeting at the tip, and the cheeks and opercle feature small black spots. A black stripe extends from under the eye to the mandible. The ventral side is densely covered with small orange spots. The membrane of the first dorsal fin is red with a blue mottling pattern between the 1 st and 2 nd spinous rays. The second dorsal fin has a transparent membrane with dense black mottling and a white outer edge. The anal fin exhibits a white margin with reddish dots on the ventral part of the reddish membrane. The pectoral fin is transparent, with a milky white basal portion. In females, the head and body are yellowish, with paired brown stripes on the snout meeting at the tip. There are single black diagonal lines below the eyes, and irregular black patches on the ventral side. Both the dorsal and anal fin are transparent, and the pectoral fin is transparent with a milky white basal portio.

Distribution and habitat.

Rhinogobius sudoccidentalis was initially discovered in a small stream in Xiushan, Chongqing, where it predominantly inhabits areas characterized by large cobblestone substrates and slow-flowing water at depths ranging from approximately 30 to 50 cm. Additionally, small populations of this species were also observed in Tongren, Guizhou Province. In the Xiushan area, R. sudoccidentalis is the dominant fish species, utilizing the cobblestone bottom as an egg deposition site, with eggs characterized as large (size 1.6–2.1 mm). During periods of high water levels in the creek, individuals aggregate near the shore to seek refuge from the rapids.

Etymology.

This species, discovered in Chongqing and Guizhou Province in the southwestern region of China, has been named R. sudoccidentalis . The Latin roots “ sud ” meaning “ south ” and “ occidentalis ” meaning “ western ” combine to signify “ southwestern ”. The suggested Chinese name for this species is 西南吻虾虎鱼.

Figures

Figure 2. Dorsal (A), lateral (B), and ventral (C) views of preserved holotype of Rhinogobius sudoccidentalis sp. nov. (RS 20230001 male) and dorsal (D), lateral (E), and ventral (F) views of preserved paratype of Rhinogobius sudoccidentalis sp. nov (RS 20230101 female).

Figure 3. The skeletal system of R. sudoccidentalis sp. nov. Radiograph graphs of the whole body for paratype RS 20230102, male.

Figure 4. Dorsal (A), lateral (B), and ventral (C) views of the head of the preserved holotype of R. sudoccidentalis sp. nov. Red circles indicate sensory canal pores; red dots represent sensory papillae. Abbreviations: AN, anterior nare pore; PN, posterior nare pore

Figure 5. Photographs of R. sudoccidentalis sp. nov. captured underwater in a tank A male B female. Photographed by Mr Zhi.

Figure 6. Stream environment in Xiushan, Chongqing where R. sudoccidentalis sp. nov. was collected.

Figure 7. Eggs of R. sudoccidentalis sp. nov. at the type locality.