Luciogobius dongyinensis Chen & Shao & Chou & Chen & Chang 2024, n. sp.

Luciogobius dongyinensis n. sp. (Figs. 5–7) [New English name: Dongyin earthworm goby] [Chinese name: Þmṃḛ] Material examined Holotype. NTOUP-2023-05-305, 58.2 mm SL, Beiao, Dongyin Island, Matsu Islands, Lianjiang County, coll. W.Y. Zhang, 21 March, 2024. Diagnosis Luciogobius dongyinensis can be distinguished from all other congeneric species by the following unique combination of features: (1) second dorsal fin rays: I/16 and anal fin rays I/16; (2) pectoral fin rays modally 14 and with three upper, very short free soft rays; (3) vertebral count: 18 + 23= 41; and (4) specific coloration: a long infraorbital deep brown stripe below eye; a long deep brown stripe above and along upper jaw; pectoral fin with many small patches of melanophores except posterior, distal 1/5 region; and caudal fin brown with many light rounded spots. Description Body very slender, cylindrical anteriorly and somewhat compressed posteriorly (all morphometric data is shown in Table 1). Head flat and depressed. Cheek slightly fleshy. Eye small. A horizontal dermal fold with papillae row on upper part of cheek and below orbit. Snout flat and short. Anterior nasal opening as a protruded, horizontal short tube and posterior nasal opening as a round hole. Interorbital region rather wide. Mouth oblique and large, maxillary extending beyond middle vertical of orbit. Lower jaw more prominent compared to upper jaw. Teeth rather minute, with 4–5 rows of tiny conical teeth, with outer rows larger in both jaws. Tongue somewhat pointed, but anterior tip bilobed. Gill-opening rather restricted, extending merely slightly below lower margin of pectoral base. Anus located in posterior half of body. Vertebral count 18 + 23 = 41. Fins. D2 I/16, A I/16, P 14. D1 absent. D2 with middle one third portion of rays longest. A shape similar to D2. Both first spines in D2 and A relatively short. A origin in front of D2 origin. D2 origin inserted vertically between 1st and 2nd branched rays of A. Both rear tips of D2 and A far from procurrent rays of C when depressed. P rounded and its length much shorter than postorbital length. P with three free soft rays on upper margin near upper basal region. C elliptical. V as a round sucking disc with complete frenum and rather small. Scales. Both body and head entirely naked without any scales. Head lateral-line system Head canals: whole head lacking any canal and head pores. Sensory papillae: series of infraorbital sensory papillae, all representing a typically longitudinal pattern. Row a long and extending to snout, which upward to surrounded eye diameter in interorbital region. Row b rather long starting above middle of dermal ridge. Row c mainly below dermal fold and rather long. A single cp located below rear Row c. Row d slightly shorter than row c. Row f paired only as two papillae. Opercle with three rows ot, os, and oi. Rows os and ot well separated. Rows z as single vertical row. Other papillae are shown in detail in Fig. 6. Coloration when fresh Body and head light creamy yellow to yellowish brown background. Head and body with small, tiny deep brown spots. A long, infraorbital deep brown stripe below eye. A long deep brown stripe above and along upper jaw. Belly yellowish with about 5 major brown cross bands anteriorly. Second dorsal fin brown with tiny white spots. Anal fin whitish or yellowish. Pectoral fin with many small patches of melanophores except posterior, distal 1/5 region (Fig. 7). Caudal fin brown with many light, rounded spots. Pelvic fin creamy white. Distribution Till present, this species is only known from the Dongyin Island, Matsu Islands, Lianjiang County of Taiwan. It is an intertidal species on the island. Etymology The specific name, dongyinensis, refers to the type locality from the Dongyin Island, Matsu Islands, Taiwan. Remarks The current new species, Luciogobius dongyinensis n. sp., is rather similar to Luciogobius grandis Arai, 1970 by having upper free rays of pectoral fin with 3–4 free rays above the pectoral fin compared to any other congeneric species. However, the new species, Luciogobius dongyinensis n. sp., can be well distinguished from the endemic, Japanese Luciogobius grandis by the following features: (1) fin rays: second dorsal fin rays I/16 vs. I/15; anal fin rays I/16 vs. I/15; (2) presence of free rays: pectoral fin upper free rays 3 vs. 4; lower free rays 0 vs. 2; and (3) vertebral count 18 + 23 = 41 vs. 19 + 22 = 41.