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

Luciogobius matsuensis n. sp. (Figs. 2–4) [New English name: Matsu earthworm goby] [Chinese name: DZḂṃḛ] Materials examined Holotype. NTOUP-2023-05-306, 37.7 mm SL, Zhuluo, Nangan Island, Matsu Islands, Lianjiang County; coll. C.L. Lee, 2 March, 2023. Paratypes. —NTOUP-2023-05-307, 2 specimens, 28.1–39.0 mm SL, Zhuluo, Nangan Island, Matsu Islands, Lianjiang County; coll. C.L. Lee, 2 March, 2023. Diagnosis Luciogobius matsuensis can be well distinguished from all other congeneric species by the following unique combination of features: (1) second dorsal fin rays: I/12 and anal fin rays: I/12; (2) pectoral fin rays modally 16 and with one upper, very short free soft ray; (3) vertebral count: 17 + 20–21 = 37–38; and (4) specific coloration: second dorsal fin translucent with tiny brown spots; caudal fin with many tiny brown spots; anal fin pale yellow and translucent, spotless, and darker in its rays; and pectoral fin creamy yellow with anterior 2/3 region with tiny brownish to black 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 moderately small. A horizontal dermal fold 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, about two times of eye diameter. Mouth oblique, maxillary extending to vertical of rear margin of orbit. Lower jaw more prominent compared to upper jaw. Teeth rather minute, with about 4 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 17 + 20–21 = 37–38. Fins. D2 I/12, A I/12, P 16. 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 vertical between 2nd and 3rd branched rays of A. Both rear tips of D2 and A far from procurrent rays of C when depressed. P rounded, and its length about equal to postorbital length. P with a short, free soft ray on upper margin near upper basal region. C rounded. V as a round sucking disc with complete frenum and rather small, somewhat larger than orbit but smaller than snout length. 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 a single vertical row. Other papillae are shown in detail in Fig. 3. Coloration when fresh Body and head light creamy yellow to yellowish brown background. Head and body with many tiny brownish to blackish melanophores. Second dorsal fin translucent with tiny brown spots. Caudal fin with many tiny brown spots. Anal fins pale yellow and translucent, spotless, and darker in their rays. Pectoral fin creamy yellow with anterior 2/3 region with tiny brownish to black spots (Fig. 4). Pelvic fin whitish. Distribution Till present, this species is only known from the Matsu Islands, Lianjiang County of Taiwan. It is an intertidal species on the island. Etymology The specific name, matsuensis, refers to the type locality from the Matsu Islands, Taiwan. Remarks The current new species, Luciogobius matsuensis n. sp., is rather similar to Luciogobius ryukyuensis Chen et al., 2008 by having a lower count of pectoral fin rays with one free ray above the pectoral fin compared to any other congeneric species. However, it can be well distinguished from Luciogobius ryukyuensis by the following features: (1) fin rays: second dorsal fin rays I/12 vs. I/11; anal fin rays I/12 vs. I/11; and (2) vertebral count: anterior region as abdomen vertebrae always 17 vs. 16. Luciogobius matsuensis n. sp. can also be distinguished from Luciogobius guttatus Gill, 1859 by the following combination of features: (1) pectoral fin rays 16 vs. 18–19; and (2) anal fin rays I/12 vs. I/13.