Formosaneleotris hualienensis Chen 2024, new species

Formosaneleotris hualienensis new species (ĭjÎ塘ª) (Figs. 1–2) Material examined: Holotype.— NTOUP-2006-03-458, 44.2 mm SL, Aug. 20, 2001, coll. I-S. Chen & J-L. Huang, Jian Village, Hualien River basin, Hualien County, Taiwan, ROC. Diagnosis. The new genus and new species of current sleeper, Formosaneleotris hualienensis can be well distinguished from other remaining genera of sleepers by the following unique combination of characters: (1) fins: no first dorsal fin; second dorsal fin I/8; anal fin I/8; pectoral fin 13–14; (2) squamation: entirely body naked; (3) vertebral count: 10 + 14 = 24; (4) branchiostegal rays 6; (5) head lacking any canal and pore with longitudinal like sensory papillae; and (5) specific coloration: body and head bloody red entirely; one thin deep red infraorbital stripe to upper lip. Description. Body proportions listed in Table 1. Body very elongate and cylindrical anteriorly; turning rather compressed posteriorly. Head rather depressed anteriorly and somewhat cylindrical posteriorly. Branchiostegal rays 6. Mouth oblique and rather large, maxillary extending beyond middle vertical of eye. Lower jaw more prominent than upper jaw on anterior tip of head. Interorbital rather wide. Both jaws with 3–4 rows of conical teeth. Tongue rounded. Gill-opening restricted, extending ventrally close but not reaching middle vertical of opercle. Vertebral count: 10 + 14 = 24. Fins. —Entirely lacking first dorsal fin; D2 I/8; A I/8; P 13–14; V I/5. D2 and A with middle rays slightly higher. P median large and elongate, no upper or lower free rays. V well separated, somewhat small, no frenum, no connecting membrane. Caudal fin large and elliptical with somewhat truncate distal margin. Scales.—Entire body and head naked without scales. LR 0; TR 0; PreD 0. Head lateral-line system (Fig. 1) Canals.—No head canal and pore. Sensory papillae.—Infraorbital papillae with longitudinal row a. highly dense set of row b. Row c longitudinal. Row d interrupted in row d1 extension along upper jaw. Row z very long. Row f with 2 transverse papillae. Row z very long. Row ot, oi, os well separated. Coloration while fresh. (Fig. 2) Body and head bloody red entirely. One thin deep red infraorbital stripe to upper lip. No distinct dark mark on body and fins. Etymology of genus.— The new generic name, Formosaneleotris, refers to the type locality of the current new genus of “sleeper” that is only found in the river basins of Taiwan. The classical name of Taiwan is also called “Formosa”. Etymology of species.— The new specific name, hualienensis, refers to the type locality of the current new species of sleeper from the “ Hualien ” River basin of Taiwan. Remarks. —Among all genera of sleepers that possess six branchiostegal rays, none are lacking the first dorsal fin like the new genus, Formosaneleotris. This new genus also has the lowest vertebral count (VC 10+14=24) among the thousands of species in the gobioid fish family. The unique “deep red color” of this sleeper is also not seen in other gobioid fishes. This species is found in inland water habitats of river basins, coexisting with schools of Anguilla spp. larvae that ascend to lowland freshwater habitats in eastern Taiwan. This species could be a good example of convergent evolution of body shapes and appearances in benthic gobioids in the lower reaches of rivers for both discrete groups: Luciogobius from gobies and this Formosaneleotris from plesiomorphic sleepers. In contrast, Luciogobius tends to have a higher vertebral count of 36–42 while Formosaneleotris has a lower count of just 24, setting a record of the lowest count among all gobioid fishes. It would be interesting to discover additional fish samples to understand the detailed phylogenetic aspects through molecular biological analysis of its own mtDNA sequences.