Mugilogobius flavomaculatus, Mantelatto, 2016

Mantelatto, Ana Francisca Tamburus and Fernando Luis, 2016, Acanthonyx petiverii " H. Milne Edwards 1834, Zoological studies 55 (39), pp. 1-16 : 6-11

Mugilogobius flavomaculatus n. sp.

urn:lsid:zoobank.org:act:D0318D27-2C4A-4B31-9694-FEF9304A0FD1

Material examined: Holotype: ASIZP0078393 , 33.0 mm SL, male, estuary of Zhuan Rive, Toucheng Township , Yilan County, Taiwan, coll. S.P. Huang and M. T. Chou, 6 October, 2012 . Paratypes: NTOUP 2012-03-129, 3 specimens, 35.3-40.0 mm SL, estuary of Zhuan River, Toucheng Township, Yilan County, Taiwan, coll. S.P. Huang and M. T. Chou, 30 November, 2009. NTOUP 2013-10-107, 3 specimens, 25.7-28.1 mm SL, estuary of Zhuan River, Toucheng Township, Yilan County, Taiwan, coll. S.P. Huang and M. T. Chou, 4 November, 2013.

Diagnosis: Mugilogobius flavomaculatus n. sp. can be well distinguished from other congeners by the combination of following features: (1) second dorsal fin rays modally I/8, anal fin rays I/8, pectoral fin rays modally 15. Longitudinal scales 34-35, predorsal scales 18-21; (2) first dorsal fin rounded, without filamentous spinous ray; and (3) body with seven distinct black stripes, cheek and operculum with blackish brown network surrounding of 5-7 rounded, bright yellow spots, first dorsal fin with a somewhat horizontally broad black blotch, basal region of caudal fin membrane with a vertical black bar or two separate brownish black spots.

Description: Body elongated, subcylindrical anteriorly and compressed posteriorly. Head large. Snout slightly prominent than the lower lip. Eye rather large. Mouth medium, maxillary extending to the vertical of anterior margin of pupil. Anterior nasal as short tube, posterior nasal as round hole. Gill slit rather restricted, extending ventrally, reaching the middle vertical line of the operculum. The morphological measurements are given in table 3. VC 10 + 16 = 26 (in 3 individuals).

Fins: D1 VI; D2 I/7-8 (modally 8); A I/8; P 14- 16 (modally 15) ( Table 4). First dorsal fin rounded, without filamentous spinous ray ( Fig. 4). Second to fifth spinous rays usually longest. Second dorsal and anal fin low. Anal fin inserted below first branched rays of second dorsal fin. Pelvic fin large and rounded. Caudal fin rounded.

Scales: LR 34-35 (modally 34); TR 10; PreD 18-21 (modally 19); SDP 9 ( Table 4). Body covered with moderate size ctenoid scales. Predorsal region covered with small sized cycloid scales. Belly covered with small sized cycloid scales. Cheek naked. Upper region of operculum covered with small sized cycloid scales.

Head lateral-line system ( Fig. 5): Head pores -Head pore absent. Sensory papillae - Row a short, about half of orbit diameter. Row b long, about equal to eye diameter, and with denselyset papillae, starting from vertical of rear margin of pupil. Rows c and c1 short, length almost equal to pupil diameter. Row cp rather long, almost equal to eye diameter, and starting from vertical of anterior margin of orbit, extending to vertical of rear margin of orbit. Row d longer than eye diameter. Row s has three rows papillae. Row p completed. Opercular papillae with rows oi, os and ot. Rows ot and oi well separated. Row f has a pair papillae.

Coloration in fresh specimen ( Fig. 6): Head and body yellow or yellowish brown, body with seven distinct vertical black cross-bands, first and second stripes somewhat oblique dorsally. Upper and lower lips blackish brown. Cheek and operculum with blackish brown network surrounding of 5-7 rounded, bright yellow spots. Nape generally yellow or yellowish brown with anterior two blackish brown cross-bands radiated narrowly from anterior dorsal part curved to both lateral regions. First dorsal fin yellow, with a somewhat horizontally broad black blotch, and a distal narrow creamy yellow blotch above black blotch. First dorsal fin have rather thin black margin. Lower region of second dorsal fin membrane yellow and distal region with few black bars. Pectoral fin membrane pale grayish white, middle region of the base with a black mark. Anal fin membrane pale grayish white with deep brown spine and rays. Caudal fin membrane somewhat translucent and grayish, and its fin base usually yellow in adult males, but usually grayish white in females, basal region of caudal fin membrane with a vertical black bar in large adult individual, but usually two separate oval, brownish black marks in small size individuals (less than 3.0 mm SL). Upper region of caudal fin base with a horizontal black bar sometimes connected with the last black cross-band of caudal peduncle. Generally, no obvious sexual dimorphism existing in this new species.

Coloration in long preserved specimen: After the long preservation, all bright yellow marks faded into pale brown or grayish white, other dark coloration patterns still similar to fresh specimens. Head and body brown or gray, body side with seven vertical black cross-bands, first and second stripes somewhat oblique dorsally. Upper and lower lips blackish brown. Cheek and operculum with black network surrounding of 5-7 rounded, grayish white spots. Nape brown with two oblique black cross-bands. Belly pale brown. First dorsal fin gray, with a somewhat horizontally broad black blotch, and a distal narrow gray blotch above black blotch. Second dorsal fin, pectoral fin, anal fin, and caudal fin membranes always grayish brown. Basal region of caudal fin membrane with a vertical black bar or two separate oval, black marks. Upper region of caudal fin base with a horizontal black bar sometimes connected with the last black cross-band of caudal peduncle.

Distribution: M. flavomaculatus n. sp. is a rare species. So far, it has been found only in low salinity waters (0.1-0.4 psu) in the estuaries of northeast Taiwan ( Fig. 7).

Etymology: This new specific name, flavomaculatus , refers to its diagnostic coloration on cheek and operculum: the presence of 5-7 rounded, bright yellow spots, derived from Latin words, flavus (yellow) and maculata (spot).

Remarks: Mugilogobius flavomaculatus n. sp. can be well distinguished from all 26 valid species by the combined morphological features. This new species can be immediately distinguished from nine valid species, including M. abei , M. chulae , M. fasciatus , M. filifer , M. fusculus , M. lepidotus , M. myxodermus , M. rivulus and M. tigrinus by all spinous rays never filamentous versus first spinous dorsal ray elongated and filamentous in adult males.

Mugilogobius flavomaculatus n. sp. can also be well distinguished from M. amadi and M. platynotus by meristic features. This new species can be immediately distinguished from M. amadi by having fewer second dorsal fin rays (I/7- 8 versus to I/9-10) and fewer anal fin rays (I/8 versus to I/10-12); and it can also be separated from M. platynotus by having fewer longitudinal scales 34-35 versus to more longitudinal scales 49-59. M. flavomaculatus n. sp. can also be well distinguished from M. rexi by having different sensory types (typical longitudinal sensory papillae versus to transverse papillae below the eye).

Compared to remaining following 13 valid species, including: M. adeia , M. cagayanensis , M. cavifrons , M. fuscus , M. hitam , M. latifrons , M. littoralis , M. notospilus , M. platystomus , M. rambaiae , M. sarasinorum , M. stigmaticus and M. wilsoni by having different color patterns. For their specific differentiation as coloration patterns of caudal fin, this new species can be easily distinguished from two of these species by representing spotless caudal fin membrane except a basal vertical black bar and upper horizontal black bar versus to more than six vertical thin wavy dark brown stripes in M. cavifrons and M. rambaiae ; two basal brownish black spots in M. notospilus ; radiated diffuse dark bars or stripes in M. littoralis ; and several coalescing waving dark lines in M. cagayanensis and M. latifrons .

For the specific differentiation as coloration patterns of body, this new species can be well distinguished from M. fuscus , M. hitam and M. stigmaticus by having yellow or yellowish brown body, and with seven distinct vertical black cross-bands versus to having irregular small dark short bars in M. fuscus ; versus to body dark brown to blackish, without obvious stripes in M. hitam ; and versus to oblique bars and square blotches on body side in M. stigmaticus .

For the specific differentiation in coloration patterns on cheek and operculum, M. flavomaculatus n. sp. can be well distinguished from M. adeia , M. platystomus and M. wilsoni by cheek and operculum having blackish brown network surrounding of 5-7 rounded, bright yellow spots versus to having oblique black stripes in M. adeia ; and two horizontal stripes in M. platystomus and M. wilsoni ). For the specific differentiation as coloration patterns on first dorsal fin, this new species can be well separated from M. sarasinorum by having a somewhat horizontally broad black blotch (versus to without obvious blotch in M. sarasinorum ).

Mugilogobius flavomaculatus n. sp. is most similar to M. mertoni , both share the similar body and caudal fin base color patterns. However, this new species still can be immediately distinguished from M. mertoni by (1) first dorsal fin without filamentous spines in adult male versus to first spinous ray elongated and filamentous; (2) anal fin rays I/8 versus to I/7; (3) cheek and operculum with blackish brown network surrounding of 5-7 rounded, bright yellow spots versus to having two horizontal stripes; and (4) first dorsal fin with a somewhat horizontally broad black blotch versus to an oval black blotch ( Fig. 4).