Symphurus longirostris Lee, Munroe & Kai, 2016

Lee, Mao-Ying & Munroe, Thomas A., 2021, Unraveling cryptic diversity among shallow-water tonguefishes (Pleuronectiformes: Cynoglossidae: Symphurus) from the Indo-West Pacific region, with descriptions of five new species, Zootaxa 5039 (1), pp. 1-55 : 20-22

Symphurus longirostris Lee, Munroe & Kai, 2016

( Figs. 1 , 5 , 14 ; Tables 1–6, 13)

Symphurus longirostris Lee, Munroe & Kai, 2017 (2016 online): 71, Figs. 1–2 (off Japan, 45–100 m. Holotype: FAKU 135349 ).

Specimens examined. 37, including the holotype & 36 paratypes, 26.6–65.5 mm SL. Holotype: FAKU 135349 , mature female, 37.9 mm SL, off Kyoto, Wakasa Bay , Sea of Japan, 35º45’N, 135º20’E, 90–100 m, R / V Ryokuyomaru, 18 Mar 2013. Detailed information on the other material examined for this species can be found in Lee et al. (2017).

Diagnosis. Symphurus longirostris is distinguished from all congeners by the combination of: a 1–2–2–2–2 ID pattern; 12 caudal-fin rays; 9 (3 + 6) abdominal vertebrae; 45–48 total vertebrae; 4 hypurals; 81–88 dorsal-fin rays; 68–74 anal-fin rays; 56–66 longitudinal scale rows; and 11–14 scale rows on head posterior to lower orbit; a slender body (BD= 22.1–26.3% of HL); relatively long preanal length (PAL= 24.6–27.3% of SL); upper head lobe slightly larger than lower head lobe; head moderately long (HL= 20.5–22.6% of SL), longer than head width (HW/HL= 0.92–0.99); short postorbital length (POL= 62.5–67.5% of HL); long snout (SNL= 18.7–24.4% of HL, SNL/ED= 1.66–2.24), round to obliquely blunt anteriorly; dorsal-fin origin at vertical through posterior margin of upper eye, or at point posterior to eye; long predorsal length (PDL= 23.8–32.7% of HL); well-developed fleshy ridge on posterior part of ocular-side lower jaw; membrane covering both eyes; also with fleshy membrane continuous between ocular-side anterior nostril and lower part of eye; ocular-side pigmentation yellow to light-brown; blind-side pigmentation uniformly white without pepper-dots; both sides with obvious dermal spots on bases of anteriormost dorsal- and anal-fins; and peritoneum bluish-black on its dorsalmost aspect.

Description. Symphurus longirostris ( Fig. 5 ) is a dwarf species known from 37 specimens, the largest of which is 65.5 mm SL. Meristic characters are summarized in Tables 2– 5. Predominant ID pattern 1–2–2–2–2 (31/ 37 specimens, including holotype). Caudal-fin rays 12. Dorsal-fin rays 81–88. Anal-fin rays 68–74. Pelvic-fin rays 4. Total vertebrae 45–48; abdominal vertebrae 9 (3 + 6). Hypurals 4. Longitudinal scale rows 56–66. Scale rows on head posterior to lower orbit 11–14. Transverse scales 21–26.

Proportions of morphometric features are presented in Table 6. Body relatively elongate, moderately deep; maximum depth in anterior one-third of body, usually at point between anus and fifth anal-fin ray; body with gradual taper posterior to midpoint. Preanal length larger than body depth. Head moderately long and narrow; head width slightly shorter than head length (HW/HL = 0.92–0.99, Mean= 0.96). Upper head lobe wider than lower head lobe (UHL/LHL= 1.01–1.20, Mean= 1.08); shorter than postorbital length. Snout relatively long; slightly round to obliquely blunt anteriorly; its length usually much greater than eye diameter (SNL/ED= 1.66–2.24, Mean= 1.95). Dermal papillae present, well developed, on blind side of snout and chin. Ocular-side anterior nostril tubular and short, usually not reaching anterior margin of lower eye when depressed posteriorly. Ocular-side posterior nostril, a small, rounded tube located on snout just anterior to interorbital space. Blind-side anterior nostril, tubular, moderately long, easily distinguishable from dermal papillae; blind-side posterior nostril, a shorter and wider posteriorly directed tube situated posterior to vertical at posterior margin of jaws. Eyes moderately large (ED= 9.3–12.1% of HL), oval, and contiguous; with membrane covering both eyes; anteroventral eye membrane connected with anterior nostril by fleshy membrane. Eyes usually equal in position, or with anterior margin of upper eye slightly in advance of that of lower eye. Pupillary operculum absent. Jaws short and slightly arched; upper jaw length slightly longer than snout length; posterior margin of upper jaw usually extending to point between verticals through anterior margin of pupil and posterior margin of lower eye. Ocular-side lower jaw with well-developed fleshy ridge on its posterior half. Cheek depth narrow, slightly shorter than snout length. Lower lobe of ocular-side opercle wider than upper opercular lobe; posterior margin of lower lobe projecting slightly beyond posterior margin of upper opercular lobe. Dorsal-fin origin located at vertical through posterior margin of upper eye, or at point slightly posterior to this vertical; predorsal length relatively long. Anteriormost dorsal-fin rays obviously shorter than more posterior fin rays. Scales absent on both sides of dorsal- and anal-fin rays. Pelvic fin moderately long; longest pelvic-fin ray, when extended posteriorly, usually reaching base of third to fourth anal-fin ray. Posteriormost pelvic-fin ray connected to anal fin by delicate membrane. Caudal fin relatively long, with several (usually less than four) rows of ctenoid scales on base of fin. Scales on both sides of body numerous, strongly ctenoid.

Teeth present and recurved slightly inward on all jaws, but better developed on blind-side jaws. Ocular-side premaxilla and dentary with single row of sharply pointed, well-developed teeth. Blind-side premaxilla with two to three rows of sharp, recurved teeth. Blind-side lower jaw with three to six rows of well-developed teeth.

More detailed information, including additional morphological and molecular data, were previously provided in Lee et al. (2017).

Pigmentation. Pattern of body pigmentation generally similar for both sexes at all sizes ( Fig. 5 ). Background body coloration of ocular side generally light yellow to light brown; ocular surface darker along regions overlying pterygiophores of dorsal and anal fins; median longitudinal row of darkly pigmented melanophores present along vertebral axis on blind side of specimens usually smaller than 45 mm SL. Melanophores in dermis also present in darker regions overlying pterygiophores of dorsal and anal fins. External surface of abdominal area usually reddish to light brown with bluish-black pigmentation covering dorsalmost part. Background coloration of ocular side of head generally similar to that on body, except for one dark region behind eyes formed by dense cluster of dermal melanophores, and with obvious dermal spots at bases of anterior dorsal-fin rays. Ocular side of snout light yellow. Ocular-side anterior nostril light yellow to brown. Upper aspects of eyes and eye sockets light blue with light-bluish spots; pupils bluish-black. Ocular-side lips and chin region uniformly yellow to brown; margins of lips with small melanophores. Nearly entire outer surface of ocular-side opercle yellow to brown, similar to background coloration on body and head. Margin of opercle darker brown, especially at opercular opening. Inner surface of ocular-side opercle and isthmus with small dark brownish or blackish dot-sized melanophores. Isthmus also with pepper-dots on its surface. Blind side generally white to light-yellow, with bluish-black pigment on dorsalmost part of peritoneum showing through abdominal wall. Some specimens, usually those smaller than 45 mm SL, with median longitudinal row of darkly pigmented melanophores along vertebral axis. A single, longitudinal row of well-developed dermal melanophores present along bases of anteriormost dorsal- and anal-fin rays. Outer surface of blind-side opercle white to light yellow, generally corresponding to background coloration. Inner surface of blind-side opercle unpigmented. Fin rays of dorsal, anal, and pelvic fins uniformly yellow to brown; basal regions of fin rays and membranes covering fin rays light yellow, with diffuse scattering of yellow to brown chromatophores over entire fin membranes on both sides of fins. Dorsal and anal fins with alternating series of darkly streaked and lightly pigmented fin rays throughout entire lengths of fins. Basal margins of fin rays and associated fin membranes on blind side light yellow to light brown.

Pigmentation of recently preserved specimens ( Fig. 5 ). Similar to that of freshly caught fishes; pigmentation of older specimens preserved decades ago usually faded, but dermal spots at bases of anterior dorsal-fin rays and on isthmus, as well as bluish-black coloration on dorsalmost part of peritoneum, still clearly visible in these specimens.

Remarks. Compared with most other species of shallow-water Symphurus , S. longirostris appears to be a common species collected in shallow waters around Japan (including Pacific side and Japanese Sea).

Comparisons. Symphurus longirostris is one of three species in the S. microrhynchus species complex that features lower scale counts. Other members with lower scale counts include S. microrhynchus and S. holothuriae . These three species share a similar general body shape, and have overlapping counts of dorsal-, anal-, and caudal-fin rays, longitudinal scales, and transverse scales ( Table 6). Characters distinguishing S. longirostris from S. microrhynchus and S. holothuriae were highlighted in the Comparisons sections above for these two species, respectively.

Symphurus longirostris differs from the group of five species of the S. microrhynchus species complex ( S. brachycephalus n. sp., S. hongae n. sp., S. leptosomus n. sp., S. polylepis n. sp., and S. robustus n. sp.) featuring high scale counts by its lower numbers of longitudinal (56–66 vs. 72–94) and transverse scales (21–26 vs. 26–37 in these others). Symphurus longirostris has the head width shorter than the head length (HW/HL= 0.92–0.99), whereas, in the five species with high scale counts, their heads are wider than long with HW/HL ratios ranging from 1.02–1.20 for these species.

Despite having the same ID pattern (1–2–2–2–2) and overlapping counts for dorsal-fin rays (81–88 vs. 86–92) and anal-fin rays (68–74 vs. 73–80) as those found in S. monostigmus and S. leucochilus , S. longirostris is readily distinguished from these species by several features. For example, S. longirostris has a membranous connection between the ocular-side anterior nostril and the lower eye, and it also has a fleshy ridge present on the ocular-side lower jaw; both features being absent in these other species. Symphurus longirostris has fewer total vertebrae (45–48 vs. 48–51) than do these other species, and its head length is nearly equal to its width (HW/HL= 0.92–0.99) versus head width greater than head length (HW/HL= 1.07–1.42) in these other species. Additionally, S. longirostris has fewer longitudinal scales (56–66 vs. 75–83), fewer rows of head scales (11–14 vs. 15–19) and transverse scales (21–26 vs. 32–38), than is found in these other species. Symphurus longirostris differs further from S. monostigmus in having 12 (vs. 14) caudal-fin rays and 4 (vs. 5) hypurals, and S. longirostris also lacks the pigment spot on the abdomen that features so prominently in S. monostigmus .

Figures

FIGURE 1. Diagnostic pigmentation features on blind sides of Indo-West Pacific shallow-water species of Symphurus. (A) Example of pepper-dots and dermal spots represented by S. hongae, ASIZP0072360, male, 48.0 mm SL, Dong-Gang, SW Taiwan, 04 Jul 2007. (B) Example of an unpigmented blind side represented by S. longirostris, ASIZP0072352, female (mature), 57.3 mm SL, off Kochi, Japan, 04 Apr 1994. (C) Example of median melanophores along vertebral axis as represented by S. leucochilus, holotype, USNM 408271, mature female, 58.7 mm SL, Da-Shi fish market, northeastern Taiwan, 24 Aug 2011. (D) Example of species without median series of melanophores on vertebral axis represented by S. brachycephalus, ASIZP0072364, female (mature), 49.4 mm SL, off Nan Trang, Vietnam, 19 Apr 2009.

FIGURE 2. Symphurus microrhynchus, holotype, ZMA 108193, immature female, 42.2 mm SL, Java Sea. A. Ocular-side pigmentation of preserved specimen. B. Blind-side pigmentation of same specimen. Scale equals 10 mm.

FIGURE 5. Symphurus longirostris, holotype, FAKU 135349, mature female, 37.9 mm SL, off Wakasa Bay, off Kyoto, Sea of Japan, Japan. A. Ocular-side pigmentation of preserved specimen. B. Blind-side pigmentation of same specimen. Scale equals 10 mm.

FIGURE 14. Summarized maximum-likelihood (ML) tree of selected species of the genus Symphurus from the Indo-West Pacific Ocean based on partial COI gene dataset and results from the species delimitation analyses and other considerations (see materials & methods). Numbers above nodes indicate bootstrap values in percentage.Values below 70% not shown. Information of samples indicated in Table 1.