Symphurus leucochilus Lee, Munroe & Shao. 2014

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 : 47-49

Symphurus leucochilus Lee, Munroe & Shao. 2014

( Figs. 13 , 14 ; Tables 1–5, 12–13)

Symphurus leucochilus Lee et al. 2014: 563 , Fig. 1 (Off Japan and Taiwan, 150 m. Holotype: USNM 408271; sister group of S. orientalis ; S. microrhynchus sensu Munroe & Marsh 1997 represents composite mix of several species; meristic data overlaps that of several species in the S. microrhynchus species complex). Lee et al. 2017: 78 (compared with S. longirostris ; S. microrhynchus sensu Munroe & Marsh 1997 represents a composite mix of several species; recognized two species groups among the nominal species included in the S. microrhynchus complex).

Holotype: USNM 408271 , mature female, 58.7 mm SL, Da-Shi fish market, northeastern Taiwan, 24 August 2011. Detailed information on material examined can be found in Lee et al. (2014).

Paratypes: Seven specimens. Two non-type specimens also included in the original description. Paratypes and non-type specimens 21.7–66.9 mm SL.

Diagnosis. Symphurus leucochilus 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; 49–51 total vertebrae; 4 hypurals; 89–92 dorsal-fin rays; 76–80 anal-fin rays; 75–83 longitudinal scale rows; 32–35 transverse scale rows; 15–17 scale rows on head posterior to lower orbit; relatively deep body (BD= 26.3–32.3% of HL); moderately long preanal length (PAL= 24.3–26.0% of SL); upper head lobe much larger than lower head lobe; moderately short head (HL= 18.7–21.8% of SL), shorter than head width (HW/HL= 1.07–1.29); short postorbital length (POL= 65.6–69.5% of HL); long snout (SNL= 18.4–23.4% of HL; SNL/ED= 1.47–2.09), round to obliquely blunt anteriorly; dorsal-fin origin at point between verticals at anterior margin of upper eye and anterior margin of pupil of upper eye; relatively long predorsal length (PDL= 17.6–22.3% of HL); no fleshy ridge on ocular-side lower jaw; eyes separate, with anterior margin of upper usually equal to, or slightly in advance of, anterior margin of lower eye; anterior ocular-side nostril not connected to eyes; ocular-side pigmentation light-yellow to light-brown without melanophores; blind-side pigmentation uniformly white to light yellow; peritoneum bluish-black.

Description (from Lee et al. 2016). Symphurus leucochilus ( Fig. 13 ) is a diminutive species, known from 10 specimens, the largest reaching a maximum size of 66.9 mm SL. Meristic characters are summarized in Tables 2–5. Predominant ID pattern 1–2–2–2–2 (eight of nine specimens). Caudal-fin rays 12. Dorsal-fin rays 89–92. Anal-fin rays 76–80. Pelvic-fin rays four. Total vertebrae 49–51; abdominal vertebrae, nine (3 + 6). Hypurals four. Longitudinal scale rows 75–83. Scale rows on head posterior to lower orbit 15–17. Transverse scale rows 32–35.

Proportions of morphometric features are presented in Table 12. Body relatively deep; maximum depth in anterior one-third of body usually at point between anus and eighth anal-fin ray, body depth tapering rapidly posterior to midpoint. Preanal length usually smaller than body depth. Head moderately long and wide; head width (HW) slightly shorter than body depth, and much greater than head length (HW/HL= 1.07–1.29, Mean= 1.20). Upper head lobe wider than lower head lobe (UHL/LHL= 1.05–1.37, Mean= 1.22); slightly shorter than postorbital length. Upper lobe of ocular-side opercle wider than lower opercular lobe; posterior margin of lower lobe projecting slightly beyond posterior margin of upper opercular lobe, or both lobes equal with their posterior margins reaching similar points along same vertical plane. Snout moderately long, slightly round to obliquely blunt anteriorly; snout length much greater than eye diameter (SNL/ED= 1.47–2.09, Mean=1.83). Dermal papillae present, but not well developed, on blind side of snout. 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 and short, easily distinguishable from dermal papillae; blind-side posterior nostril a shorter, and wider, posteriorly directed tube situated posterior to vertical at rear margin of jaws. Jaws long and slightly arched; upper jaw length equal to, or slightly longer than, snout length; posterior margin of upper jaw usually extending to point between verticals through anterior margin of eye and anterior margin of pupil of lower eye. Ocular-side lower jaw without fleshy ridge. Cheek depth shorter than snout length. Eyes moderately large (ED= 10.4–12.5% of HL), oval, separated by two to three rows of small ctenoid scales in narrow interorbital space. Eyes usually equal in position, or with anterior margin of upper eye slightly in advance of that of lower eye. Pupillary operculum absent. Dorsal-fin origin located at point between verticals through anterior margin of upper eye and anterior margin of pupil of upper eye; predorsal length moderately short. Anteriormost dorsal-fin rays slightly 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 first to fourth anal-fin ray. Posteriormost pelvic-fin ray connected to anal fin by delicate membrane. Caudal fin relatively long, with several rows of ctenoid scales on its base. Both sides of body with numerous, strongly ctenoid scales.

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

Pigmentation of freshly caught specimens ( Fig. 13 ). Ocular-side background coloration of body, head and most of external surface of opercle generally light-yellow to light-brown, sometimes also with irregular, darkly shaded areas. External surface overlying abdominal area usually darker bluish-black due to dark peritoneal pigment visible through abdominal wall. Posterior margin of opercle darker brown than more lightly pigmented anterior regions. Outer surface of ocular side of isthmus without conspicuous melanophores. Inner surface of ocular-side opercle and isthmus unpigmented. Ocular-side lips and chin region light-yellow to light-brown; margins of lips with numerous small black dots. Ocular-side anterior nostril light-yellow to brown. Upper aspects of eyes and eye sockets light blue to bluish-green; pupils bluish-black. No conspicuous melanophores on head region posterior to eyes. No conspicuous dermal spots or melanophores at bases of anterior dorsal-fin rays. Blind side generally white to light yellow with darkly pigmented bluish-black region overlying peritoneum. Background of outer surface of blind-side opercle white to light yellowish; inner surface unpigmented. Small specimens with streak of black on vertebrae distinctly visible externally through body musculature.

Pigmentation of alcohol-preserved specimens. Similar to that of freshly caught fish, except bluish-black coloration of pupil of freshly caught specimens blending more gradually and eventually fading into white background coloration. 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 covering entire fin membranes on both sides of fins. Entire dorsal and anal fin with a series of dark streaks alternating with lighter areas on fins. Basal margins of blind sides of dorsal- and anal-fin rays and associated fin membranes light-yellow to light-brown.

Remarks. Information about S. leucochilus , including color photos were detailed in the description of this species by Lee et al. (2014). One additional specimen (NMMB–P21879) of S. leucochilus , discovered after the description by Lee et al. (2014), was collected in the bycatch landed at Dong-Gang fish market, Taiwan. Information regarding date of capture, depth of capture, and other ecological data are unknown for this specimen. This is a very common situation encountered when using specimens from bycatch. To collect reliable environmental data necessary for understanding the ecology (e.g. bathymetric distribution, substrata, etc.) of S. leucochilus we still need to rely on further investigations conducted by research vessels.

Comparisons. Symphurus leucochilus has the same ID pattern (1–2–2–2–2) and the same number of caudalfin rays (12), and has counts for dorsal- (89–92) and anal-fin rays (76–80), total vertebrae (49–51) and longitudinal scales (75–83) that overlap those found in members of the S. microrhynchus species complex. Some features also overlap those of S. monostigmus . Differences between S. leucochilus and members of the S. microrhynchus species complex were discussed in the Comparisons sections under the individual species accounts above.

Symphurus leucochilus is similar to S. monostigmus in that these are the only two shallow-water IWP species that lack a membranous connection between the ocular-side anterior nostril and lower eye, and these two species also lack a fleshy ridge on the ocular-side lower jaw that is found in members of the S. microrhynchus species complex. Symphurus leucochilus differs distinctly from S. monostigmus in having 12 caudal-fin rays and 4 hypurals (vs. 14 caudal-fin rays and 5 hypurals), and S. leucochilus has different pigmentation including lacking freckles on the ocular side and lacking the pigment spot on the abdomen that feature so prominently in S. monostigmus . Symphurus leucochilus also has fewer longitudinal (75–83 vs. 92) and transverse scales (32–35 vs. 36–38) than is found in S. monostigmus . Other differences between these species were discussed in the Comparisons section of the species account for S. monostigmus above.

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 13. Symphurus leucochilus, holotype, USNM 408271, mature female, 58.7 mm SL, Da-Shi Fish Market, northeastern Taiwan. A. Ocular-side pigmentation. B. Blind-side pigmentation.

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.