Symphurus brachycephalus, Lee & Munroe, 2021

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 : 23-27

Symphurus brachycephalus n. sp.

(English name: Short-headed tonguefish)

( Figs. 1 , 3 , 6 , 14 ; Tables 1–5, 7, 13)

Symphurus microrhynchus (not Weber). Munroe & Marsh 1997: 194 (misidentified as S. microrhynchus ; Vietnam). Voronina et al. 2016: 401 (21 specimens, Vietnam; meristic features, color photograph, diagnostic characters, distribution after Munroe & Marsh 1997; recognized possibility of a cryptic species).

Symphurus cf. microrhynchus (VN) . Lee et al. 2014: 576 (tentatively identified; genetic information used for resolving other taxonomic issues). Lee et al. 2017: 72 (tentatively identified; genetic information used for resolving other taxonomic issues).

Holotype: ASIZP0072365 , male, 45.2 mm SL, Off Nha Trang, southeastern Vietnam, collected by H.-C. Ho & M.- Y. Lee, 19 April 2009.

Paratypes: 18 specimens (42.3–60.4 mm SL) collected off Nha Trang , southeastern Vietnam, by H.-C. Ho & M.-Y. Lee. ASIZP0072364 , 6 specimens, 43.1–50.4 mm SL, 19 April 2009. ASIZP0072366 , male, 44.4 mm SL, 19 April 2009. ASIZP0072367 , male, 49.2 mm SL, 19 April 2009. ASIZP0072368 , 10 specimens, 42.3–60.4 mm SL, 23 April 2009.

Diagnosis. Symphurus brachycephalus 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; 81–87 dorsal-fin rays, 69–74 anal-fin rays, 72–82 longitudinal scale rows, 26–30 transverse scale rows, 15–18 scale rows on head posterior to lower orbit; moderately wide body (BD= 24.9–27.5% of SL); short preanal length (PAL= 21.4–25.9% of SL); relatively short head (HL= 17.3–20.8% of SL) with its length usually shorter than its width (HW/HL= 1.04–1.19); relatively long postorbital length (POL= 69.6–74.9% of HL); upper head lobe usually wider than lower head lobe; dorsal-fin origin at, or slightly posterior to, vertical through posterior margin of upper eye; long predorsal length (PDL= 22.4–28.9% of HL); snout relatively short (SNL= 13.4–19.4% of HL, SNL/ED= 1.21–1.71), rounded to obliquely blunt anteriorly; eyes moderate (ED= 9.5–12.7% of HL); equal in position (anterior margin of upper eye equal to anterior margin of lower eye, or slightly subequal with anterior margin of upper slightly in advance of anterior margin of lower eye); membrane covering both eyes; fleshy ridge well-developed on posterior part of ocular-side lower jaw; also with continuous fleshy membrane connecting anterior nostril to ventral part of lower eye; ocular-side pigmentation uniformly yellow to light brown; blind-side pigmentation uniformly white; both sides of body with obvious dermal spots on bases of anteriormost dorsal- and anal-fin rays; peritoneum reddish, with bluishblack pigmentation on dorsalmost surface.

Description. Symphurus brachycephalus ( Fig. 6 ) is a dwarf species known from 19 specimens, the largest of which measures 60.2 mm SL. Meristic characters summarized in Tables 2–5. Predominant ID pattern 1–2–2–2–2 (17/ 19 specimens). Caudal-fin rays 12. Dorsal-fin rays 81–87. Anal-fin rays 69–74. Pelvic-fin rays 4. Total vertebrae 45–48; abdominal vertebrae 9 (3 + 6). Hypurals 4. Longitudinal scale rows 72–82. Scale rows on head posterior to lower orbit 11–14. Transverse scales 21–26.

Proportions of morphometric features presented in Table 7. Body moderately deep, maximum depth in anterior one-third of body usually at point between anus and fourth anal-fin ray, and with gradual taper posterior to midpoint. Preanal length slightly shorter than body depth. Head moderately short and wide; head width greater than head length (HW/HL= 1.04–1.14, Mean= 1.08). Upper head lobe wider than lower head lobe (UHL/LHL= 1.05–1.48, Mean= 1.23); much shorter than postorbital 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. Snout relatively short, slightly rounded to obliquely blunt anteriorly, its length slightly greater than eye diameter (SNL/ED= 1.21–1.71, Mean=1.44). Dermal papillae present, well developed, on blind-side 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 and 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. Jaws short and slightly arched; upper jaw length much longer than snout length; posterior margin of upper jaw usually extending to point between verticals through anterior margin of lower eye and midpoint of lower eye. Ocular-side lower jaw with welldeveloped fleshy ridge on its posterior half. Cheek depth narrow, slightly shorter than snout length. Eyes moderate (ED= 9.5–12.7% of HL), oval, and contiguous; fleshy membrane covering both eyes; eye membrane connected to anterior nostril by fleshy membrane. Eyes unequal with anterior margin of upper eye usually in advance of anterior margin of lower eye. Pupillary operculum absent. Dorsal-fin origin located between verticals through posterior margin of pupil of upper eye and posterior margin of upper eye; 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 fourth to sixth analfin ray. Posteriormost pelvic-fin ray connected to anal fin by delicate membrane. Caudal fin relatively long, base of fin with several (usually less than four) rows of ctenoid scales. Scales on both sides of body numerous, strongly ctenoid.

Teeth present and recurved slightly inwards 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 three to four rows of sharp, recurved teeth. Blind-side lower jaw with four to six rows of well-developed teeth.

Pigmentation. Pattern of body pigmentation generally similar for both sexes at all sizes. Ocular-side background pigmentation of body generally light-yellow to light-brown ( Fig. 6 ); body pigmentation above pterygiophore regions of dorsal and anal fins usually the same as background pigmentation on other parts of body; no dark melanophores along vertebral axis in any specimens. Melanophores absent in dermis overlying pterygiophores. External surface of abdominal area usually reddish to light brown. Background pigmentation of ocular side of head generally similar to that on body, except for one dark region formed by cluster of dermal melanophores posterior to eyes. Ocular of side of snout light yellow; obvious dermal spots at bases of anterior dorsal-fin rays and also on isthmus. Outer surface of ocular-side opercle yellow to light-brown, usually with light-red to dark-red pigmentation on opercle, margin of opercle yellow to light-brown, with same background pigmentation as that on body and head. Inner surfaces of ocular-side opercle and isthmus with small, dark brown or blackish dots; ocular-side lips and chin region uniformly yellow to brown, margins of lips pigmented with small black melanophores. Ocular-side anterior nostril light-yellow to brown. Dorsal aspects of eyes and eye sockets light blue with darker spots; pupils bluishblack. Blind side generally white to light yellow; peritoneum reddish, with bluish-black pigmentation only on dorsalmost part. No median longitudinal row of darkly pigmented melanophores along vertebral axis of specimens at all sizes. Outer surface of blind-side opercle white to light yellow similar to that of background pigmentation. 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 covering entire fin membrane on both sides of fins. Entire dorsal and anal fins with regularly scattered streaks separating fins into darker and lighter areas. Basal margins of fin rays and associated fin membranes on blind side light yellow to light brown.

Pigmentation of recently preserved specimens ( Fig. 6 ). Similar to that of freshly caught fishes, except reddish pigmentation of ocular-side opercle and peritoneum faded after fixation. Dermal spots at bases of anterior dorsal-fin rays and on isthmus, as well as bluish-black pigmentation at dorsalmost part of peritoneum, similar to that of fresh specimens.

Size and Sexual Maturity. A total of 19 specimens ranging in size from 42.5–60.2 mm SL were available to this study. Males (n = 10, 44.4–53.1 mm SL) attain similar sizes to those of mature females (n= 5, 42.5–60.2 mm SL). Four of the nine females (47.3–49.3 mm SL) are immature with little elongation of the ovaries. Five females (42.5–60.2 mm SL) are mature with elongate ovaries, but none are gravid, and all ovaries are without obvious ova. Voronina et al. (2016) examined 21 specimens (sex not reported) from Vietnam that ranged in size from 47.0 to 60.0 mm SL .

Distribution. Symphurus brachycephalus is known from specimens taken from fish landings at Nha Trang, Vietnam ( Fig. 3 ). In addition to specimens examined in the present study, Munroe & Marsh (1997) misidentified two specimens as S. microrhynchus that were also collected in Nha Trang Bay that likely are S. brachycephalus . Voronina et al. (2016) examined 21 specimens, likely S. brachycephalus , collected from Nha Trang and Vân Phong Bay, Vietnam.

Based on information provided by the collector (Hans Ho, person. comm.) for specimens examined in the present study, S. brachycephalus were recovered from landings that also contained an assemblage of fish species which generally live at, or about at, depths shallower than 100 m. Based on this observation, we hypothesize that S. brachycephalus is a shallow-water species of tonguefish (i.e., inhabiting depths of approximately 100 m or so). Further investigation providing more specific details about capture localities, bathymetric distribution, and substrata inhabited by this species are needed.

Etymology. The name brachycephalus , derived from the Greek, brachy meaning short, and cephalus, meaning head, in reference to the relatively shorter head of this species compared with those of similar shallow-water tonguefishes.

Comparisons. Among the high scale count group of species within the S. microrhynchus species complex, S. brachycephalus is most similar to S. polylepis n. sp.. These two species are the only ones among the high scale count species lacking pepper-dots and dermal melanophores associated with bases of the anterior dorsal- and anal–fin rays. In comparing meristic values between these two species, S. brachycephalus has relatively fewer rows of head scales (15–18 vs. 17–19 in S. polylepis n. sp.), fewer transverse scales (26–30 vs. 32–34 in S. polylepis n. sp.), and much lower counts of longitudinal scales (72–82 vs. 88–94) compared with those of S. polylepis n. sp. In its morphometric features, S. brachycephalus differs from S. polylepis n. sp. in its head shape, which is relatively shorter (HL= 17.3–20.8% of SL vs. 21.9–23.8% of SL in S. polylepis n. sp.) and narrower (HW= 19.5–23.5% of SL vs. 23.1–25.8% of SL in S. polylepis n. sp.), with a shorter postorbital length (POL= 12.6–15.2% of SL vs. 15.7–16.6% of SL in S. polylepis n. sp.). Also, the lower head lobe (LHL= 8.0–10.9% of SL vs. 10.7–12.2% of SL in S. polylepis n. sp.) is smaller, and the predorsal length is shorter (PDL= 4.4–5.7% of SL vs. 5.7–6.7% of SL in S. polylepis n. sp.). Symphurus brachycephalus usually has a mostly reddish peritoneum, with bluish-black pigmentation present only on the dorsalmost part (vs. peritoneum entirely bluish-black in S. polylepis n. sp.), and its ocular-side pigmentation is uniformly light brown without crossbands (vs. ocular side usually with several incomplete or complete crossbands in S. polylepis n. sp.).

Meristic and morphometric characters of S. brachycephalus partially or totally overlap those of S. robustus n. sp., S. leptosomus n. sp., and S. hongae n. sp., the other species in the S. microrhynchus species group possessing high scale counts. However, S. brachycephalus is easily distinguished from these others by differences in pigmentation. Symphurus brachycephalus lacks pepper-dots and dermal melanophores at both sides of the bases of dorsal- and anal-fin rays (vs. well-developed pepper-dots and dermal melanophores at bases of dorsal- and anal-fin rays on both sides or only on the blind side of these fin rays in these other three species). And, S. brachycephalus has a reddish peritoneum (vs. bluish-black peritoneum in these three other species).

Although sharing some similarities with the group of three species ( S. microrhynchus , S. holothuriae and S. longirostris ) featuring low scale counts, S. brachycephalus differs from these three species in a number of features. Overall, S. brachycephalus has relatively higher counts of head scales (15–18 vs. 15 in S. microrhynchus , 16 in S. holothuriae , and 11–14 in S. longirostris ), relatively more transverse scales (26–30 vs. 25 in S. microrhynchus , 25 in S. holothuriae , and 21–26 in S. longirostris ), and more longitudinal scales (72–82 vs. 64 in S. microrhynchus , 60 in S. holothuriae , and 56–66 in S. longirostris ). In morphometric features, head width is larger than head length in S. brachycephalus compared with that for S. microrhynchus , S. holothuriae and S. longirostris (HW/HL= 1.04–1.19 in S. brachycephalus vs. HW/HL= 0.94 in S. microrhynchus, HW /HL= 0.97 in S. holothuriae , and HW/HL= 0.92–0.99 in S. longirostris ). Other differences between S. brachycephalus and these species were highlighted in the Comparisons sections in the species accounts above for S. microrhynchus , S. holothuriae and S. longirostris , respectively.

Symphurus brachycephalus has the same ID pattern (1–2–2–2–2) and similar counts for dorsal-fin rays (87 vs. 86–92) and anal-fin rays (73 vs. 73–80) as those found in S. monostigmus and S. leucochilus . However, S. brachycephalus is readily differentiated from both S. monostigmus and S. leucochilus in having a fleshy ridge on the posterior half of the ocular-side lower jaw (vs. no fleshy ridge on ocular-side lower jaw in these others), and it has a membranous connection between the ocular-side anterior nostril and lower eye (vs. no fleshy membranous connection between anterior nostril and eye in these other species). Symphurus brachycephalus has fewer transverse scales (26–30 vs. 32–38) than is found in either of these other species.

Symphurus brachycephalus differs from S. leucochilus in that the dorsal-fin origin is usually located at, or posterior to, the vertical line through the posterior margin of the upper eye (vs. dorsal-fin origin at vertical located at anterior margin of upper eye in S. leucochilus ). The eyes of S. brachycephalus are contiguous and covered by a fleshy membrane (vs. upper and lower eye usually separated by narrow interorbital space, and both eyes not covered by fleshy membrane in S. leucochilus ).

Symphurus brachycephalus has comparatively fewer fin rays (dorsal-fin rays 81–87 vs. 89–92 in S. leucochilus ; anal-fin rays 69–74 vs. 76–80), and fewer total vertebrae (45–48 vs. 49–51) than that found in S. leucochilus .

Symphurus brachycephalus has fewer longitudinal (72–82) scales than is found in (92) in S. monostigmus . Symphurus brachycephalus also differs further from S. monostigmus in having 12 (vs. 14) caudal-fin rays and 4 hypurals (vs. 5 hypurals), and in lacking the pigment spot on the abdomen that features so prominently in S. monostigmus . Symphurus brachycephalus also has a narrower head (HW/HL= 1.04–1.19) versus that of S. monostigmus (HW/HL= 1.38–1.42).

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 3. Geographic distribution of Symphurus microrhynchus, S. holothuriae, and five new species of Indo-West Pacific shallow-water tonguefishes based on specimens examined in this study. Symbols may represent more than one locality and/or more than a single collection from each locality.

FIGURE 6. Symphurus brachycephalus n. sp., holotype, ASIZP0072365, male, 45.2 mm SL, Off Nha Trang, Southeastern Vietnam. A. Ocular-side pigmentation of freshly caught 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.