Silhouettea ghazalae, Kovačić & Sadeghi & Esmaeili, 2020

Kovačić, Marcelo, Sadeghi, Reza & Esmaeili, Hamid Reza, 2020, New species of Silhouettea (Teleostei: Gobiidae) from Qeshm Island, Iran and the DNA barcoding of the Persian Gulf and Oman Sea gobies, Zootaxa 4750 (1), pp. 49-66 : 55-63

Silhouettea ghazalae sp. nov.

English name: Ghazal goby

Persian name:

( Fig. 2 )

Holotype. PMR VP4678 , female, 27.35 + 6.29 mm, Iran: Hormuzgan prov.: Qeshm city, Qeshm Island, Persian Gulf, 26° 55’ 47.7’’ N, 56 ° 15’ 26.9’’ E; R. Sadeghi , 19 Oct. 2016.

Paratypes. ZM-CBSU 2135 , female, 26.8 + 6.19 mm ; ZM-CBSU 2160 , female, 25.32 mm SL, caudal fin missing ; ZM-CBSU 2024 , female, 25.32 mm SL, caudal fin missing; all paratypes with head damaged, i.e. with longitudinal incision on head (in preliminary study of the collected material, Silhouettea specimens were not suspected to be new species and was processed by RS as all other collected gobies, including extraction of the otoliths, except for the one specimen); all paratypes with the same data as the holotype .

Diagnosis. Silhouettea ghazalae sp. nov. differs from its nine known congeners by the combination of the following selected characters: (1) small mental fold present on chin, (2) head length 31.4–32.4% of standard length, (3) head width 24.5% of standard length, (4) second dorsal fin I/11, (5) anal fin I/13, (6) breast with large cycloid scales, three scales along midventral breast, (7) predorsal area naked, with upper edge of scaled area more or less straight from upper end of pectoral fin base to the first dorsal fin origin, (8) suborbital row b anteriorly beginning below anterior edge of pupil, posteriorly ending below pore β, (9) suborbital row c anteriorly extending more than row b and posteriorly extending less than row b, (10) suborbital row cp oblique with four papillae, (11) body with four ill-defined midlateral blotches and a fifth triangular mark on the caudal fin base and no clearly defined pale saddles on back, (12) the first dorsal fin pigmented with dots and with dark blotch present anteriorly.

Description (all morphometric values and meristics in the text are presented as holotype first and paratypes, if different, in parentheses). General morphology ( Fig. 2 ): Body proportions are given in Table 1 . Body moderately elongate, its depth at pelvic-fin origin 5.53 (5.69–6.84) in SL, at anal-fin origin 5.96 (6.48–7.24) in SL, laterally compressed posteriorly, with caudal peduncle moderately deep, caudal peduncle depth about equal caudal peduncle length ( Fig. 2 ). Head large, the length 3.13 in SL (3.09–3.18), width 4.08 in SL, depth 7.24 in SL, and depressed, its depth 1.77 of width (all paratypes with head damages distorting and preventing measuring of head width and head depth values). Postorbital profile subhorizontal. Cranial roof covered by dorsal axial musculature to opposite preopercle. Snout short, gently oblique, convex in transverse section, shorter than eye, its length 78.8% (84.4–93.9%) of eye diameter, 6.03 (5.14–6.89) in head length. Anterior naris in a short nasal tube without process from the rim, posterior naris pore-like. Eyes dorsolateral, more dorsal than lateral, moderately large, eye diameter is 4.76 (4.82–5.82) in head length, orbit elevated above dorsal profile. Interorbital narrow, 4.60 (4.27–5.97) in eye diameter. Mouth oblique, jaws subequal, lower jaw ending anteriorly slightly in front of upper jaw, upper lip narrow, width uniform. Mouth large, posterior angle of jaws ending posteriorly below posterior edge of pupil. Cheek moderately deep. Chin with small mental fold ( Fig. 1A ). Teeth in jaws erect, caniniform, pointed and moderately curved towards the buccal cavity. Lower jaw with 3-4 rows of teeth medially, upper jaw with 3 rows medially. In both jaws number of rows decreasing laterally, those of outermost row enlarged, those of innermost row the most curved towards the buccal cavity. Tongue truncate. Branchiostegal membrane attached along half to most of lateral margin of isthmus. Membranous edge of opercle extended, covering all or most of pectoral base and extending slightly in the middle on pectoral fin origin ( Fig. 1B ). Extended membranous edge also developed on ventrolateral head ridge, divided from membranous edge of opercle by indentation ( Fig. 1D ). No spines on preopercle. Pectoral girdle without dermal flaps on anterior edge.

Fins. First dorsal fin VI, second dorsal fin I + 11; anal fin I + 13 (not visible on paratype ZM-CBSU 2135 due to damage); branched caudal-fin rays 13, segmented 16 (not visible on paratypes due to damage), pectoral-fin rays 15 (not visible in paratypes ZM-CBSU 2135 and ZM-CBSU 2160), pelvic fins I + 5/5 + I. Fin morphometrics in proportion to standard body length given in Table 1 . Spines of first dorsal fin not elongate or filamentous, the third and fourth spine longest, spines progressively decreasing backwards; only spines IV and V of first dorsal fin barely reach the origin of second dorsal fin when folded down. Origin of first dorsal fin behind vertical at pectoral-fin base. Interdorsal space distinct, without membranous connection between dorsal fins. Second dorsal fin originates clearly behind vertical of anus, with the longest rays not reaching base of uppermost caudal-fin rays, ending on caudal peduncle before caudal fin. Origin of anal fin slightly in front of vertical of origin of second dorsal fin, anal fin longest rays reaching the base of uppermost caudal-fin rays. Pectoral-fin lowermost ray not branched and upper rays not free at tips. Pectoral fins extending posteriorly just to below origin of the second dorsal fin. Pelvic disc complete, long, with rounded posterior margin, all rays branched; anterior transverse membrane well-developed (anterior membrane in midline depth about 2/3 of spinous ray), with finely crenate edge. Pelvic fins ending behind anus. Caudal fin rounded, shorter than head, 1.39 (1.38), caudal fin damaged in paratypes ZM-CBSU 2160 and ZM- CBSU 2124) in head length.

Scales. Body scaled with ctenoid scales. Scales in lateral series 24 (24–26, not visible on paratype ZM-CBSU 2024 due to damage), with paired large scales over origin of the caudal fin rays, above and below lateral midline, not counted; in transverse series 7; in circumpeduncular scales 10. Uppermost and lowermost scales at caudal fin origin not elongate and with short ctenii. Head with cheek and opercle naked. Predorsal area naked, with upper edge of scaled area more or less straight from upper end of pectoral fin base to the first dorsal fin origin ( Fig. 1E ). Prepectoral naked, breast with large cycloid scales, 3 scales along midventral breast. Belly with cycloid scales.

Lateral line system ( Fig. 3 ). On the holotype, rows of head sensory papillae were counted on the both sides and presented left then right or single if the value is the same. Head lateral-line system with anterior and posterior oculoscapular canals and preopercular canal with pores σ, λ, κ, ω, α, β, ρ, ρ 1, ρ 2, and γ, δ, ε respectively, all small; pores λ and κ median, single, pore ω on short branch from anterior and oculoscapular canal. Head sensory papillae small and elongated and individually hardly recognizable for count resulting in most of rows having the appearance of short dashed lines ( Fig. 1C ). Preorbital rows: snout with lateral longitudinal row s (6, 7) near nostrils, no upper row r, and three transverse median rows: row s 1 (3, 5) at posterior nostril, row s 2 single papilla in the level of anterior nostril, and row s 3 horizontal (7) above upper lip. Lateral series c with rows c 2, c 1 and c 2 connected in a single row c 21 2 from posterior upper lip to below posterior naris (20, 18) and lower c 1 (4, 3) posterior to c 2. Suborbital rows: rows a and c, including cp, without transverse proliferation; longitudinal row a (26, 29) around lower edge of orbit from anteriorly below anterior edge of eye, posteriorly to pore α; row b (37, 35) anteriorly beginning below anterior edge of pupil, posteriorly ending below pore β, row c (31, 30) anteriorly extending more than row b and posteriorly extending less than row b; row cp oblique row of four papillae, placed behind vertical of posterior eye edge, below row c and above row d; row d (28) continuous, ending posteriorly behind vertical of posterior eye edge. Preoperculo-mandibular rows: external row e (28 + 32) and internal row i (14 + 26) divided into anterior and posterior sections; row f a single continuous transverse mental row (6 + 6). Oculoscapular rows: anterior longitudinal row x 1 divided in two parts (6 + 7, 6 + 6), anterior part above pore β and posterior part above from pore ρ 1 to pore ρ 2, posterior longitudinal row x 2 (5, 5) above pore ρ 2; transversal row z (6, 6) short behind pore γ; rows q and y longitudinal: row u (4, 4) between pores ρ and ρ 1, row y (4, 4) behind pore ρ 2. Axillary rows as 1, as 2, as 3, la 1 and la 2 not visible. Opercular rows: transverse row ot (27, 26); superior longitudinal row os (17, 15); inferior longitudinal row oi (4). Anterior dorsal rows: rows n (5) longitudinal from pore ω; rows g, o, m and h not visible. Interorbital papillae absent.

Coloration. Freshly collected female ( Fig. 2A ). Head and body whitish to dusky with brown pigmentation. Snout pale with widely scattered brown dots. Predorsal area with melanophores in irregular marbled pattern of dark brown dots and brown marks combined with whitish brown dotted areas. Nape with conspicuous white spot at mid dorsal above the preopercular edge and pale transversal band above opercle ( Fig. 4A ). Irregular pattern of brown and dark brown dots and marks at upper cheek, preoperculum and operculum. Lower half of the cheek behind posterior end of mouth, lower opercle and preopercle whitish. Underside of head with dark brown dotted X mark at gular and anterior isthmus regions, inside from ventrolateral head ridge, rest of area unpigmented. Iris similarly brown and whitish marbled as is surrounding skin, pupil dark. Body with four ill-defined midlateral blotches and a fifth triangular mark on caudal fin base. Brown pigmentation at upper half of body mostly present along the scale margins but whitish and brown marks result in a more irregular pattern than a recognizably reticulate pattern. On dorsal side pale saddles on back hardly visible. Lower half of body and ventral side whitish. First dorsal fin pigmented with dots and with dark blotch present anteriorly. Second dorsal fin pigmented with dots arranged in oblique rows. Anal fin dark with transparent edge. Caudal fin with triangular mark extended from caudal peduncle edge onto the caudal fin origin and three narrow vertical bands of dots followed by poorly pigmented area posteriorly. Pectoral fin with white marks. Ventral fins mostly transparent, poorly pigmented with small brown dots.

Color of preserved females ( Fig. 2B ). The colour of preserved specimens pale yellow to white brown (beige to tan), with dark brown markings. Snout pale with scattered small dots. Predorsal area with melanophores concentrated in dark brown marks combined with scattered small dots forming paler areas. Nape with conspicuous unpigmented spot at mid dorsal, above the preopercular edge ( Fig. 4B ). Scattered melanophores present also on upper cheek, preoperculum and operculum. Lower half of cheek behind posterior end of mouth, lower opercle and preopercle not pigmented. Underside of head with dark brown dotted X mark at gular and anterior isthmus regions, inside from ventrolateral head ridge, the rest of the area unpigmented. Eyes dark, with grey pupil. Melanophores on body forming four ill-defined midlateral blotches and the fifth triangular mark on the caudal fin base. Melanophores also present along the scale margins at upper half of body, forming reticulate pattern. No recognizable pattern visible from dorsal view except for reticulate pattern of pigmented scale margins, no defined pale saddles on back. Melanophores very rarely present elsewhere on the body. Ventral side, including belly whitish. First dorsal fin pigmented with dots and with dark blotch present anteriorly. Second dorsal fin pigmented with dots. Anal fin dark with transparent edge. Caudal fin with triangular mark extended on the caudal fin origin from caudal peduncle edge and three narrow vertical bands of dots followed by poorly pigmented area posteriorly. Pectoral and ventral fins mostly transparent, poorly pigmented with small dots.

Osteology. A total of 27 vertebrae including urostyle (10 precaudal and 17 caudal vertebrae). Dorsal-fin pterygiophore insertion pattern: 3-22110. NS PU3 and HS PU3 are larger and wider than preceding neural and haemal spines; NS PU2: very short with wide base, triangular shape; HS PU2: large and wide; epural: large with an appendix to posterior in its base; hypural 5 and parhypural: short and slender ( Fig. 5 ).

Etymology. The species is named after Ghazal, daughter of the last author.

Distribution and ecology. Until now, S. ghazalae is known from the intertidal zone at the coast of Qeshm Island, Persian Gulf. It was found in rocky pools with some gravels and a little sand and algae ( Fig. 6 ).

Remarks. The genus Silhouettea includes the presently described species and nine other valid species. The comparative data for Silhouettea species were based on the Silhouettea genus revision and species descriptions ( Larson & Miller 1986; Miller 1988; Randall 2008) and illustrations in Smith (1959) and Masuda et al. (1984). Silhouettea ghazalae sp. nov. differs from known congeners by various characters among which the most useful are chosen for diagnosis and elaborated here. The important additional characters, not used in diagnosis, are also separately noted and compared individually for some species. Silhouettea ghazalae sp. nov. differs from all other Silhouettea species by mental fold present (vs. mental fold absent). Silhouettea ghazalae sp. nov. differs from another large headed Silhouettea , S. capitlineata by second dorsal fin I/11 and anal fin I/13 (vs. second dorsal fin I/10 and anal fin I/11–12), predorsal area and opercle naked (vs. 6–7 transversal predorsal rows of scales and embedded scales dorsally on opercle), three scales along midventral (vs. four scales along midventral in S. capitlineata ), different coloration of body and lack of posterior spot on the first dorsal fin (vs. posterior spot present in S. capitlineata ). In addition, the posterior angle of jaws ends posteriorly below the posterior edge of pupil (vs. nearly or just reaching a vertical at posterior edge of orbit in S. capitlineata ). Silhouettea ghazalae sp. nov. differs from Australian S. evanida and S. hoesei by head length 31.4–32.4% and width 24.5% of standard length (vs. head length 23.4–30.0% and width 12.2–13.8% in S. evanida and head length 24.6–25.4% and width 12.0–12.8% in S. hoesei ), different coloration of body, the first dorsal fin with anterior dark spot (vs. no dark spot anteriorly on the first dorsal fin in Australian species) and different length of suborbital rows b and c, and row cp of four papillae (vs. row cp single papilla in Australian species). In addition, it differs from S. hoesei in the second dorsal and anal fin meristics: second dorsal fin I/11 and anal fin I/13 (vs. second dorsal fin I/10 and anal fin I/ 12 in S. hoesei ). The new species is different from two other Pacific species, S. nuchipunctatus from Philippines and S. dotui from Japan, by head length 31.4–32.4% and width 24.5% of standard length (vs. head length 24.6–29.1% and width 12.2–14.9% in S. nuchipunctatus and head length 20.1–21.1% and width 11.6-12.4% in S. dotui ), different coloration of body, the first dorsal fin with anterior dark spot (vs. dark spot posteriorly in S. nuchipunctatus and S. dotui ). In addition, it differs from S. nuchipunctatus in the first spine of the first dorsal fin not elongate (vs. the first spine very long in S. nuchipunctatus ), pectoral fin rays 15 (vs. 16 in S. nuchipunctatus ) and scales in transverse series 7 (vs. 8 in S. nuchipunctatus ). It is additionally different from S. dotui in the second dorsal and anal fin meristics: second dorsal fin I/11 and anal fin I/13 (vs. second dorsal fin I/10 and anal fin I/ 12 in S. dotui ), in different length of suborbital rows b and c, and in having row cp with four papillae (vs. row cp not recorded in S. dotui ). Silhouettea ghazalae sp. nov. is different from the East Indian S. indica by second dorsal fin I/11 and anal fin I/13 (vs. second dorsal fin I/10 and anal fin I/ 12 in S. indica ), predorsal area naked with no scales in front of line from the upper end of pectoral fin base to the first dorsal fin origin (vs. five predorsal scales noted in S. indica ), breast scaled with three scales along midventral (vs. breast naked in S. indica ), different coloration of body, the first dorsal fin with anterior dark spot (vs. dark spot posteriorly in S. indica ). Silhouettea ghazalae sp. nov. differs from the Red Sea S. aegyptia by head length 31.4–32.4% and width 24.5% of standard length (vs. head length 20.7–29.4% and width 12.9–15.5% in S. aegyptia ), second dorsal fin I/11 and anal fin I/13 (vs. second dorsal fin I/10 and anal fin I/ 11 in S. aegyptia ), breast scaled with three scales along midventral (vs. breast naked in S. aegyptia ), different coloration of body, the first dorsal fin with anterior dark spot (vs. three dark bands in S. aegyptia ), and different length of suborbital rows b and c and row cp of four papillae (vs. row cp single papilla in S. aegyptia ). Silhouettea ghazalae sp. nov. differs from Western Indian Ocean S. sibayi by the first spines of the first dorsal fin not elongate (vs. the spines very long in S. sibayi ), breast scaled with three scales along midventral (vs. breast naked in S. sibayi ), different coloration of body, the first dorsal fin with anterior dark spot (vs. three dark spots along the fin in S. sibayi ), and different length of suborbital rows b and c, and row cp of four papillae (vs. row cp single papilla in S. sibayi ). In addition, posterior angle of jaws ending posteriorly below posterior edge of pupil (vs. nearly reaching a vertical at posterior edge of orbit in S. sibayi ), scales in lateral series 24 (vs. 26–27 in S. sibayi ) and in transverse series 7 (vs. 8 in S. sibayi ). Silhouettea ghazalae sp. nov. differs from Western Indian Ocean S. insinuans by head length 31.4-32.4% and width 24.5% of standard length (vs. head length 24.3–28.2% and width 12.7–14.8% in S. insinuans ), predorsal area naked with no scales in front of line from the upper end of pectoral fin base to the first dorsal fin origin (vs. 5-6 scales laterally to midopercle in S. insinuans ), different coloration of body, different length of suborbital row c and row cp of four papillae (vs. row cp with 1–3 papillae in S. insinuans ). Moreover, caudal fin coloration with triangular mark extended on the caudal fin origin from caudal peduncle edge and four to five narrow vertical bands of dots (vs. dark distally with white edges in S. insinuans ).

Phylogenetic relationship. We compared three COI nucleotide sequences of S. ghazalae sp. nov. with 72 sequences of other gobiid species done in the present study or retrieved from other studies and GenBank ( Tables 2 and 3 , Fig. 7 ).

Seven species ( Cryptocentroides arabicus , Acentrogobius dayi , Coryogalops tessellatus , Bathygobius meggitti , Palutrus scapulopunctatus , Silhouettea ghazalae sp. nov. and Aulopareia ocellata ) were sequenced for the first time ever and five species ( Istigobius ornatus , Coryogalops adamsoni , Favonigobius reichei , Bathygobius cocosensis , and Cryptocentrus cyanotaenia ) were sequenced for the first time from the Persian Gulf and Oman Sea.

The molecular tree shown in Fig. 7 is based on the final COI aligned sequences of 47 specimens of 12 species of family Gobiidae from the Iranian coasts of Persian Gulf and Oman Sea Analysis of the COI sequence data place the included Silhouettea ghazalae sp. nov. as sister group of Cabillus tongarevae (Fowler, 1927) , in the same group with two other gobies, Palutrus scapulopunctatus (de Beaufort, 1912) and Glossogobius giuris (Hamilton, 1822) . Silhouettea ghazalae sp. nov. is characterised by a minimum K2P distance of 21% to its closest relative in our dataset, Cabillus tongarevae , in the mtDNA COI barcode region. Unfortunately, no data of the COI sequences is available for any known Silhouettea species. All the nominal species (33 species, except outgroup) were recovered as monophyletic ( Fig. 7 ). The three conceptually different molecular species delimitation methods equally delimited 34 potential species ( Fig. 7 ). Out of 33 nominal species, 29 (88%) species including Silhouettea ghazalae sp. nov. were delimited precisely through these three methods. All methods indicated potential species-level diversity (cryptic diversity) in two nominal species including Istigobius ornatus and Bathygobius cocosensis (both from Indian Ocean and west Pacific species) which need further taxonomic investigations. In addition, based on all three methods, the identity of specimens lodged in GenBank as Acentrogobius viridipunctatus (Valenciennes, 1837) and Exyrias puntang (Bleeker, 1851) should be re-examined.

Figures

FIGURE 1. Silhouettea ghazalae sp. nov., PMR VP4678, reversible stained holotype, female, 27.35 + 6.29 mm, Qeshm Island, Persian Gulf: A: chin with mental fold outlined, head down position; B: membranous edge at opercle, extension on the pectoral rays origin marked; C: preopercular edge, head sensory papillae rows resembling longitudinally dashed lines (e.g. row c) or transversal stiches (e.g. row ot). D: membranous edge at ventrolateral head ridge (vhr) divided from opercular membrane (om) by indentation (marked by arrow); E: nape and predorsal region naked; Photos by M. Kovačić.

FIGURE 2. Silhouettea ghazalae sp. nov., PMR VP4678, holotype, female, 27.35 + 6.29 mm, Qeshm Island, Persian Gulf. A: freshly collected specimen; B: preserved specimen. Photos by R. Sadeghi (A), M. Kovačić (B).

FIGURE 3. Silhouettea ghazalae sp. nov. Head lateral line sensory papillae and canal pores: PMR VP4678, holotype, female, 27.35 + 6.29 mm, Qeshm Island, Persian Gulf. Terminology in text. Drawing by M. Kovačić.

FIGURE 4. Silhouettea ghazalae sp. nov., PMR VP4678, holotype, Qeshm Island, Persian Gulf. Nape and predorsal region with median white spot marked: A: freshly collected specimen; B: preserved specimen. Photos by R. Sadeghi (A), M. Kovačić (B).

FIGURE 5. Silhouettea ghazalae sp. nov., PMR VP4678, holotype, female, 27.35 + 6.29 mm, Qeshm Island, Persian Gulf: A: whole lateral view with the vertebrae numbered; B) close-up image of the caudal fin skeleton: EPU=epural, HS PU=haemal spine of preural centrum, HYP=hypural, NS PU=neural spine of preural, centrum, PHY=parhypural, PU=preural centrum, UR=urostyle, DPR, dorsal procurrent rays; VPR, ventral procurrent rays. X-ray by H.R. Esmaeili and U.K. Schliewen.

FIGURE 6. Intertidal coast of Qeshm Island, Iran, type locality of Silhouettea ghazalae. Photo by R. Sadeghi.

FIGURE 7. Bayesian tree visualizing the results of the three different molecular species delimitation methods based on COI. ABGD: Automatic Barcode Gap Discovery; SP: reversed Statistical Parsimony; and bPTP: Bayesian Poisson tree process model. Posterior probability values are provided at the nodes.