Soleichthys microcephalus ( Günther, 1862 )

Munroe, Thomas A. & Menke, S. B., 2004, Two New Soleid Flatfishes (Pleuronectiformes: Soleidae: Soleichthys) from Australian Waters, With a Re-description of Soleichthys microcephalus (Günther), Records of the Australian Museum 56 (2), pp. 247-258 : 250-253

Soleichthys microcephalus ( Günther, 1862)

Figs. 1, 2; Tables 1, 2

Smallhead sole

Solea microcephala Günther, 1862: 466 (original description with counts, measurements; New South Wales, Australia); Kner, 1867: 288 (counts, measurements; off Sydney , New South Wales) ; Macleay, 1882: 135 (counts, measurements; Port Jackson , New South Wales) ; Ogilby, 1886: 49 (listed, common in Port Jackson ; coastal waters of New South Wales) ; Waite, 1904: 44 (listed; New South Wales); Stead, 1908: 105 (brief description with figure, size estimate, common in estuaries on mud bottoms; New South Wales); Roughley, 1916: 176 (description, counts, measurements, figure; coast of New South Wales, Australia; common in estuaries) .

Soleichthys microcephalus .— McCulloch, 1917: 90 (assigned to Soleichthys ; New South Wales); McCulloch, 1921: 47 (in key, figure, partial synonymy, uncommon in estuaries; New South Wales); McCulloch, 1922: 37 (in key, figure, partial synonymy, uncommon in estuaries; New South Wales); Norman, 1926: 286–287 (synonymy, in key; New South Wales); McCulloch, 1927: 37 (in key, figure, partial synonymy, uncommon in estuaries; New South Wales); McCulloch, 1929 –1930:283 (listed; New South Wales); Wongratana, 1975: 27 (comparisons with S. siammakuti ); Yearsley et al., 1997 (listed in Appendix D).

Aesopia microcephala .— Chabanaud, 1930: 555 (assigned to Aesopia ); Chabanaud, 1934: 427 [in key; counts, including vertebrae; considered S. borbonica (Regan) as a subspecies of A. microcephala (Günther) ]; Kuiter, 1993: 389 (description; size to 22 cm; colour photographs, including juvenile; New South Wales in estuaries and inshore waters, at 3–20 m).

Aesopia microcephalus .— Munro, 1938: 70 (description, with counts, measurements, colour figure; New South Wales).

Type material. SYNTYPE, BMNH 1855.9 .19.1247, 159 mm SL, Australia .

Other material examined. AMS I.26311-003, 151.1 mm SL, east of Urunga , 30°27–32'S 153°8'E, 33–43 m ; AMS I.37360-001, 145.1 mm SL, off Newcastle 32°51'S 151°55'E, 31–34 m ; AMS I.37372-001, 4(151.3–169.4 mm SL), off Newcastle, 32°51'–52'S 151°53'E ; AMS I.19117- 003, 137.0 mm SL, Sydney Harbour 33°48'S 151°14'E ;

Fig

AMS I.19117-003, 137.0 mm SL, Sydney

Harbour , Australia, 33°48'S 151°14'E .

USNM 59956, 140.2 mm SL, off Port Jackson 33°51'S 151°16'E ; USNM 47886 , 2 (122.8–159.7 mm SL), off Port Jackson 33°51'S 151°16'E ; AMS I. 1103, 171.7 mm SL, off Port Jackson 33°51'S 151°16'E ; QM I.1189, 171.0 mm SL, off Port Jackson 33°51'S 151°16'E ; QM 1191, 165.1 mm SL, off Port Jackson , 33°51'S 151°16'E ; QM 1192, 113.4 mm SL, off Port Jackson 33°51'S 151°16'E .

Distinguishing characters. Soleichthys microcephalus is readily distinguished from congeners by its combination of: low meristic features (43–45 vertebrae, 71–84 dorsalfin rays, 61–71 anal-fin rays, and 81–89 lateral-line scales), its ocular-side pigmentation pattern consisting of a series of 8–10 dark-brown to black, mostly complete crossbands on the body, with body crossbands noticeably wider than the alternating lighter-coloured crossbands, with three darkbrown crossbands continuous across head, two conspicuous white spots in longitudinal series on the ocular-side midline, in having two elongated ocular-side pectoral-fin rays of nearly equal length or with the second fin ray longer than first, and in having small scales present on bases and proximal halves of elongated ocular-side pectoral-fin rays.

Description. Meristic and morphometric features for a syntype and 14 non-type specimens are summarized in Tables 1 and 2. Body oblong, greatest depth at point between gill opening and just anterior to body mid-point, body depth nearly uniform throughout most of length with rapid taper only in posterior one-fifth of body; body thick, especially in region of pectoral fins. Head ca. 0.41–0.45 BD; wider than long (HW ca. 1.3–1.5 HL), with dorsal and ventral contours smoothly arching posteriorly. Snout slightly squarish in anterior profile; about equal to or just slightly longer than ED; snout tip slightly anterior to horizontal through dorsal margin of fixed eye. Ocular-side anterior nostril usually extending to mid-point of fixed eye when depressed posteriorly. Posterior margin of jaws usually reaching to vertical through anterior margin of pupil of fixed eye. Ocular-side lips generally smooth; blind-side lips with obvious plicae. Gill covers fringed with conspicuous cirri, especially that on blind side; ocular-side opercle connected by thin membrane to dorsalmost pectoral-fin rays (usually rays 1–3 or 1–4) from their bases to mid-points. Blind-side opercle broadly connected by thick membrane to entire lengths of first three or four blind-side pectoral-fin rays. Ocular-side lateral line arching anteriorly over operculum and continuing onto head to about region dorsal to anterior margin of migrated eye. Dorsal-fin origin on midline of head usually at vertical equal to point between mid-point and anterior margin of migrated eye, or just slightly anterior to anterior margin of eye. Anterior dorsal-fin rays shorter than others. Dorsal-fin pterygiophore formula 1-0-2 or 1- 1-2. Ocular and blind sides of dorsal- and anal-fin rays noticeably scaly; anterior dorsal- and anal-fin rays with small ctenoid scales basally (anterior rays of blind-side dorsal and anal fins usually without scales); at approximately body mid-point, both sides of dorsal and anal fins with series of ctenoid scales covering proximal one-third to one-half of fin rays; in posterior one-third of body, scales on dorsal- and anal-fin rays gradually increasing in number and eventually covering nearly entire lengths of fin rays or at least proximal two-thirds of their lengths. Caudal fin relatively large with distal margin nearly square; with 16– 18 caudal-fin rays. Both sides of caudal fin scaly nearly to distal tips of fin rays. Ocular-side pectoral fin long, pointed, with 8–11 rays, the two dorsalmost rays elongate with remainder progressively decreasing in size. Ocular-side elongate pectoral-fin rays nearly equal in length, or with second ray slightly longer than first; elongated pectoral-fin rays covered with strong ctenoid scales on proximal onethird of their lengths; remainder of fin scaly on basal region. Blind-side pectoral fin squarish, with 7–11 short rays, those in dorsal third of fin longer than others; blind-side pectoral fin with a few small scales along bases of fin rays and with noticeably scaly fin base. Base of ocular-side pelvic fin slightly anterior to that of blind-side fin. Scales on body relatively small and rounded, slightly wider than long and strongly ctenoid. Ctenii on blind-side body scales not as strongly developed as those on ocular-side scales. Lateralline scales smaller than surrounding scales, cycloid, diamond-shaped, and with small, slightly elevated pore.

Pigmentation (based on live specimen from Kuiter, 1993). General background colouration of ocular side light brown with a series of prominent, dark-brown to black crossbands alternating with lighter-brown crossbands. Ocular side of head with three black and one white crossbands continuous across head and with one incomplete black band from dorsal margin to about midpoint of head (about equal with horizontal through migrated eye); anteriormost black crossband located on snout and chin; second black crossband located immediately posterior to eyes; third black band crossing head at distal margin of opercle. White band crossing head at posterior region of eyes. Upper surfaces of eyes white. Anterior ocular-side nostril conspicuously dark-brown to black. Body usually with nine, black, relatively straight, crossbands of nearly uniform width and bands usually continuous across body from base of dorsal fin to base of anal fin. Total number of black crossbands (head and body combined) 13. Crossbands on body broader, sometimes as much as twice as wide, than proximate lighter-coloured crossbands. Dark crossbands sometimes extending onto dorsal and anal fins. No conspicuous, rounded, white spots in longitudinal series on midline of ocular side of body. Ocular sides of dorsal, anal and caudal fins brilliantly pigmented with alternating series of mostly similarly-sized bright blue and black blotches throughout entire lengths of fins.

Life colours of a juvenile specimen ( Kuiter, 1993), photographed in July at about 5 m in Camp Cove, Sydney Harbour (Kuiter, pers. comm.), strikingly different than that of adult. Ocular surface background coloration uniformly off-white with an irregular series of rounded or oblong darker blotches posterior to pectoral fin. Anterior snout, upper lip, and especially anterior ocular-side elongate nostril, dark black. Mouth and ventral margin of head silhouetted in orange. Basal halves or slightly more of dorsal, anal and caudal fins with similar coloration as that of body; two continuous longitudinal bands of darker pigment on distal halves of these fins, an inner orange band situated at about two-thirds the length of the fin rays which is bordered throughout lengths of fins by distally positioned dark-black band.

Pigmentation (in alcohol, Fig. 1). General background coloration of ocular side dark brown with a series of prominent, darker-brown to black crossbands alternating with yellowish to cream-coloured crossbands. Ocular side of head with three dark-brown or black crossbands continuous across head; anteriormost crossing snout and chin; second crossband located immediately posterior to eyes; third crossband on body dorsally and crossing head on distal margin of opercle. Interorbital space and upper surfaces of eyes dark brown. Posterior one-third of anterior ocular-side nostril dark brown; basal two-thirds of nostril whitish. Body with 8–10, dark-brown or black, relatively straight, crossbands of nearly uniform width and usually continuous across body from base of dorsal fin to base of anal fin; occasionally crossbands in body mid-region interrupted in their mid-sections. Total number of crossbands (head and body combined) 11–13. Crossbands on body broader, sometimes as much as twice as wide, than proximate lighter-coloured crossbands. Both dark and lighter crossbands extending onto dorsal and anal fins in anterior one-half of body. Ocular side of body on some specimens with two, conspicuous, rounded, similar-sized white spots in longitudinal series on midline, one situated above posterior tips of elongated pectoral-fin rays between dark body crossbands 1–2 and the other on posterior onethird of body between dark crossbands 5–6. White spots nearly equal to, or slightly smaller than, eye diameter. Isthmus and inner opercular lining on ocular side dark with numerous pepperdot melanophores; blind-side inner opercular linings and isthmus with pepper dots. Inner lining of mouth black. Blind side generally uniformly whitish to yellowish, with dense concentrations of pepperdot melanophores on body regions overlying pterygiophores of dorsal and anal fins. Pepper dots extending onto body scales in middle and posterior quarter of blind-side body in more darkly-pigmented specimens. Ocular sides of dorsal and anal fins darkly pigmented; each with continuous, uniformly black or dark-brown longitudinal band on distal one-half of fin rays throughout lengths of these fins, which widens on dorsal and anal fins in posterior one-half of body; basal halves of dorsal and anal fins usually lighter than distal halves; distalmost tips of dorsal- and anal-fin rays white. Blind sides of dorsal and anal fins uniformly black throughout their lengths. Ocular-side pectoral fin darkly pigmented; that on blind side whitish at base. Pelvic fins uniformly brown, except posteriormost part of blind-side fin with lighter pigment consisting of scattered melanophores. Ocular side of caudal fin with dark band on basal one-third of fin rays; with lighter band on middle one-third of fin; and with dark black band on distal one-third of fin forming continuous outline with black band on dorsal and anal fins; distalmost tips of caudal fin white. Blind side of caudal fin yellowish on its basal half, dark black on its distal half, and with fin-ray tips white.

Distribution and habitat ( Fig. 2). Warm-temperate estuarine and neritic waters of New South Wales, Australia, from about 33°52'S to 30°27'S. Occurs on muddy bottoms in estuaries, harbours and in coastal waters at 3–20 m ( Stead, 1908; Roughley, 1916; Kuiter, 1993). The few museum collections with accompanying depth data indicate that this species is taken from shallow waters to depths of at least 43 m.

Remarks. Chabanaud (1934) considered Solea borbonica , a species described on the basis of a single specimen, as part of a subdivision of a subspecies in his expanded taxon, Aesopia japonica microcephala natio borbonica . Quéro (1997) re-examined the holotype of Solea borbonica and concluded that S. borbonica was instead a valid species of Soleichthys that is endemic to Reunion Island, Indian Ocean. Fricke (1999), after comparing results of his study of the holotype of Solea tubifera Peters collected at Mauritius, concluded that S. tubifera and S. borbonica were conspecific, and therefore, S. tubifera was the appropriate name for this species. Soleichthys tubiferus (including S. borbonicus ) differs most distinctively from S. microcephalus in its ocular-side coloration (uniformly greyish brown without crossbands) and more numerous (97 vs. 89 or less) lateral-line scales.

McCulloch (1921, 1922, 1927) tentatively suggested that Solea lineata Ramsay, 1883 , described from a small, damaged specimen taken off Port Stephens, NSW, was a juvenile S. microcephalus , or more likely, based on its coloration (6 narrow crossbands on head, 25 crossbands on body) this nominal species was conspecific with ( McCulloch, 1916, 1917), or a distinct species but one closely resembling S. heterorhinos ( McCulloch, 1921, 1922, 1927). Whether Solea lineata and S. heterorhinos are conspecific needs further study. However, based on ocular-side colour patterns (numerous, narrow crossbands in S. lineatus vs. fewer, wider crossbands in adult S. microcephalus and uniformly pigmented ocular side without crossbands in juvenile S. microcephalus ; see photo in Kuiter, 1993) and higher and non-overlapping meristic features for the holotype of S. lineatus : 95 dorsal-fin rays, 80 anal-fin rays, 109 lateralline scales (scale count according to McCulloch, 1916), this nominal species is distinct from S. microcephalus .

Comparisons. Soleichthys microcephalus is readily differentiated from S. heterorhinos , S. nigrostriolatus , S. lineatus and S. multifasciatus by its lower meristic features (43–45 vs. 48–53 total vertebrae, 71–84 vs. 85–105 dorsal-fin rays, 61–71 vs. 74–91 anal-fin rays and 81–89 vs. 100–124 lateral-line scales in these other species, respectively) and in its pigmentation pattern including having only three crossbands (vs. 5 or more) on its head and in having fewer (8–10), wider crossbands on the body (vs. 17–31 crossbands in these others).

It is distinguished from S. serpenpellis (see below) in body shape, and conspicuous differences in colour pattern, especially in having complete, and more numerous, crossbands on its ocular surface (compare Figs. 1 and 3). Soleichthys microcephalus is readily distinguished from S. oculofasciatus (see below) in having two equally elongated ocular-side pectoral-fin rays and by the presence of scales on these ocularside pectoral-fin rays (vs. first pectoral-fin ray longer than second and scales absent on pectoral fin in S. oculofasciatus ) and by its different body shape and ocular-side coloration (compare Figs. 1 and 4). Soleichthys microcephalus is readily distinguished from S. siammakuti and S. maculosus by its ocular-side colour pattern featuring bold, wide crossbands and in lacking conspicuous spots on the dorsal, anal and caudal fins (vs. crossbands not bold and wide or absent altogether, and spots present in these others). Soleichthys microcephalus differs conspicuously from S. tubiferus which has a uniformly pigmented ocular side (vs. prominent crossbands in S. microcephalus ) and higher, non-overlapping counts of dorsal- and anal-fin rays, and lateral-line scales (see Remarks above).