Nesogobius tigrinus, Hammer, Michael P., Hoese, Douglass F. & Bertozzi, Terry, 2015

Hammer, Michael P., Hoese, Douglass F. & Bertozzi, Terry, 2015, A new species of Near-shore Marine Goby (Pisces: Gobiidae: Nesogobius) from Kangaroo Island, Australia, Zootaxa 4057 (3), pp. 371-384 : 375-382

Nesogobius tigrinus sp. nov.

Tiger sandgoby

Figures 3–7

Material. HOLOTYPE: SAMA F11946, 28.3 mm male, Western Cove, Kangaroo Island, South Australia, 35°44'1" S, 137°35'18" E, 31 Aug 2008, 0.3-0.8 m over sand and broken shell, seine at low tide, M. Hammer, T. Bertozzi and J. Doube (figures 3 & 4).

PARATYPES: SAMA F11947, 33.5 mm female, collected with holotype; SAMA F11967, 31.9 mm male, Bay of Shoals, Kangaroo Island, 35°35'30" S, 137°30'21" E, 2 Sept 2008, 0.5 m over sand and Hormosira , seine at low tide, M. Hammer, T. Bertozzi and J. Doube; SAMA F12513, 6 (27.0– 32.4 mm), collected with holotype; SAM F12265, 29.6 mm male, American River, Kangaroo Island, 10 March 1978, D. Hoese and party; AMS I.46512– 0 0 1, 5 (26.3–32.4 mm), collected with holotype and AMS I.46512–002, 1(29.6), cleared and stained; NMV A31188 –001, 5 (26.6–31.2 mm), collected with holotype; NTM S.17854–001, 31.8 mm male, collected with holotype; NTM S.17855–001, 31.5 mm female, collected with holotype.

OTHER MATERIAL: SAMA F14139, 26.1 mm male & SAMA F14140, 3 (21.2–22.8 mm), Western Cove, Kangaroo Island, South Australia, 35°44'1" S, 137°35'18" E, 25 March 2008, 0.5-1.0 m over sand, broken shell and sparse Zostera , seine at low tide, M. Hammer, T. Bertozzi and R. Gannon; SAMA F14239, 6 (24.5–33.9 mm), collected with holotype; SAMA F14138, 6 (27.2–32.1 mm), Bay of Shoals, Kangaroo Island, 35°35'30" S, 137°30'21" E, 25 Aug 2010, 0.3-0.5 m over sand and Hormosira , seine at low tide, M. Hammer, K. Lashmar and J. Sullivan; SAMA F11956, 25.0 mm male & SAMA F11957, 26.8 mm male, American River, Kangaroo Island, South Australia, 35°48'38" S, 137°44'44" E, 1 Sept 2008, 0.8 m over sand/mud and Zostera , seine at low tide, M. Hammer, T. Bertozzi and J. Doube.

Diagnosis. A species of Nesogobius that is distinctive from previously described species in lacking scales before the pelvic fin, in having the first dorsal fin with six spines, and with males having a dusky to black first dorsal fin and four prominent short, black vertical or oblique bars on the body. It differs further by the following combination of characters: a spine in the second dorsal and anal fins and in having head pores.

Description. Based on 12 males (26.6–32.4 mm SL) and 11 females (28.8–33.5 mm SL). First dorsal 6(23*); second dorsal-fin rays 8(4), 9(19*); anal-fin rays 6(1), 7(3), 8(10), 9(9*); no spine in second dorsal or anal fin; pectoral-fin rays 15(10*), 16(8*), 17(5), branched; segmented caudal-fin rays 13(22*), 14(1); branched caudal-fin rays 9(16*); midline predorsal scales 0(23*); total gill rakers on outer face of first arch 7(1), 8(2), 9(4); lower gill rakers on first arch 6(2), 7(2), 8(5); lower gill rakers on second arch 2(2), 3(4), 4(1); longitudinal scale count 27(1), 28(3), 29(2), 30(7), 31(7*), 32(2), 33(1); TRB 7(5*), 8(12), 9(3); pterygiophore formula 3(12210); vertebrae 10+19(1), 10+20(1), 11+19(9*); a single epural.

Head (27–31% SL), slightly broader than deep. Snout convex in side view, with a distinct bump formed by ascending process of premaxilla, forming an angle of about 45–50° with body axis, eye moderate slightly shorter than snout (6.8–7.8% SL). Mouth small, oblique, forming an angle of 20–30° with body axis, rear end of jaws below a point between anterior margin of pupil and anterior margin of eye; upper lip thick anteriorly, thin posteriorly; lower lip thin with shallow free ventral margin separating lip from chin lobe; chin with a transverse oval lobe with 2–4 small sensory papilla along margin (figures 6 & 7). Tongue tip truncate to slightly rounded. Posterior nostril with elevated rim, about two nostril diameters in front of middle of eye; anterior nostril at end of short tube, positioned midway between eye and upper jaw, close to posterior nostril. Gill rakers on outer face of first arch 1–2 + 6–8 = 7–9; 2–4 short rakers on outer face of second arch; rakers very short on both faces of all arches, except first; teeth in upper jaw small, conical, curved, 2–3 inner rows of slightly smaller teeth than those of outer row, close-set teeth anteriorly tapering to 1 row laterally; teeth in lower jaw small, conical, curved with 6–8 teeth on outer face of dentary in outer row, 2 inner rows of teeth of a similar size, rows tapering laterally to 1 row. Body very slender, body depth at anal origin 10.6–13.0 % SL. First dorsal-fin origin above and behind pelvic-fin insertion by about one pupil diameter; second dorsal-fin origin just behind first dorsal fin, separated by one or two scale rows and above urogenital papilla; anal-fin origin below and just behind second dorsal-fin origin, below second ray of second dorsal fin; pelvic fin large, origin below a point just behind pectoral-fin insertion; pectoral-fin margin rounded; caudal fin small, with rounded margin to truncate margin (damaged in most specimens); first ray in second dorsal fin unbranched, second rarely unbranched, other rays branched, last branched to base; first one or two anal rays unbranched, other rays branched, last branched to base; pectoral rays branched, except for uppermost one or two rays and rarely lowermost ray.

The sensory papillae of the head are shown in Figure 7 . Papillae reduced, with papillae in some rows arranged irregularly. Drawing is a composite of several specimens. Head pores present ( Figure 7 ) include an anterior nasal pore, posterior nasal pore, median posterior interorbital pore, infraorbital pore and terminal lateral canal pore above and just behind posterior preopercular margin, no preopercular pores, but a shallow depression sometimes extending ventrally behind preoperculum. Gill opening wide, reaching forward to below posterior preopercular margin; head naked, anterior body scales reaching forward to a line from first dorsal origin to above pectoral- fin base.

Body scales ctenoid, in 31–32 rows; midline of belly without scales; pectoral base without scales; area before pelvic without scales; body slender, depth at anal origin much less than caudal fin length and about half head length. First dorsal fin low, with rounded or triangular shaped margin.

Males with 4 prominent short, black vertical bars, first below and just behind first dorsal origin, second just behind second dorsal origin, third behind end of second dorsal fin and fourth on caudal peduncle closer to caudal fin than end of second dorsal fin; often a thin fifth band on base of caudal fin; females with horizontally elongate spots in same positions as bands in males and with smaller black spots between these spots and a thin vertical bar on base of caudal fin. Males with vertical black bar below eye and black bar ventrally on anterior operculum; females with vertical bar below eye and short black line extending forward to upper lip, a black oval spot and posteroventral margin of eye and a slanted U-shaped black mark dorsally on the operculum; dark bands and spots often faded in preserved material; first dorsal fin of male dark, without distinct spots, fin with pale or with grey mottling along middle of fin in females.

Urogenital papillae of male very elongate, length about 4 times width at base. Papilla of female triangular, without lobes, broad at base and length about 1.5 time width at base.

Preserved coloration. Head and body light brown. Males: lips often with dark spots forming line crossing lip; scattered melanophores forming a distinct to diffuse band from anteroventral margin of eye to posterior end of upper lip and slightly behind; melanophores forming a diffuse vertical band on operculum, just behind posterior preopercular margin; upper operculum with melanophores forming a circle or U shaped mark; a thin black line above operculum on each side, sometimes extending upward and forward toward similar spot on other side of head; an elongate thin black spot on the dorsal midline above operculum; a thin black elongate mark on each side of nape just before first dorsal origin; nape spots sometimes faint or absent; ventral surface of head without melanophores or with scattered melanophores; upper pectoral base with a dark gray to black spot, much smaller than pupil diameter; body with four prominent short, black vertical or oblique (sloping downward posteroventrally) bars, first below and just behind first dorsal origin, second just behind second dorsal origin, third behind end of second dorsal fin and fourth on caudal peduncle closer to caudal fin than end of second dorsal fin; often a thin fifth band on base of caudal fin; first dorsal fin usually dusky to black, sometimes with distal tip of fin with little pigment; second dorsal and anal fin clear to covered with black mottling, sometime forming indistinct bands. Pectoral, pelvic and caudal fins translucent, with no melanophores, except sometimes a few scattered melanophores on pelvic fin. Females: coloration of lips and top of head as described for male; ventral surface of head without melanophores, pectoral base without spot or with a very faint dark gray spot, much smaller than pupil diameter; body with horizontally elongate spots in same positions as bands in males and with smaller black spots between these spots and a thin vertical bar on base of caudal fin; melanophores forming a gray to black vertical bar below eye and short black line extending forward to upper lip, a black oval spot and posteroventral margin of eye and a slanted Ushaped black mark dorsally on the operculum; dark bands and spots often faded in preserved material. First dorsal fin with gray mottling along middle of fin; fins usually without melanophores, in some specimens first dorsal fin with gray mottling along middle of fin.

Variation. Sex ratios were found to be almost even with 12 males (average size 29 mm SL) and 11 females (average size 31 mm SL) in the type material. Considerable sexual dimorphism exists in coloration and becomes more apparent in larger males as described above. Depressed dorsal and pelvic fin also are typically slightly shorter in females and immature males, with the depressed dorsal fin usually not reaching the second dorsal origin, but usually extending to the first or second ray in males over 29 mm SL. Some larger females have the spines extending to just beyond the first ray. Similarly, the pelvic fin usually does not reach the anal-fin origin in females, but extends between the first to third ray in males over 29 mm SL.

Anal-ray counts were found to normally be 8 or 9, but one specimen had 7 and one 6. In these two specimens it appeared to be abnormal with the anal fin displaced away from the anus.

Distribution, habitat & ecology. Despite extensive shore based searches in South Australia, Nesogobius tigrinus sp. nov was only detected from three sites within the sheltered waters/embayment of north-east Kangaroo Island (northern Shoal Bay, Western Cove and upper American River: Figure 1 ). Moreover it appears to occupy a narrow strip of habitat at the lower intertidal and start of the sub-tidal over sand and mud with broken shell and sometimes in association with sparse marine eel grass Zostera and the algae Hormosira ( Figure 8 ), but appears not to occupy fringing ribbon weed Posidonia in clean sands of deeper water. These observations are supported by a lack of previous reports for an otherwise fairly obviously coloured fish (at least adult males) from diving and general observations around south eastern Australia ( Kuiter 1993; Hoese & Larson 2008), however more detailed distribution and habitat mapping is required. Radiographs revealed small shells (micro-molluscs) in the stomach content of most fish screened ( Figure 4 ), suggesting a benthic predatory/omnivorous diet. Limited sampling points to a possibly annual lifecycle, with smaller fish represented in autumn, and only larger adults captured in spring most of which displayed nuptial colours or were gravid at this time.

Etymology. From the Latin tigrinus meaning banded.

Remarks. The species also occurs in a similar habitat to that of Favonigobius lateralis ( Macleay, 1881) and can be confused with that species. It differs from F. lateralis in having 13 segmented caudal rays (versus 17); no spine in the second dorsal and anal fins (versus first element in each fin a soft spine), usually no interorbital head pores (versus median anterior and posterior interorbital pores present) and presence of isolated vertical bands on the body (versus paired spots or vertically elongate spots on the midside posteriorly).

Figures

FIGURE 1. Map of near shore marine survey sites undertaken in South Australia (SA) from 2001 – 2010 (circles), including record locations for Nesogobius tigrinus sp. nov. on Kangaroo Island (triangles).

FIGURE 3. Holotype (SAMA F 11946) of Nesogobius tigrinus sp. nov. showing life colouration (adult male).

FIGURE 4. Radiograph of Nesogobius tigrinus sp. nov. (holotype). Food items visible in the gut are micro-molluscs.

FIGURE 5. Field aquarium photos of Nesogobius tigrinus sp. nov. (A) Male, (B) female, and (C) individual buried in sand (SAMA F 14138).

FIGURE 6. Morphological features of Nesogobius tigrinus sp. nov. (A) Preserved head colouration (SAM F 11947), (B) scaleless predorsal (SAMA F 12153), and (C) chin papillae (SAM F 12265).

FIGURE 7. Composite head papillae patterns of Nesogobius tigrinus sp. nov. (A) Top view; N = nostrils, AN = anterior nasal pore, PN = posterior nasal pore, PIO = posterior interorbital pore, IFO = infraorbital pore, TLC = terminal lateral canal pore, (B) side view, and (C) ventral view showing rounded mental frenum.

FIGURE 8. Near shore marine habitat of Nesogobius tigrinus sp. nov. (low tide; the species occupies an area just beyond the intertidal zone) at (A) Western Cove and (B) Shoal Bay.