Gobius auratus Risso, 1810

Herler, J., Patzner, R. A. & Sturmbauer, C., 2005, A preliminary revision of the Gobius auratus species complex with redescription of Gobius auratus Risso, 1810, Journal of Natural History 39 (14), pp. 1043-1075 : 1048-1059

Gobius auratus Risso, 1810

( Figures 2A, 2B , 3A, 3B , 4 )

Material

Colour morph 1 (uniformly yellow). Eastern Mediterranean : Croatia (n 56): 1 „, 46.5 + 13.6 mm, near Island of Murter, May 1999, J. Herler; 2♀♀, 34.3 + 9.7 and 44.4 + 12.5 mm ( NMW 94843), 2 „„, 33.1 + 9.3 and 36.2 + 10.7 mm ( NMW 94844), and one juvenile, 28.4 + d mm, near Island of Murter, April 2002, T. Puchner .

Colour morph 2 (yellow with red dotted lines). Eastern Mediterranean: Croatia (n 554): 6♀♀, 48.0 + 13.9 to 64.3 + 18.3 mm, and 8 „„, 51.8 + 15.5 to 69.9 + 21.9 mm, Selce , south of Rijeka, May + July 1999, J. Herler ; 7♀♀, 35.0 + 10.4 to 49.9 + 13.3 mm, and 2 „„, 45.0 + 13.3 and 55.6 + 15.4 mm, Island of Krk (east), Sveti Marak, May + July 1999, J. Herler ; 10♀♀, 31.0 + 9.3 to 60.3 + 16.5 mm, 10 „„, 33.0 + 9.9 to 65.0 + 20.6 mm, and 11 juveniles, 21.4 + 6.9 to 32.1 + 9.0 mm, Island of Cres (west), near Martinscica, June 1999, J. Herler. Two females and two males are stored at the Naturhistorisches Museum Wien with numbers NMW 94845–94848 .

Compared material

Colour morph 1. Western Mediterranean : France (n 51): 1♀, 51.9 + 14.1 mm ( MNHN 1988 /0630, neotype by Heymer and Zander 1992), Le Lavandou, La Formigue, 5 September 1987, A. Heymer .

Identification

Maximum total length about 9 cm. Gobius auratus occurs in two main colour morphs in the Adriatic Sea. In the northern Adriatic (southern Istria and Kvarner area) the life coloration observed is a pale to vivid yellow basic coloration, with numerous red dots forming distinct longitudinal lines on the head, trunk and median fins. In more southern parts such as the central Adriatic coast of Croatia, specimens can be recognized in the field by their unique canary yellow basic coloration. A large black spot is usually visible at the base of the upper P-rays but is not always present. The branchiae appear as a distinct red area underneath the somewhat translucent opercle. The head appears somewhat tipped and the dorsal body side is more curved than the ventral side. Pelvic disc deeply emarginated, to almost half of its length. Important meristics are D2 I/14 (13–15), A I/13 (12–14) and LL 44–47 (42–48).

General morphology

As described in Heymer and Zander (1992, 1994) and in Miller (1986: as G. luteus ). Body proportions for Croatian specimens and for the neotype designated by Heymer and Zander (1992) from France are given in Table II. Body moderately elongate, posterior half of trunk laterally compressed. Head large, length almost one-third of SL, ventral side anteriorly obtuse-angled due to oblique mouth bending upwards. Posterior angle of jaw below middle of pupil (UJ 11.6% of SL). Snout slightly tipped and oblique, shorter than eye. Eyes large, diameter about 30% of H, dorsolateral with narrow interorbital space. Teeth in jaws in several rows, larger in first row, erect and caniniform in both jaws and pharynx. Pelvic disc deeply emarginate, divided medially almost half of its length. C slightly emarginate, truncate or slightly rounded, and shorter than head. Swim bladder well developed.

Fins (Table III)

D1 VI; D2 14 (13–15); A I/13 (12–14); C 14 (13–16) branched rays; P 18–19 (17–20); V I/ 5 + 5/I. Fin bases and lengths given in Table II. No remarkable elongation of D1 spines, fifth usually slightly projecting. Interdorsal space without membrane narrow, but present. D2 origin anterior of A origin. Fin rays in D2 and A grow longer, especially in males during breeding season, with rear tips reaching C origin. C usually slightly emarginate but almost rounded in large specimens. P, when pressed against the body, reaching back to below D2 3 in small specimens and males and to D2 2 in females. Three uppermost P-rays moderately free from membrane, with bifid ends. Pelvic disc deeply emarginate to almost half of its length (see Figure 2 and V 4l /V5l ratio in Table II) with anterior membrane reduced to skin fold or absent. On average, longest tip of V reaches anus, exceeding it rather in males than in females but especially in smaller specimens.

Scales

LL 45 (42–48; Table III); TR 12–13 (11–14). Trunk mainly covered by ctenoid scales, but cycloid scales also present anterior of imaginary lines from dorsal P-base to D1-end or D2- origin and from ventral P-base to V-origin, respectively. Cheek naked. Nape, predorsal area and pectoral base with small cycloid scales. Opercle naked or with a few small cycloid scales on latter (especially in larger specimens). Larger cycloid scales on breast.

Coloration

Colour morph 1 ( Figure 3A ). This variant of G. auratus was found in the central Adriatic and western Mediterranean. The specimens exhibit a distinct canary yellow colour over the entire body including the upper rim of the eye, which in particular may exhibit a deep yellow colour. The opercle is somewhat translucent and the branchiae appear as a distinct red area underneath. A large black spot at the dorsal base of P is typical; its size is variable and its shape is rounded to rectangular. Hardly visible red dots can occur depending on the mood of the fish, especially when excited or stressed or in captivity, forming weak longitudinal lines along the lateral line and the median fins. The most obvious line is formed along the proximal part of A. Nevertheless, this colour pattern is not persistent and rarely displayed in the field, and it is never as intensive as it is in the second colour morph described below. When narcotized or freshly preserved in formalin, the red dots along the lateral midline and A remain weakly visible. D1, D2 and A may exhibit a reddish golden colour caused by small, irregularly distributed erythrophores. The yellow colour becomes distinctly darker due to numerous tiny black melanophores expanding all over the body. Some areas, such as parts of the cheek and opercle, may retain their yellow coloration because they lack dark melanophores. Transferred to 70% ethanol, the specimens lose their yellow and red colours soon and remain in a greyish brown basic coloration with a distinct pectoral spot and weak dotted lines along the median fins and the lateral midline, which represent the red dots in living specimens. The dark tiny dots all over the body may be denser in some areas, forming five hardly visible broad vertical bands on the trunk, the first below D1, the second below D1-end and D2-origin, the third and fourth below D2 and the fifth on the caudal peduncle.

Colour morph 2 ( Figure 3B ). The second variant, exhibited by populations of the northern parts of the Adriatic Sea, shows a distinct life coloration throughout the year. It is similar to that of G. xanthocephalus in some aspects, which may cause problems in discrimination. The basic coloration is yellow and covers the entire body but is usually brightest on head. Branchiae appear reddish underneath the translucent opercle. Pectoral spot may not be visible in living specimens, but is large in territorial males and bluish to black, bordered white posteriorly. In many specimens, four small red spots on pectoral base, two dorsally and two ventrally. Head and body covered with numerous orange to red dots forming longitudinal lines over entire length. The most distinct line is formed along the lateral midline by about 11 red horizontally doubled dots. Dorsally, four to five longitudinal rows with middle row reddish and originating at orbit. Underneath one or two rows of goldenorange dots, above two darker rows, the uppermost originating from interorbit and running along the dorsal fin bases. Below lateral midline row two rows of golden-orange dots. Dorsal fins with four, caudal fin with five red dots along the fin rays forming horizontal and vertical rows, respectively. Interspaces and fin membrane on D1 and D2 yellowish. Anal fin with one distinct longitudinal row of red dots near its base. Fin membranes of C, A and V often with a bluish gleam. Along P-rays, dark red or brownish dots, especially in large specimens, forming concentric lines. Predorsal area with numerous yellow dots mixed up with the red longitudinal rows described above. Head shows a characteristic coloration pattern. Eyes exhibit six dark red to brown radial stripes from pupil to rim of orbit, dorsally sometimes confluent. A V-shaped pattern is found on the snout, formed by two stripes from each anterior orbit that fuse at the upper lip. Along the upper part of the cheek and opercle a red line runs from the lower orbit to the dorsal P-base. Two to three dark dots can be found ventrally on the cheek in a line from the jaw angle to the preopercle. A large brown W-shaped pattern occurs on the anterior lower lip. Posteriorly, there is a distinct dot near the jaw angle. Dark dots are also found as five, rarely three or four geniohyoid dots and on the opercle. Small white dots can also be distributed over the ventral cheek and the opercle. Territorial males show a white-edged D1 and D2, and, especially during agonistic behaviour, a dark head. The latter was observed in the field as well as in the aquarium and was also found in females. After narcotization, the entire body becomes darker in most specimens. Preserved in 70% alcohol, the fish lose their yellow and red coloration and show a specific coloration: the red dots all over the body become pale, while the basic coloration becomes brown, lighter in the ventral parts. The most distinct patterns which remain are the black pectoral spot, extending ventrally as light brown, the dark geniohyoid dots and lines of grey dots on the median fins. The orbits become dark grey, and the jaw angle is also bordered by a dark grey area, reaching to the orbit. The trunk exhibits five broad darker vertical bands, the first below D1, the second below D1-end and D2-origin, the third and fourth below D2 and the fifth on the caudal peduncle. In the lateral midline there are sometimes 10 darker blotches, especially in large specimens. In large males, the fins and the head show a dark grey pigmentation.

Lateral line system

Head canal system fully developed with anterior and posterior oculoscapular canal and preopercular canal, with pores Ơ, λ, κ, ω, OE, β, ρ; ρ 1, ρ 2, and γ, δ, E, respectively. The variations of neuromast counts in head rows are given in Table IV. Arrangement of rows ( Figure 4 ) generally as in Miller (1986: as G. luteus ) and Sanzo (1911: as G. auratus ). The papillae of rows c 2, c 1, c 2 and c 1 are simply named as c because of irregular arrangement and difficult assignation. Suborbital row 2 and especially row 3 sometimes extending down to or below row d, dividing it into two or three sections. But this separation of row d can also be observed without elongate rows 2 or 3. Row 5 usually divided into superior and short inferior section by longitudinal row b, although latter does not extend much anteriorly. Row 6i extends to below level of row d. Single papilla near pore α (row ‘‘ α ’’) always present. In the oculoscapular area, between pores ρ and ρ1, there are three papillae arranged in a longitudinal row, designated as row u. Sometimes, the last papillae of both x1 and u show a ventral extension of one papilla, indicating a row tr. The real assignation of these papillae is uncertain. Left and right anterior dorsal row o slightly separated from each other or confluent in midline. Trunk rows arranged in dorsal series ld1 (9–19 papillae) below D1 II, ld2 (3–9) below D1-end, ld3 (5–12) on caudal peduncle, in ventral series from below Porigin to anus, lv1 (10–27), lv2 (9–22), lv3 (9–19) and in 25–32 median trunk series ltm (up to 17 papillae, longest rows below D1 and on caudal peduncle). The caudal fin shows three rows lc (19–47).

Biology

Gobius auratus is found in abundant populations on coasts with steep bedrock. Populations in the central Adriatic (colour morph 1) were observed to occur in deeper regions with minimum depths of about 15 m, while populations in the northern parts of the Adriatic (colour morph 2) also occurred in more shallower water of about 5 m depth. In the northern Adriatic the maximum depth of distribution was about 35 m and mostly limited by sand bottom. The specimens typically hover up to 30 cm above the substratum. The species is shy and difficult to collect due to long flight distances and hiding in deep clefts. This species was also observed in the Tyrrhenian Sea around the Islands of Elba and Giglio (R. Patzner, personal observation). Details on the habitat choice will be given in a separate paper.

Figures

Figure 2. Morphology of the pelvic disc of closely related Gobius species. (A) G. auratus (colour morph 1), MNHN 1988-630 (neotype of G. auratus by Heymer and Zander 1992), male, 57.1 + 15.0 mm (right fourth ray damaged); (B) G. auratus (colour morph 2), female, 60.7 + 16.5 mm; (C) G. fallax, female, 55.3 + 15.2 mm; (D) G. xanthocephalus, male, 55.4 + 15.2 mm. Scale bar: 5 mm.

Figure 3. Life coloration of (A) G. auratus (colour morph 1: central Adriatic, Island of Murter, Croatia); (B) G. auratus (colour morph 2: northern Adriatic, Island of Cres, Croatia); (C) G. fallax (northern Adriatic, Island of Krk, Croatia); (D) G. xanthocephalus (western Mediterranean, Banyuls-sur-Mer, France). Scale bar: 1 cm.

Figure 4. Lateral line system of G. auratus (colour morph 2), male, 61.6 + 19.9 mm, from the northern Adriatic Sea in dorsal (A), lateral (B) and ventral (C) view. Scale bar: 5 mm.