Millerigobius macrocephalus (Kolombatović, 1891)

Kovačić, Marcelo, Bonello, Juan Jose & Evans, Julian, 2013, Three new records of Gobiidae from Malta with morphology, colouration and identification of the smallest known juveniles of two small gobiid species, Cybium 37 (4), pp. 233-239 : 236

Millerigobius macrocephalus (Kolombatović, 1891)

Material examined

Juvenile of unidentified sex, PMR VP2879 , 8.5 + 2.4 mm, Manoel Island (I1), Malta, 31 Aug. 2011, coll. J.J. Bonello and J. Evans ( Fig. 3A ); juvenile of unidentified sex, PMR VP2880 , 11.4 + 2.8 mm, Manoel Island (I1), Malta, 31 Aug. 2011, coll. J.J. Bonello and J. Evans; juvenile of unidentified sex, PMR VP2881 , 11.5 + 2.9 mm, Manoel Island (I1), Malta, 31 Aug. 2011, coll. J.J. Bonello and J. Evans ( Fig. 3B ); juvenile of unidentified sex, PMR VP2883 , 10.2 + 2.6 mm, Tigné (H2), Malta, 23 Aug. 2011, coll. J.J. Bonello and J. Evans; ( Figs 1 , 3C ) .

Diagnosis

(1) Suborbital papillae of lateral-line system without longitudinal row a; (2) anterior oculoscapular and preopercular canals present, posterior oculoscapular canal absent; (3) pelvic fins forming disc; (4) interorbital papillae present.

Description

Anterior nostril tubular, long, reaching upper lip, without process from rim. Posterior nostril slightly raised. Branchiostegal membrane attached to entire side of isthmus. First dorsal fin VI; second dorsal fin I/10; anal fin I/9; caudal fin with 12-13 branched rays and 16-17 segmented rays; pectoral fin 15-16; pelvic fins I/5+I/5. Pelvic fins forming disc, with anterior transverse membrane. Body with ctenoid scales, scales in lateral series 28-31. Head, predorsal area and breast naked. Preserved colour: Specimen PMR VP2881 ( Fig. 3B ), 11.5 + 2.9 mm with body yellowish brown. About seven vertical dark brown bands on the body, darkest anteriorly, posteriorly, bands lighter and blurred, present along lateral side below dorsal fins. About nine dark lateral midline spots present at vertical bands, posteriorly on caudal peduncle bands no longer visible. Reticulate pattern, formed by dark markings along the scale margins, visible. Pectoral fin base, isthmus and breast pale compared to rest of body, but pigmented. Belly unpigmented. Head unequally pigmented, with palest part behind eye at level of pupil and on opercle. Specimens PMR VP2880, 11.4 + 2.8 mm, PMR VP2883, 10.2 + 2.6 mm and PMR VP2879 ( Fig. 3A ), 8.5 + 2.4 mm with body greyish brown, dominated by grey-brown melanophores. Vertical dark bands and dark lateral midline spots on the body indistinct. Reticulate pattern, formed by dark markings along scale margins, visible in PMR VP2880, 11.4 + 2.8 mm, but still not developed in specimens PMR VP2883, 10.2 + 2.6 mm and PMR VP2879, 8.5 + 2.4 mm. Pectoral fin base, isthmus, breast and belly pale compared to rest of body, unpigmented in PMR VP2879, 8.5 + 2.4 mm, and pigmented in specimen PMR VP2880, 11.4 + 2.8 mm. Head colouration pattern also dominated by densely scattered grey-brown melanophores. Fin colouration similar in all specimens. First dorsal fin with one transparent longitudinal band at middle of fin and two broad dark bands above and below it. Second dorsal fin with irregularly scattered bright dots; in smallest specimen PMR VP2879, 8.5 + 2.4 mm with two dark longitudinal bands. Dark brown 3-shaped mark present on origin of caudal fin, reaching caudal peduncle at midline and leaving pale areas at upper and lower caudal fin base, indistinct in smallest specimen PMR VP2879, 8.5 + 2.4 mm. Anal fin pigmented. Pectoral and pelvic fins pale. Head with anterior and preopercular canals, with pores σ, λ, Χ, ω, α, β, ρ and γ, δ, ε respectively, except in specimen PMR VP2879, 8.5 + 2.4 mm where parts of both canals are present as open furrows. Rows of sensory papillae: No suborbital row a. Seven transverse suborbital rows of sensory papillae. Row b anteriorly beginning below rear border of eye. Two or four interorbital papillae present behind pore λ.

Figures

Figure 1. - Map of the Maltese Islands showing the sixteen sampling locations: (▲) sites with gobiid records; (●) sites from where no gobiid species were identified. Key: A: Wied l-Ghasri; B: Ħondoq Bay; C: Ix-Xatt l-Ahmar; D: Mġarr ix-Xini; E: Mellieha Bay; F: Mistra Bay; G: Qawra; H1-H6: Tigné A – Tigné F; I1-I2: Manoel Island A – Manoel Island B; J1-J4: Ta’ Xbiex A – Ta’ Xbiex D; K: Ħofra ż-Żghira; L: Marsaxlokk; M: Wied ix-Xoqqa; N: Wied iż-Żurrieq; O: Fomm ir-Rih Bay; P: Ġnejna Bay.

Figure 3. - Millerigobius macrocephalus. A: Preserved specimen, PMR VP2879, juvenile of unidentified sex, 8.5 + 2.4 mm, Manoel Island B, Malta. B: Preserved specimen, PMR VP2881, juvenile of unidentified sex, 11.5 + 2.9 mm, Manoel Island B, Malta. C: Map of the Mediterranean showing previous records (▲) and new find- ing (●).