Rotund Blenny

Oviparous, distinct pairing (Ref. 205).

Dorsal spines (total): 1113; Dorsal soft rays (total): 1112

Oviparous. Eggs are demersal and adhesive (Ref. 205), and are attached to the substrate via a filamentous, adhesive pad or pedestal (Ref. 94114). Larvae are planktonic, often found in shallow, coastal waters (Ref. 94114).

Omobranchus rotundiceps (Macleay)

(For synonymy see subspecies)

COMPARISONS.—Omobranchus rotundiceps is a member of the elongatus species group (see “Comparisons” under O. elongatus). Omobranchus rotundiceps is the only species in the group with modally 12 dorsal-fin spines; the others have modally 13 spines. It further differs from the other species in the group in having the dark spot posterior to the eye either closer to the preopercular series of pores than to the circumorbital series or about midway between the two series. In the other species the dark spot is either absent or closer to the circumorbital series of pores. Aside from its species group characters, O. rotundiceps is separaable from most of the other species of Omobranchus only by a combination of characters.

Omobranchus rotundiceps rotundiceps (Macleay)

Petroscirtes fasciolatus Macleay, 1881:8 [Port Jackson; secondary junior homonym of Blennechis fasciolatus Ehrenberg in Cuvier and Valenciennes, 1836, which also belongs in Omobranchus].

Petroscirtes rotundiceps Macleay, 1881:9 [Port Jackson; lectotype designated below].

Salarias furcatus DeVis, 1884b:696 [St. Helena, Moreton Bay].

Salarias furtivus DeVis, 1886:60 [Moreton Bay].

Petroscirtes macleayi Ogilby, 1887:38 [replacement name for Petroscirtes fasciolatus Macleay].

Graviceps angelus Whitley, 1959:320 [Heron Island, Capricorn Group, Queensland].

DESCRIPTION (see also Table 15).—Dorsal fin XI–XIII (XII in 85.2% of specimens), 18–24 = 30–36 (rarely 30); anal-fin II, 20–26 (rarely 20); both anal-fin spines of males discernible externally; segmented caudal-fin rays 11–14 (13 in 95.2% of specimens; 11 in only 1 of 230 specimens); dorsal + ventral procurrent caudal-fin rays 10–16; vertebrae 10–11 + 27–33 (rarely 27 or 33) = 37–43 (rarely 37); epipleural ribs 11–14 (rarely 11); prenasal pores present; interorbital pores 1–4 (3 in 96.8% of specimens); circumorbital pores 6–9 (8 in 94.7% of specimens; 6 in only 1 of 251 specimens); lateral-line tubes 0–5 (rarely 4 or 5); lateral-line tubes, when present, extending posteriorly to below level of dorsal-fin spine 1–6 (rarely 5 or 6); gill opening varying from restricted to area dorsal to level of dorsalmost pectoral-fin ray to extending ventrally to opposite 5th ray (rarely extending below level of 3rd ray); lower-lip flap present; circumorbital bones 5; lower jaw teeth 18–31; upper jaw teeth 16–29 (Figure 45); no fleshy bladelike crest on top of head of either sex (head of some presumably mature males swollen in appearance).

COLOR PATTERN (described first from northern and western Australian specimens exhibiting most developed pattern, followed by comparison with eastern Australian specimens).—Males: Head: Narrow, dark band extending anteroventrally from anteroventral margin of orbit across mouth, just anterior to corner of jaws, to chin, confluent across chin with corresponding band of opposite side. Four slightly to considerably diffuse, posteroventrally slanted, narrow, dusky bands posteriorly on lower half to third of head and prepelvic area; anteriormost band extending from below posteroventral edge of orbit to ventral surface of head, usually with interruption and slight anterior shift of ventral part of band at preopercular series of pores; succeeding bands evenly spaced, paralleling 1st band; each band originating slightly higher on side of head than preceding band; 3rd and/or 4th band arising dorsally from diffuse, dusky area on operculum and continuing onto perpelvic area; additional (5th) small band originating on operculum and continuing onto prepectoral area; anterior bands usually confluent with corresponding bands of opposite side at ventral midline of head; posterior bands frequently interrupted on ventral surface of head. Large, oval to dome-shaped, dark area, approximately size of eye, present posterior to eye between circumorbital and preopercular series of sensory pores; dome-shaped area encircled by narrow, pale margin, which is less distinct ventrally; intense dark spot, equal to or smaller than pupil of eye, at dorsoposterior corner of domeshaped area. Free opercular membrane pale. Predorsal area dark dusky with scattered dark spots in some specimens.

Trunk: Ten to 12 broad, ventrally tapering, dark dusky bands present on side of body; anterior 2 or 3 bands merging together to form dark dusky area; posterior 4 or 5 bands each represented as midlateral spot, or bands (spots) joined together to form narrow, midlateral stripe (especially in large specimens); anterior 5 or 6 bands slanted posteroventrally, usually not extending onto upper quarter of body; all bands terminating dorsal to ventral body contour; pigment of each band often narrowly intensified along central, vertical axis of band; some specimens with bands represented only as dark, midlateral blotches (in freshly preserved specimens, midlateral portion of bands more intense, forming interrupted midlateral stripe extending onto head); posterior bands and midlateral spots with slender dorsoposterior extensions; approximately 9th band (spot) prolonged dorsally into narrow, posteriorly extending stripe dorsal to midlateral stripe; both stripes directed ventrally at caudal-fin base and continuing onto fin. Adjacent body bands, posterior to 2nd or 3rd band, each separated by vertical, well-defined, slender, pale line; pale lines nearly reaching ventral body contour, terminating dorsally at level of dorsal ends of body bands, or directed sharply anteriorly anterior to about 6th body band, or angled posteriorly posterior to about 7th body band; free longitudinal pale lines sometimes present above dorsal ends of vertical, pale lines. Series of approximately 8 pairs of dark, dorsally open half-rings along base of dorsal fin; rings of each anterior pair joined. Dark peritoneum visible through abdominal wall.

Pectoral Fins: Slightly dusky. Fleshy base with dark band midway between opercular edge and bases of rays; vertically oriented pair of dark spots or faint bar at base of fin rays.

Pelvic Fins: Pale.

Dorsal Fin: Transparent with dark markings. Spinous portion with 3 pairs of broad, dorsoanteriorly directed or vertical bands; each pair above corresponding pair of dark, dorsally open half-rings. Segmented ray portion with approximately 8 narrow, dark stripes; tips of rays abruptly pale; large, diffusely dusky to black, oval spot on distal portion of fin in area of 10th to 16th (usually centering on 14th or 15th) segmented rays. Large specimens with spinous portion dusky except for 2 large, pale spots near distal edge: 1 near central spines, 1 near posteriormost spines; segmented ray portion of fin dusky near distal edge, transparent proximally; black, oval spot apparent.

Anal Fin: Dusky to dark distally, transparent proximally. Tips of rays abruptly pale.

Caudal Fin: Pale with 2 narrow, dark stripes directed posteriorly and slightly ventrally from posterior ends of midlateral and more dorsal posterior body stripes (each stripe sometimes intensified as dark spot at caudal-fin base).

Females: Similar to males except: midlateral intensifications of body bands darker, generally broader, better defined, reaching farther ventrally; dusky portion of bands surrounding intensifications reduced, fainter; areas between posterior bands on lower half of body with additional intense, dark bands or spots; dorsal extensions of posterior bands (spots) broken into spots; posterior midlateral stripe and more dorsal stripe indicated only by 2 longitudinal series of spots; body more mottled or spotted dorsally; dorsal fin less pigmented, especially distally; dark bands of spinous dorsal fin, if present, much narrower; black, oval spot and all but basal dark stripes of segmented ray position of dorsal fin absent; stripes on caudal fin better defined or present as intense, dark streaks.

Eastern Australian Specimens: Head bands narrow, broken into dashes or irregular series of spots, often completely replaced by large number of fine spots and speckles (Figure 29a,b); complete head bands, when present, usually occur only posteriorly.

GEOGRAPHIC VARIATION (see also “Color Pattern”).—Population variation was noted in most meristic characters of O. rotundiceps, both within a subspecies and between subspecies (Tables 15 and 16). The meristics of O. r. rotundiceps generally ranged and averaged higher in number than they did in O. r. obliquus. The northern Australian population of O. r. rotundiceps, which are geographically closest to the population of O. r. obliquus, are intermediate in meristics between the two subspecies (see also “Color Pattern” under O. r. rotundiceps).

The Western Australian populations of O. r. rotundiceps exhibit increases in numbers of precaudal, caudal, and total vertebrae. Similar increases are exhibited by the Western Australian populations of O. germaini, whereas the Western Australian populations of O. punctatus exhibit an increase in the number of precaudal, but not caudal and total, vertebrae. Increase in number of precaudal vertebrae is not encountered in any other species of Omobranchus. It is noteworthy, even if presently inexplicable, that three species of Omobranchus exhibit increases in number of precaudal vertebrae in about the same geographic area.

Although covariance comparisons of numbers of jaw teeth (Table 16) were not feasible for all populations of O. rotundiceps, almost all the tests that were performed between pairs of populations were either significant or almost significant.

GEOGRAPHIC DISTRIBUTION (Figure 5).—From Cottesloe (near Perth), Western Australia, northward around Australia to Sydney, New South Wales.

HABITAT.—Shallow marine and brackish water; in tide pools, around ironstone reefs, rocks, and coral. Most often taken in marine habitats.

COMPARISONS.—Omobranchus r. rotundiceps is completely separable from O. r. obliquus only on the nature of the dark spot posterior to the orbit. In O. r. rotundiceps this spot is much closer to the preopercular series of pores than to the circumorbital series (Figures 28a and 29a) and consists of a concentration of pigment along the posterodorsal portion of a dark dusky, dome-shoped area. In O. r. obliquus the spot is about midway between the circumorbital and preopercular series of pores and consists of a concentration of pigment over the dorsal portion of a dark dusky, dome-shaped area (Figure 29c). Omobranchus r. rotundiceps may have the color pattern on the underside of the head consisting of about 3 or 4 narrow, dark bands (Figure 28b; northern and Western Australian populations) or of a group of dark spots and slender bands (Figure 29b; eastern Australian populations). In O. r. obliquus the pattern under the head consists of dark, slender bands (Figure 29d). Where populations of the two subspecies are geographically closest, there is broad overlap in all meristic characters (Table 15).

NOMENCLATURAL

The Rotund blenny, Omobranchus rotundiceps, is a species of combtooth blenny found in the western Pacific Ocean, around Queensland, Australia.