Omobranchus aurosplendidus (Richardson 1846)

Omobranchus aurosplendidus (Richardson)

Blennius? auro-splendidus Richardson, 1846:265 [Macao].

Petroscirtes lini Herre, 1934:292 [oyster beds, Heungchow, Kwangtung Province, China].

DESCRIPTION (see also Table 5).—Dorsal fin XI–XII (XI in 8 of 10 specimens), 25–26 = 36–37; anal fin II, 25–27; both anal-fin spines of males discernible externally; segmented caudal-fin rays 13–15 (14 in 3 and 15 in 1 of 10 specimens); vertebrae 10–11 (11 in 1 of 10 specimens) + 31–32 = 41–42; epipleural ribs 11–13; prenasal pores present; interorbital pores 3; circumorbital pores 7–8 (7 in 7 of 9 specimens); lateral-line tubes 0–2; lateral-line tubes, when present, extending posteriorly to below level of 2nd or 3rd dorsal-fin spine; gill opening restricted to area dorsal to level of dorsalmost pectoral-fin ray; lower-lip flap present; circumorbital bones 5; lower jaw teeth 22–28; upper jaw teeth 21–26 (Figure 47); fleshy bladelike crest on top of head of both sexes.

COLOR PATTERN.—Males: Head: Broad, dusky to dark dusky band extending from anteroventral margin of orbit across corner of mouth to chin, where it joins corresponding band of opposite side; band interrupted by eye, continuing on dorsoposterior margin or orbit as rounded dark blotch; background very pale along anterior and posterior margins of band; pale area broadest posterior to dorsal segment of band. Fleshy head crest pale with dark dusky vermiculations. Snout dusky; lower lip pale. One specimen with broad, pale area extending from just below 1st dorsal-fin spine to upper end of operculum, then posteroventrally to gill slit, and ventrally along anterior fleshy pectoral-fin base to pelvic-fin base. Single (occasionally as many as 4) small, intensely dark spot posterior to eye midway between circumorbital and preopercular sensory pores. Remainder of head indistinctly marked with dusky to dark dusky pigment.

Trunk: Background dusky, palest ventrally, darkest dorsoanteriorly, with fairly even spread of small, intensely dark spots and moderately small, pale spots and blotches.

Pectoral Fin: Pale.

Pelvic Fin: Pale with even spread of fine, dark specks of pigment.

Dorsal Fin: Dusky to dark dusky anteriorly and anteroventrally, becoming pale to transparent dorsoposteriorly. Anterior portion of fin with moderately narrow, pale stripe extending from 1st to about 9th spine midway up fin; several dorsoposteriorly angled, narrow, pale lines present distally; posteriorly, dark dusky background differentiates into numerous dorsoposteriorly directed, narrow lines with pale to transparent interspaces; interspaces broader than adjacent dark dusty lines. Several small, pale spots present on midbase of fin.

Anal Fin: Dusky with 5 or 6 narrow, pale stripes running length of fin; fin darker anteriorly.

Caudal Fin: Pale dusky, slightly paler proximally.

Females: Similar to males except: background color of head and body generally paler; dark band on head slightly narrower, more distinct; segment of band above eye extending unbroken, or as a series of irregular dark markings, nearly to dorsal edge of crest; other markings on crest larger, darker, often forming an almost complete dark border to free margin of crest; markings on dorsal and anal fins much fainter except for large, dark, oblong spot near outer edge of fin between 1st and 4th or 5th dorsal-fin spines (spot absent in males).

GEOGRAPHIC DISTRIBUTION (Figure 5).—Hong Kong, Macao, and vicinity.

HABITAT.—Shallow, brackish water in oyster beds.

COMPARISONS.—Omobranchus aurosplendidus is one of the most distinctive species of Omobranchus; however, only large adult specimens are available, and it is questionable whether all the characters that set aurosplendidus off from its congeners will be true of smaller specimens. The long filamentous dorsal-fin spines of male aurosplendidus are unique in Omobranchus, and the large, black spot on the anterior dorsal-fin spines of females may also be unique, although the single (30 mm SL) female O. verticalis available has a prominent spot between the first two dorsal-fin spines. Omobranchus aurosplendidus has more segmented dorsal-fin rays than any other Omobranchus species, but there is overlap with other species in total number of dorsal-fin elements. Although several other species approach or overlap aurosplendidus in having a large number of segmented anal-fin rays and vertebrae, such species lack the fleshy crest on top of the head that is present in both sexes of aurosplendidus. Only aurosplendidus and lineolatus have modally 11 dorsal-fin spines, and only aurosplendidus and elegans have modally 7 circumorbital pores. Of the ten specimens of aurosplendidus available, seven have 13, two have 14, and one 15, segmented caudal-fin rays. No other species of Omobranchus has such a large percentage of its specimens with more than 13 segmented caudal-fin rays (0.0–7.9% in the other taxa), but perhaps this is due to the small sample of aurosplendidus. The large numbers of segmented caudal-fin rays in aurosplendidus are associated with relatively small total numbers of procurrent caudal-fin rays, indicating the probability that some of the procurrent rays became segmented.

NOMENCLATURAL