Mangrove Blenny

Oviparous, distinct pairing (Ref. 205).

Dorsal spines (total): 11 - 13; Dorsal soft rays (total): 18 - 21; Analspines: 2; Analsoft rays: 20 - 23

Occurs among corals, rocks, and rubble of shallow waters (Ref. 1602). Adults inhabit mangroves and sheltered bays (Ref. 90102).

Adults inhabit mangroves and sheltered bays (Ref. 90102). Occur among corals, rocks, and rubble of shallow waters (Ref. 1602, 58302). Benthic (Ref. 58302). 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 obliquus (Carman)

Petroscirtes obliquus Garman, 1903:237 [Suva, Fiji Islands].

Hypleurochilus loxias Jordan and Seale, 1905:802 [Negros, Philippine Islands].

Hypleurochilus samoensis Seale, 1935:374 [Pago Pago. Tutuila Island, Samoa].

DESCRIPTION (see also Table 15).—Dorsal-fin spines XI-XIII (XII in 95.0% of specimens); segmented dorsal-fin rays 18–21 (rarely 21); total dorsal-fin elements 30–33 (rarely 33); anal fin II, 20–23; both anal-fin spines of males discernible externally; segmented caudal-fin rays 11–13 (1 specimen each, of 210, with 11 and 12 rays); dorsal + ventral procurrent caudal-fin rays 10–15; vertebrae 10–11 (rarely 11) + 27–30 (rarely 30) = 37–40 (rarely 40); epipleural ribs 11–15 (rarely 11 or 15); prenasal pores present; interorbital pores 1–4 (rarely 1); circumorbital pores 7–9 (modally 8, rarely 9); lateral-line tubes 0–6 (rarely 5 or 6); lateral-line tubes, when present, extending posteriorly to below level of dorsal-fin spine 1–7 (rarely 1 or 7); gill opening extending ventrally to opposite 2nd to 8th pectoral-fin ray (to 7th in 0 and 8th in 2 of 170 specimens; of the 2, 1 each had the opening of the opposite side at the level of the 4th and 5th rays); lower-lip flap present; circumorbital bones 5; lower jaw teeth 19–29; upper jaw teeth 18–28 (Figure 45); no fleshy bladelike crest on top of head of either sex (head of some presumably mature males swollen in appearance).

COLOR PATTERN.—Closely resembles O. r. rotundiceps (q. v.) with the following notable exceptions:

Males: Bands on head better defined; band at posteroventral margin of eye not interrupted at preopercular series of sensory pores; it and following band confluent on underside of head with corresponding bands of opposite side; last 2 bands often separated from corresponding bands of opposite side by narrow, pale space; last band continuous dorsally with broad, dusky area. Dome-shaped, dark dusky area posterior to eye, reaching farther ventrally; intense dark spot, larger than pupil of eye, occupying entire dorsal portion of dome-shaped area. Vertically elongate, less dark, oval area outlined, except occasionally ventrally, by narrow, pale margin, present on operculum just posterior to broad, dusky area continuous with 4th head band; vertically elongate, dark smudge just posterior to pale, margined, oval area, confluent with dark area on top of head. No spots on top of head. Bands on trunk better defined; dark intensifications of body bands broad, not extending below midlateral line of body. Posterior midlateral stripe and more dorsal stripe not developed; midlateral stripe represented by series of dark spots; tips of anterodorsal and posterodorsal extensions of body bands disjunct from bands, forming longitudinal series of dark spots or dashes. Dark bar on fleshy pectoral-fin base well defined, continued anteroventrally onto prepelvic area. Dorsal fin largely transparent with several narrow, dark stripes extending length of fin; diffuse concentration of pigment on segmented rays and dorsoposteriorly on interradial membranes; diffuse, dusky to black, oval spot placed more anteriorly, between 8th and 12th (usually between 9th and 11th) segmented rays. Anal fin with slender, evenly spaced, posteroventrally inclined dusky bands; distal edge of fin dusky with abruptly pale ray tips. Caudal fin with vertically oriented pair of large, dark spots at base; stripes faint to absent, often only ventral stripe apparent.

Females: Sexual dimorphism as in O. r. rotundiceps except dark intensifications of body bands not extending much farther ventrally; additional bands or spots not developed ventrally between main body bands; dorsal spotting and vermiculations intensified and more numerous.

GEOGRAPHIC VARIATION.—See O. r. rotundiceps.

GEOGRAPHIC DISTRIBUTION (Figure 5).—Car Nicobar Island, Indian Ocean, west to Hawaii, but apparently absent from the eastern Caroline, Marshall, and Gilbert islands.

A completely faded specimen ZMA 113.013 (Female, 27.2 mm), from Sumbawa Island, Indonesia, is identifiable as O. r. obliquus or O. elongatus. We questionably allocate it to O. r. obliquus based on its having 12 dorsal-fin spines, a number uncommon in O. elongatus. Characters for the specimen are: dorsal fin XII, 19; anal fin II, 21; total procurrent caudal-fin rays 13; vertebrae 10 + 27; epipleural ribs 14; 1 lateral-line tube, positioned below 5th dorsal-fin spine; interorbital pores 3; circumorbital pores 8.

Menon and Rama Rao (1963) recorded O. kallosoma from Madras and Mandapam, India, and the Andaman Islands. Their specimens from India are O. elongatus, whereas their specimen from the Andaman Islands (actually Car Nicobar Island, Nicobar Islands), is O. r. obliquus. The Car Nicobar specimen, which represents the only Indian Ocean record for the subspecies, arrived too late to be included in Table 15. Meristics for the Car Nicobar specimen are as follows: dorsal fin XII, 19; anal fin, II, 21, vertebrae 10 + 28; epipleural ribs 13; lateral-line tubes 1, reaching to below 2nd dorsal-fin spine; gill opening extending ventrally to opposite pectoral-fin ray 4.

HABITAT.—Shallow, usually close to shore, marine waters. Frequently in tidepools, on muddy to sandy bottoms with eel grass and algae, and near the edge of mangrove swamps; once taken at the junction of a small freshwater stream and marine bay. Live and dead coral often recorded as present. Also taken from a concrete tank in Hawaii (Strasburg, 1956), and from around a rusting barge in the western Caroline Islands.

COMPARISONS.—See O. r. rotundiceps.

NOMENCLATURAL

Omobranchus obliquus, the roundhead blenny or the mangrove blenny, is a species of combtooth blenny found in coral reefs in the Pacific and Indian oceans.