Omobranchus ferox (Herre 1927)

Omobranchus ferox (Herre)

Petroscirtes ferox Herre, 1927:277 [60 syntypes from vicinity of Ambulong, Talisay, and around Volcano Island, all in Lake Taal; neotype designated below].

Petroscirtes kranjiensis Herre, 1940:25 [mangrove swamp drained by Kranji River, Singapore Island].

Petroscirtes waterousi Herre, 1942:112 [swamp on Waterous Hacienda, Mangarin, Mindoro, Philippine Islands].

Petroscirtes feliciana Herre, 1942:112 [mangrove swamp beside Fishery Station at Cagayan, Oriental Misamis, Mindanao, Philippine Islands].

Omobranchus dealmeida J. L. B. Smith, 1949:104 [rock pool, Ponte Maone, Delagoa Bay].

DESCRIPTION (see also Tables 5 and 9).—Dorsal fin XI–XIII (XII in 85.2% of specimens), 20–23 = 32–35; anal fin II, 22–26; both anal-fin spines of males discernible externally; segmented caudal-fin rays 13–15 (13 in 95.4% of specimens); dorsal + ventral procurrent caudal-fin rays 10–15 (12–14 in 96.7% of specimens); vertebrae 10–11 (11 in only 1 of 75 specimens) + 28–30 = 38–40; epipleural ribs 10–13 (11–12 in 96.5% of specimens); prenasal pores present; interorbital pores 2–3 (3 in 96.8% of specimens); circumorbital pores 8–9 (8 in 96.8% of specimens); lateral-line tubes 0–4; lateral-line tubes, when present, extending posteriorly to below level of dorsal-fin spine 2–7; gill opening extending ventrally to level of pectoral-fin ray 3–6; lower-lip flap present; circumorbital bones 4; lower jaw teeth 16–22; upper jaw teeth 14–21 (Figure 37); no fleshy bladelike crest on top of head of either sex.

COLOR PATTERN (available specimens all greatly faded).—Males. Head: Two very faint, dusky bands present below eye; distinctive, almost vertical, narrow, pale line, approximately two-thirds eye diameter in length, bordered posteriorly by intense dark line of similar length, present along posteroventral margin of orbit; lower dorsoanterior edge of pale line also with very narrow, intensely dark, marginal line. Dark dusky blotch apparent posteriorly on operculum in some specimens.

Trunk: Up to 12 or 13 evenly spaced, moderately narrow, dark dusky bands reaching almost from dorsal to ventral body contour present in some specimens (most specimens with color pattern almost totally faded); bands nearly vertical, though apparently with slight anteriorly directed angle at lateral midline of body; bands only about half as broad as adjacent pale dusky interspaces; some bands incomplete dorsally or dorsal ends separate from rest of band. Row of paired dark blotches present on dorsal body contour, each pair at dorsal end of corresponding body band.

Pectoral Fin: Pale with even spread of dark specks of pigment; very fine, threadlike, dark line running length of each ray. Dusky blotch present on dorsal half of fleshy pectoral-fin base.

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

Dorsal Fin: Pale with scattered fine, dark spots. Indication of some color pattern in the dorsal fin, possibly 1 or 2 longitudinal stripes as described by Herre for O. waterousi; however, not apparent on best marked specimen available. Large, dark spot, diffuse in some specimens, present distally between last 3 or 4 segmented rays.

Anal Fin: Dark dusky, ray tips abruptly pale.

Caudal Fin: Pale, membranes transparent distally, dorsal and ventral edges dusky. Two broad, longitudinal, dark dusky streaks present on fin, 1 just above and 1 just below lateral midline of fin.

Female: Apparently similar to males except for absence of dark blotch on posterior distal portion of dorsal fin.

GEOGRAPHIC VARIATION.—There is some evidence (Table 9) that the Indian population of O. ferox has greater numbers of meristic elements than do the other populations. Rama Rao (1968) also reported a high number of segmented dorsal- and anal-fin rays for his specimens from India.

GEOGRAPHIC DISTRIBUTION (Figure 4).—Philippine Islands, South China Sea, west to Delagoa Bay, Mozambique. The two specimens known from Mozambique (Smith, 1959) may possibly be the result of artificial introductions similar to that we propose for O. punctatus (p. 63) from the same area. The wide gap in distribution between the Mozambique locality and the nearest locality of occurrence to the east (India), together with the estuarine habitat of the species, furnishes circumstantial evidence favoring a hypothesis of artificial introduction.

We have examined specimens of O. ferox from India only from Vizgapatnam (about 17° 3′ N) on the Bengal coast. Rama Rao (1968) has reliably reported and illustrated the species, as Cruantus dealmeida, from Nizampatnam (above 16°00′N) on the same coast.

HABITAT.—Shallow waters, most frequently collected in mangrove swamps and river estuaries; also from a freshwater lake. One collection was recorded as having come from oysters in a river.

COMPARISONS.—Omobranchus ferox differs from all other species of Omobranchus except O. zebra, with which it is broadly sympatric, in having 4 circumorbital bones (4 bones is a unilateral variant in the other species). It differs from O. zebra most obviously in having the gill opening extending ventrally to opposite the 3rd to 6th pectoral-fin ray (versus never extending ventral to level of dorsalmost ray), in lacking well-defined bands on the head, and in having a shorter head (see key couplet 13).

Omobranchus ferox may be most readily separated from the other species of Omobranchus that occupy the same general geographic area as follows: from O. aurosplendidus and fasciolatoceps in lacking a fleshy crest on the head and in having the gill opening extending much farther ventrally (restricted to area dorsal to dorsalmost pectoral-fin ray in the other species); from O. meniscus in having lateral-line tubes (versus lacking tubes), 20–23 segmented dorsal-fin rays (versus 19 rays), males without a fleshy crest, and no dark, crescentic marking extending dorsally from the postorbital margin; from O. punctatus in having the gill opening extending farther ventrally (never below level of dorsalmost pectoral-fin ray in punctatus), and no more than 4 lateral-line tubes (versus rarely less than 4); from O. elongatus and germaini in not having any distinct, dark markings on the underside of the head and on the body, and in the nature of the dark spot behind the eye (compare Figure 29f with Figures 29e and 13–15).

Males of O. ferox are unique in Omobranchus in having a dark spot distally at the posterior end of the dorsal fin (Figure 18).

NOMENCLATURAL