Red Sea Mimic Blenny

Dorsal fin typically XIII, 16-19 (rarely 16 or 19), spinous and segmented-ray portions with moderate notch in-between. Anal fin II,18-21 (rarely 18 or 21). Pectoral fin 13-15 (rarely 13, typically 14). Segmented caudal-fin rays 13. Vertebrae 10 or 11 (rarely 10) + 24-26 (rarely24) = 35-37 (rarely 35). Dentary incisor teeth which includes anterior canine teeth very similar in appearance with incisors, 44-54; posterior dentary canines 0 or 1 (typically 1) on each side. Lateral line lacking pairs of pores, terminating posteriorly at a point between verticals from dorsal-fin spines 8 and 11 (rarely as far anteriorly as 8). With cirrus on posterior rim of anterior nostril; absent on anterior rim. Two color patterns: pale (northern) and dark (southern).

Oviparous, distinct pairing (Ref. 205).

Dorsal spines (total): 12 - 14; Dorsal soft rays (total): 16 - 19; Analspines: 2; Analsoft rays: 18 - 21; Vertebrae: 35 - 37

Mimics Meiacanthus nigrolineatus (Ref. 9710). 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).

aquarium: commercial

Ecsenius gravieri (Pellegrin)

Salarias gravieri Pellegrin, 1906:93 [Bay of Tadjourah; holotype, MNHN 04-319].

Ecsenius klausewitzi Lotan, 1969:371 [Entedebir, Dahlak Archipelago; holotype, HUJ E-62/3708].

Ecsenius (Ecsenius) gravieri.—Springer, 1971:22.

Ecsenius gravieri.—Springer and Smith-Vaniz, 1972:2.

DESCRIPTION.—Dorsal fin XII–XIV (modally XIII), 16–19 (rarely 16 or 19), moderately notched between spinous and segmented-ray portions. Anal fin II,18–21 (rarely 18 or 21). Pectoral fin 13–15 (rarely 13, modally 14). Segmented caudal-fin rays 13. Vertebrae 10 or 11 (rarely 10) + 24–26 (rarely 24) = 35–37 (rarely 35). Dentary incisor teeth (includes anterior canine teeth, which differ little, if at all, in appearance from incisors) 44–54; posterior dentary canines 0 or 1 (modally 1) on each side. Lateral line without pairs of pores, terminating posteriorly at a point between verticals from dorsal-fin spines 8 and 11 (rarely as far anteriorly as 8). Cirrus present on posterior rim of anterior nostril; none on anterior rim.

Color Pattern: There are two color patterns: pale (northern) and dark (southern), the difference being the intensity and area covered by the dark markings. There is no problem recognizing the two types (see Figures 15 and 16) from Ras Muhammad, Sinai Peninsula, north, or from Massawa, Ethiopia, south, but the few available specimens from intermediate geographic areas are somewhat intermediate in their markings.

Preserved Color: In preservative, specimens of the northern type have the head relatively darkly dusky with the intensity of the pigment decreasing gradually on the body and becoming quite pale posteriorly; however, the abdominal area is dark gray. At about the midposterior margin of the orbit of most specimens there is a dark, almost black, stripe, or diffuse evidence of one, that extends posteriorly across the head, darkens greatly on the body, and usually continues at least to below the middle of the spinous dorsal fin, but terminates anterior to the caudal peduncle. On the body posterior to the termination of the stripe are several variably placed small black spots. There may also be a few small dark spots on the body ventroanterior to the termination of the stripe. Occasional specimens may lack the dark stripe or spots, but not both. The spinous dorsal fin bears a row of jet-black spots restricted mostly to the interspinous membranes. These spots decrease in size and intensity and disappear at some point along the segmented-ray portion of the fin. The dorsal and ventral caudal-fin lobes are darkly dusky; there are no other noticeable markings on the fins.

Specimens of the southern type differ from those just described in having the dark pigment generally blacker and covering a larger area. The stripe on the body may be almost completely obscured anteriorly by the body pigment (the stripe is absent in the holotype of E. gravieri, see Smith, 1959, for reasonably good illustration of the holotype). In addition, some specimens exhibit dark pigment at the tips of some dorsal-and anal-fin rays.

Live Color (based on color photographs of living specimens, Plate 1, taken in the Gulf of Aqaba): The head and body anterior to the anal-fin origin are generally blue gray; the remainder of the body is bright yellow. The iris of the eye is divided diagonally by a dark stripe into equal anterodorsal and posteroventral sections; except for the dark (black) stripe, which is interrupted by the pupil, the iris is blue gray with two short, fine, bright yellow arcs margining the pupil. The animal is able to rotate the eyes somewhat, but often, the dark stripe is positioned as a continuation of the black postorbital stripe. The black and dusky markings of the dorsal and caudal fins, and a suffusion of yellow along the dorsal-fin base, represent the only fin pigmentation. Other black marks on the head and body are the same as in preserved specimens.

SEXUAL DIMORPHISM.—Primarily restricted to size: the largest males are about 15 mm (or about one-third) longer than the largest females. It is noteworthy that there is essentially no distinction between the sexes in the relative lengths of the longest caudal-fin ray (Springer, 1971: table 9), although the ray is usually long and filamentous. In all the other species of Ecsenius the longest ray, when filamentous, is relatively longer in males.

GEOGRAPHIC VARIATION.—The main such variation noted is described in the above section on color pattern.

DISTRIBUTION.—Gulf of Aqaba, Red Sea south to westernmost Gulf of Aden.

MATERIAL (* = new material).—Gulf of Aqaba: TAU NS-3580 (3 specimens: 20–48 mm SL); HUJ F-4382 (1:39), F-4377 (2:20, 21), E-64/30A (2:20, 32); USNM 204542 (9:32–56), 204555 (15:19–33), 204546 (9:18–23), 204544 (22:20–53), 204543 (3:20–61), 227982* (7:22–33), 204697* (7:20–45). Gulf of Suez: USNM 204548 (3:50–55). Red Sea: Ras Muhammad, Sinai Peninsula, USNM 204545 (9:28–44), 204547 (2:28, 41); Egypt, Al Ghardaqa, SMF 5122-23 (2:30, 35); Saudi Arabia, Jiddah, USNM 217730* (1:28), 217723* (1:26); Sudan, Suakin, BPBM 19739* (1:37); Dahlak Archipelago, HUJ E-62/3708 (holotype of Ecsenius klausewitzi: 15); Isola Delemme, USNM 204479 (1:56); Sheikh el Abu, USNM 204480 (3:30–40). Bay of Tadjourah: MNHN 04-319 (holotype of Salarias gravieri: 54).

Ecsenius (Ecsenius) gravieri (Pellegrin)

Salarias gravieri Pellegrin, 1906, p. 5 [Bay of Tadjourah].

Ecsenius klausewitzi Lotan, 1969, p. 371 [Entedebir, Dahlak Archipelago].

DESCRIPTION.—Dorsal spines 12–14 (usually 13); dorsal rays 16–19 (rarely 16 or 19); segmented anal rays 18–21 (rarely 18 or 21); pectoral rays 13–15 (rarely 13); segmented caudal rays 13; dorsal procurrent caudal rays 7–9 (usually 8); ventral procurrent caudal rays 7–9 (usually 8); total caudal elements 27–31; gill rakers 12–16; pseudobranchial filaments 6–8 (rarely 8); lower incisor teeth 44–54; lower jaw posterior canines 0–1; total lower jaw posterior canines 0–2 (usually 2); precaudal vertebrae 10–11 (rarely 10); caudal vertebrae 24–26 (rarely 24); total vertebrae 35–37 (rarely 35); epipleural ribs 12–15. Lateral line with no paired pores, extending posteriorly to below level of 8th to 10th (rarely 8th) dorsal spine. Dorsal fin notched two-ninths to six-ninths length of first dorsal ray. Third (innermost) pelvic ray not obvious in specimens over 25 mm SL. One cirrus on each anterior nostril.

Color pattern: This is a distinctively marked species. In Gulf of Aqaba, Gulf of Suez, and northern Red Sea specimens, 17.5–60.8 mm SL, the head is relatively dark with the intensity of the pigment decreasing gradually on the body and becoming quite pale posteriorly. At about the midposterior margin of the orbit of most specimens there is a dark stripe, or diffuse evidence of one, that extends posteriorly across the head, darkens greatly on the body, and usually extends to below at least the middle of the spinous dorsal fin, but terminates anterior to the caudal peduncle. At its termination the stripe continues as a row of variably spaced dark spots to the base of the dorsal caudal rays. There are also a variable number of dark spots posteriorly on the body. In a few specimens the dark stripe or the spots (but not both) may be absent.

The spinous dorsal fin bears a jet black row of dark spots, restricted mostly to the interspinous fin membranes. These spots decrease in size and intensity posteriorly and may extend onto the interradial membrane of the rayed dorsal for a varying distance. There is no pigment distally on the rayed dorsal or anal fins. The upper and lower lobes of the caudal are dusky.

Specimens from the southern Red Sea and the Bay of Tadjourah, outside the entrance to the Red Sea, differ from those described above in having the dark pigment generally blacker and covering more area. The stripe on the body may be almost completely obscured anteriorly by the surrounding body pigment, but the stripe is absent in the holotype (see Smith, 1959, fig. 12, for an illustration of the holotype). In addition, some specimens exhibit dark pigment at the tips of some of the dorsal and anal rays. Specimens from the northern and southern Red Sea (including the Bay of Tadjourah, type locality) are easily distinguishable (Figures 17 and 18). I do not believe that the northern populations merit nomenclatural distinction, however, as there is a good possibility that the two forms gradually merge somewhere in the midportion of the Red Sea. There are no specimens available from the approximately 1500 km between the southernmost collections of the northern form and the northernmost collections of the southern form.

The two types of color pattern described here are paralleled in the unrelated blenniid genus Meiacanthus, which co-occurs with E. gravieri (see discussion of mimicry on page 6).

In life, E. gravieri is generally slate blue anteriorly grading into pale yellow posteriorly. The black markings are black.

REMARKS (see also discussion under E. aroni).—In the northern Red Sea and Gulf of Aqaba, E. gravieri occurs commonly in depths of 2 to 10 meters, but is rarely seen at greater depths. The species is frequently seen swimming freely, but such activity is punctuated by long periods of rest on the bottom. E. gravieri is apparently territorial and during several periods of observation, individuals were noticed to have a few favorite perching spots. An individual might leave one of these spots and swim around, up to about 5 meters distance from such a spot, but it always returned to one of the favored spots to perch.

Klausewitz (1960) illustrated E. gravieri but identified the specimen as E. nigrovittatus, a synonym of E. frontalis.

Lotan (1969) compared E. klausewitzi with E. gravieri, differentiating E. klausewitzi by its having a black line on the body, which the holotype of E. gravieri lacked. The presence or absence of such a dark line is variable, as noted in the color pattern description above. The holotype of E. klausewitzi is a small specimen of the southern Red Sea dark form of E. gravieri.

MATERIAL (localities abbreviated).—(Pale form) Gulf of Aqaba: UTAI NS–3580 (3: 20.4–48.1), HUI HUJ–F–4382 (38.6), HUJ–F–4377 (2: 20.4–21.0), E–64/30A (2: 20.0–32.4), USNM 204542 (9: 32.1–55.9), 204555 (15: 19.3–33.2), 204546 (9: 17.5–23.3), 204544 (22: 20.2–52.7), 204543 (3: 19.5–60.8); Ras Muhammad, southern tip of Sinai Peninsula, Red Sea: USNM 204545 (9: 27.8–44.1), 204547 (2: 27.8–41.3); Et Tur, Sinai Peninsula, Gulf of Suez: USNM 204548 (3: 50.1–54.7); Al Ghardaqa, Egypt, northern Red Sea: NFIS 5122–23 (2: 29.6–34.6).

(Dark form) Dahlak Archipelago, Red Sea: HUI E–62/3708 15.1, holotype of Ecsenius klausewitzi); Isola Delemme (15°30.5’ N, 39°54’ E), Red Sea: USNM 204479 (56.5); Sheikh el Abu (16°08’ N, 39°36.5’ E), Red Sea: USNM 204480 (3: 30.5–40.1); Bay of Tadjourah: MNHN 04–319 (54.2, holotype of Salarias gravieri).

In addition to the above, a large number of uncataloged USNM specimens I collected in the Gulf of Aqaba were examined for color pattern and ecological data.

Ecsenius gravieri, the Red Sea mimic blenny, is a blenny from the Western Indian Ocean. It occasionally makes its way into the aquarium trade. It grows to a size of 8 cm in length. The specific name honours the French zoologist Charles Gravier (1865-1937), the collector of the type.

A mimic of Meiacanthus nigolineatus (Sabretooth blenny) with venomous fangs. The mimic not only closely matches the colour but has adopted the same mode of swimming just off the bottom.