Aron's Blenny

Ecsenius (Ecsenius) aroni

DESCRIPTION.—Dorsal spines 12–14 (usually 13); dorsal rays 17–18; segmented anal rays 19–20; pectoral rays 13–15 (usually 14); segmented caudal rays 13; dorsal procurrent caudal rays 6–9 (usually 7 or 8); ventral procurrent caudal rays 6–9 (usually 7 or 8); total caudal elements 25–30; gill-rakers 12–15; pseudobranchial filaments 6–7; lower incisor teeth 46–57; lower jaw posterior canines 0–1; total lower jaw posterior canines 0–2 (usually 2); upper incisor teeth 130–132 (three counts); precaudal vertebrae 10 or 11 (rarely 10); caudal vertebrae 23–26 (rarely 23); total vertebrae 34–37 (rarely 34); epipleural ribs 11–14. Lateral line with no paired pores, extending to below level of 8th to 10th dorsal spine (usually 9th or 10th). Dorsal fin notched six-ninths to nine-ninths length first dorsal ray. Third (innermost) pelvic ray barely or not obvious. One cirrus on each anterior nostril.

Color pattern: The color pattern of preserved specimens is not very variable. The head is dark brown, but pale underneath. The body is generally dusky brown with a dark spot on the caudal peduncle that extends well onto the caudal fin. For most of its length, the dorsal fin bears a narrow suprabasal dusky stripe, but is otherwise scarcely marked. The anal fin is generally dusky and in mature males the tips of the rays are pale. The other fins are pale or unmarked.

In life the body is generally dark tan with a black spot with blue overtones at the base of and on the caudal fin. Some individuals exhibited a bright orange stripe along the dorsal body contour. The head and anal fin are dark brown. The other fins are pale or unmarked.

HABITAT AND DISTRIBUTION.—Ecsenius aroni is known only from the Red Sea and Gulf of Aqaba coasts of the Sinai Peninsula. It occurs in coral areas only and is commonest at depths greater than 10 meters. It was only rarely seen or taken at depths as shallow as 3 meters. The species was seen (but not collected) at the nature preserve in Eilat at depths as great as 36.6 meters, but was not found at greater depths, down to 45.7 meters (two dives planned primarily to search for the species). It prefers the undersides of ledges and pockets in the reefs and was not seen in the open areas above or about the reefs.

RELATIONSHIPS.—Ecsenius aroni is closely related to E. gravieri, with which it generally occurs in the Gulf of Aqaba, and E. pulcher, which occurs in the Persian Gulf and northern Arabian Sea. With these two species it shares the following unique combination of characters: typically 13 dorsal spines, a notched dorsal fin, 11 precaudal vertebrae, typically 14 pectoral rays, and 13 segmented caudal rays. It differs from these two species primarily in color pattern, proportions and meristics as indicated in key couplets 16 and 17. In addition it differs from the sympatric E. gravieri in that caudal filaments are primarily restricted to males (well developed in both sexes in E. gravieri), and in males the longest caudal ray tends to increase in relative length regularly with increase in standard length (Figures 11). In general, for either sex, E. aroni has a relatively shorter caudal than E. gravieri (Figures 11). E. aroni attains a much smaller maximum size than either E. gravieri or E. pulcher (Figures 11).

E. aroni occurs more commonly in greater depths than the sympatric E. gravieri, which is usually found in less than 10 meters depth. The two species behave quite differently. E. gravieri is an obvious species on the reef and is frequently seen swimming above the bottom over open sandy areas closely adjacent to the reef. E. aroni is secretive and was seen (rarely) free swimming only within small holes in the reef.

ETYMOLOGY.—This species is named for Dr. William Aron of the Smithsonian Institution in appreciation for his making possible my field work in the Red Sea. The results of that work form an invaluable contribution to this and other of my studies.

HOLOTYPE.—USNM 204468, male, 36.8 mm SL, bay at El Himeira, Sinai Peninsula, Gulf of Aqaba. Depth of collection, to 18 meters. Collected by V. G. Springer et al., 16 July 1969. Original field number, VGS 69–2.

PARATYPES (all Sinai Peninsula).—USNM 204690 (12:18.5–40.8), collected with the holotype; USNM 204560 (21:19.4–31.5), 204550 (2:21.4–27.0), 204558 (24.7), all collected in same vicinity as holotype but on different dates and at different depths; USNM 204557 (2:21.3–35.4), Marsa Muqabila, Gulf of Aqaba; USNM 204556 (33.1), bay between Marsa Mokrakh and El Himeira; USNM 204561 (40.8) and 204562 (7:25.8–40.5), Ras Muhammad, Red Sea. Some paratypes will be deposited with the Hebrew University after publication of this paper.