Ecsenius caeruliventris, Victor G. Springer & Gerald R. Allen, 2004

Victor G. Springer & Gerald R. Allen, 2004, Ecsenius caeruliventris and E. shirleyae, two new species of blenniid fishes from Indonesia, and new distribution records for other species of Ecsenius., Zootaxa 791, pp. 1-12 : 3-5

Ecsenius caeruliventris , new species

Bluebelly blenny

(Figures 1a -c, 2 a, 3; Table 1)

Ecsenius bandanus (not Springer), in part, Kuiter & Tonozuka, 2001:605 (Sangihe Islands) .

E. sp. Allen & Adrim, 2003:54 & 19, fig. 71 (Togean & Sangihe islands).

Holotype: MZB 12094, male, 24.3 mm SL, S entrance to Batudak Passage, Togean Islands, Sulawesi, Indonesia (00.27’S, 121°56.18’E, 3-5 m, quinaldine, G. Allen, 31 Oct 1998.

Paratypes (five specimens, all with same collection data as holotype): WAM P 31492-001 (2 females, 22.8-23.0; 2 males, 15.6-20.1) and USNM 379435 (1 female, 23.7) .

Diagnosis. A species of the Prooculis group of Ecsenius with the following combination of characters: Body without alternating dark and pale stripes or distinct dark spots; dark stripe extending posteriorly from orbital margin across head and variably for short distance onto body anteriorly. In life, dark post-orbital stripe bordered ventrally by bright white stripe; other bright markings on head, white with at most a very faint tinge of yellow; belly bluish.

Description (only differentiating characters or characters not otherwise mentioned in the introduction, identification key, and Table 1 are discussed). Preserved specimens (Figure1a -c) are most noteworthy for their general lack of distinguishing characters. There is a diffusely dusky spot on the orbital margin at about the three o’clock position. On each side of the ventral surface of the head of the male holotype (Figure 1b), there is a small dark spot, surrounded by a pale halo, in the area external to articulations of the anterior branchiostegals with the ceratohyal. A second, inconspicuous, faintly dusky spot is present near the anteriormost mandibular sensory pore. The body is darkly dusky anteriorly below the spinous dorsal fin, but becomes gradually paler posteriorly. The fins are unremarkable except for an immaculate basal stripe-like area in the segmented-ray portion of the dorsalfin rays (fine melanophores are on the fin rays dorsal to the stripe, and in the posteriormore interradial membranes) and the anal fin has a general covering of fine melanophores. The other two, smaller, males lack ventral head markings and the immaculate basal area in the segmented-ray portion of the dorsal fin. Females also lack the fin stripe, and the dark spots on the ventral head surface are replaced by one or two pairs of larger, pale spots (Figure 1c) in the positions occupied by the dark spots of the male.

In life (Figure 2a), the most obvious color markings are the deep blue of the abdominal area, a vertical pair of white stripes extending through the orbit dorsal and ventral to the pupil, a pair of small white spots in the interorbital region anteriorly, and a small, mid-dorsal white spot between the dorsoposterior margins of the orbits. The dusky post-orbital spot is bordered dorsally by a fine white spot and ventrally by a fine, pale, whitish stripe that continues faintly across the head and separates the pale yellowish cheeks dorsally from the brownish color of the head dorsally. The blue of the abdomen pales posteriorly and the body becomes faintly yellow similar to the cheeks. Specimens may or may not bear evidence of broad dusky bands on the body (see Allen & Adrim, 2003: figure 71).

Comparisons. Within the Prooculis group, Ecsenius caeruliventris appears to be most similar to E. shirleyae and E. bandanus in having a blue abdomen, in that some specimens have broad, very faintly dusky bands on the body, and in lacking distinct dark spots or stripes on the body. It differs from both species in lacking a distinct dark stripe that extends posteriorly from the posterior margin of the orbit across the head. It further differs from E. shirleyae in that the pale stripe margining the dusky postorbital spot is not intensely white and does not clearly extend across the head and enter the body, and in the more intense manifestation of the blue color of the abdomen. It further differs from E. bandanus in that the pale markings on the head and iris are white rather than bright yellow.

Remarks. This is one of the smallest species of Ecsenius ; the 23.7 mm female has well-developed, apparently ripe, ovaries. The 15.6 mm male has well-developed dentary teeth, including obvious posterior canines. In most Ecsenius species this size, the posterior canines are not present and the number of other dentary teeth does not appear to have been completely established.

Etymology: The specific name is derived from the Latin caeruleus (sky-blue) + ventris, (belly), and refers to the blue abdominal area of the species; used here as a noun in apposition.