Eviota mikiae Allen

Greenfield, David W. & Jewett, Susan L., 2011, Eviota rubriceps, a new goby from the Southwestern Pacific Ocean, with comments on E. mikiae and E. raja (Teleostei: Gobiidae), Zootaxa 3134, pp. 53-62 : 59-60

Eviota mikiae Allen

White-line dwarfgoby

Allen, G.R., 2001: 125–130.

Material examined. One hundred sixty eight specimens from two localities in the western Indian Ocean; total range 9.2–17.8 mm; size range for gravid females 11.8–13.4mm. AMIRANTE ISLANDS (collected during the International Indian Ocean Expedition of 1964 by J.E. Böhlke et al.)- ANSP 146522, 13.6, male, ANSP 146521 (5), USNM 221747 (11), USNM 221749 (5), AMS I.22201-001 (5), CAS 47916 (5), ANSP 146516 (9), ANSP 146520 (1), ANSP 146519 (3), ANSP 146517 (6), ANSP 146518 (1). CHAGOS ARCHIPELAGAO (collected during the Joint Services Chagos Expedition, from Feb.–Mar. 1979, by R. Winterbottom and A.R. Emery)- ROM 36435 (1), ROM 36434 (1), ROM 36433 (2), ROM 36432 (6), ROM 36431 (4), ROM 36430 (2), ROM 36429 (15), ROM 36428 (4), ROM 36427 (10), USNM 221756 (21), ROM 36426 (8), ROM 36425 (3), ROM 36424 (27), ROM 36423 (12), ROM 36422 (10), ROM 36421 (7), NMC 80-616 (3), NMC 80-617 (3).

Additional description. Meristic differences were found in the dorsal and anal fin-ray counts between specimens from the Amirante Islands and the Chagos Archipelago. Amirante Islands: Dorsal-fin rays VI-I,9 (1), V-I,10 (10); anal-fin rays I,8 (1), I,9 (10). Chagos Archipelago: Dorsal-fin rays VI-I,6 (1), VI-I,9 (8); anal-fin rays I,8 (8), I,9 (1). For both localities: Pectoral-fin rays 15 (2), 16 (12), 17 (6); pelvic-fin rays I, 4 2/10 (3), I, 4 3/10 (17); branches on fourth ray of pelvic fin 7–11, average 9.4; number of segments between consecutive branches of the fourth pelvic-fin ray 1–3, average 1.1; pelvic-fin membrane reduced; branched caudal-fin rays 10 (2), 11 (2); segmented caudal-fin rays 17 (19); scales highly deciduous, lateral scale rows 21 (1), 22 (4); transverse scale rows 6 (1), 7 (2); breast scaleless; vertebrae 10 (11), 11 (1) precaudal and 14 (1), 15 (11) caudal, total 25 (12). NA pores and sensory canals absent, AITO pore present, opening anteriorly, PITO and IT pores absent. Cephalic sensory pore system is pattern 6; cutaneous papillae system is pattern C, but papillae are very weak, the pattern not visible on many specimens.

Specimens measured include 7 males, 14.3–17.8 mm, 15.7, and 7 females, 12.2–15.6 mm, 13.2; body slender, depth of trunk at dorsal-fin origin, 15.8–19.1, 17.9 males; females 17.8–20.7, 19.1; width of trunk at dorsal-fin origin, 9.0–12.2, 10.4 males; females 9.6–12.8, 11.3; least depth of caudal peduncle, 10.5–12.1, 11.4 males; females 9.6–11.2, 10.6.

Color in preserved specimens. The only difference we observed in the coloration of this species between the two localities at which it was found is a prominent, dark anterior nasal tube in almost all specimens from the Amirante Islands ( Fig. 9 ), whereas the specimens from the Chagos Archipelago have anterior nasal tubes that are either pale, or have a small amont of dusky pigment at the tips ( Fig. 10 ).

Head dorsally behind eyes with two patches of dense, dark brown chromatophores, separated by a narrow pale area along midline; a short narrow dark brown horizontal bar behind eye, about at level of upper margin of pupil, laterally separated from the dorsal patch by a narrow pale interspace; a narrow dark stripe from tip of snout laterally on upper lip, passing beneath eye and extending posteriorly to end of opercle where it is slightly wider than on snout; remainder of head pale. Body with a characteristic dark, narrow ventral midline stripe from origin of anal fin to end of caudal peduncle; this stripe appears to be contiguous with a faint, narrow subcutaneous band along ventral portion of body that separates at anal origin and passes around genital papila and anal aperature, and then blends with a large subcutaneous pigmented belly patch; posteriorly on peduncle the ventral midline stripe intersects a pronounced, small, dark spot on lower caudal peduncle at the procurrent rays, then extends onto lower caudal fin as a wider dark streak, ventrally excluding the area from the tips of the lower procurrent rays to about the outer half of the first branched ray; remainder of body pale. First and second dorsal fins with a dark horizontal band through the basal third of fins, the band extending to extremity of second dorsal fin in region of last 2–3 rays; outer margin of second dorsal sometimes with weak narrow dark pigmentation. Upper procurrent rays and upper 1 or 2 segmented rays of caudal fin with some dark pigmentation but not as dark as the streak extending out onto lower fin; pale area present on basal caudal fin between upper procurrent rays and the dark horizontal streak on lower fin; distal two-thirds of upper and middle caudal fin light dusky. Pectoral, pelvic and anal fins pale.

Specimens from the Amirante Islands are older collections and therefore are considerably more faded than specimens from the Chagos Archipelago. The characteristic color pattern that persists most often in collections from both localities is the stripe on the ventral midline of body, spot on lower procurrent caudal-fin rays, and the horizontal streak on the lower caudal fin.

Distribution. Reported from the Comoro Islands east to the Indo-Australian Archipelago and Thailand.

Remarks. Allen (2001) described E. mikiae based on nine specimens from northern Sumatra, Indonesia. The 168 specimens reported here are all from the Indian Ocean, the Amirante Islands and Chagos Archipelago, both a considerable distance from Indonesia. Specimens of E. mikiae from the Amirante Islands have some dark pigmentation on the anterior nasal tubes, almost always prominently black colored, and the dorsal/anal fin formula is almost always I, 10/I,9, whereas specimens from the Chagos Archipelago almost always have a pale anterior nasal tube and a reduced dorsal/anal fin formula of I, 9/I,8. The counts of dorsal and anal-fin rays of the Indonesian specimens align with those of specimens from Chagos Archipelago rather than those from the Amirante Islands, whereas the black nasal tubes of the Amirante specimens are more similar to those of the Indonesia specimens. Photographs of fresh specimens from the Comoro Islands, close to the Amirante Islands, also have black nostrils (pers. comm. R. Winterbottom) and underwater photographs on the web of individuals from the Maldives show that they have light nostrils, similar to those in the adjacent Chagos Archipelago. R. Winterbottom (pers. comm.) informed us that ROM specimens from Thailand align with the Indonesian specimens. We suspect that these three different combinations of counts and coloration imply that more than one species is involved, one in the western Indian Ocean ( Comoros Islands & Amirante Islands), another in the central Indian Ocean (Chagos Archipelago & Maldives), and the third in the Indo-Australian Archipelago and Thailand.

Figures

FIGURE 9. Eviota mikiae, ANSP 146522, 13.6 mm male, Amarante Islands.

FIGURE 10. Eviota mikiae, USNM 221756, 14.6 mm male, Chagos Archipelago.