Yaeyama Coralblenny

Inhabits coral-rich areas of sheltered lagoon reefs.

Dorsal spines (total): 11 - 13; Dorsal soft rays (total): 13 - 15; Analspines: 2; Analsoft rays: 14 - 17

Y-shaped mark on pectoral fin base (Ref. 559).

Oviparous, distinct pairing (Ref. 205).

Adults occur solitary or in small groups on boulder habitats (Ref. 90102) sitting on rock and living coral (Ref. 9710) in shallow coastal reefs. Common species on coastal and inner reef crests with rich coral growth (Ref. 48636). 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 yaeyamaensis (Aoyagi).–Springer, 1971:32

DESCRIPTION.–Dorsal fin XII, 14–15 (only 1 of 7 specimens XII, 15); anal fin II, 16–17; pectoral fin 13 (1 of 7 specimens with 14 rays on 1 side only); segmented caudal fin rays 13; dorsal procurrent caudal fin rays 6–8; ventral procurrent caudal fin rays 7; total caudal fin elements 26–28; lower jaw incisor teeth 43–46; lower jaw posterior canines 1, each side; vertebrae 10+22–23; epipleural ribs 12–13; lateral line with no paired pores, extending posteriorly to below level of 10th–12th dorsal fin spine; dorsal fin notched eight-ninths to nine-ninths length first dorsal fin ray; third, innermost, pelvic fin ray obvious; one cirrus on rim of each anterior nostril. (For proportions see Table 1.)

COLOR PATTERN (males and females).–Most noticeable mark on head a dark stripe extending from midupper portion of opercle ventroanteriorly to underside of head, ceasing before meeting similar stripe from other side. Discontinuous dark spot may appear anterior to anterior end of stripe. Scattered dark spots present or absent on side of head, other markings on head diffuse, irregular. Three dark, longitudinal stripes on body; dorsalmost beginning just anterior to dorsal fin origin, continuing on dorsal body contour, ending in region of anterior third of rayed portion of dorsal fin; middle stripe beginning at dorsal end of gill opening, continuing to caudal fin base; posterior third of middle stripe usually appearing as series of dark dashes and spots with diffuse extension of posteriormost spot onto caudal fin rays; ventralmost stripe beginning in area covered by appressed pectoral fin, continuing posteriorly similarly to middle stripe. One specimen exhibited about nine diffusely dusky, vertical bands crossing stripes. Fleshy pectoral fin base with two short stripes, which may extend onto fin rays basally; stripes separate for entire length. Posterior portion of dorsal fin with dusky distal edging. Anal fin with narrow subterminal dark or dusky stripe over entire length; other fins, except as noted, immaculate or bearing diffusely dusky marks.

RELATIONSHIPS.–E. trilineatus is a member of the E. yaeyamaensis species group, and appears to belong to the E. oculus subgroup (see relationships under Ecsenius fourmanoiri). E. trilineatus keys closest to E. oculus and E. yaeyamaensis in my 1971 key (Springer, 1971:10–12). It can be differentiated from both of these species by the presence of two nonconverging stripes on the fleshly pectoral fin base. To determine that the two stripes are separate for their entire lengths may necessitate raising the gill cover, which overlaps the anterior end of the fin base.

REMARKS.–In the material list for E. yaeyamaensis (see Springer, 1971:33), I reported on a single poorly preserved specimen, now identifiable as E. trilineatus, from the Banda Sea. While I noted that the color pattern of this specimen was different from all other specimens of E. yaeyamaensis I believed that it probably represented only a variant population of that species. In one of the New Guinea collections made by B. B. Collette both E. yaeyamaensis and E. trilineatus were taken together, thus providing evidence that the two forms represent different species. The locality, Banda Sea, was tentatively assigned the specimen of E. trilineatus based on information provided in the appendix to my paper. The new material of E. trilineatus from the Trobriand Islands and Madang Harbor, New Guinea, near the Banda Sea, provides evidence in support of the Banda Sea locality (on my 1971 distribution map, figure 2, the symbol for E. yaeyamaensis in the Banda Sea refers to the Banda Sea specimen of E. trilineatus).

HOLOTYPE.–USM 205705, male, 25.6 mm SL, New Guinea, Trobriand Islands, off Towai Pt., NW pt. Kiriwina Island, 0–7.6 m, collected by B. B. Collette, et al., 8 June 1970.

PARATYPES.–USNM 206378, 2 males and female, 26.2–27.2 mm SL, taken with the holotype; USNM 205703, male, 25.9 mm SL, Briwadi Island, Trobriand Islands, 1.5–7.6 m, collected by B. B. Collette, et al., 9 June 1970; USNM 205704, female, 27.0 mm SL, Massas Island, Madang Harbor, New Guinea, 10.7–13.7 m, collected by B. B. Collette, et al., 26 May 1970; USNM 202477, male, 26.6 mm, presumably Banda Sea (Banda or Amboina), collected by W. H. Longley.

ETYMOLOGY.–Named trilineatus in reference to the characteristic three longitudinal stripes on the body.

ADDITIONAL MATERIAL.–A single specimen, BPBM 12122, male, 26.2 mm SL, from Efate, New Hebrides, is tentatively identified as E. trilineatus. This specimen differs somewhat in color pattern from that described for the typical specimens. Dusky spots are present anteriorly in the position of the two ventral body stripes. The spots intensify posteriorly and are similar to those in typical specimens. The two stripes on the pectoral fin base and the stripe on the opercle are only diffusely represented, but are identifiable. There is a narrow dusky stripe running most of the length of the dorsal fin just distal to the base of the fin, and there is a distal dusky edging on the rayed portion of the fin. Other markings and characters (meristic, proportional, qualitative) are closely similar to those of the typical specimens. In view of the differences noted I hestitate to designate this specimen as a paratype of E. trilineatus.

Ecsenius (Ecsenius) yaeyamaensis (Aoyagi)

Salarias yaeyamaensis Aoyagi, 1954, p. 213 [in part, Iriomote Island, Riukius].

DESCRIPTION.—Dorsal spines 12–13 (rarely 13); dorsal rays 13–15 (usually 15); segmented anal rays 15–17 (usually 16); pectoral rays 12–14 (rarely 12 or 14); segmented caudal rays 13 (14 in one of 120 specimens); dorsal procurrent caudal rays 6–9 (usually 7–8); ventral procurrent caudal rays 6–8 (usually 7); total caudal elements 25–30 (rarely 25 or 30); gill-rakers 11–16 (rarely 11 or 16); pseudobranchial filaments 5–8 (rarely 5 or 8); lower incisor teeth 43–56; lower jaw posterior canines 0–1 (usually 1); total lower jaw posterior canines 0–2 (usually 2); upper incisor teeth 97–127 (6 counts); precaudal vertebrae 10; caudal vertebrae 21–23 (usually 22); total vertebrae 31–33 (usually 32); epipleural ribs 11–14 (rarely 11); lateral line without paired pores, extending posteriorly to beneath level of 10th–12th dorsal spine (one specimen each, of 110, to 8th and 12th spine). Dorsal fin notched seven-ninths to eight-ninths length first dorsal ray (usually eight-ninths). Third (innermost) pelvic ray varying from obvious to not obvious (usually not obvious). One cirrus on each anterior nostril.

Color pattern: Aside from a complex and variable color pattern, E. yaeyamaensis comprises several geographic populations that are distinguishable only on color pattern. Although treated here as a separate species, E. nalolo may more properly be placed with E. yaeyamaensis. In contrast with the color pattern populations of E. yaeyamaensis, which are generally of limited geographic occurrence, E. nalolo occurs over most of the Indian Ocean and Red Sea with little noticeable geographic variation in color pattern.

The major feature of the color pattern that links all the populations of E. yaeyamaensis is a dark, forked stripe on the fleshy pectoral base. The arms of the stripe extend onto the bases of the fin rays; no other species of Ecsenius has such a mark. (E. nalolo has a single, unforked, stripe on the fleshy pectoral base.)

The commonest color pattern is best typified by that illustrated in Figure 27. This color pattern is found in specimens from the South China Sea, Taiwan, the Ryukyus, Palaus and adjacent islands, New Britain, and New Georgia. The illustrated specimen has a fully developed pattern. Other specimens from the localities just cited are quite variable and are allied by lacking specific features that are found in specimens from other localities.

Banda Sea: A single specimen is available (Figure 29), which has a pattern unlike that from any other locality. The distinctive features are two long, narrow, dark stripes on the body below the anterior dorsal rays, continuous as dark dashes and ultimately as four dark spots on the caudal peduncle. (A single, badly faded specimen of E. yaeyamaensis was available from Flores. Only faint remnants of the forked stripe on the pectoral base were visible. In view of the color pattern exhibited by the specimen from the Banda Sea, which is relatively close to Flores, it would be important to know what color pattern is exhibited by specimens of E. yaeyamaensis from the various islands surrounding the Banda Sea.)

New Hebrides: Three specimens (none illustrated), with two aligned, lengthwise rows of short, dark dashes on the body grading into spots below the posterior dorsal rays. If the dashes were to fuse anteriorly, they would form stripes as in the preceding form. The fact that the Banda Sea and the New Hebrides are quite distant from each other and that almost midway between these two localities, at New Britain and New Georgia, the common color pattern occurs, leads me to conclude that the populations are probably distinct.

Australia: All of a considerable number of specimens (not all cited in the material list) from the Capricorn group of islands at the southern end of the Great Barrier Reef and Endeavour Reef, off northern Queensland, exhibit numerous fine, dark spots on the posterior half of the body (Figure 28). These spots occur in at least two horizontally aligned rows, but there is usually a sprinkling of unaligned spots both above and between the rows. All of the specimens are larger than those from the New Hebrides and it may be that Australian specimens of sizes equal to those from the New Hebrides will be similar in color pattern.

Ecsenius (Ecsenius) yaeyamaensis (Aoyagi)

New locality records for this species are Madang Harbour, New Guinea (USNM 205706, 33.3 mm SL) and Ceylon (USNM 206381, 9 specimens, 21.9–33.4 mm SL; USNM 206382, 16 specimens, 28.547.0 mm SL; USNM 206383, 8 specimens, 24.6–31.4 mm SL; and several other uncataloged lots). Both the New Guinea and Ceylon specimens exhibit the most common color pattern for this species (Springer, 1971, fig. 27). Fin-ray, vertebral and tooth counts for these specimens are within the ranges of those I reported.

The Ceylon specimens are of interest because they represent the westernmost records of E. yaeyamaensis and the first records from the Indian Ocean. Ceylon is very near Addu Atoll, Maldive Islands, the easternmost known occurrence of the closely related E. nalolo. These two species are distinguishable only in that E. nalolo has a single dark stripe on the fleshy pectoral fin base and E. yaeyamaensis has a Y-shaped mark in the same area. There are no islands between Ceylon and the Maldives, where one might look for transitional populations. Inasmuch as only one specimen of E. nalolo is known from the Maldives, additional specimens from that area will be necessary to determine whether a transitional population exists. If so, E. nalolo should be recognized only as a subspecies of E. yaeyamaensis.

I (1971) reported a single specimen of E. yaeyamaensis from the Banda Sea. This specimen had a unique striped pattern (Springer, 1971, fig. 29) not found in the other specimens available to me. Additional material of this striped form from New Guinea, together with a sympatric specimen of E. yaeyamaensis with the typical color pattern, has caused me to re-examine the status of the striped form, which I describe below as a new species, E. trilineatus.

Ecsenius yaeyamaensis (Aoyagi)

New locality records for E. yaeyamaensis are given in “New Material.” All specimens in the list, including the Western Australian specimen, do not have the fine dark spots posteriorly on the body that are typical of specimens from the Great Barrier Reef, but instead have the common color pattern.

Springer (1971) reported three specimens of E. yaeyamaensis from New Hebrides with variant color patterns similar to that of the species he subsequently described as E. trilineatus. The recent collection of normally patterned E. yaeyamaensis from New Hebrides has prompted us to reassess the identification of the earlier specimens, and we find them to represent a new species, E. isos (see “Relationships” for E. isos).

NEW MATERIAL.—WESTERN AUSTRALIA. Dampier Archipelago, WAM P25107-021. INDONESIA. JAVA SEA: Seribu Islands, USNM 211994; Karimundjawa Islands, USNM 211981; Bawean Island, USNM 211974. CELEBES: Boeton (= Butung) Island, USNM 211967. MOLUCCAS: Ambon Island, BPBM 18051, USNM 209735; Haruku Island, USNM 209603; Saparua Island, USNM 211924. SOLOMON ISLANDS. Guadalcanal, AM I.17486-002; Florida Island, AM I.17497-002. NEW HEBRIDES. Efate Island, USNM 214819, BPBM 19577.

Ecsenius yaeyamaensis (Aoyagi)

Salarias yaeyamaensis Aoyagi, 1954:213 [in part, Iriomote Island, Riukius; holotype probably destroyed].

Ecsenius (Ecsenius) yaeyamaensis.—Springer, 1971:32 [in part]; Springer, 1972:2.

Ecsenius yaeyamaensis.—McKinney and Springer, 1976:23.

DESCRIPTION.—Dorsal fin XI–XIII,13–15 (rarely XI or XIII), deeply incised between spinous and segmented-ray portions. Anal fin II,14–17 (rarely 14 or 17). Pectoral fin 12 or 13 (rarely 12). Segmented caudal-fin rays 13. Vertebrae 10 + 21 to 23. Dentary incisor teeth (includes anterior canines, which differ little, if at all, in appearance from incisors) 41–53 in males and 44–55 in females, averaging more in females than males (Table 20); posterior canines 0 or 1 (usually 1). Lateral line without vertical pairs of pores, extending posteriorly to point between verticals from tenth and eleventh dorsal-fin spines. Cirrus present on posterior rim of anterior nostril; none present on anterior rim.

Preserved Color: The main features of the color pattern of E. yaeyamaensis are those of the group and are described in the account of the Yaeyamaensis Group. The color pattern of E. yaeyamaensis is mainly distinguished by its having a Y-shaped dark mark (arms of Y directed posteriorly) on the fleshy pectoral-fin base and fin and lacking a sparse peppering of fine dark spots on the posterior half of the body. Of all the material examined, one specimen, of 21, from Tioman Island, Malaysia, had a single stripe on the fleshy pectoral-fin base on both sides, and might be confused with E. nalolo or E. dentex. In this specimen, however, the stripe enters the fins along the sixth from dorsalmost ray on one side and between the sixth and seventh rays on the other side. In E. nalolo and E. dentex the stripe enters the fin between the fifth and sixth rays. The cheeks below the level of the mid-postorbital stripe are never peppered with fine, dark spots. There is a wide gap between the dorsal end of the dark, ventroanteriorly curving opercular line and the extension of the mid-postorbital stripe at the dorsal margin of the opercle (the stripe may be interrupted and appear as an isolated spot above the opercle). The abdominal flanks may have one or two dark spots, but these are not particularly conspicuous.

Live Color (based on live and freshly killed specimens): Allen (1985, fig. 379) published a color photograph of a fresh specimen from Western Australia. In this specimen the dark pigments of the head and body are shades of brown (mid-postorbital and pectoral-fin base stripes are almost black). The upper half of the eye is much darker than the lower half, and the iris has eight evenly spaced spokes, with a perimetric pale spot in each space between spokes. The dark mid-postorbital stripe is margined dorsally by a diffuse, fine, pale stripe, and ventrally by a brighter pale stripe of lesser depth than the mid-postorbital stripe. This latter pale stripe, which is margined ventrally by a fine, brown pinstripe, expands and becomes less definite on the opercle and as it extends onto the body. The dark opercular line is dusky and obvious only on the pale ventral surface of the head.

The color pattern of the Western Australian specimen is scarcely different from that of one from the Solomon Islands (Plate 9: figure 3), but the dark line on the opercle is obvious in the latter.

In a color photograph (Plate 9: figure 1) of a living specimen from Sri Lanka, the pale brown markings on the body ventroanteriorly are suffused with yellow, and dorsally, particularly on the head, the markings have pinkish overtones; the Y-shaped mark on the pectoral-fin base is yellow brown, rather than blackish as in preserved specimens, and other markings on the abdominal flank are also yellow brown; there is no noticeable dark curving line on the opercle. Finally, a live specimen (Plate 9: figure 2) from Palau is pallid with a highly contrasting dark opercular line and two dark, dash-like spots posterodorsally on the head.

DISTRIBUTION.—Ceylon east to the southern Ryukyus, Sorol Island (Carolines), and south to New Hebrides.

MATERIAL (* = new material).—Ceylon: USNM 206381 (9 specimens: 22–33 mm SL), 206382 (16:28–47), 206383 (8:25–31). Malaysia: Tioman Island, BPBM 21981* (21:24–36). Taiwan: USNM 203133 (1:35), 203134 (2:38, 39), 203135 (1:42), 203136 (2:40, 43), 203137 (10:26–49), 203138 (4: 38–42). Philippine Islands: Luzon, USNM 225051 (6:23–36)*; Siquijor, USNM 227538* (1:36); Palawan, USNM 222138* (1:33); Cuyo Islands, USNM 219312* (9:27–48)), 227539* (1:36), 227540* (1:30). Viet Nam: CAS 24487 (1:39). Caroline Islands: Palau, CAS 24462 (1:46), 24463 (11:32–43), 24468 (2:25, 30), 24470 (1:40), 24471 (4:30–39), 24475 (6:32–44), 24479 (1:46), 24480 (1:42); Sorol, CAS 24474 (1:32); Yap, USNM 24466 (9:26–52), 24473 (11: 22–34), 24481 (4:29–35), 24482 (1:25), 24483 (1:36.7), 24484 (2:34, 40), 24485 (1:32), 24486 (1:38). Indonesia: Seribu Islands, USNM 211994 (1:30); Karimundjawa, USNM 211981.(1:30); Bawean, USNM 211974 (5:20–24); Boeton, USNM 211967 (2:15, 40); Ambon, USNM 209735 (5:33–40), BPBM 18051 (1:not measured); Haruku, USNM 202381 (14: 13–33), 209603 (14:12–33); Saparua, USNM 211924 (50: 14–42); Flores, ZMA 109.100 (1:33). Papua-New Guinea: Madang, USNM 205706 (1:33); Basilaki Island, USNM 217564* (1:34); Watts Island, CAS 56578* (1:38) Muschu Island, USNM 221240* (13:26–41); Ninigo Islands, USNM 222968* (7:14–34), 227541* (2:24, 37), 227542* (1:38); Hermit Islands, USNM 222543* (1:29), 227544* (1:14), 227545* (3:14–28), 222546* (2:27, 32), 227547* (2:26, 32); New Britain, USNM 200428 (3:38–39, including one cleared and stained), 201812 (1:32). Solomon Islands: Bougainville, USNM 201824 (2:30, 40); Guadalcanal, AMS I.17486-002 (10:not measured); Florida Island, AMS I.17497-002. New Hebrides: Efate, USNM 214819 (2:35, 42), BPBM 19577 (2: not measured). Australia: Western Austalia, Dirk Hartog Island, WAM P.27970-024*, in part (1:37); Northwest Cape area, AMS 19641-015* (2:32, 38), AMNH 33982* (11: 20–41); Montebello Islands, NTM S. 10805-009* (34–48), S.10808-004* (6:22–39); Dampier Archipelago, NTM S.10809-008* (1:32), S.10814-005* (11:26–38); Northern Territory, Gove Peninsula, AMS 21963-019* (9:19–42).

OPSIFRONTALIS GROUP

This group comprises nine species: E. alleni, E. australianus, E. axelrodi, E. bathi, E. dilemma, E. fijiensis, E. fourmanoiri, E. opsifrontalis, and E. tigris.

The synapomorphies that I hypothesize as uniting the species as a monophyletic group are manifested primarily by living or freshly dead specimens: the presence on the body of pinkish to reddish to brownish-orange stripes and/or bands in at least one color-pattern form of each species. These colors may be obscured by blackish stripes and/or bands in darkly-pigmented forms, but indications of the orange pigment usually persist.

Three species of the Opsifrontalis Group (E. axelrodi, E. bathi, E. dilemma) have two markedly different color-pattern types, striped and banded, which I propose is a synapomorphy for these species within the Opsifrontalis Group. All the other species in the group have but one type pattern. In the three species with two patterns, the striped form lacks the orange pigment. None of the species in the other species groups of Ecsenius have live coloration similar to that of the Opsifrontalis Group. In the two non-Opsifrontalis Group species (E. frontalis, E. bicolor) with more than one type pattern and which have a striped pattern, the stripe is poorly developed and markedly different in appearance from that of the Opsifrontalis Group. Furthermore, neither of these two species exhibits a banded pattern.

In preserved specimens, the basic color pattern of the Opsifrontalis Group is one composed of two dark or dusky stripes on the body (the dorsalmore originating at the mid-postorbital margin) crossed by several dark or dusky bands (a third, less distinct stripe may be present on the dorsal body contour). The stripes and bands are present in the same relative positions on the body in all the species. The basic striped and banded pattern is not present in other Ecsenius species.

The manifestations of the stripes and bands, whether uninterrupted or broken into spots, faint or intensely dark, present as two forms within a species, or other variations, usually are the main characters that define the species and clusters of species in the group. Two other color-pattern characters, which are not synapomorphies, typify the group: a dark stripe, margined dorsally and ventrally by fine pale stripes, extending posteriorly from the midpostorbital margin, and extensions of the body stripes onto the caudal fin. The postorbital stripe may be very faint in preserved specimens, but is usually noticeable in living or freshly collected specimens. The caudal extensions of the stripes may also be faint or even absent in species with both banded and striped forms.

Additional, non-synapomorphic characters defining the group are relatively small size, a deeply notched dorsal fin, and relatively low counts for fin-rays and dentary incisors. The species all lack a dark spot anterior to the anus, pale or dark spots on the ventral head surface (such as define the Prooculis group), a reddish-orange spot on the chin, and multiple posterior dentary canines, which are useful in defining other species groups of Ecsenius.

I have been unable to present a reasonable hypothesis of the sister-group relationships of the Opsifrontalis Group, and I have no intuitive opinion of what they might be, other than that they lie among those groups with deeply notched dorsal fins, low meristics, and dark postorbital stripes.

I also have been unable to hypothesize reasonably a complete set of interrelationships of the species within the group, although I have proposed some probable relationships in discussions under individual species accounts. I have hypothesized some partial vicariance scenarios that might explain the distributions of some of the related species (see under account of E. australianus).

DISTRIBUTION.—The Opsifrontalis Group species are all allopatric. There are extensive expanses of ocean lacking islands and reefs that separate various populations of a particular species of the Opsifrontalis Group. On the other hand, a species may occur at an island closely adjacent to another island inhabited by a different species of the group, indicating to me that simple dispersal cannot account for the distributions of the individual species.

The distributions of E. fourmanoiri, E. fijiensis, and E. opsifrontalis (Figure 40) relative to each other, and E. australianus and E. tigris (Figure 41) relative to each other, are probably indicative of how sharply defined are the distributions of the species of the Opsifrontalis Group.

Ecsenius fijiensis has been collected only from the reefs of the closely spaced islands of Fiji. Most of these reefs are quite close to one another reef; they are often separated by much less than 50 km. The most isolated reef, Vatoa, where E. fijiensis occurs is about 60 km (south) from the nearest neighboring reef. The closest known occurrence of E. fourmanoiri to E. fijiensis is at Ono-i-Lau, which is about 85 km south of Vatoa. There are no reefs between Ono-i-Lau and Vatoa. The significance of this narrow gap between the ranges of the two species is emphasized by the fact that, aside from Vatoa to the north and two small islets (Tuvana Itholo, Tuvana Ira) less than 40 km to the south of Ono-i-Lau, the closest reefs to Ono-i-Lau, other than the closely-spaced islands of Fiji (inhabited by E. fijiensis), are the Minerva Reefs (about 350 km south), the Tonga Islands (nearest about 350 km east), and Theva-i-Ra (= Conway Reef, about 500 km west). Ecsenius fourmanoiri occurs in the Tonga Islands (Tongatapu), but is unknown at the Tuvanas, Minerva Reefs, and Theva-i-Ra (no species of Ecsenius is known from these islands, of which only Minerva has ever been the subject of collecting). The nearest locality inhabited by E. fourmanoiri to the west of Ono-i-Lau is southeastern New Caledonia, about 1500 km distant. There are, however, some reefs punctuating the area between New Caledonia and Theva-i-Ra, and I predict that if a species of the Opsifrontalis Group occurs at any of those islands, the Tuvanas, Minerva Reefs, or Ceva-i-Ra, it will be E. fourmanoiri or a species yet unknown.

Ecsenius opsifrontalis is widely distributed among the islands of the Pacific Plate and eastern margin of the Philippine Plate. In the vicinity of Fiji, it has been taken only at Tutuila (American Samoa) and Rotuma. Rotuma is about 400 km north of Fiji (but uncollected Balmoral Reef, about 125 km northwest of Fiji and 350 km south of Rotuma, is a stepping-stone between them), and Tutuila is somewhat further northeast. However, it is possible to chart a stepping-stone route from Rotuma to Samoa with no stepping-stone separated from another by more than about 125 km (most much less), and from Samoa to Fiji or Tongatapu with no stepping-stone separated from another by more than 100 km (most much less). If simple dispersal explained the distribution patterns exhibited by the Opsifrontalis Group species, it would seem that some combination of E. fijiensis, E. foumanoiri, and E. opsifrontalis would either occur together at several localities in the vicinity of Fiji, or else there would be a mosaic of distributions of the three species. Instead, each of the species exhibits a cohesive distribution.

Ecsenius opsifrontalis also occurs at some localities that are either relatively close to, or connected by closely spaced stepping-stone islands to, localities where E. axelrodi occurs. If dispersal is an important factor in the distribution of the Opsifrontalis Group species, one can wonder why only E. opsifrontalis occurs at Pacific Plate islands, and why it is restricted to those islands (and islands along the bordering eastern margin of the Philippine Plate).

There are several islandless and reefless gaps of lengths greater than 100 km among the islands of the Pacific Plate surrounded by the known occurrences of E. opsifrontalis. It would be of considerable interest to determine if E. opsifrontalis or some other species of the Opsifrontalis Group occurs at these “isolated” islands, for example, Nauru and Ocean islands. Indeed, there are other islands and chains of islands, for example, New Hebrides and Santa Cruz (see Figure 40), isolated by gaps of more than 100 km from the nearest locality that might be expected to harbor a species of the Opsifrontalis Group, but from which no specimens of the Group are known. All of these localities would be of importance to collect in order to reach a better understanding of the factors that resulted in the present distribution of the Group.

As for the distributions of three species discussed above, it is instructive to note the circumstances of the distributions of E. australianus and E. tigris (Figure 41). Ecsenius australianus occurs only on the northern Great Barrier reef. Ecsenius tigris is known only from the northernmost reefs of the Coral Sea Islands Territory of Australia, offshore of the Great Barrier Reef (Figure 41). The Coral Sea reefs rest on ocean bottom that comprises the Queensland Plateau (Kroenke et al., 1983; Kroenke, 1984, figure 8.1). The Queensland Plateau was once continuous with the Lord Howe Rise (Coleman, 1980:110, fig. 5; Kroenke, 1987, pers. comm.), which rise was rifted from the east coast of Australian Gondwana (Coleman, 1980, fig. 2) about 80–100 m.y.a. The Queensland Plateau appears always to have been adjacent to the coast of Australia, although the narrow Queensland and Townsville troughs separate the Plateau from the coastal Great Barrier Reef of Australia. I infer from this topography that the Plateau was rifted from the coast of Australia even though its distancing has not been great. This history might make it seem likely that E. tigris and E. australianus arose from a common ancestor whose distribution was split by the rifting. I hypothesize, however, that E. australianus is the sister group of E. fourmanoiri (see “Comparisons” and “Remarks” sections under E. australianus). The sister group of E. tigris is undecided, but there is evidence, perhaps, that it is either E. fijiensis or the clade of three species, including E. axelrodi, that exhibit two different color pattern types (see “Comparisons” and “Remarks” sections under E. tigris).

All the reefs in the Coral Sea that might possibly harbor E. tigris are shown in Figure 41. Ecsenius tigris is known only from three of the four northernmost reefs (Shark Reef, almost continuous with northernmost Osprey Reef, has not been sampled, but it would appear certain that E. tigris occurs there). The distance between Shark Reef and Bougainville Reef, the next nearest Coral Sea reef, and one where E. tigris occurs (documented in photographs), is approximately 160 km, whereas the closest reefs on the Australian coast, where E. australianus exists or can be expected, are only about 140 km from Osprey Reef. If E. tigris occurs at the Flinders Reefs (next reefs SSE of Holmes Reef, where E. tigris has also been photographed but not collected), the distance from the nearest reefs on the Great Barrier Reef would only be about 120 km. The distribution of E. australianus, however, is not known to occur as far south as the latitude of Flinders Reefs.

The point of the present discussion is that populations of E. tigris are isolated from their closest conspecifics by distances greater than those that isolate them from populations of another species in the same species group. Such circumstances seem to indicate limited dispersal ability, and that, together with the fact that the species distributions correspond with geological features, leads me to believe that the distributions are reflective of vicariance events, even though there is inadequate information on which to formulate these events.

分布於印度-西太平洋區，由斯里蘭卡至萬那杜，北至日本、台灣。台灣分布於南部、東部、綠島、蘭嶼及小琉球等海域。

小型魚類，色彩豔麗，是受歡迎的水族用魚。

體延長，稍側扁，似圓柱狀；頭鈍短。前鼻孔具1鼻鬚；無眼上鬚及頸鬚。上頜齒可活動，齒骨後方具犬齒0-1。側線無成對側線孔。D. XII-XIII, 13-15；A. II, 15-17；P. 2-14；V. I, 3。背鰭具缺刻背鰭、臀鰭最後軟條與尾柄以鰭膜相連；尾鰭鰭條均不分枝。體淡褐色；體側散布許多大小不一之淡圓斑；另具4條暗色縱帶，上方兩條延伸至眼部後緣，或間斷呈連續短紋或短斑，而下方兩條於胸鰭基部癒合而成平躺之Y型紋。頰部下緣另具一暗弧紋。以前所記錄之斑點無鬚鳚(/Ecsenius stictus/)為本種之誤鑑。

主要棲息於沿岸礁石區，常出現於活珊瑚繁生之區域。以藻類及碎屑為食。

Ecsenius yaeyamaensis, known commonly as the Yaeyama blenny in Guam and Micronesia, and also known as the Yaeyama clown blenny in Micronesia, or the Pale-spotted combtooth-blenny in Indonesia is a species of combtooth blenny in the genus Ecsenius. It is found in coral reefs in the western Pacific and Indian oceans. It can reach a maximum length of 6 centimetres. Blennies in this species feed primarily off of plants, including benthic algae and weeds, and are commercial aquarium fish.