Gobiopsis exigua Lachner & McKinney 1979

Gobiopsis exigua

HOLOTYPE.—AMS I.18052–004, female, 41.5 mm SL, from Gilbert Islands, Abiang Atoll, Leeward Reef crest, 1/2 mi N of southern end of atoll, D. F. Hoese Sta 73–51, 11 Nov 1973.

PARATYPES.—AMS 1.18052–005, female, 34.8 mm SL, taken with holotype; USNM 216209, male, 33.4 mm SL, female, 37.0 mm SL, taken with holotype; BPBM 11373, gravid female, 40.2 mm SL, Fiji Islands, Viti Levu, Rat-Tail Pass, collected by J. E. Randall, 7 Aug 1971; BPBM 20320, female, 32.3 mm SL, Fiji Islands, outside Mbengga barrier reef, near E end of Frigate Passage, J. E. Randall Sta 25, 11 Mar 1973; ANSP 134776, female, 25.6 mm SL, Amirantes Islands, Remire Reef, NE of Eagle Island, J. E. Böhlke Sta F-82, 4 Mar 1964; CAS 33610, female, 32.6 mm SL, Grand Comore Island, N of Hotel Itsandra, in front of “Coelacanth Grotto,” 50 m from shore, J. E. McCosker Sta 75–17, 19 Feb 1975.

DIAGNOSIS.—Cephalic sensory pores present, anterior interorbital pore (AITO) present, IT pore absent; head barbels reduced in number and size, one on each side of chin, a pair on snout; outer preoperculo-mandibular row of papillae ascends on posterior portion of preopercle; postorbital row of papillae long; fleshy cheek fold reduced; interorbital narrow; dark mark at base of pectoral fin small, indistinct; anal rays I,10.

DESCRIPTION.—Dorsal fin rays VI—I, 10 (img), VI–I, 11 (1); anal rays I,10 (8); pectoral rays 18(1), 19(img), 20(6); pelvic rays 1,5 (5); segmented caudal rays 17 (8); branched caudal rays 15 (4), 16 (3), 17 (1); lateral scale rows 30–37 (8); transverse scale rows 13–17 (8); predorsal scales 11–17 (7).

Scales cycloid, eccentric, narrow focus, primary radii in anterior fields 4–5, secondary radii 1–2, no radii in posterior field.

Gill rakers of first gill arch short, stout, about 10 on lower limb, 3 on upper limb.

Vertebrae 10+16 (img); pterygiophore formula 3 (22110); neural and haemal spines of PU2 narrow and spinelike.

Measurements of features of the head and trunk for the holotype and a male and female paratype are given in Table 1.

Physiognomy of the head and trunk similar to that of G. springeri.

Tongue slightly bilobed, the tip free; pectoral fin pointed, the posterior margin typically reaching vertical through anterior margin of anal aperture; pelvic fin moderate in length, 67–75 percent of distance from pelvic fin insertion to anal fin origin; pelvic frenum fairly well developed, inner pelvic rays connected nearly to tips by membrane; first dorsal fin slightly higher than second dorsal; first dorsal fin distinctly free from second dorsal fin; caudal fin rounded or slightly pointly, longer than deep, shorter than head length.

Scales somewhat crowded anteriorly on trunk, absent on cheek and opercle, present on breast, nape, and anteriorly nearly to eyes.

Genital papilla of male short, round, and tapers to point; papilla in female short, bulbous.

Teeth of upper jaw consisting of an outer row of enlarged caninoids, longer than the spaces between them, numbering about 25–30 across jaw; moderate to broad patch of villiform teeth behind outer row; inner row behind villiform patch consists of slightly posteriorly recurved caninoids, smaller than those of outer row, about 20 across jaw. Teeth of lower jaw composed of outer row of enlarged caninoids, longer than spaces between them, numbering about 7–10, extending only across anterior half of jaw; moderate villiform patch extending over entire jaw posterior to outer row; near inner border of villiform patch is a row of small caninoids, slightly recurved posteriorly, less than one-half length of those in outer row and numbering about 16–20 across jaw. No vomerine or palatine teeth.

The following sensory pores present on all specimens: NA, AITO, PITO, SOT, and AOT. The pores are moderate in size and round, lacking flaps, not at end of tubes and none margined by dense, dark pigment.

Barbels on chin short, stumplike, I on each side; 2 simple anterior internasal barbels; barbels of cheek tuft reduced to 3 enlarged papillae-like structures.

The cutaneous papillae system (Figure 4) is conspicuous and resembles rather closely that of G. springeri but differs as follows: papillae on inner preoperculo-mandibular row not as elongate; the vertical portion of outer preoperculo-mandibular row located more posteriorly; nasal row reduced to a few papillae on snout.

Cheek fold as in G. springeri.

COLOR IN PRESERVATION.—Top of head and predorsal area of body with 3 brown transverse bands, the anterior one widest and separated from eyes, extending laterally onto upper preopercle and opercle; the second band extends laterally to margin of upper opercle; the third band extends laterally to level of upper pectoral fin insertion and also passes posteriorly, joining dorsolaterally with the anterior saddle of the first dorsal fin. First dorsal saddle passes through spines 1–4, extends ventrally on body and coalesces with a brown, vertically oblong lateral spot beneath pectoral fin. Second dorsal saddle passes through end of first dorsal fin; third dorsal saddle passes through rays 1–4 of second dorsal fin; fourth saddle passes through rays 6–8 of second dorsal fin; fifth saddle, smaller than others, passes over caudal peduncle at end of second dorsal fin; sixth saddle, about equal in size to fifth saddle, passes over end of peduncle at origin of dorsal procurrent caudal rays. Saddles 2–6 do not join lateral spots on body on Pacific specimens but do so on Indian Ocean specimens. Posterior to spot beneath pectoral fin are 7 brown spots, mostly deeper than wide, on middle or ventrolateral region of trunk, the anterior ones larger and more intense than those on peduncle. Area between saddles and spots weakly mottled.

Midsnout area before eyes, area above rictus and midcheek with scattered brown pigment. An oblique, faint brown bar from eye downward and posteriorly to midpreopercle. Lower head, belly, and lower peduncle uniformly light.

First and second dorsal fin elements most heavily pigmented basally where saddles occur; some fine spots, linearly arranged in 2 rows, mainly on second dorsal fin, on proximal half of rays. A weakly pigmented brown bar basally on caudal fin rays; scattered brown pigment farther out on fin rays on Indian Ocean material. Upper base of pectoral fin with a diffuse spot or blotch of scattered chromatophores, mostly on rays. Remainder of fins clear.

GEOGRAPHIC DISTRIBUTION.—Known from four localities in two widely disjunct regions, the Gilbert and Fiji Islands, Pacific Ocean, and the Comores and Amirantes Islands, western Indian Ocean.

ECOLOGY.—Specimens were captured from surface waters to depths of 22 m. A specimen from Fiji was taken near a vertical reef front over a bottom of rubble and coarse sand.

ETYMOLOGY.—The specific name is from the Latin exiguus, meaning “little,” “short,” or “scanty,” and refers to the short, poorly developed head barbels.

Gobiopsis exigua is a species of goby of the genus Gobiopsis found in the Western Central Pacific Ocean.