Blackfin Dwarfgoby

Eviota nigripinna

MATERIAL EXAMINED.—206 specimens from 5 localities in the Indian Ocean, totaling 50 males, 58 females, 98 juveniles; total size range 8.6–14.0; largest male 14.0, largest female 13.9; smallest gravid female 12.0.

Holotype: USNM 213929, (12.5), male; Agalega Is., North I., 17 Apr 1976, V. G. Springer, 76–24.

Paratypes: COMORES ISLANDS: GRAND COMORE ISLAND (collected by J. E. McCosker in 1975): CAS 33436, 7 (10.5–13.4), 2 males (12.2), 5 females (13.4); 1 Mar, 75-29. USNM 213919, 1 (13.0), male; 9 Feb, 75-4. CAS 43536, 5 (9.3–13.4), 2 juv., 2 males (13.4), 1 female (12.2); 15 Feb, 75-11. AGALEGA ISLANDS: NORTH ISLAND (collected by V. G. Springer in 1976): USNM 213925, 93 (8.6–14.0), 68 juv., 11 males (14.0), 14 females (13.7); 17 Apr, 76-24. USNM 213926, 6 (13.0–13.9), females; 18 Apr, 76-26. USNM 213927, 1 (13.1), female; 19 Apr, 76-28. USNM 213928, 74 (9.5–13.0), 28 juv., 22 males (13.0), 24 females (12.5); 19 Apr, 76-29. ANSP 141139, 5 (11.4–13.2), 3 males (13.2), 2 females (12.2); same as above. AMS I.20801-001, 5 (11.4–12.6), 3 males (12.6), 2 females (12.3); same as above. MAURITIUS: RUSI 1963, 1 (11.7), male; La Preneuse, 8 Mar 1971, T. H. Fraser, THF-SA-31. REUNION: BPBM 16285, 1 (ca. 12.4), male; Cap Houssaye, 27 Oct 1973, J. E. Randall. CHAGAS ARCHIPELAGO: DIEGO GARCIA ATOLL (collected by H. A. Fehlmann in 1967): USNM 213902, 1 (10.9), male; 9 Jul, 67-38. USNM 213903, 3 (12.4–13.5), females; 23 Jul, 67-51. USNM 213904, 2 (11.8, 12.1), males; 27 Jun, 67-20.

DIAGNOSIS.—Eleventh through the fifteenth pectoral fin rays always branched; spinous dorsal fin not elongate; pelvic fin moderate in length, almost always not extending to anal fin origin; pelvic fin rays I,4, never a rudimentary fifth ray; subcutaneous dark caudal peduncle spot large and centrally located; first dorsal fin black; transverse bars dorsally on head and nape straight, almost never broken into spots, the margins of the bars darker than internal area.

DESCRIPTION.—Dorsal fin VI-I,8 (19), VI-I,9(3); anal fin I,8 (22), I,9(1); pectoral fin 15(1), 16(9), 17(2), 18(1); pelvic fin I,4 (23); fourth ray of pelvic fin averages 8 branches; segments between consecutive branches of the fourth pelvic fin ray mostly 1; pelvic fin membrane reduced; branched caudal fin rays 11(3), 12(9), 13(3); segmented caudal fin rays 17 (22); lateral scale rows 22(2), 23(5), 24(1); transverse scale rows 5(3), 6(5). Scales with 16–23 ctenii, 10–14 radii; breast scaleless. Most specimens devoid of scales, apparently scales highly deciduous.

Spinous dorsal fin not elongate; pelvic fin moderate in length, usually reaching anal aperture, rarely to anal fin origin.

Cephalic sensory pore system is pattern 1. Cutaneous papilla system is pattern A, although poorly developed in most specimens.

Genital papilla in male not fimbriate, broad, flat, slightly tapered and fringed at tip; female papilla short, bulbous, with 4–8 fingerlike projections at tip.

Gravid females range in length from 12.0 to 13.0 mm SL (3).

Vertebrae 10 (21) precaudal and 16 (20), 17(1) caudal, total 26 (20), 27(1).

COLOR IN PRESERVATION.—Males: Head with large, dark chromatophores on cheek and preopercle, usually scattered but sometimes arranged in a pattern approaching marks in E. nebulosa; opercle with finer and less dense dark chromatophores; head dorsally and nape with well-defined transverse bars, the borders of which are heavily pigmented with large, dark chromatophores, the interiors of the bars with finer, less dense chromatophores or lacking pigmentation, and the spaces between the bars usually without pigmentation, bars immediately behind eyes may be irregular, divided into 2 or 3 short bars or disassociated forming a patch of large chromatophores; bars or clear interspaces transgress onto upper pectoral base, resulting in a light area margined sometimes by dark chromatophores; the bars also transcend onto the dorsolateral trunk region forming a pattern that consists of light V-shaped areas descending from the dorsal midline to the dorsolateral area and continue posteriorly, but less defined, to the end of the second dorsal fin; the margins of the V-marks with heavier, dark chromatophores; remainder of trunk laterally and sometimes pectoral base with fine, dense, pale to brown pigmentation; ventral midline with 5 small, dark, subcutaneous spots from the origin of the anal fin to end of caudal peduncle, the fifth spot often connected with the central peduncle spot; same area of trunk with 4 subcutaneous bars on upper trunk and 5 below, the fourth lower bar sometimes rudimentary; a large, dark, mostly subcutaneous spot on midcaudal peduncle, anterior to base of caudal fin; caudal spot usually deeper than wide, its depth equal to or greater than one-half depth of peduncle, spot sometimes obscure; pectoral rays bordered with a fine line of dark chromatophores, sometimes line broken into fine spots, membrane clear; pelvic fin clear; membrane of first dorsal fin dense blackish, the spines clear; second dorsal fin dusky with fine dark chromatophores on membrane, rays clear; anal fin pale to light dusky, the basal portion usually with fine, dark pigmentation, the outer portion clear; caudal fin mostly clear with some fine scattered chromatophores.

Dark pigmentation usually reduced in females, resulting in a pale-colored body compared to males. Spinous dorsal fin as in males or with pigmentation reduced to a dark border, in some entirely lacking; pigmentation on second dorsal and anal fins reduced or fins clear; predorsal transverse bars less intensely developed; trunk coloration pale, lacking uniform brownish of males.

GEOGRAPHIC DISTRIBUTION.—Known from 5 small, insular localities in the Indian Ocean (Figure 15).

ETYMOLOGY.—The specific name nigripinna is from the Latin nigra (black) plus pinna (fin) and is in reference to the black first dorsal fin.