Eviota rubriceps, Greenfield, David W. & Jewett, Susan L., 2011

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 : 54-59

Eviota rubriceps n. sp.

Red-headed warfgoby

Eviota sp. 3. Kuiter & Tonozuka, 2001: 699.

Eviota sp. 1. Allen & Erdmann, 2009: 617.

Eviota Raja Ampat sp. 1. Dimara et al., 2010 (pg. 21, Fig. 2 I).

Holotype: CAS 233447, 13.5 mm, male, Indonesia, Raja Ampat Islands, Waisilip, West Waigeo Island, 0 0.2582°S, 130.3575°E, 3–6 m, clove oil, M. V. Erdmann, 28 August 2010.

Paratypes: Papua New Guinea: USNM 222548, 13.1 mm, male, Bismark Archipelago, Ninigo Islands, S.E. of Ami Island, 0 1.2333°S, 144.3667°E, 0–9.1 m, patch reef, rotenone, field number VGS78-3, V.G. Springer, et al., 23 October 1978. Indonesia: USNM 222550, 10.0 & 11.5 mm, males, Banda Islands, Gunung Api, 0 4.5361°S, 129.8861°E, 0–3 m, coral rubble, rotenone, field number VGS74-8, V.G. Springer & M. Gomon, 7 March 1974; USNM 209978, 4 males, 10.2–11.5 mm, 12.7 mm female, Saparua, ca. 0 3.5528°S, 128.9194°E, isolated coral head, rotenone, field number VGS73-14, V.G. Springer & M. Gomon, 18 January 1973; ROM 85198, 11.9 mm, male, Indonesia, Raja Ampat Islands, Waisilip, Waigeo Island, 0 0.2612°S, 130.3561°E, Porites patch reef, 3–5 m, clove oil, field number RW10-24A, M. V. Erdmann, 29 January 2010; CAS 233448, 10.6 mm, male, 10.7 & 10.8 mm females, taken with holotype; ROM 88204, 10.8 & 11.8 mm females, taken with holotype; WAM P.3353-001, 10.0 mm male, four females 8.5–10.8 mm, Indonesia, Maluku, Banda Islands, Banda Harbor, 0 4.5075°S, 129.8808°E, 5 m, clove oil, M.V. Erdmann & G.R. Allen, 28 October 2010; BPBM 41076, five females 8.9–10.7 mm, taken with WAM P.3353-001; MZB 20024, four females 8.0– 10.7 mm, taken with WAM P.3353-001.

Non-types: USNM 222549, 12.7 mm, male, Philippine Islands, Palawan Province, N. N-E. side of Bararin Island (Cuyo Island), 10.8783°N, 120.9456°E, 0–17.4 m, coral, rotenone,, field number SP78-21, L. Knapp, V. Springer, J. Libbey, 24 May, 1978; CAS 233449, 11 females 7.8–8.9 mm, taken with WAM P.3353-001.

Diagnosis. The following combination of characters distinguish E. rubriceps from congeners: cephalic sensory-pore system pattern 2 (only IT pore missing); dorsal/anal fin-ray formula almost always 8/7; pectoral-fin rays unbranched; first three dorsal spines may be filamentous in males; 5th pelvic-fin ray absent or rudimentary to 20% maximum of 4th ray; strong black pigment along scale pockets on ventral two-thirds of sides and peppering of dark chromatophores on nape and upper back when preserved; snout, top and sides of head red in life; dark area of abdomen not crossed by a curved yellow-gold line in life.

Description. Dorsal-fin rays VI-I,8; anal-fin rays I,7 (26), I,8 (3); pectoral-fin rays 15 (14–16, usually 15), rays not branched; pelvic fin I,4 (I,4+ a rudiment to 20%); branches on 4th pelvic-fin ray 5 (3–5), 2 (2–6) segments between branches; 11 branched caudal-fin rays; segmented caudal-fin rays 17; lateral scale rows 24 (21–24); transverse scale rows 6; breast and pectoral-fin base scaleless; first three dorsal spines may be filamentous in males, the second spine longest, reaching to end of second dorsal-fin base; depressed pelvic fin always extends beyond analfin origin; cephalic sensory-pore system pattern 2 (only IT missing); male genital papilla non-fimbriate; precaudal vertebrae 10, caudal vertebrae 15, total 25.

Measurements (based on holotype and 14 paratypes, 10.1–13.5 mm). head length 31.8 (29.5–33.3, 31.2); origin of first dorsal fin 33.7 (32.4–39.0, 35.9); origin of second dorsal fin 55.5 (54.8–59.5, 56.7); origin of anal fin 58.5 (55.2–62.7, 59.5); caudal-peduncle length 24.4 (16.9–29.0, 23.8); caudal-peduncle depth 11.8 (9.1–12.7, 10.9); body depth 22.2 (17.8–23.8, 21.7); eye diameter 8.5 (8.5–11.3, 10.3); snout length 4.4 (2.8–4.7, 3.8); upperjaw length 10.7 (7.6–13.7, 9.9); pectoral-fin length 22.2 (22.2–33.6, 29.9); pelvic-fin length 31.1 (23.3–40.6, 33.2).

Color of preserved specimens ( Fig. 1 ). The characteristic color pattern consists of dark pigmentation on the lower two-thirds of the body, pale coloration on the dorsal portion of nape and upper one-third of body but with a peppering of dark chromatophores, and obliquely arranged dark subcutaneous bars on lower caudal peduncle. The coloration of the holotype, as shown in Fig.1 , is typical of the species except for the subcutaneous bars that are indistinct on this specimen. The salient color characters of the species are the fine, dense brown chromatophores on snout, laterally on head, on pectoral-fin base, and present on lower two-thirds of body. The scale pockets are typically pronounced, pigmented with a narrow to wide margin of dark chromatophores, the pattern becoming less intense posteriorly; lower two-thirds of body also with dusky subcutaneous shading; upper third of body and dorsalmost portion of nape pale, but with a peppering of dark chromatophores. About five dark oblique subcutaneous bars directed upward and forward from faint spots along lower margin of caudal peduncle to just above midline of body and may or may not be in line with, but separated from, small dark subcutaneous spots dorsally along caudal peduncle and beneath second dorsal fin, spots often obscure ( Fig. 2 ).

Lower portion of first dorsal fin with narrow to wide dusky pigmentation, outer portion pale, the filamentous spines with tiny spots formed by fine dark chromatophores. Second dorsal fin dusky throughout, more intense basally. Anal fin similar to second dorsal fin. Caudal fin dusky but paler than dorsal and anal fins, some specimens with heavier irregular pigmentation on fin, especially basally. Pectoral and pelvic fins pale.

Color in life ( Figs. 3–4 ). Body translucent white. A black band running from behind head to caudal-fin base. Band widest over abdomen, slightly above midline down to lower portion of belly, narrowing posteriorly to vertebral column with six obvious black lines extending ventrally along posterior half of body. Black band over abdomen sprinkled with tiny gold flecks. Brown scale edges over white background extending above band to dorsal-fin bases. A peppering of dark chromatophores on nape. Head and snout from level of ventral eye margin dorsally reddish. Upper and tip of lower lip reddish. Lower part of head below eye white, extending posteriorly along belly to caudal-fin base. Top of head with a narrow white line from between eyes posteriorly to nape. Fins translucent white with redish bands across first dorsal fin. Two rows of small red dots running along bases of second dorsal and anal fins. Membranes with a peppering of fine dark chromatophores. Pupil and iris of eye black, often with a narrow white line running across upper third onto head.

Distribution. Known from the Raja Ampat Islands, Banda Islands, and Maluka Islands in Indonesia; the Bismark Archipelago, Papua New Guinea; and the Palawan Province, Philippines.

Etymology. The specific epithet is an adjective combining the Latin rubrum (red) and caput (head), referring to the distinctive red head in life.

Comparison. Eviota rubriceps belongs to the cephalic sensory-pore pattern 2 of Lachner and Karnella (1980), lacking only the IT pore, and differs from species in that group as listed in Gill and Jewett (2004), Greenfield and Randall (2008), and Greenfield & Suzuki (2010) as follows. Only eight described species in pattern group 2 have simple unbranched pectoral-fin rays as in E. rubriceps : E. cometa Jewett and Lachner (1983) , E. nigrispina Greenfield and Suzuki (2010) , E. pellucida Larson (1976) , E. prasites Jordan and Seale (1906), E. sigillata Jewett and Lachner (1983) , E. spilota Lachner and Karnella (1980) , E. storthynx Rofen (1959) , and E. zebrina Lachner and Karnella (1978) . Of these, only E. nigrispina , E. prasites , E. pellucida , and E. storthynx have a dorsal/anal formula of 8/7 as in E. rubriceps . Eviota rubriceps differs from both E. prasites and E. pellucida by having the 5th pelvic-fin ray about 20% or less of the 4th ray, versus about 40%. Eviota rubriceps differs from E. storthynx by lacking the dark postocular spot and vertical bars or dark reticulated markings on the caudal fin present in that species. Eviota rubriceps shares the most characters with E. nigrispina , but differs by lacking a curved yellow-gold line across the abdomen ( Fig. 5 ) in life and in having a peppering of small dark spots on the nape and upper back lacking in E. nigrispina ( Fig. 6 ). The small dark spots on the nape and upper back are very obvious in fresh material, but tend to fade in older specimens (30 plus years) and high magnification is needed to see them. The species also differ in caudal-peduncle depth, with E. nigrispina having a slightly deeper caudal peduncle ( Fig. 7 ). The E. nigrispina specimens in Fig. 7 are types from Japan and two specimens from Indonesia (ROM 85168, 11.4 & 12.1 mm).

Other material examined. Eviota nigrispina —OMNH-P35615, holotype, Ryukyu Islands, Japan; CAS 229934, paratype, Ryukyu Islands, Japan; OMNH-P35614, paratype, Ryukyu Islands, Japan; OMNH-P35640, paratype, Ryukyu Islands, Japan; ROM 85168 (2), Indonesia, Raja Ampat Islands, Waigeo Island.

Remarks. While conducting a survey of the fishes at Raja Ampat, Indonesia, Gerald R. Allen and Mark V. Erdmann found a species of Eviota with a distinctive red head and a body that was dark on the lower half, which they referred to as Raja Ampat sp. 1. Subsequently they sent photographs to us and we recognized the similarity to the specimens previously given a manuscript name and awaiting description.

Prior to this, Greenfield and Suzuki (2010) described an Eviota species from Japan, E. nigrispina , that also has a dark band on the ventral portion of the body when preserved. Comparison of photographs of live individuals of E. nigrispina and E. rubriceps showed that they were quite different in coloration, however, they are very similar when preserved and have the same counts. As discussed in the Comparisons section, in addition to the live coloration, there also are differences in preserved coloration and caudal-peduncle depth. There also are habitat differences between the two at the Raja Ampat Islands. Erdmann (pers. comm., 20 July 2011) reports that E. rubriceps is a dominant species in shallow waters (mostly 2–4 m, maximum 6 m). Two specimens of E. nigrispina (ROM 85168) were taken at a depth of 22 m at Waigeo Island, Raja Ampat Islands ( Fig. 8 ). Although E. nigrispina has been seen in shallow water at the Ryukyu Islands, Japan where the water is cooler (pers. comm., T. Suzuki, 21 July 2011), the holotype was collected from 20 m.

Except for the close difference in caudal-peduncle depth, only color separates these two species. Color alone has been found to separate some other coral-reef fish species. Greenfield (1979) found that several species of the labrisomid genus Starksia could only be distinguished on the basis of color. Baldwin et al. (2011) reevaluated the species using cytochrome c oxidase (CO1) sequences and concluded that the data “support his decision to recognize the species almost entirely on the basis of minor differences in pigment Species in the gobiid genus Elacatinus provide another example of species that are separated only by color but are genetically distinct. Tayor and Hellberg (2005) suggest that color-based mate choice and ecological differences may have contributed to diversification in this genus.

Craig et al. (2006), in discussing two genetically distinct grouper species that differ in coloration but are very similar morphologically, suggest that “the evolution of external colours precedes or occurs more rapidly than changes in molecular markers……

Victor & Randall (2010) described Gramma dejongi based solely on color, adult size, behavior, and ecological differences. In this case the barcode CO1 mtDNA was the same as a sympatric congener and they suggested recent speciation.

Bowen et al. (2006), however, in discussing Atlantic pygmy angelfish species (Centropyg e) could find no genetic differences between differently colored species and favored the conclusion that the species were color morphs of the same species. But they also stated that “color morphs subject to sexual selection or ecological differentiation (and lacking morphological or molecular diagnostics) are the raw edge of emerging species on coral reefs.

The small size of the dwarfgobies in the genus Eviota , as well as some other small gobies such as those in the genus Trimma , poses problems because this reduction in size often results in the reduction of the number of scales, fin rays and pores of the laterosensory canal system ( Weitzman & Vari, 1988). As a result the potential for variation in morphological characters is reduced and many of the species of Eviota are primarily distinguished by their color patterns.

Figures

FIGURE 1. Eviota rubriceps, holotype, CAS 223447, 13.5 mm male, photograph by D. W. Greenfield.

FIGURE 2. Eviota rubriceps, paratype, USNM 209978, 11.5 mm male. Drawn by G. (Trudy) Nicholson, Smithsonian Institution, NMNH, Division of Fishes.

FIGURE 3. Eviota rubriceps, underwater photograph, Halmahera, Pulau Gifao, Buli Bay, 00 ° 47.447 N, 128 ° 19.298 E, 10 m, Maluku Islands, Indonesia. Photograph by G. R. Allen.

FIGURE 4. Eviota rubriceps, underwater photograph, Pulau Mommon, 03 ° 56.377 S, 132 ° 48.208 E, 12 m, Fakfak Peninsula, West Papua. Photograph by G. R. Allen.

FIGURE 5. Eviota nigrispina. Figure 4 from Greenfield & Suzuki (2010).

FIGURE 6. Eviota nigrispina. Figure 5 from Greenfield & Suzuki (2010).

FIGURE 7. Caudal-peduncle depth as percentage of SL. Blue diamonds = E. rubriceps; Magenta squares = E. nigrispina.

FIGURE 8. Eviota nigrispina, ROM 85168, Raja Ampat Islands.