Gnatholepis knighti

Larson, Helen K. & Buckle, Duncan J., 2012, A revision of the goby genus Gnatholepis Bleeker (Teleostei, Gobiidae, Gobionellinae), with description of a new species, Zootaxa 3529 (1), pp. 1-69 : 39-43

Gnatholepis knighti Jordan and Evermann, 1903

( Figs 12D , 19 –20, Tables 5–8, 12)

Gnatholepis knighti Jordan and Evermann, 1903: 204 (Hilo, Hawaii).— Jordan and Evermann 1905: 11 (coral reefs at Oahu); Jordan and Evermann 1926: 12 (Hawaii); Koumans 1940: 133, 155; Böhlke 1953: 112; Böhlke 1984: 107; Ibarra and Stewart 1987: 40; (in part); Thacker 2004b: 578–579 .

Gnatholepis anjerensis — Randall et al. 1985: 70 (Johnston Island); Randall and Greenfield 2001: 3, 5–6 (in part); Greenfield and Randall 2004: 524–525 (Kane’ohe Bay, O’ahu).

Diagnosis. A large stocky Gnatholepis (up to 64 mm SL) with cycloid scales on predorsal region, cheek and pectoral fin base, distinct flap present at end of lower lip; at least three dark spots along first spine of first and second dorsal fins, followed by at least three rows of dark spots or short streaks, pectoral fin plain translucent to pale brownish; transverse black line crossing upper part of eye usually split in two; anal fin plain dusky, often with one to several blackish rounded to oval spots posteriorly, or with dark streaks following membrane; second dorsal and anal fin rays nearly always I,11; pectoral rays 15–17, usually 16; lateral scales 25–29, usually 27, 7–10

Material Examined. NORTH-WESTERN HAWAIIAN ISLANDS: BPBM 34873, 5(29–36), Midway Atoll, wreckage at shore between cargo pier and launching ramp, J.E. Randall and J.L. Earle, 18 September 1991. HAWAII: Paratypes of Gnatholepis knighti, CAS-SU 7468, 7(32.5–43), Hilo, D.S. Jordan and B.W. Evermann, 1901–1902. Paratypes of Gnatholepis knighti, USNM 144094, 5(30.5–43), Hilo, D.S. Jordan and B.W. Evermann, 1901. Paratype of Gnatholepis knighti, BPBM 1699 , 1(34), Hilo, U.S. Fish Commission, 1901. USNM 78072, 23(24.5–44), Hawaii, U.S. Fish Commission, 1901; BPBM 19665, 10(58–65), SW side Oahu, Campbell Industrial Park, B. Carlson, J. McKinney and A. Suzumoto, 11 September 1975; BPBM 28720, 1(42.5), South Kahala, Waiulua Bay, J.E. and H.A. Randall, 11 August 1982. LINE ISLANDS: BPBM 34045, 3(27–45), Johnston Atoll, R.K. Kosaki and party, 25 July 1989.

Description. Based on 28 specimens, 32.5–64.0 mm SL.

First dorsal VI–VII (usually VI); second dorsal I,10–I,12 (mean I,10.9); anal I,10–11 (mean I,10.9), pectoral rays 15–17 (mean 16.1), segmented caudal rays nearly always 17; caudal ray pattern usually 9/8; branched caudal rays 6/7 to 8/7 (usually 7/6); lateral scale count 25–29 (mean 27.1); TRB 8–11½ (mean 10.3); predorsal scales 7–10 (mean 8.7); circumpeduncular scales always 12. Gill rakers on outer face of first arch 1+4 (in 2).

Body compressed, width at anus 11.4–15.7% (mean 13.2%) of SL. Body rather stocky in appearance, body depth at anus 20.6–26.0% (mean 23.2%) of SL, body depth at first dorsal fin origin 21.0–26.1% (mean 23.8%) of SL. Head compressed, broader ventrally, slightly deeper than wide, HL 25.0–29.9% (mean 27.3%) of SL; head depth at posterior preopercular margin 66.3–85.6% (mean 74.5%) of HL; head width at posterior preopercular margin 61.2–80.0% (mean 70.9%) of HL; head profile bluntly pointed; nape profile low, relatively straight. Mouth subterminal to nearly terminal, slightly oblique; jaws generally reaching to below anterior margin of eye; upper jaw large specimens, dorsolateral, 24.8–32.0% (mean 27.6%) of HL; preorbital width 19.1–27.9% (mean 22.5%) of HL. Snout bluntly pointed, 28.6–44.0% (mean 36.4%) of HL; posterior naris round to almost triangular, close to anterior margin of eye; anterior naris in short tube, higher on posterior margin of eye, about level with middle of eye or somewhat ventral to it. Interorbital narrow, 6.1–10.4% (mean 8.6%) of HL. Caudal peduncle compressed, length 15.2–19.0% (mean 17.0%) of SL; caudal peduncle depth 10.2–13.5% (mean 11.9%) of SL.

First dorsal fin rounded to almost square, with no spines greatly elongate; first, second or third spine longest; when adpressed, spine tips reaching to first or second element of second dorsal fin. First spine length 14.3–25.6% (mean 19.3%) of SL; second dorsal spine length 14.7–20.2% (mean 16.1%) of SL; third dorsal spine length 14.5–18.4% (mean 16.3%) of SL. Second dorsal fin as tall as first dorsal fin, rays longer anteriorly than posteriorly, fin pointed to slightly rounded posteriorly. Anal fin lower than second dorsal fin, anteriormost rays shorter than posterior few rays; fin pointed to slightly rounded posteriorly. Second dorsal and anal fin rays, when adpressed, usually reaching caudal fin. Pectoral fin rounded to slightly pointed, central rays longest, 23.1–28.5% (mean 25.8%) of SL; fin reaching back to above anal fin spine or first few anal fin elements. Pelvic fins fused, frenum with distinctive finely fimbriate margin, fins round to somewhat oval, reaching to first few anal fin rays, 22.6–29.6% (mean 25.9%) in SL. Caudal fin moderate, oval to rounded, 26.1–35.6% (mean 29.7%) of SL.

Gill opening restricted, extending anteriorly to lower edge of pectoral fin base. Gill raker form generally as in G. anjerensis ; about a quarter of first gill arch bound by membrane to inner face of opercle. Tongue bilobed.

Teeth as in G. anjerensis .

Predorsal scales cycloid, ctenoid scales on body reaching over pectoral fin base, sometimes reaching onto side of nape over opercle, nape midline always with cycloid scales. Opercle with cycloid scales, upper or central part occasionally with ctenoid scales. Preopercular scales cycloid, which may extend anterior to vertical dark cheek bar below eye. Breast with cycloid scales, extending forward nearly to rear edge of preopercle. Pectoral fin base scales cycloid. Belly scales usually cycloid; ctenoid scales present on posterior half of belly midline in some specimens.

Head pores and sensory papillae as in G. anjerensis ( Fig. 1 ).

Coloration of fresh material. This species has been described and illustrated in Greenfield and Randall (2004: 524–526, fig. 64); the dark spots on the white anal fin are visible in this figure. A photograph by Jack Randall of a large dead specimen from Oahu resembles G. anjerensis but the pectoral fin is translucent with fine whitish speckles on the fin rays; the anal fin is relatively plain dusky white, and the dorsal part of the body has scattered small dense black spots (and see Figs 19 –20 from Kaneohe Bay).

Coloration of preserved material. The colour pattern is basically the same as that of G. anjerensis (see that species’ account), but differs from it in that the pectoral fin is plain dusky, with no rows of dark brown speckles; the dusky anal fin may have distinct rounded to elongate dark brown spots along the centre of the fin, or a dark streak present on the membrane parallel to the fin rays; and the blackish line on the dorsal surface of the eye is usually split into two thin or diffuse blackish lines (often diverging), which may be indistinct or broken-up ( Fig. 12D ). The dark brown mark (which may be indistinct) over the pectoral fin base is a blotch surrounding a small pale central spot (spot often indiscernible in preserved specimens) or short brown bar running below pale central spot.

Distribution. This species is known only from the Hawaiian island chain. Thacker (2004) identified some specimens from Rarotonga ( Cook Islands) and Moorea (Society Islands) as G. knighti , based by their having a “dash-shaped mark on the shoulder”. These specimens were used in the 2004 genetic analysis and appear as sister to the Hawaiian specimens of G. knighti (Thacker 2004: Fig. 2 ; Thacker pers. comm.). However, we have seen no specimens identifiable as G. knighti from these localities (only G. cauerensis ).

Ecology. Most specimens have been taken from shallow habitats, tidepools or “brackish pools”, at depths of 0–5 m, from sand and mangrove areas.

pheromone (which Asterropteryx did). Cole (1990) described the sex ratio and gonad structure of this species (as G. anjerensis ; her material was all from Hawaii).

Comparisons. Gnatholepis knighti is very similar to G. anjerensis but has cycloid scales on the predorsal region and the transverse black line on upper part of eye is often split in two (always a single line in G. anjerensis ) ( Fig. 12B, D ).

The very brief description of G. knighti provided in Thacker (2004b) emphasises the presence of a dash-shaped dark mark or line dorsal to the pectoral fin as being diagnostic for the species. From our examination of specimens and colour photographs of live and freshly dead Gnatholepis , we found that this mark to be variably developed in both G. anjerensis and G. knighti .

Specimens from Rarotonga and Moorea identified by Thacker as G. knighti appeared as sister to the Hawaiian G. knighti in a strict parsimony consensus tree ( Thacker 2004a: Fig. 2 ; Thacker pers. comm.). Thacker et al. presented further genetic analysis of a smaller number of Gnatholepis specimens in which the same groups (Rarotonga/Moorea and Hawaii) were sisters in the parsimony consensus tree but the Rarotonga/Moorea specimens were sister to G. anjerensis in the Bayesian analysis ( Thacker et al. 2008: fig. 1). As the specimens no longer exist it is not possible to discover what these fish actually were.

Remarks. The holotype (USNM 50653) has been noted as missing since 1948 and may have never been received by USNM. Thacker (2004b) remarked, but not Randall and Greenfield (2001) nor Greenfield and Randall (2004), that the holotype of G. knighti is lost. However, 10 lots of paratypes exist in six American museums: CAS- SU 7468, FMNH (5), ANSP 24222 (1, missing), MCZ 28903, USNM 144094 and AMNH 2294. The holotype was illustrated by Jordan and Evermann (1905: 360, pl. 58).

The oldest material of G. knighti was collected in Oahu by the medical officers aboard the USS Portsmouth in 1873–74 ( Jordan and Evermann 1905).

Figures

FIGURE 1. Sensory pores and papillae in Gnatholepis anjerensis, SAIAB 2112, Mauritius, 46 mm SL male. Scales omitted.

FIGURE 2. Canonical analysis of principal co-ordinates plot for the seven Gnatholepis species with vectors overlaid. CAP axes 1 and 2 explain 62% of the variation from 13 canonical axes.

FIGURE 12. A, Sketch of dorsal view of head of Gnatholepis caudimaculata n. sp., showing characteristic oblique mark on

FIGURE 19. Gnatholepis knighti, 2 m depth, Kaneohe Bay, Hawaii. Photo by Rob Myers.