Flabellicauda bolini ( Briggs, 1962 )

Fujiwara, Kyoji, Conway, Kevin W. & Motomura, Hiroyuki, 2021, Description of a New Genus and Two New Species of Indo-Pacific Clingfishes (Gobiesocidae: Diademichthyinae) with Redescription and Reassignment of Two Species Previously Assigned to Lepadichthys Waite, 1904, Ichthyology & Herpetology 109 (3), pp. 753-784 : 768-773

Flabellicauda bolini ( Briggs, 1962)

Bolin’s Clingfish

Figures 4F–J , 7C , 8E , 9 , 14 , 15 , 18 , 19A–C ; Tables 1–3, 5

Lepadichthys bolini — Briggs, 1962: 424, fig. 1 (original description; type locality: Palikulo Bay , Espiritu Santo Island, Vanuatu) .

Lepadichthys species — Allen and Erdmann, 2012: 841, unnumbered fig. (brief description; Manus, Papua New Guinea: based on underwater photograph).

Holotype.— CAS 158341 , 28.8 mm SL, Palikulo Bay , Espiritu Santo Island, Vanuatu, 15829 0 10 00 S, 167814 0 37 00 E, 0.6–3.7 m, R. Bolin and A. Persson, 7 October 1958, rotenone.

Non-type specimens.— 29 specimens, 11.5–23.1 mm SL. Papua New Guinea: CAS 65629 , 16.4 mm SL, Nagada Mission , 05809 0 20 00 S, 145847 0 50 00 E, 1.5–3.7 m, S. Poss et al., 8 May 1987 ; CAS 65630 , 15.8 mm SL, Nagada Mission , 05809 0 20 00 S, 145847 0 50 00 E, 0.9–3.7 m, S. Poss et al., 1 May 1987 ; USNM 360161 , 2 , 21.6–23.1 mm SL, Kranket Island , Madang, 1.5– 7.6 m, B. Collette, 30 May 1970 ; USNM 360164 , 11.5 mm SL, Kranket Island , Madang, 05811 0 30 00 S, 145850 0 42 00 E, 0.9 m, V. Springer et al., 7 November 1978 . Fiji: ANSP 128248 , 2 , 18.9– 20.6 mm SL, Nukumbutho Island, Lauthala Bay , Suva, W. Smith-Vaniz, 15 April 1974 ; CAS 224415 , 17.5 mm SL, Yadua Island , 16838 0 07 00 S, 178818 0 41 00 E, 1.5–6.4 m, D. Greenfield et al., 19 March 2002 ; CAS 224416 , 19.8 mm SL, Daveita Bay, Vanua Levu Island , 16845 0 35 00 S, 179854 0 37 00 E, 7.6–12.2 m, D. Greenfield et al., 26 May 2003 ; CAS 224418 , 15.9 mm SL, Navatu, Vanua Levu Island , 16856 0 54 00 S, 178858 0 14 00 E, 1.2–3.7 m, D. Greenfield et al., 21 March 2002 ; CAS 224419 , 3 , 13.2– 18.2 mm SL, Nasau Bay, Vanua Levu Island , 16843 0 39 00 S, 179853 0 58 00 E, 0.9–4.6 m, K. Longenecker et al., 25 May 2003 ; CAS 224420 , 4 , 16.0– 20.1 mm SL, Nananu-i-Cake Island, 17819 0 28 00 S, 178814 0 15 00 E, 3–15 m, D. Greenfield et al., 15 March 2002 ; CAS 224422 , 12 , 14.7–22.4 mm SL, Nasese, Suva , 18810 0 24 00 S, 178825 0 17 00 E, D. Greenfield et al., 10 February 2002 .

Diagnosis.— A species of Flabellicauda ( Figs. 4F–J , 18 ) very similar to F. alleni and sharing the following characters: 12– 15 (13) dorsal-fin rays; 10–12 (11, rarely 10) anal-fin rays; upper end of gill opening level with base of 12 th to 14 th pectoral-fin ray in lateral view; head sensory canal pores relatively developed, including usually 2 nasal, 2 lacrimal, and 2 postorbital pores ( Fig. 19A–C ); disc region A without papillae at center ( Fig. 7C ); and body black with white stripes ( Fig. 8E ). Flabellicauda bolini differs from F. alleni in having fewer gill rakers (4–6 [5] on first to third arches, respectively and 12–17 [14] total [first þ second þ third arches] gill rakers in F. bolini vs. 5–8 [6, rarely 5], 6–8 [6], and 6–8 [7], respectively and 18–24 [19] total gill rakers in F. alleni ; Table 3). When compared at the same size, the species has slightly larger head (compared as values of head length 28.7–36.4 [34.1] % SL in F. bolini vs. 28.5–36.7 [31.9] % SL in F. alleni and pre-disc length 23.4–31.7 [28.9] % SL vs. 22.8–31.8 [26.8] % SL; Fig. 9A, B ), the difference emphasized when those values combined (52.0–68.1 [63.0] % SL vs. 51.4–67.7 [58.7] % SL; Fig. 9C ) and orbit diameter (7.0–12.7 [9.8] % SL vs. 6.4– 11.4 [8.3] % SL; Fig. 9D ) than F. alleni . Flabellicauda bolini is further distinguished from congeners by having a relatively longer and thicker caudal-peduncle length and depth proportions (4.1–5.6 [4.9] % and 5.6–7.8 [6.8] % SL, respectively in F. bolini vs. 3.2–3.9% and 5.3–6.0% SL, respectively in F. akiko ; 2.7–5.3 [3.8] and 4.2–6.8 [5.5] % SL, respectively in F. alleni ; 3.3–4.8% and 5.1–6.3 % SL, respectively in F. cometes ; Fig. 15A, B ). The value of caudal-peduncle length plus caudal-peduncle depth is also useful for distinguishing between the four species of Flabellicauda (10.4–13.1 [11.8] % SL in F. bolini vs. 8.5–9.5% SL in F. akiko ; 7.0–11.8 [9.3] % SL in F. alleni ; 9.3–11.0% SL in F. cometes ; Fig. 15C ).

Description.— Measurements given in Table 5. Body slender, cylindrical, compressed at caudal peduncle. Body width narrower than head width. Anus situated closer to anal-fin origin than to posterior margin of disc (disc to anus length 64.1 [60.3–72.4, mean 65.7] % of disc to anal-fin origin length). Vertebrae 33 (2 specimens), 34 (3), or 35 (6), based radiographs of 11 specimens, not including holotype. Head large, becoming smaller with growth ( Fig. 9A ), depressed anteriorly, its length and width 3.5 (2.7–3.1 [mean 2.9]) and 5.6 (4.8–6.2 [5.6]) in SL, respectively. Snout moderate, its length 14.9 (9.8–12.5 [11.0]) in SL, becoming shorter with growth ( Fig. 9E ), its tip slightly pointed in lateral view, semi-elliptical (or duck beak-shaped) in dorsal view; dorsal profile of snout slightly concave anteriorly. Mouth terminal, small, restricted to tip of snout. Anterior tip of upper jaw slightly pointed, extending slightly beyond that of lower jaw. Upper lip fleshy, weakly expanded, lower lip thin. Posterior 2/3 of both jaws covered by thick skin on lateral surface of snout. Single row of small similarly sized teeth in both jaws; upper-jaw teeth incisiviform, compressed laterally, with hook-like tips strongly curved posteriorly (ca. 908); lower-jaw teeth with pointed conical tips, inner surface slightly curved. Premaxillae separated anteriorly by large circular gap in dorsal view (based on radiographs of 1 specimen). Anterior and posterior nostrils larger than head sensory canal pores, former slightly smaller than latter; both with a membranous tube, that of former much longer than latter. Eye size slightly large, becoming smaller with growth ( Fig. 9D ), diameter slightly larger (slightly smaller in 7 specimens) than snout length, 14.3 (7.9–12.3 [10.3]) in SL. Interorbital region flattened. Gill opening tiny, slit-like. Upper end of gill opening level with base of 14 th (12 th to 14 th) pectoral-fin ray in lateral view (number of pectoral-fin ray given in Table 2); lower 9 th (8 th [13 specimens] or 9 th [12]) pectoral-fin-ray base attached to disc by membrane. First to third gill arches with two rows of gill filaments, 4 th arch without filaments (gill description based on 26 specimens). Gill rakers slender, short and pointed (gill raker counts listed in Table 3). Gill membranes on each side united ventrally, attached to isthmus. Head sensory canal pores relatively developed, including 2 nasal, 2 (1 on left side only in 2 specimens) lacrimal, and 2 postorbital pores; preopercular and mandibular pores absent; all pores similarly sized with minute membranous tube; NC1 located in front of anterior nostrils in dorsal view (or between anterior and posterior margins of anterior nostril); NC2 before anterior margin (level with anterior margin [5 of 30 specimens], between anterior and posterior margins [18 specimens], or level with posterior margin [3 specimens]) of posterior nostril; LC1 located in front of anterior margin of eye; LC2 located just below LC1 (postero-ventrally below LC1 [18 of 29 specimens]); PO1 located just behind posterior margin of orbit; PO2 on slightly higher horizontal level of PO1 ( Fig. 19A–C ).

Dorsal- and anal-fin-ray counts listed in Table 2. Origin of dorsal fin slightly anterior to vertical through anal-fin origin. Dorsal and anal fins located posteriorly, their bases relatively long, lengths 5.3 (4.3–6.1 [5.1]) and 5.7 (4.7–6.6 [5.8]) in SL, respectively; strongly connected to caudal fin by membranes, giving appearance of single, continuous median fin around posterior part of body (easily damaged). Upper and lower hypural plates completely fused, forming single large fan-like hypural plate (radiographs of 10 specimens, not including holotype). Post-dorsal-caudal length 4.0 (3.7–7.0 [4.7]) in dorsal-fin base length. Dorsal- and anal-fin heights almost equal, except anteriorly. Pectoral- and caudal-fin margins rounded. Pectoral-fin rays 30 (27 [4], 28 [7], 29 [10], or 30 [5]). Upper and lowermost pectoral-fin rays minute, longest ray extending beyond vertical through posterior margin of disc. All soft-fin rays unbranched and segmented. Pelvic fins and pectoral-girdle elements forming a circular, extremely small ‘‘single’’ adhesive disc ( Fig. 7C ), its length and width 9.0 (8.3–11.3 [9.4]) and 10.2 (7.4–11.2 [9.5]) in SL, respectively. Disc region B bell-shaped, equal in size to region A. Anterior margin of disc region A smooth, posterior margin of disc region B with fringe. Disc regions A and B with flattened papillae (disc papillae description based on 12 specimens). Center of disc region A lacking papillae; anterolateral part with (2 or 3) rows of papillae, number of rows slightly decreasing toward apapillate center; both sides of disc region A (except margins) covered with papillae; papillae of inner rows slightly larger than papillae of outer rows. Disc region B with 5 (4 or 5) rows of papillae; papillae of inner rows slightly larger than outer rows, anterior part of disc region B without papillae ( Fig. 7C ). Disc region C lacking papillae.

Coloration.— Based on Figures 4F–J , 8E , 18 . Body black with white stripes on dorsal midline and lateral side, stripe pattern very similar to those of F. alleni (see Coloration of F. alleni ). Preserved coloration uniformly yellowish ( Fig. 18 ). Black melanophores present on body of small specimens (ca., 16 mm SL), forming an upper and lower stripe (somewhat indistinct in large specimens; Fig. 4F, G ); upper and lower stripes located dorsally and laterally, respectively, former extending from nape to most posterior point of dorsal-fin base, latter extending from pectoral-fin base to caudal-fin base ( Fig. 4F–J ).

Distribution.— Known from Papua New Guinea, Vanuatu, and Fiji ( Fig. 14 ).

Remarks.— Flabellicauda bolini was originally described as Lepadichthys bolini by Briggs (1962) on the basis of a single specimen (CAS 158341, 28.8 mm SL; Fig. 18A–C ) collected from Vanuatu. Although this species has previously been considered to be widely distributed throughout the Indo-West Pacific by several authors (e.g., Briggs, 1969a; Winterbottom et al., 1989; Fujiwara and Motomura, 2018), these previous records refer either to F. alleni or F. cometes (described above). Based on available material, F. bolini appears to be restricted to the western Pacific, from Papua New Guinea to Fiji ( Fig. 14 ).

Dorsal-fin rays 10 11 12 13 14 15 F. alleni , new species 5 25H 15 2 F. cometes , new species 3 3H 2 F. bolini 4H 17 7 1 F. akiko 2 3H Anal-fin rays 9 10 11 12 13 F. alleni , new species 1 19 16H 5 F. cometes , new species 3 4H 1 F. bolini 1 18H 9 F. akiko 1 4H Number of pectoral-fin ray at same level with upper end of gill membrane 9 th 10 th 11 th 12 th 13 th 14 th F. alleni , new species 18H 11 8 F. cometes , new species 2 6H F. bolini 7 9 9H F. akiko 1 4H

In their book of the reef fishes of the East Indies, Allen and Erdmann (2012) included an underwater photograph of unidentified species of Lepadichthys taken at Papua New Guinea ( Fig. 8E ). Judging from its general appearance (e.g., mouth and vertical fins shape) and the locality, the photographed individual likely belongs to F. bolini .

Figures

FIG. 4. Preserved small specimens of (A–E) Flabellicauda alleni, new species, and (F–J) Flabellicauda bolini. (A, B) YCM-P 36726, 19.7 mm SL, Sabah, Malaysia; (C–E) YCM-P 36727, 11.5 mm SL, Sabah, Malaysia; (F, G) CAS 224422, 16.2 mm SL, Suva, Fiji; and (H–J) CAS 224419, 13.2 mm SL, Vanua Levu Island, Fiji. (A, C, F, H) Lateral views. (B, D, G, I) Dorsal views. (E, J) Ventral views.

FIG. 7. Pelvic discs of (A) F. alleni, new species, USNM 360264, holotype, 26.2 mm SL; (B) F. cometes, new species, ROM 55929, holotype, 17.3 mm SL; (C) F. bolini, ANSP 128248, 20.6 mm SL; and (D) F. akiko, WAM P. 33772-002, 11.5 mm SL. Scale bars ¼ 0.5 mm. Black dots indicate lacking disc papillae patch.

FIG. 8. Underwater photographs of (A–D) F. alleni, new species, (E) F. bolini, and (F–H) F. akiko. (A–C) 1.5 m depth, Rinca Island, West Flores, Indonesia. Photos by M. Erdmann. (D) 7 m depth, Bohol, Philippines. Photo by K. Yamasaki. (E) 5 m depth, Manus, Papua New Guinea. Photo by G. Allen. (F) 70 m depth, West Papua, Indonesia. Holotype. Photo by G. Allen. (G) 70 m depth, West Papua, Indonesia. Photo by M. Erdmann. (H) 40 m depth, Okinawa Island, Japan. Photo by N. Shirakawa. (A–E, G, H) Specimens not collected. (E, F) Reproduced from Allen and Erdmann (2012) with permission.

FIG. 9. Relationships of (A) head length, (B) pre-disc length, (C) head length plus pre-disc length, (D) orbit diameter, and (E) snout length (as % of standard length) to standard length (mm) in F. alleni, new species (red diamonds) and F. bolini (blue circles), showing (A–D) differences and (E) morphological change with growth.

FIG. 14. Distributional map of species of Flabellicauda: F. alleni, new species (red diamonds), F. cometes, new species (yellow squares), F. bolini (blue circles), and F. akiko (green triangles). Closed and open symbols indicate records based on specimens examined in this study and published photographs, respectively. Arrowheads indicate type locality.

FIG. 15. Relationships of (A) caudal-peduncle length, (B) caudal-peduncle depth, (C) caudal-peduncle length plus caudal-peduncle depth, (D) head width, (E) anterior interorbital width, and (F) posterior interorbital width (as % of SL) in F. alleni, new species (red diamonds), F. cometes, new species (yellow squares), F. bolini (blue circles), and F. akiko (green triangles).

FIG. 18. Preserved specimens of Flabellicauda bolini. (A–C) CAS 158341, holotype, 28.8 mm SL, Espiritu Santo Island, Vanuatu; (D) USNM 360161, 21 mm SL, Madang, Papua New Guinea; (E) ANSP 128248, 18.9 mm SL, Suva, Fiji. (A, D, E) Lateral views. (B) Dorsal view. (C) Ventral view.

FIG. 19. Head sensory canal pores of (A–C) Flabellicauda bolini and (D–F) Flabellicauda akiko. Illustrations based on (A–C) ANSP 128248, 20.6 mm SL and (D–F) WAM P. 33772-002, 11.5 mm SL. (A, D) Dorsal views. (B, E) Lateral views. (C, F) Ventral views. Scale bars ¼ 1 mm. Abbreviations as in Figure 6.