Flabellicauda cometes, Fujiwara & Conway & Motomura, 2021

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 : 765-767

Flabellicauda cometes , new species urn:lsid:zoobank.org:act:60F323CC-305D-4296-B2E0-5497C6D919A2

Comet Clingfish

Figures 2B , 6D–F , 7B , 14–17 ; Tables 1–4

Lepadichthys bolini (not of Briggs)— Briggs, 1969a: 464 (brief comments; Amirante Islands, Seychelles: based on ANSP 150416); Winterbottom et al., 1989: 14, fig. 63 (listed; Peros Banhos and Salomon Atolls, Chagos Archipelago: based on ROM 55928, 55929).

Holotype.— ROM 55929 , 17.3 mm SL, Salomon Atoll, Chagos Archipelago, 05821 0 18 00 S, 72812 0 58 00 E, 3–13 m, A. Emery and R. Winterbottom, 14 March 1979, rotenone.

Paratypes.— 4 specimens, 10.3–15.0 mm SL. ANSP 150416 , 14.9 mm SL, Amirante Islands , Seychelles, 04854 0 S, 53823 0 E, 3.7 m, J. Böhlke et al., 3 March 1964; ROM 55928 , 3 (1 of 3 CS), 10.3–15.0 mm SL, Peros Banhos Atoll, Chagos Archipelago, 05826 0 44 00 S, 71847 0 42 00 E, 3–13 m, R. Winterbottom, 6 March 1979, rotenone .

Non-type specimens.— 3 specimens, 10.1–12.9 mm SL. AMS I. 18051-039, 12.9 mm SL, Tebontibike , Abaiang Islands, Gilbert Islands, Kiribati, 01843 0 48 00 N, 172858 0 48 00 E, D. Hoese and B. Goldman ; AMS I. 20755-073, 11.4 mm SL, off Cape Melville , Queensland, Australia, 13856 0 S, 144836 0 E, D. Hoese et al., 9 February 1979 ; AMS I. 21974-001, 10.1 mm SL, Lizard Island , Queensland, Australia, 14840 0 S, 145827 0 E, D. Hoese et al., 11 February 1975 .

Diagnosis.— A species of Flabellicauda ( Fig. 16 ) distinguished from congeners by the following combination of characters: 10–12 dorsal-fin rays (vs. 12–15 [13] in F. alleni and F. bolini ; Table 2); 9–11 anal-fin rays (vs. 10–13 [11, rarely 10] in F. alleni and F. bolini ; Table 2); upper end of gill opening level with base of 12 th to 14 th pectoral-fin ray in lateral view (vs. 9 th or 10 th in F. akiko ); 5 gill rakers on first and second arches (vs. 5–8 [6, rarely 5], 6–8 [6], and 6–8 [7] on first to third arches, respectively in F. alleni ; Table 3); head sensory canal pores poorly developed, including 2 nasal and 1 postorbital pore (vs. usually 2 nasal, 2 lacrimal, and 2 postorbital pores in F. alleni and F. bolini ; 1 nasal pore in F. akiko ; Fig. 6 ); disc region A without papillae at center (vs. disc region A with papillae at center in F. akiko ; Fig. 7B, D ); and body maroon with white stripes (vs. body red with white stripes in F. akiko ; Figs. 8F–H , 16F ).

Description.— Measurements given in Table 4. 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 63.4 [56.4–64.4] % of disc to anal-fin origin length). Head size medium, depressed anteriorly, its length and width 2.8 (2.7–2.9) and 5.3 (5.0–6.3) in SL, respectively. Snout moderate, its length 10.7 (10.9–12.3) in SL, its tip slightly pointed in lateral view, 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. Anterior and posterior nostrils larger than head sensory canal pores, former slightly smaller than latter; both with a membranous tube, that of former longer than latter. Eye size moderate, diameter slightly larger (slightly smaller in 2 specimens) than snout length, 10.6 (9.4–12.6) in SL. Interorbital region flattened. Gill opening tiny, slit-like. Upper end of gill opening level with base of 13 th (12 th or 13 th) pectoral-fin ray in lateral view (number of pectoral-fin rays given in Table 2); lower 8 th (8 th [3 specimens] or 9 th [4]) pectoral-fin-ray base attached to disc by membrane. First to third gill arch with two rows of gill filaments, 4 th arch without filaments (gill description based on 3 specimens). Gill rakers slender, pointed and very short, somewhat indistinct (not visible in 1 of 3 specimens; gill raker counts listed in Table 3). Gill membranes on each side united ventrally, attached to isthmus. Head sensory canal pores poorly developed, including 2 nasal and 1 postorbital pore; lacrimal, 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 between anterior and posterior margins (before anterior margin [2 of 5 specimens] or level with anterior margin [1 specimen]) of posterior nostril; PO1 located just behind posterior margin of orbit ( Fig. 6D–F ).

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 6.4 (4.4–6.7) and 7.0 (5.3–7.6) in SL, respectively; strongly connected to caudal fin by membranes, giving appearance of single, continuous median fin around posterior part of body (easily damaged). Post-dorsal-caudal length 3.3 (4.6–6.6) in dorsal-fin base length. Dorsal- and anal-fin heights almost equal, except anteriorly. Pectoral- and caudal-fin margins rounded. Pectoral-fin rays 27 (27 [2] or 28 [5]). Upper and lowermost pectoral-fin rays minute, longest ray extending beyond vertical through posterior margin of disc. All soft-fin rays unbranched. Principal caudal-fin rays segmented. Pelvic fins and pectoral-girdle elements forming a circular, extremely small ‘‘single’’ adhesive disc ( Fig. 7B ), its length and width 8.5 (8.3–9.0) and 8.0 (6.7–9.5) in SL, respectively. Disc region B bell-shaped, equal in size to disc 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 5 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 outer rows. Disc region B with 4 (5) rows of papillae; papillae of inner rows slightly larger than papillae of outer rows, anterior part of disc region B without papillae ( Fig. 7B ). Disc region C lacking papillae.

Osteological description based on CS specimen (1 of ROM 55928) and CT-scanned image ( Fig. 17 ). General osteological characters as in Figures 2B , 17 . As described for F. alleni except for the following minor differences: ceratobranchial 5 supporting 1–2 tiny conical teeth; vertebrae 33 or 34; and 12 caudal-fin rays associated with hypural plate.

Coloration.— Based on Figure 16 , fresh coloration described only from dorsal view ( Fig. 16F ). Body maroon with white stripe on dorsal midline and lateral side of body; stripe on dorsal midline extending from snout tip to dorsal-fin origin, its width broad anteriorly, gradually narrower toward posterior; lateral stripes extending from posterior point of jaws, past dorsal margin of eye, to posterior part of body (becoming indistinct posteriorly). Snout tip dark red, jaws reddish orange. Pupil black. Preserved coloration uniformly yellowish ( Fig. 16A–E ).

Distribution.— Known from the Indian Ocean ( Seychelles and Chagos Archipelagoes) and western Pacific Ocean (Queensland, Australia, and Kiribati; Fig. 14 ).

Etymology.— From the Latin cometes , a comet, a reference to the bold white stripe along the dorsal midline, reminiscent of the trailing tail of a traveling comet against the night sky. A noun in apposition.

Remarks.— Our description of F. cometes is based only on eight individuals, collected from widely separate localities in the Indian and Pacific Oceans. We have chosen to tentatively identify this material as conspecific because we could not identify significant differences between specimens from these different localities. Additional investigation, including assessment of life colors (which was not possible for specimens from localities in the Pacific), is warranted.

Figures

FIG. 2. Caudal skeletons of (A) Flabellicauda alleni, new species, FMNH 127786, 17.1 mm SL; (B) Flabellicauda cometes, new species, ROM 55928, 10.3 mm SL; (C) Lepadichthys frenatus, AMS I. 27134-018, 30.3 mm SL; (D) Lepadichthys minor, ROM 73449, 13.4 mm SL; (E) Discotrema crinophilum, ROM 85350, 25.4 mm SL; (F) Diademichthys lineatus, ROM 65282, 35.6 mm SL; (G) Gobiesox funebris, AMNH 5557, 46.7 mm SL; and (H) Acyrtus rubiginosus, UF 149202, 20.0 mm SL. Scale bars ¼ 1 mm. Abbreviations: AFR, anal-fin ray; DFR, dorsal-fin ray; DRC, cartilaginous distal radial; Ep, epural; EpC, epural cartilage; HP, hypural plate; HSPU2, hemal spine of preural centrum 2; LHP, lower hypural plate; NSPU2, neural spine of preural centrum 2; Ph, parhypural; PhC, parhypural cartilage; P-MR, proximalmiddle radial; PU, preural centrum; UC, ural centrum; and UHP, upper hypural plate. Asterisks indicate diastema between UHP and LHP.

FIG. 6. Head sensory canal pores of (A–C) Flabellicauda alleni, new species, and (D–F) Flabellicauda cometes, new species. Illustrations based on (A–C) USNM 360264, holotype, 26.2 mm SL and (D–F) ROM 55929, holotype, 17.3 mm SL. (A, D) Dorsal views. (B, E) Lateral views. (C, F) Ventral views. Scale bars ¼ 1 mm. Abbreviations: AN and PN, anterior and posterior nostrils, respectively; LC, lacrimal canal pores; NC, nasal canal pores; PO, postorbital canal pores.

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. 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. 16. Preserved (A–E) and fresh (F) specimens of Flabellicauda cometes, new species. (A–C) ROM 55929, holotype, 17.3 mm SL, Salomon Atoll, Chagos Archipelago; (D) ANSP 150416, 14.9 mm SL, Amirante Islands, Seychelles; (E) AMS I. 20755-073, 11.4 mm SL, Queensland, Australia; (F) ROM 55928, 15.0 mm SL, Peros Banhos Atoll, Chagos Archipelago. (A, D, E) Lateral views. (B, F) Dorsal views. (C) Ventral view.

FIG. 17. CT-scanned skeleton of Flabellicauda cometes, new species, ROM 55928, 15.0 mm SL. (A) Lateral view of whole body. (B) Dorsal view of anterior body. (C) Lateral view of anterior body. (D) Ventral view of anterior body. Abbreviations as in Figure 10.

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.