Nemateleotris helfrichi Randall & Allen, 1973

Tea, Yi-Kai & Larson, Helen K., 2023, Synopsis of the ptereleotrine goby genus Nemateleotris, with description of a new species from the western and central Pacific Ocean (Teleostei: Gobiidae), Raffles Bulletin of Zoology 71, pp. 248-266 : 254-255

Nemateleotris helfrichi Randall & Allen, 1973

Helfrich’s Dartfish Other names: Helfrich’s Firefish ( Figs. 1 , 2G, 4A–C , 5 , 8A, C , 9A , 10C 1–C 2, 11; Table 2)

Nemateleotris helfrichi Randall & Allen, 1973: 355 , fig. 4 (holotype BPBM 11595, Papeete Harbour, Tahiti, Society Islands [reproduced here in Fig. 4A ]; paratypes from Takaroa, Tuamotu Archipelago, and Avera, Rurutu, Austral Islands, but not those from Palau, Guam, or the Marshall Islands); Randall & Connell, 2013: fig. 3 (image of holotype, BPBM 11595).

Diagnosis. Dorsal-fin rays VI, I,30 (I,29–30); anal-fin rays I,26 (I,25–27); pectoral-fin rays 20 (20–21); pelvic-fin rays I,5; segmented caudal-fin rays 17; upper procurrent caudal-fin rays 9 (9–14); lower procurrent caudal-fin rays 12 (11–12); total caudal-fin rays 37–43; gill rakers 6 (5–7) + 17 (17–18) = 23 (22–24); elevated portion of first dorsal fin blue on anterior edge; median fins pale yellowish green, caudal fin without any markings, outermost edge of second dorsal and anal fin tipped with a yellow or orange spot, one in each interradial membrane space, spots sometimes coalescing; body lavender to lilac in life; pelvic fins blacktipped; dorsal edge of iris with a black mark at 1 o’clock position, sometimes continuing onto interorbital space as a short streak; maxilla black (in life and preservation); snout bright pink in life.

Remarks. Nemateleotris helfrichi is known from deep reefs in the south-eastern Pacific Ocean. In French Polynesia, it is reported from Tahiti (type location; Fig. 4A ) and Moorea (USNM 410981; Fig. 4B ) in the Society Islands, Takaroa in the Tuamotu Archipelago (paratype, BPBM 13326), Rurutu in the Austral Islands (paratype, BPBM 13095), Mohotane Island in the Marquesas Islands (USNM 439150), and the Gambier Islands. It is also reported from Rarotonga in the Cook Islands ( Fig. 4C ). It frequents seaward sand channels and rubble pans in deep mesophotic reefs at depths between 25–100 m, where it occurs either singly or in pairs.

Etymology. The species is named after Dr Philip Helfrich, Associate Director of the Hawaii Institute of Marine Biology of the University of Hawaii and Director of the Enewetak Marine Biological Laboratory. He was among those who collected the first specimen of this species ( Randall & Allen, 1973).

Figures

Fig. 1. Laterosensory pores and neuromasts based on holotype of Nemateleotris helfrichi (BPBM 11595). A, lateral view; B, dorsal view. Letter codes (in blue) for laterosensory pores follow Akihito et al. (1984). ANP, anterior nasal pore; PNP, posterior nasal pore; AOC, anterior oculoscapular canal; PC, preopercular canal; FDF, first dorsal fin. Arrowhead indicates position where gill membranes are attached to the isthmus.

Fig. 4. A–C, Nemateleotris helfrichi; D–F, N. lavandula, new species. A, BPBM 11595, holotype, 43.3 mm SL, Tahiti, Society Islands; B, USNM 410981, 35.6 mm SL, Moorea, Society Islands, French Polynesia; C, ZRC 61811, 62.4 mm SL, aquarium specimen from the Cook Islands; D, BPBM 10153, paratype (also paratype of N. helfrichi), 30.9 mm SL, Rigili Islet, Enewetak Atoll, Marshall Islands; E–F, ZRC 62990, paratypes, 36.1 mm SL and 29.8 mm SL respectively, aquarium specimens from Kwajalein Atoll, Marshall Islands, Micronesia. Photographs by: A, C, D, J.E. Randall; B, J.T. Williams; E, F, H.H. Tan.

Fig. 5. Distribution records for selected species of Nemateleotris based on examined specimens and literature records: lavender squares, Nemateleotris lavandula, new species; blue circles, Nemateleotris helfrichi. Type localities represented by outlined symbols.

Fig. 8. Species of Nemateleotris and their putative hybrids. A, N. helfrichi, underwater photograph from Rarotonga, Cook Islands; B, N. lavandula, new species, underwater photograph from Siaes Tunnel, Palau; C, head profiles of N. helfrichi (left) and N. lavandula, new species, (right) showing difference in colouration of the head and maxilla; D, N. magnifica, underwater photograph from Bali; E–F, N. decora, showing variability in colouration of the anterior body, underwater photograph from Fiji and the Maldives (the latter = N. exquisita sensu Randall & Connell, 2013) respectively; G, putative N. magnifica × N. decora, underwater photograph from Izu Peninsula, Japan; H, putative N. magnifica × N. lavandula, new species, underwater photograph from Okinoerabu Island, Japan. Photographs by: A, P.Jaletzky; B, R. Spangler; C, Y.K. Tea; D, V. Chalias; E, J. Heard; F, M. Harada; G, Y. Yamada; H, K. Uehara.

Fig. 9. Frontal head profiles of selected species of Nemateleotris. A, N. helfrichi, aquarium specimen from Cook Islands; B, N. lavandula, new species, ZRC 62990, paratype in life, specimen from Kwajalein Atoll, Marshall Islands, Micronesia; C, N. decora, underwater photograph from Bali, Indonesia; D, N. magnifica, underwater photograph from Bali, Indonesia. Photographs by: A, B-box Aquarium, Japan; B, H.H. Tan; C–D, V. Chalias.

Fig. 10. Species of Nemateleotris in life (A1–E1) and preserved colouration (A2–E2). A1, N. magnifica, aquarium specimen from Indonesia, specimen not retained; A2, N. magnifica, ZRC 47157, 36.6 mm SL, Bali, Indonesia; B1, N. decora, aquarium specimen from Indonesia, specimen not retained; B2, N. decora, ZRC 47158, 51.3 mm SL, Bali, Indonesia; C1, N. helfrichi, aquarium specimen from the Cook Islands, specimen not retained; C2, N. helfrichi, ZRC 61811, 62.4 mm SL, Cook Islands; E1–E2, N. lavandula, new species, ZRC 62990, paratype, 38.9 mm SL, aquarium specimen from Kwajalein Atoll, Marshall Islands, Micronesia. Photographs by: A1–B1, E2, Y.K. Tea, C1, S.W. Michael; E1, H.H. Tan; A2–C2, K. Lim.