A New Species of Photonectes from the Pacific Ocean off Oahu, Hawaii with a Revised Identification Key for the Genus (Teleostei: Stomiidae: Melanostomiinae)
A new species of scaleless black dragonfish, Photonectes klepadloae, new species, is described on the basis of a single specimen collected in the central north Pacific Ocean off the Hawaiian Islands. The new species is readily distinguished from all congeners by the postorbital organ shifted forward to below eye, by the presence of the blue luminous tissue on the body arranged in two widely spaced interrupted lines between IV photophores and a streak-like patch on each side above 10th to 12th PV photophores, and by the structure of the mental barbel lacking a bulb, but having the long unpigmented distal appendage without a terminal swelling, and a pair of enlarged stalked photophore-like structures on the distal extremity of the stem. A revised key of the known species of Photonectes is presented.
Holotype of Photonectes klepadloae, new species, USNM 258739, 119 mm SL; 21°20′00″N, 158°20′00″W, 660–805 m. (A) Lateral view; (B) ventral view. Scale bar = 10 mm.
Holotype of Photonectes klepadloae, new species, USNM 258739, 119 mm SL; head, lateral view (A) and jaw dentition, schematic drawing (B). Abbreviations: lj, lower jaw (boundary between the dentary and articular bones not indicated; missing or replacing teeth depicted by dashed line); mx, maxilla; pm, premaxilla; po, postorbital organ; sm, supramaxilla; so, suborbital organ. Scale bar = 2.5 mm.
Holotype of Photonectes klepadloae, new species, USNM 258739, 119 mm SL; disposition of blue luminous tissue and IP photophores. (A) Isthmus, ventral view; (B) area of IP and anteriormost PV photophores, ventrolateral view; (C) prepelvic area, ventrolateral view showing arrangement of blue luminous tissue associated with PV photophores. 1, longitudinal lines of blue luminous tissue on isthmus; 2, longitudinal lines of blue luminous tissue between PV rows of photophores; 3, patch of blue luminous tissue above PV-10–12; 4, concentrations of pale bluish to whitish luminous spots between IP and PV rows of photophores; 5, ditto, along preopercle; 6, ditto, at place of pectoral fin; 7, ditto, on flank; 8, first IP photophore; 9, gap between IP-8 and IP-9. Scale bars: (A, B) = 2.5 mm, (C) = 5 mm.
Holotype of Photonectes klepadloae, new species, USNM 258739, 119 mm SL, mental barbel. (A) Dorsal view (stalked photophore-like structures arrowed); (B) schematic drawing. Abbreviations: df, distal filament; ip, internal pigmentation of stem apex; ph, stalked photophore-like structure; st, stem. Scale bars: (A) = 1 mm, (B) = 0.5 mm.
Holotype of Photonectes venetaenia, ZMMU 23811, 89 mm SL; 01°15′S, 142°46′E, 1000–0 m; relative position of eye and circumorbital light organs. 1, Suborbital organ; 2, anteroventral extension of the jet-black tissue encircling the photogenic gland of postorbital organ; 3, photogenic gland of postorbital organ. Scale bar = 2 mm.
Holotype of Photonectes venetaenia, ZMMU 23811, 89 mm SL; ventrolateral view of isthmus and anteriormost flank (A) and ventral view of isthmus (B) showing arrangement of blue luminous tissue and shape of mental barbel. 1, first IP photophore; 2, longitudinal lines of blue luminous tissue on isthmus before IP rows of photophores; 3, streak of blue luminous tissue above PV-1–4; 4, terminal swelling of filament of mental barbel. Scale bar = 4 mm.
Contributor Notes
Associate Editor: M. P. Davis.