Photonectes klepadloae Prokofiev & Frable, 2021

Prokofiev, Artem M. & Frable, Benjamin W., 2023, New specimens and supplementary descriptions of two rare dragonfishes Photonectes klepadloae and P. litvinovi, with comments on the distribution of P filipendulus (Teleostei: Stomiidae: Melanostomiinae), Zootaxa 5228 (4), pp. 489-500 : 490-492

publication ID	https://doi.org/ 10.11646/zootaxa.5228.4.7
publication LSID	lsid:zoobank.org:pub:2A02E146-7643-4C5C-8A16-D667FF237284
DOI	https://doi.org/10.5281/zenodo.7540064
persistent identifier	https://treatment.plazi.org/id/32248794-FFAB-FFD8-95FE-6A80FD8DF8E5
treatment provided by	Plazi
scientific name	Photonectes klepadloae Prokofiev & Frable, 2021
status

Treatment

Figs. 1–4 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 ; Table 1 View TABLE 1

Holotype. USNM 258739 View Materials , male, 119 mm SL, central north Pacific Ocean , Hawaiian Islands, off Oahu, 21°20′00′′ N, 158°20′00′′ W, 660–805 m, R / V Teuthis Cruise V , station 30, 10-ft opening-closing trawl, 13:52–16:52, 18 March 1971. GoogleMaps

New material. SIO 76-6 View Materials , unsexed, 93 mm SL ( Fig. 1A View FIGURE 1 ), central north Pacific Ocean , 30°41′00′′– 30°21′00′′ N, 147°18′00′′– 147°13′00′′ W, 1200 m wire out GoogleMaps , FCRG 71-2 , Tow 42, Isaacs-Kidd midwater trawl, 19:00–01:28, 09 November 1971, S. Imsand . USNM 258733 View Materials , unsexed, 64 mm SL ( Fig. 1D View FIGURE 1 ), central north Pacific Ocean , Hawaiian Islands, off Oahu, 21°25′01′′ N, 158°25′01′′ W, 610–650 m, El Pescadero III Expedition GoogleMaps , R / V Teritu , 10-ft IsaacsKidd midwater trawl, 10:56–13:50, 28 February 1971 , T. A. Clarke . USNM 320468 View Materials , likely male, 68 mm SL ( Fig. 1E View FIGURE 1 ), central north Pacific Ocean , 27°10′48′′ N, 170°54′00′′ W, 250 m, 19:36, 19 July 1955, H. M. Smith GoogleMaps .

Diagnosis. Species of Photonectes , subgenus Photonectes s. str. (Prokofiev 2019: 393), unique in postorbital organ shifted forward below orbit, blue luminous tissue on body arranged in two widely spaced interrupted lines between IV photophores and streak-like patch on each side above 10 th to 13 th PV photophores ( Figs. 1 View FIGURE 1 , 2 View FIGURE 2 ), and mental barbel with pair of stalked photophore-like structures on distal extremity of its stem ( Fig. 3 View FIGURE 3 ).

Description. Measurements, vertebral, and fin element counts are shown in Table 1 View TABLE 1 . Snout moderate, 1.3 times smaller than eye. Dorsal and anal fins opposed, shifted backward; pelvic fins inserted closer to caudal fin than to snout. Medial fins not covered by skin; pelvic and caudal fins broken at tips. Photophores: BR 9, IP 11 (interspaces between posteriormost three IP photophores approximately 1.5 times greater than previous ones), PV 21, IV 32, OV 20 or 21, VAV 13 (3 over anal-fin base), VAL 11 (2 over anal-fin base), AC 12, IC 57. Blue luminous tissue on body arranged as described for holotype ( Prokofiev & Frable 2021) ( Figs. 1 View FIGURE 1 , 2 View FIGURE 2 ), but streak-like patch above PV photophores is slightly longer and situated above 10 th to 13 th photophores in two smallest specimens (64–68 mm SL) with two small faint round patches posteriorly also not present in larger specimens ( Fig. 1C View FIGURE 1 ). In specimen SIO 76-6, blue luminous tissue in pectoral area is more developed than in other specimens, forming elongate patch originating above IP-11 and ending midway between PV-2 and PV-3 photophores ( Fig. 1A, B View FIGURE 1 ). Postorbital organ long, its anterior half situated below eye ( Fig. 1A View FIGURE 1 ).

Jaw dentition heterogeneous; premaxillary dentition biserial, with 2 teeth in outer row and 7–8 teeth in inner row; teeth in outer row and first tooth in inner row small and pointed, remaining inner teeth long, of unequal size, with barbed tips. Outer premaxillary teeth opposite bases of second and third teeth of inner row. Maxilla bears 7–8 moderately long, unequal-length teeth with barbed tips, followed by 9–12 smaller, inclined, comb-like teeth with pointed tips. Lower-jaw teeth 26 (SIO 76-6 and USNM 320468) or 23+/26 (USNM 258733), tips of longer teeth barbed. Vomer with 1 or 2 teeth on each side (anterior largest, posterior potentially a replacement), palatine teeth absent. Basibranchial teeth with two tooth patches, anterior patch with two pairs of sharp conical teeth, posterior patch with two or three pairs of teeth. First ceratobranchial with 7 clusters of denticles, from 1–3 each. Gill filaments of first ceratobranchial not reduced, similarly developed along whole length of bone. Posterior process of anguloarticular well-developed.

Barbel 1.2–1.6 times in head, with thick pigmented stem and thin unpigmented terminal filament ending in bulbous swelling ( Fig. 3 View FIGURE 3 ) (missing in SIO 76-6). Terminal filament is 1.9–2.3 times longer than stem. Distal extremity of stem unpigmented and possibly luminous, base of luminous tip with internal black pigmentation and pair of stalked photophore-like organs, not as pronounced in SIO 76-6.

Remarks. In all respects, the new specimens are similar or identical to the holotype of P. klepadloae , showing only slight but invaluable differences in some counts, morphometrics, degree of development of the blue luminous tissue, and in barbel structure. The most obvious is the presence of a bulbous swelling at tip of terminal filament in two smaller specimens, which is lacking in the holotype and SIO 76-6. Most probably, the absence of this swelling is an artifact resulting from damage incurred during the collecting haul, as the tip of the filament looks incomplete in the two larger specimens. The general pattern of distribution of the blue luminous tissue is identical in all specimens, although the size of individual patches is somewhat variable between the specimens.

Distribution. Photonectes klepadloae is still only known from the central north Pacific Ocean between 21 to 30° N and 147 to 171° W ( Fig. 4 View FIGURE 4 ).