Three New Species of the Genus Photonectes (Teleostei: Stomiiformes: Stomiidae: Melanostomiinae) from the Pacific Ocean Cynthia Klepadlo1
Copeia 2011, No. 2, 201–210
Three New Species of the Genus Photonectes (Teleostei: Stomiiformes: Stomiidae: Melanostomiinae) from the Pacific Ocean Cynthia Klepadlo1 Three new species of the mesopelagic fish genus Photonectes (Stomiidae, Melanostomiinae, subgenus Photonectes) are described from the Pacific Ocean with species descriptions augmented by new characters: origin of the IP-photophore series, gill-filament length, and jaw-tooth length. Photonectes coffea, new species (central equatorial, north, and western Pacific) has an elongate barbel with two bean-shaped light organs; IV photophores 37–39; dorsal-fin rays 12– 13; no blue luminous tissue; one white luminous shoulder spot; all jaw teeth small canines; and gill filaments on first arch extending beyond opercular opening. Photonectes barnetti, new species (North Pacific Gyre) has an elongate barbel with a single ovoid bulb and a white area along the stem; IV photophores 37–39; dorsal-fin rays 13–15; no blue luminous tissue; one or two white luminous shoulder spots; jaw teeth of variable length; and reduced gill filaments on first arch. Photonectes corynodes, new species (central equatorial Pacific) is known from a single specimen and has a barbel with a single hourglass-shaped bulb and a bifid terminal filament, both branches ending in small light organs; IV photophores 34; dorsal-fin rays 15; no blue luminous tissue or white luminous shoulder spots; jaw teeth of variable length; and gill filaments neither reduced nor elongated. A key to the subgenus Photonectes is provided.
S
TOMIID fishes of the subfamily Melanostomiinae (or scaleless black dragonfishes; Nelson, 2006) are elongate deep-sea predators with two ventrolateral rows of photophores, canine teeth, and no true gill rakers as adults. Small secondary photophores are often present on the head, body, and fin rays; clusters or spots of luminous tissue may occur around the head, on the caudal peduncle, or on the lateral surface of the body. The chin barbel can be very small to long, simple to complex. The dorsal and anal fins are opposite and set far posteriorly on the body (Morrow and Gibbs, 1964; Harold, 2003; Nelson, 2006). The genus Photonectes is separated from all other melanostomiine genera by the following combination of characters: the lower jaw is longer than the upper and strongly curved dorsally; the snout is short and abrupt; teeth are present on the vomer; the pectoral fin has 0–3 rays; a large postorbital light organ but no suborbital light organ; and the mesocoracoid is present but unossified or absent (Morrow and Gibbs, 1964; Fink, 1985; Harold, 2003). Several species have one or two white luminous spots at the upper end of the opercular opening (‘‘shoulder spots’’); a specimen of P. margarita (Scripps Institution of Oceanography SIO 98-5) has additional spots on the lateral surface of the body and on the caudal peduncle. Some species of Photonectes have two lines of what is referred to as blue luminous tissue along the ventral midline from the isthmus to the anal-fin origin (Morrow and Gibbs, 1964); short transverse branches may be present between each PV photophore, and small patches may occur along the isthmus, lower jaw, and end of the maxillary (Morrow and Gibbs, 1964). The barbel bulb and postorbital light organ have been reported to produce light with various colors in freshly caught specimens (Beebe and Crane, 1939). Paxton (pers. comm.) noted the barbel bulb in a freshly caught specimen displayed different colors in incandescent light than it did in UV light; these color differences have been previously reported by Beebe and Crane (1939). Of the 22 nominal species described for Photonectes, 12 are considered valid and are placed in four subgenera following Morrow and Gibbs (1964) based on the presence or absence of black skin covering the dorsal- and anal-fin rays, the 1
pelvic-fin insertion closer to either the caudal-fin base or the snout, and the number of IV (IP + OV, isthmus to pelvic fins) photophores (Table 1). The three new species are placed in the subgenus Photonectes based on the following combination of characters: pectoral fins absent, pelvic fins inserted closer to the caudal-fin base, dorsal- and anal-fin rays not covered by black fleshy tissue, and IV photophores 30–39. Species of Photonectes are distinguished mainly by differences in the barbel structure, presence or absence of extra luminous tissue spots, and presence or absence of blue luminous bands or spots (Morrow and Gibbs, 1964), any of which may be damaged or destroyed during collection. This study found additional characters useful for identification of species: IP (isthmus) photophore origin (extending the full length of the isthmus or beginning posterior to the mandibular symphysis after a gap of approximately 50% of the isthmus length; Fig. 1B, 1C), gill-filament length (Fig. 2), and tooth length (Fig. 3). MATERIALS AND METHODS Measurements were made with vernier calipers to the nearest 0.1 mm and include: standard length (SL), head length (HL), barbel length, and lengths from snout to pelvic fin (Sn–V), from pelvic fin to vent (V–vent), and from vent to base of caudal fin (vent–C). Percent of SL (% SL) was also calculated and is given in Table 2. Due to the limited number of specimens, standard deviations were not calculated and, by SIO Collection policy, dissections were not made for sex determination. Meristic data include fin rays, teeth, and lateral and ventral photophores. Tooth counts are reported as premaxillary, maxillary, mandibular, vomerine, palatine, and basibranchial; maxillary teeth are divided into ‘‘erect’’ (anterior canines) and ‘‘oblique’’ (posterior series of very small inclined teeth). Photophore terminology (Fig. 1) follows Morrow and Gibbs (1964). Institutional abbreviations are as listed at http://www.asih.org/node/204. Gill-filament length on first branchial arch (Table 1) is defined as ‘‘reduced’’ (less than one-half arch depth; Fig. 2A), ‘‘normal’’ (longer than arch depth but not extending beyond opercular opening; Fig. 2B), or ‘‘very
Scripps Institution of Oceanography, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0208; E-mail:
[email protected]. Submitted: 7 October 2009. Accepted: 22 November 2010. Associate Editor: W. L. Smith. DOI: 10.1643/CG-10-184 F 2011 by the American Society of Ichthyologists and Herpetologists
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Table 1. Selected Meristic and Morphological Characters of Subgenera and Species of Photonectes.
Subgenus/ species
Fin-ray counts D
A
P
D&A V fin skin insertion
Photophore counts IP, gap
VAV
VAL
IV
Gill filaments
Luminous tissue Blue
White
Melanonectes braueri dinema leucospilus
15–18 17–21 15–18 18–21 16 18–20
2 2–3 2–3
no no no
caudal 7–8+2–3, gap 14–15 12–14 30–33 reduced caudal 7–8+2, gap 14–18 14–17 28–33 very long caudal 8+2, gap 14–15 12–14 33–34 reduced
no none no 1, snout no 1, snout
Trachinostomias margarita munificus parvimanus
15–19 18–24 19 21 17–19 21–24
0–1 0 2
yes yes yes
caudal 8–11, no gap 11–13 11–14 41–45 normal caudal 8, (?) 12 2–4 49–50 (?) normal caudal 10–11, no gap 12–14 12–14 43–49 normal
no shoulder, body no none no (?)
Dolichostomias gracilis
18–22 21–23
0
no
snout
8–9, gap
14–15
13
30–32 normal
yes none
0 0 0 0 0 0 0 0
no no no no no no no no
caudal caudal caudal caudal caudal caudal caudal caudal
8+4, gap 8+4, gap 7–8, gap 8+2–3, gap 8, gap 7, gap 8+1–2, gap 8, gap
12–13 13–15 13–15 11–12 12–13 12 11–12 11–12
11–12 12–14 12–15 11–12 13–14 11 10–12 12–13
31–34 37–38 38–39 32–34 37–39 34 33–34 30–31
yes no no yes no no yes no
Photonectes achirus 15–17 albipennis 13–15 barnetti n. sp. 13–15 caerulescens 17–19 coffea n. sp. 12–13 corynodes n. sp. 15 mirabilis 16–17 phyllopogon 20–23
18–19 15–17 15–16 18–21 15–17 16 19–20 22–25
very long normal reduced very long very long normal reduced reduced
1–2, shoulder 2, shoulder 1–2, shoulder none 1, shoulder none none none
Sources: Regan and Trewavas, 1930; Morrow and Gibbs, 1964; Gibbs, 1968; material examined. long’’ (much greater than depth of arch and extending beyond opercular opening; Fig. 2C). Most specimens were collected by Isaacs-Kidd midwater trawl (IKMT). One specimen, SIO 72-17, was collected by an IKMT modified to collect plankton (IKPT; Williamson and McGowan, 2009), SIO 77-195 was collected by a neuston net, and SIO 77-200 was collected by a dredge box. Collection depths are given in meters (m), fathoms (fm), or meters-wire-out (mwo). Photonectes coffea, new species Figures 3A, 4–6; Tables 1, 2 Holotype.—SIO 73-168, 149.0 mm SL, central equatorial Pacific Ocean, 0u01.49S–05.19N, 154u58.7–155u00.19W, R/V
Fig. 1. (A) Photophore notation: PV–ventrally, from pectoral-fin base to pelvic-fin base; IV–IP plus PV; VAV–ventrally, from pelvic-fin base to anal-fin origin; AC–from anal-fin origin to caudal-fin base; OV–laterally, from pectoral-fin origin to pelvic-fin origin; VAL–laterally, from pelvic-fin origin to anal-fin origin or slightly beyond; (B) and (C) IP–along isthmus to pectoral-fin base with insertion at mandibular symphysis or posteriorly halfway along isthmus length, respectively.
Melville, 10-ft IKMT, depth approx. 500 m (1070 mwo), 16 July 1972. Paratypes.—SIO 73-168, 113.2 mm SL, captured with holotype; SIO 77-195, 37.0 mm SL, 7u329S, 168u299W, neuston net, surface, 14 November 1972; LACM 56904-1 (ex SIO 77-167), 112.8 mm SL, 17u40–48.49N, 119u55.4– 55.59E, 10-ft IKMT, 0–3000 mwo, 2 August 1976. Non-type material.—SIO 77-200, 146.6 mm SL, 30u389N, 164u24.49W, R/V Sea Scope, dredge box, 3000 fm, 6 July 1972. Diagnosis.—A member of the subgenus Photonectes based on the following combination of characters: dorsal- and analfin rays not covered with black fleshy skin; pectoral fins absent; pelvic fins inserted closer to the caudal-fin base; IV photophores 37–39; and IP photophores begin halfway posteriorly on the isthmus. Within the subgenus, Photonectes coffea differs from P. achirus, P. caerulescens, and P.
Fig. 2. Gill-filament lengths on first branchial arch: (A) reduced, or less than one-half branchial arch depth; (B) normal, or longer than one-half branchial arch depth but not extending beyond opercular cover; and (C) very long, or longer than branchial arch depth and extending beyond opercular cover.
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Photophores: IV 37–39 (IP 8 + PV 29–31); VAV 12–13; AC 9–12; BR 6–7; OA 37–39 (OV 24–26 + VAL 13–14), last one or two photophores over anal-fin base; IP series with gap, begins posteriorly about halfway along isthmus length (Fig. 1C). Secondary photophores on head and cheeks, and along dorsal- and anal-fin rays; on body extend in irregular lines from dorsal midline to each OV photophore, occur in small clusters below each OA and PV, and in two narrow lines along the body above PV series (Fig. 4). Postorbital photophore teardrop-shaped, approximately equal in length to eye diameter. One white luminous shoulder spot. No blue luminous tissue. Premaxillary teeth 8–11; maxillary teeth 6–13 erect and 8– 13 oblique; mandibular teeth 29–35; vomerine teeth 2–3 pairs, lateral teeth longest; palatine teeth 2–4 pairs, first and third pairs longest; basibranchial teeth absent or 6 pairs (when present, a gap after the first three pairs (3 pairs, gap, 3 pairs), with posterior tooth in third and sixth pairs longest). Upper and lower jaw teeth very short, no long canines present (Figs. 5A, 7). Barbel elongate, 11.2–16.9 mm (9.9–11.7% SL), stem pigmented, without secondary photophores and with two large ovoid bulbs; proximal organ at about one-quarter distance from base of dorsal side of stem; distal bulb flat on posterior side and on anterior side a V-shaped line of dark tissue extending distally along length of bulb giving bulb a resemblance to a coffee bean; dark tissue continues distally on posterior side of bulb onto long whip-like filamentous tip. Distribution.—Known from the central equatorial and the central North Pacific and from the western Pacific near Luzon Island, Philippines (Fig. 6).
Fig. 3. Schematic of left lateral view of tooth patterns with upper and lower jaws shown disarticulated. Arrows indicate junctures of premaxillary and maxillary bones. (A) P. coffea, new species, holotype, SIO 73168, 149.0 mm; (B) P. barnetti, new species, holotype, SIO71-296, 41.6 mm; (C) P. corynodes, new species, holotype, SIO 73-170, 24.1 mm.
mirabilis by blue luminous tissue absent (vs. present); differs from P. phyllopogon by dorsal-fin rays 12–13 (vs. 20–23) and IV photophores 38–39 (vs. 30–31); differs from P. corynodes by an elongate barbel with filamentous terminal barbel (vs. short barbel with bifid terminal barbel) and one white luminous shoulder spot (vs. none); differs from P. barnetti and P. albipennis by barbel with two bulbs (vs. one) and gillfilament length on first branchial arch very long, extending beyond opercular opening (vs. reduced or normal, not extending beyond opercular opening). Description.—Meristics and morphometrics given in Tables 1 and 2. Body elongate, 37.0–149.0 mm SL. HL 12.2–14.2 mm (8.3–11.7% SL); Sn–V 64.1–87.1 mm (55.3–58.4% SL); V– vent 22.3–31.5 mm (19.8–21.1% SL); vent–C 25.4–31.0 mm (20.4–23.4% SL). Gill filaments extremely long, extending beyond gill openings. Color of body in alcohol fading to dark brown-black. Dorsal-fin rays 12–13; anal-fin rays 15–17; pelvic-fin rays 7; pectoral fins absent. Dorsal and anal fins not covered with black fleshy skin. Pelvic fins inserted closer to caudal fin than to snout; length of longest ray unknown as tips broken. Caudal fin forked, ventral lobe longer than dorsal lobe.
Etymology.—The specific name refers to the shape of the terminal barbel bulb which resembles a coffee bean. Photonectes barnetti, new species Figures 3B, 6–8; Tables 1, 2 Holotype.—SIO 71-296, 41.6 mm, central North Pacific, 27u25.5–28.59N, 155u26.3–27.39W, R/V Thomas Washington, IKMT, 0–1500 mwo, 29 September 1971. Paratypes.—SIO 71-296, 25.4 mm SL, captured with the holotype; USNM 395048 (ex SIO 71-297), 23.4 mm SL, 27u23.4–25.19N, 155u10.6–27.29W, IKMT, 0–3000 mwo, 29 September 1971; LACM 57213-1 (ex SIO 71-305), 22.3 mm SL, 27u25.6–25.89N, 155u30.9–33.59W, IKMT, 0–1500 mwo, 1 October 1971. Non-type material.—SIO 71-310, 23.4 mm SL, 27u27.0– 28.29N, 155u28.6–47.09W, IKMT, 0–3000 mwo, 2 October 1971; SIO 72-9, 23.4 mm SL, central North Pacific, 27u21.6– 24.09N, 155u24.4–26.69W, IKMT, 0–3000 mwo, 23 September 1971; SIO 72-17, 20.6 mm SL, 27u21.5–21.69N, 155u22.4– 23.99W, IKPT, 0–1000 mwo, 27 September 1971. Diagnosis.—A member of the subgenus Photonectes based on the following combination of characters: dorsal- and analfin rays not covered with black fleshy skin; pectoral fins absent; pelvic fins inserted closer to the caudal-fin base; IV photophores 38–39; and IP photophores begin halfway posteriorly on the isthmus. Within the subgenus, P. barnetti
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Table 2. Meristics and Morphometrics of the Pacific Ocean New Species of Photonectes. Values for holotypes; range for all known specimens given for P. coffea and P. barnetti.
Size (mm)
P. coffea (n = 5)
P. barnetti (n = 7)
P. corynodes (n = 1)
149.0 (37.0–149.0)
41.6 (20.6–41.6)
24.1
Fin rays Dorsal Anal Pectoral Pelvic
13 (12–13) 16 (15–17) 0 7
Photophores IP PV VAV AC OV VAL BR
31 13 12 26 13 7
Teeth Premaxillary Maxillary Erect Oblique Mandibular Vomerine Palatine Basibranchial Morphometrics (% SL) Head Barbel Sn–V V–vent Vent–C
8 (29–31) (12–13) (9–12) (24–26) (13–14) (6–7)
9 (8–11) 12 12 32 3 4 6 9.5 10.9 58.4 21.1 20.4
(6–13) (8–13) (29–35) (2–3) pr. (2–4) pr. (0–6) pr. (8.3–11.7) (9.9–11.7) (55.3–58.4) (19.8–21.1) (20.4–23.4)
differs from P. achirus, P. caerulescens, P. coffea, and P. corynodes by gill-filament length on first branchial arch reduced (vs. normal or very long); differs from P. phyllopogon by dorsal-fin rays 13–15 (vs. 20–23) and IV photophores 38– 39 (vs. 30–31); differs from P. mirabilis by blue luminous tissue absent (vs. present) and barbel with elongate stem and whiplike filament (vs. short stem and bifid filament). Description.—Meristics and morphometrics given in Tables 1 and 2. Small-sized fish with elongate body, 20.6–41.6 mm SL. HL 2.5–6.1 mm (10.7–14.9% SL); Sn–V 12.2–25.4 mm (59.2–64.9% SL); V–vent 2.1–7.1 mm (9.0–17.1% SL); vent–C 3.8–8.1 mm (16.2–23.3% SL). Gill filaments extremely short on first gill arch, increasing in length on each succeeding arch, but not extending beyond gill cover. Body color in alcohol rusty-brown; probably blackish in life. Dorsal-fin rays 13–15; anal-fin rays 15–16; pelvic-fin rays 7; pectoral fins absent. Dorsal and anal fins not covered with black fleshy skin; rays outlined with small white luminous tissue spots. Longest pelvic-fin ray extends at least to vent; pelvic fins insert closer to caudal fin than to snout. Caudal fin forked and elongate; ventral lobe longer than dorsal lobe. Photophores: IV 38–39 (IP 7–8 + PV 30–31); VAV 13–15; AC 8–12; BR 6–7; OA 39–42 (OV 26–27 + VAL 12–15), last two or three photophores over anal-fin base; IP series with gap, begins posteriorly about halfway along isthmus length
15 (13–15) 16 (12–16) 0 7
15 16 0 7
8 (18–31) (13–15) (8–12) (18–27) (12–15) (6–7)
8 26 12 11 22 11 7
30 14 11 26 13 7
11 (6–12) 3 10 26 2
(3–6+) (6–10) (17–26) (1–2) pr. 1 pr. 3 (2–3) pr.
14.7 9.8 61.1 17.1 19.5
(10.7–16.1) (8.6–13.4) (59.2–64.9) (12.8–17.1) (16.2–22.9)
4 6 7 16 1 pr. 1 pr. 1 + 1–2 pr. 15.8 18.7 64.3 14.5 21.6
(Fig. 1C). Secondary photophores on body similar in pattern and occurrence to P. coffea. Postorbital photophore ovoid, length approximately equal to eye diameter. One or two white luminous shoulder patches. No blue luminous tissue. Small patches of white luminous tissue outline dorsal- and anal-fin rays. Premaxillary teeth 6–12, first two teeth smallest followed by longer canines; maxillary teeth 3–6 erect and 6–10 oblique; mandibular teeth 17–26; vomerine teeth 1–2 pairs, lateral tooth longest; palatine teeth 1–2 pairs; basibranchial teeth 2–3 pairs, small gap between first and second pairs. Jaws with needle-like canines; 3–5 smaller teeth between each longer canine (Fig. 3B). Barbel elongate, 2.0–4.1 mm (8.6–13.4% SL); stem without discernible secondary light organs; proximal and distal thirds of stem pigmented, middle third pale (‘‘white,’’ unknown if luminous or reflective); barbel ends in a large ovoid bulb, with V-shaped wedge of pigmented tissue on anterior side extending in a thin line across bulb and ending at the base of a pale elongate terminal filament; bulb encased in a clear sheath. Distribution.—North Pacific Gyre, approximately 27uN, 155uW (Fig. 6). Etymology.—Named in honor of the late Michael Barnett, who collected and recognized the new species.
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Fig. 4. Left lateral view of Photonectes coffea, new species, holotype, SIO 73-168, 149.0 mm.
Photonectes corynodes, new species Figures 3C, 6, 9–10; Tables 1, 2
anal-fin rays (vs. 19–20); no blue luminous tissue (vs. present); and no light organs inside the lower jaw (vs. three pairs).
Holotype.—SIO 73-170, 24.1 mm SL, central equatorial Pacific, 0u03.89S–0u07.09N, 154u54.5–56.09W, R/V Melville, 10-ft IKMT, depth approx. 1280 m, 17 July 1972.
Description.—Meristics and morphometrics given in Tables 1 and 2. Small, elongate specimen, 24.1 mm SL. HL 3.8 mm (15.8% SL); Sn–V 15.5 mm (64.3% SL); V–vent 3.5 mm (14.5% SL); vent–C 5.2 mm (21.6% SL). Gill filaments extend just to edge of gill cover; tips of filaments dark. Color of body in preservative faded to light rust-brown; probably black in life. Dorsal-fin rays 15; anal-fin rays 16; pelvic-fin rays 7; pectoral fins absent. No black fleshy tissue over dorsal- and anal-fin rays. Pelvic fins inserted closer to caudal fin than to snout; pelvic-fin rays extend at least to vent. Caudal fin forked, ventral lobe longer than dorsal lobe. Photophores: IV 34 (IP 8 + PV 26); VAV 12, last two photophores over anal-fin origin; AC 11; OA 33 (OV 22 +
Diagnosis.—A member of the subgenus Photonectes based on the following combination of characters: dorsal- and analfin rays not covered with black fleshy skin; pectoral fins absent; pelvic fins inserted closer to the caudal-fin base; IV photophores 34; and IP photophores begin halfway posteriorly on the isthmus. Differs from all other species in the subgenus except Photonectes mirabilis by a barbel with a small side-branch on the terminal filament. Differs from P. mirabilis in gill filaments ‘‘normal’’ (vs. very reduced); jaw teeth variable length (vs. short) canines; 16
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Etymology.—From the Greek koryne, meaning mace or club, referring to the appearance of the terminal bulb. DISCUSSION
Fig. 5. Left lateral view of barbel, Photonectes coffea, new species, holotype, SIO 73-168, 149.0 mm, with anterior view of terminal bulb.
VAL 11); BR 7; IP series with gap, begins about midway on the isthmus (Fig. 1C). Small secondary photophores present on head body, in vertical lines from mid-dorsal to each VAV, and along dorsal- and anal-fin rays. Postorbital photophore length 0.5 mm, about equal to eye diameter. No blue luminous tissue or white luminous shoulder spots. Premaxillary teeth 4; maxillary teeth 6 erect and 7 oblique; mandibular teeth 16; vomerine teeth 1 pair; palatines each with a single tooth; basibranchial teeth 2–3 widely separated pairs (one pair followed by a gap and then 1–2 pairs). Jaw teeth composed of long and short canines (Fig. 3C). Barbel short, 4.5 mm (18.7% SL); stem of barbel short, ,0.5 mm (,14% of barbel length), and black-pigmented, followed by a large white bulb, about twice as long as wide and with an hourglass shape, with a narrow (about 12.5% of bulb width) bifid black filament distally; shorter branch ends in a luminous bulb tipped with a small tuft of filaments and longer branch ends in a mace- or club-shaped luminous bulb. All three bulbs surrounded by a thin transparent sheath. No secondary photophores along stem. Distribution.—The only known specimen, the holotype, was captured in the equatorial eastern Pacific (Fig. 6).
Specimens of Photonectes are often difficult to identify to species. Large adults may have rather deep flaccid bodies subject to damage during collection, losing barbels, ventrolateral photophores, and luminous tissue. Barbels may undergo ontogenetic changes (e.g., P. parvimanus and P. fimbria; Beebe and Crane, 1939; Morrow and Gibbs, 1964). The additional characters found during this study (gillfilament length, gap/no gap before the IP series, and overall tooth length) increase the combination of available characters used for identification. Within the subgenus Photonectes, P. coffea, P. barnetti, and P. albipennis share a high IV photophore count (37–39), one or two white luminous shoulder spots, absence of blue luminous tissue, and an elongate barbel with a single terminal filament. Photonectes barnetti differs from P. coffea and P. albipennis by having a barbel with a single large ovoid bulb, one or two pairs of palatine teeth (vs. 2–4 pairs), both jaws with variable-length (vs. short length) canines, and gill filaments very reduced on the first branchial arch. Photonectes coffea differs from P. albipennis in having a shorter barbel (,12% SL vs. .20% SL) with two large bulbs (vs. one minute bulb), and very long gill filaments extending beyond the opercular opening (vs. not extending beyond the opening). The barbel of P. corynodes is most similar to the barbel of P. mirabilis (Parr, 1927:figs. 59–60) in having a side branch along the terminal filament. It differs in the absence of blue luminous tissue, fewer anal-fin rays (16 vs. 19–20), ‘‘normal’’ gill filaments on the first branchial arch (vs. very reduced), no light organs inside the lower jaw, a single pair of teeth each on the vomer and the palatines (vs. two pairs each), and both long and short canines in both jaws (vs. short even canines in both jaws). The length of the gill filaments on the first branchial arch is variable within the genus and within the subgenus Photonectes (Table 1; Fig. 2) and is probably related to the oxygen content of the water mass where the species occur. The extremely long gill filaments of P. achirus, P. caerulescens, and P. coffea suggest low-oxygen habitats and have been reported in other deep-sea fishes such as Cyclothone (DeWitt, 1972) and Scopelarchoides nicholsi (Johnson, 1974). The gill filaments of reduced length in P. barnetti, P. mirabilis, and P. phyllopogon suggest a relatively welloxygenated water as indicated for some species of Platytroctidae (Matsui and Rosenblatt, 1987:12). Data on the oxygen content were not checked for this paper but are available in cruise reports on file at the Scripps Institution of Oceanography. The absence of the gap between the mandibular symphysis and the origin of the IP photophores appears to be unique to the subgenus Trachinostomias (Table 1; Fig. 1B, 1C). While not present in the subgenus Photonectes, this character adds to the definition of the subgenera and will aid in the future identification of species of Photonectes. Sexual dimorphism of the postorbital organ (PO) has been noted in many stomiid fishes (Krueger and Gibbs, 1966; Gibbs, 1969; Clarke, 1998, 1999; Sutton and Hartel, 2004; Kenaley, 2007; Borodulina, 2009), including some species of Photonectes (cited in Herring, 2007:table 3). However, following curatorial policy at SIO, dissections for sex
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Fig. 6. Distribution of Photonectes coffea (closed circle), P. barnetti (closed square), P. corynodes (closed triangle). Symbols may represent more than one record.
determination were not done. The size of the PO organs within a species were not noticeably different. Availability of more specimens may show otherwise.
2b.
_______________________________________________________________________
3a. KEY TO THE SPECIES OF PHOTONECTES (PHOTONECTES) 1a.
A lateral or midlateral band of blue luminous tissue present, often with superficial luminous tissue on underside of lower jaw and/or light organs inside 2 lower jaw No lateral or midlateral blue luminous tissue or 4 other superficial luminous tissue Three pairs of light organs inside lower jaw; gill filaments on first arch short, length about half of P. mirabilis arch depth
________
3b.
______
4a.
____________________________________________________________________________________
1b.
___________________________
4b.
_____________________________________
2a.
___________________________________________________________
No light organs inside lower jaw; gill filaments on first arch longer, length about equal to or greater than arch depth 3 Barbel length 50–66% HL, with a small bulb and a long slender translucent terminal appendage P. achirus Barbel length ,40% HL, without a bulb but with a long slender terminal appendage P. caerulescens Barbel length greater than head length, with a slender stem, and ending in a slender terminal filament; 1 or 2 white shoulder spots 6 Barbel length less than head length, with a short base and a more complex terminal structure; no white shoulder spots 5 Dorsal-fin rays 15; anal-fin rays 16; barbel with an hourglass-shaped bulb and a bifid terminal fila_____________________________________________________________
5a.
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Fig. 7. Photonectes barnetti, new species, holotype, SIO 71-296, 41.6 mm.
ment, each branch ending in a small bulb; gill filaments on first branchial arch ‘‘normal’’ (Fig. 2B), length about equal to arch depth P. corynodes, new species Dorsal-fin rays 20–23; anal-fin rays 22–25; barbel with round bulb bearing a terminal appendage ending in a translucent leaf-like expansion with serrated edges and four terminal filaments; gill filaments on first branchial arch reduced (Fig. 2A), length about half arch depth P. phyllopogon Barbel with a single distal bulb; length of gill filaments on first branchial arch less than or equal to arch depth 7 Barbel with a distal bean-shaped bulb and a proximal bulb; length of gill filaments on first branchial arch very long, extend beyond opercular opening P. coffea, new species Length of gill filaments on first branchial arch very long, twice depth of first arch depth; dorsal-fin rays 12–13; barbel with single minute bulb and a stem entirely pigmented; premaxillary and maxillary teeth all short canines P. albipennis Length of gill filaments on first branchial arch short, #0.53 arch depth; dorsal-fin rays 14–15; barbel with one large ovoid distal bulb and an unpigmented area about midlength; premaxillary and maxillary teeth a combination of long and short canines P. barnetti, new species __________
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MATERIAL EXAMINED Photonectes achirus: SIO 76-6, 1 (93), 30u319N, 147u15.59W; SIO 88-194, 1 (24.5), 24u40.59N, 76u169W; USNM 320468, 1 (69.5), 27u119N, 170u549W. Photonectes albipennis: AMS I.22809-030, 1 (219), 18u409S, 116u429E; SIO 63-72, 1 (42), 35u149N, 159u049E; SIO 73-149,
1 (195.7), 28u13.29N, 154u40.99W; SIO 73-159, 1 (136), 31u09.89N, 154u599W; SIO 73-332, 1 (163.5), 28u17.99N, 154u36.99W; SIO 91-25, 1 (162), 32u489N, 124u069W; SIO 9367, 1 (42), 05u059S, 146u009E; SIO 93-69, 1 (190), 18u409S, 116u409E; USNM 257280, 2 (17–21), 21u009N, 158u009W; USNM 292472, 2 (30–42), 00u599N, 153u00.59W; USNM 300009, 1 (227), 21u22.59N, 158u22.59W; USNM 301268, 1 (23), 10u329S, 160u419E. Photonectes braueri: AMS I.20305-013, 1 (125), 33u339S, 152u189E; SIO 69-25, 1 (26.3), 28u02.39S, 66u03.69E; SIO 70122, 1 (39), 24u349S, 154u509W; SIO 73-146, 6 (23.6–28.2), 25u30.49S, 155u23.69W; SIO 75-631, 1 (26.2), 14u55.69S, 155u17.49W; SIO 75-632, 1 (30.6), 25u13.39S, 155u01.59W; USNM 234320, 1 (33.5), 31u469N, 64u309W; USNM 300152, 1 (227), 26u249S, 65u029E. Photonectes caerulescens: AMS I.19753-037, 2 (25–31), 05u519S, 147u209E; AMS I.24859-002, 1 (75), 33u409S, 152u059E; USNM 256901, 1 (119), 01u54.59S, 158u10.59W; USNM 258733, 1 (54), 21u259N, 158u259W; USNM 258739, 1 (120), 21u209N, 158u209W. Photonectes dinema: USNM 234325, 1 (193), 32u139N, 64u169W; USNM 234328, 1 (34.2), 31u489N, 63u499W. Photonectes gracilis: AMS I.20941-010, 3 (119–189), 12u409S, 144u019E; SIO 70-340, 1 (138), 19u08.69N, 122u41.79E. Photonectes leucospilus: SIO 97-11, 1 (45), 27u009N, 86u009W; USNM 214457, 1 (19), 21u209N, 158u209W; USNM 234337, 2 (25–37), 33u009N, 64u459W. Photonectes margarita: LACM 9530-23, 2 (122–147), 28u409N, 117u129W; LACM 9586-29, 1 (161), 32u20.89N, 120u20.29W; LACM 9726-9, 1 (130), 29u119N, 118u169W; SIO 60-249, 1 (185), 17u199N, 154u109W; SIO 61-129, 1 (107.1), 00u06.59N, 179u56.59W; SIO 63-377, 1 (130), 30u28.79N, 122u12.79W; SIO 68-478, 1 (235), 22u09.59N, 171u369W; SIO 69-354, 1 (45), 17u49.29N, 143u45.69E; SIO 87-41, 1 (44), 31u009N, 158u559W; SIO 89-11, 1 (132), 33u04.99N, 124u23.49W; SIO 93-287, 1 (44), 32u26.69N, 127u44.69W; SIO 93-289, 1 (72), 32u26.19N, 127u44.69W; SIO 96-149, 1 (125), 01u209N, 88u009W; SIO 97-
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USNM 201856, 1 (110), 01u489–02u009S, 90u19–109W; USNM 234297, 1 (207), 32u109N, 63u539W. Photonectes phyllopogon: USNM 258744, 1 (25), 09u579S, 64u559E. ACKNOWLEDGMENTS R. Rosenblatt, P. Hastings, and H. J. Walker, Jr. provided helpful critiques of the manuscript, and encouragement and support of this project. Curatorial assistance was provided by H. J. Walker (SIO), R. Feeney (LACM), and J. Williams and S. Smith (USNM). Photographs by M. Soave and C. Sheridy (UCSD-SIO). LITERATURE CITED
Fig. 8. Left lateral view of barbel, Photonectes barnetti, new species, holotype, SIO71-296, 41.6 mm.
12, 1 (254), 27uN, 86uW; SIO 97-88, 1 (57), 31uN, 145uW; SIO 97-104, 1 (214), 31uN, 127uW; SIO 98-5, 1 (129), 34u52.99N, 124u28.89W; USNM 257285, 1 (78), 21u009N, 158u209W; USNM 257286, 1 (218), 21u009N, 158u009W; USNM 257287, 1 (190), 21u009N, 158u009W; USNM 257288, 1 (91), 21u009N, 158u009W; USNM 297063, 1 (42), 31u48.49N, 120u55.59W; USNM 320469, 1 (57), 00u449S, 149u469W. Photonectes mirabilis: AMS I.19739-018, 1 (32.5), 07u099S, 148u529E; USNM 256912, 1 (54.7), 00u219N, 150u11.59W; USNM 270613, 2 (22–23), 25u259N, 78u049W. Photonectes parvimanus: AMS I.20315-023, 2 (251–261), 33u539S, 152u029E; SIO 76-136, 1 (33), 24u379S, 155u04.59W;
Beebe, W., and J. Crane. 1939. Deep-sea fishes of the Bermuda oceanographic expeditions: family Melanostomiatidae. Zoologica 24:65–238. Borodulina, O. D. 2009. External structure of the postorbital organ in some representatives of the family Melanostomiidae (Stomiiformes). Journal of Ichthyology 49:698–701. Clarke, T. A. 1998. Pelagic fishes of the genus Eustomias (Melanostomiidae) presently associated with Eustomias achirus Parin and Pokhilskaya with the description of five new species. Copeia 1998:676–686. Clarke, T. A. 1999. Pelagic fishes of the genus Eustomias (Melanostomiidae) similar to Eustomias dendriticus Regan and Trewavas with the description of seven new species. Copeia 1999:1002–1013. DeWitt, F. A., Jr. 1972. Bathymetric distributions of two common deep-sea fishes, Cyclothone acclinidens and C. signata, off southern California. Copeia 1972:88–96. Fink, W. L. 1985. Phylogenetic interrelationships of the stomiid fishes (Teleostei: Stomiiformes). Miscellaneous Publications, Museum of Zoology, University of Michigan 171:1–127. Gibbs, R. H., Jr. 1968. Photonectes munificus, a new species of melanostomiatid fish from the South Pacific Subtropical Convergence, with remarks on the convergence fauna. Contributions in Science (Los Angeles) 149:1–6. Gibbs, R. H., Jr. 1969. Taxonomy, sexual dimorphism, vertical distribution, and evolutionary zoogeography of the bathypelagic fish genus Stomias (Stomiatidae). Smithsonian Contributions in Zoology 31:1–25. Harold, A. S. 2003. Melanostomiidae: scaleless dragonfishes, p. 907–912. In: FAO Species Identification Guide for Fishery Purposes. The living marine resources of the western central Atlantic. Vol. 2: Bony fishes part 1 (Acipenseridae to Grammatidae). K. E. Carpenter and R. W. Walker (eds.). FAO, Rome. Herring, P. J. 2007. Sex with the lights on? A review of bioluminescent sexual dimorphism in the sea. Journal of the Marine Biological Association, United Kingdom 87:829–842. Johnson, R. K. 1974. A revision of the alepisauroid family Scopelarchidae (Pisces: Myctophiformes). Fieldiana (Zoology) 66:1–249. Kenaley, C. P. 2007. Revision of the Stoplight Loosejaw genus Malacosteus (Teleostei: Stomiidae: Malacosteinae), with description of a new species from the temperate Southern Hemisphere and Indian Ocean. Copeia 2007:886–900. Krueger, W. H., and R. H. Gibbs, Jr. 1966. Growth changes and sexual dimorphism in the stomiatoid fish Echiostoma barbatum. Copeia 1966:43–49.
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Fig. 9. Photonectes corynodes, new species, holotype, SIO 73-170, 24.1 mm.
Fig. 10. Left lateral view of barbel, Photonectes corynodes, new species, holotype, SIO 73-170, 24.1 mm.
Matsui, T., and R. H. Rosenblatt. 1987. Review of the deepsea fish family Platytroctidae (Pisces: Salmoniformes). Bulletin of the Scripps Institution of Oceanography 26:1–160. Morrow, J. E., and R. H. Gibbs, Jr. 1964. Family Melanostomiatidae, p. 351–522. In: Fishes of the Western North Atlantic. Vol. 1. Part 4. H. B. Bigelow, C. M. Breder, D. M. Cohen, G. W. Mead, D. Merriman, Y. H. Olsen, W. C. Schroeder, L. P. Schultz, and J. Tee-Van (eds.). Memoir of the Sears Foundation for Marine Research, Yale University, New Haven, Connecticut. Nelson, J. S. 2006. Fishes of the World. Fourth edition. John Wiley and Sons, New York. Parr, A. E. 1927. The stomiatoid fishes of the suborder Gymnophotodermi (Astronesthidae, Melanostomiatidae, Idiacanthidae) with a complete review of the species. Scientific results of the third oceanographic expedition of the ‘‘Pawnee’’ 1927. Bulletin of the Bingham Oceanographic Collection Yale University 3(art. 2):1–123. Regan, C. T., and E. Trewavas. 1930. The fishes of the families Stomiatidae and Malacosteidae. Danish Dana Expedition 1920–22 6:1–143. Sutton, T. T., and K. E. Hartel. 2004. New species of Eustomias (Teleostei: Stomiidae) from the western North Atlantic, with a review of the subgenus Neostomias. Copeia 2004:116–121. Williamson, M., and J. A. McGowan. 2009. The copepod communities of the north and south Pacific central gyres and the form of species-abundance distributions. Journal of Plankton Research 32:273–283.
