Polyipnus notatus, Harold, Antony S., Kemp, Iris M. & Shore, Sarah K., 2016

Harold, Antony S., Kemp, Iris M. & Shore, Sarah K., 2016, A new species of Polyipnus (Teleostei: Stomiiformes) from the western Pacific, with comments on the P. triphanos species complex, Zootaxa 4111 (5), pp. 555-564 : 556-562

Polyipnus notatus new species

Fig. 2 , Table 1

Polyipnus triphanos (non Schultz): Harold, 1994:495 (in part, CAS 56034 only, and map, fig. 30).

Polyipnus triphanos Schultz 1938 . In part (USNM 103028, one specimen, 21.2 mm SL, Celebes Sea, P. triphanos paratype).

Holotype: USNM 361926 (27.7 mm), 22°17’N, 120°21’E, South China Sea, SW of Taiwan, (0–) 200 m, 1000– 1200 h, R/V Jen-Ming-Fa, coll. by J. Ta-Ming Wang, 0 5 Feb 1995.

Paratypes. (22, 17.6–30.7 mm). ASIZP 62376 (10, 21.8–30.7 mm), 22°44'N, 120°55'E, South China Sea, off Tungkang, Taiwan. CAS 56034 (10, 17.6–30.0 mm; one specimen, 29.5 mm, cleared and counter-stained), 22°23'N 120°25'E, South China Sea, off Tungkang, Taiwan, coll. by Weise Chang, field number WC 18-XI-83, 18 Nov 1983. USNM 427221 (2, 18.3–26.2 mm), collected with holotype.

Non-types. USNM 103028 (1 of 2, 21.2 mm), 0 8°37'45"N 124°36'45"E, Celebes Sea, (0–) 488 m, R/V Albatross Sta. 5500, 0 4 Aug 1909, Polyipnus triphanos paratype (17.6 mm specimen in this lot cannot be reliably identified to species). ZMUC P206962 (1, 28.9 mm), off Batangas, Philippines, 13°32’N, 121°21’E, 600 mwo, depth 450 m, R/V Dana, Sta. 3733-2, 15 Oct 1929. ZMUC P206963 (2, 26.5–30.4 mm; 30.4 mm specimen cleared and counter-stained), north of Mindanao, Philippines, 0 9°17’N, 123°58’E, 600 mwo, depth 1770 m, R/V Dana, Sta. 3736-6, 28 Jun 1929.

Diagnosis. Unique pattern of dark dorsal pigmentation, with narrow, distinctly triangular vertical lateral bar extending ventrally of predorsal blade to near midline ( Fig. 2 ), compared with a typically broad lateral pigment bar in the other members of the P. asteroides species group, P. as t e ro i d e s Schultz, 1938, P. bruuni Harold, 1994 , P. clarus Harold, 1994 , P. l aternat us Garman, 1899, P. po l l i Schultz, 1961, and P. triphanos Schultz, 1938 ( Harold, 1994: figs. 27, 29, 31, 32, 33, 34, respectively). Ventral margin of dorsal pigment anterior of lateral pigment bar nearly straight and horizontal ( Fig. 2 ), not arched as in other members of the species group. Very small gap between ACB and ACC photophore clusters in most specimens (mean 1.9 left side, 1.8 right side, range 0.9–3.2 % SL, in specimens greater than 20 mm SL), compared with mean 5.6 left side, 5.5 right side, range 2.4–7.8 % SL in P. triphanos (sensu stricto) and 2.2–5.8 combined range for other members of the P. as t e ro i de s species group. Other characters in combination: ACB photophores 9–10 (7 and 8 observed in 17.6 mm specimen); 7–9 in P. triphanos species complex ( Table 2 ), values of 10 or higher present only in Atlantic species P. asteroides , P. c l ar u s and P. laternatus , and gill rakers 14–15 (16–24 total range for remaining members of group) ( Table 3 ).

Description. 23 specimens: (27.7 mm) 17.6–30.7 mm. Maximum observed body size 30.7 mm SL. D (11) 10– 12 [23]. A (18) 17–18 [22]. Posteriormost ray of both dorsal and anal fins divided completely to its base. P (14) 12– 14 [22]. V (7) 6–7 [6]. C 10 dorsal and 9 ventral segmented rays. Dorsal adipose fin present. GR (4) 4–5 + (10) 9– 11 = (14) 14–15 [16]. Branchiostegal rays 10 (7 anterior ceratohyal + 3 posterior ceratohyal). Total vertebrae (33) 33–34 [22]. Scales deciduous. Remaining scales thickened and modified in association with photophores. Body profile anterior of dorsal fin and pelvic fin broadly elliptical, although dorsal profile of head from premaxilla to occiput nearly straight, from that point to dorsal-fin origin nearly straight, with a broadly obtuse angle, its apex located at occiput. Profile from dorsal-fin origin to caudal peduncle nearly straight, but with slight convexity posteriorly; ventral margin of abdomen (PV photophore outline) slightly convex, profile from pelvic-fin base to anal-fin origin (ventral margin of VAV photophore scales) slightly convex, profile of anal-fin base gently sinusoidal with slight concavity anteriorly; caudal peduncle slightly elongate and tapered posteriorly.

Orbit slightly ovate, with elongation in anterodorsal to posteroventral direction. Dentition characters based on one cleared and counter-stained specimen (CAS 56034, 29.5 mm): premaxillary teeth uniserial, 39 left and 36 right, conical to slightly recurved; maxillary teeth minute and conical, biserial with 19 left to 22 right teeth in lateral series on margin of bone and about 6 in medial series scattered along length of bone. Ventral margin of dentary gently convex, with lower jaw terminating posteriorly in acute ventrally directed angle. Dentary teeth slightly larger than maxillary teeth, conical to slightly recurved, 14 in main series along length of bone, two additional series of 5 or 6 recurved teeth near symphysis. Palatine teeth 2, anteriormost tooth conical and about half the length of medial premaxillary teeth, posterior tooth about a quarter the length of other tooth (both sides of cleared and stained specimen). Endopterygoid teeth absent. Vomerine teeth about equal in size to medial premaxillary teeth, recurved, 3 on left lateral process, 2 medially, and 2 on right lateral process, no teeth present on elongate posteromedian process. Gill rakers moderately elongate, with 3–5 longitudinal series of minute conical teeth confined to medial and lateral surfaces. Pseudobranch present, with 10 filaments. Parietal crest discontinuous; anterior portion a laterally compressed, sheet-like ridge, posterior region with two conical spines in the median plane, directed anteriorly and posteriorly; gap between anterior and posterior portions of crest variously occluded by ossification. Parietal with small conical spine posteriorly. Posttemporal spine relatively short, (5.9) 4.8–13.1 % HL), acutely triangular, non-serrate, posterodorsally directed. Exserted anteroventral margin of cleithrum (pectoral shield) with three or four posteroventrally-directed small conical spines. Preopercular rami smooth, lacking serration; one short preopercular spine, (3.8) 5.0–9.8 % HL, in posteroventral angle. Dorsal spinous process with smooth exterior surfaces, terminating posterodorsally in bilateral conical posterodorsally-directed spines. Pelvic (iliac) spine single, acutely triangular but with slight concavity on anterior surface, directed posteroventrally. Anal-fin pterygiophore spine absent, with rounded body of cartilage present only.

Ventral margins of photophore scales lacking spines or denticles. ACA 1+2 with #2 and #3 highly elevated with respect to #1. ACB (10) 7–10 [23], 9 or 10 in all but smallest specimen (17.6 mm SL), with dorsal step between #3 and #4, very small gap between ACB and ACC, mean 1.9 left side, 1.8 right side, (2.4) 0.9–3.2 % SL in specimens greater than 20 mm SL ( Fig. 3 ), appearing in some specimens as a nearly continuous series from ACB to ACC. OVB 1+1+1, in a V configuration but with anteriormost photophore (#1) elevated with respect to #3. Counts of remaining photophore series/clusters consistent with other species of Polyipnus : BR 6, IP 6, L 1, OP 1+1+1, ORB 1, OVA 3. PV 10, VAV 5.

Pigmentation in preservative. Ventral margin of dark brown dorsal pigment below dorsal fin nearly parallel to fin base, not extended ventrally in the form of a saddle ( Fig. 2 ). Dorsal pigment with a distinct predorsal inflection or notch extending dorsally towards but not reaching anterior base of dorsal fin; ventral margin of dorsal pigment below dorsal fin nearly parallel to base of fin, not forming a ventrally extended saddle-like pattern. Moderately long, typically acutely triangular (occasionally rounded termination), lateral pigment bar extending ventrally from near anterior portion of predorsal blade, not reaching lateral midline. Ventral margin of dark dorsal pigment anterior of lateral pigment bar nearly straight and horizontal ( Fig. 2 ). Dorsal pigment also with areas of concentrated dark chromatophores in series along base of dorsal fin, continuing posteriorly to dorsal surface of caudal peduncle where pigment is most concentrated as a blotch. Dark brown to black chromatophores delineating pattern of body segments, including pleural ribs and posterior myosepta, and passing through lateral midline where pigment is most concentrated, creating effect of midlateral row of pigment spots, most visible in posterior half of body. Other dark pigment associated with glandular portion of photophores and photophore reflectors (modified scales), dorsal margin of orbit, frontal and parietal crests, cheek and opercular region, lateral surface of head immediately posterodorsally to orbit and immediately anterior to external rami of posttemporal, posteriormost ventral margin of lower jaw, and exterior surfaces of eye. Dorsal surface of caudal peduncle with a concentration of dark pigment in the form of a blotch; bases of caudal-fin rays, unpigmented or with only one or two dark chromatophores.

Etymology. The specific epithet notatus is a Latin adjective meaning marked, or having been marked, in reference to the distinctive shape of the lateral pigment bar.

Distribution. Polyipnus notatus is known almost entirely from collections from off Taiwan in the South China Sea. Other occurrences are restricted to the Celebes Sea (USNM 103028) and two localities off the Philippines (ZMUC P206962 and ZMUC P206963). Precise depth of capture is unknown because the specimens were all collected by open tow. Available collection data show the maximum depth of capture to be 200 m for the holotype (USNM 361926), and 450, 488 and 1770 m for the three non-type lots, indicating a position in the upper water column at the transition between the meso- and epipelagic zones.

Figures

FIGURE 2. Polyipnus notatus, holotype, 27.7 mm SL, USNM 361926, South China Sea.

FIGURE 3. Scatterplot of ACB-ACC D (right side) versus standard length for Polyipnus notatus and P. triphanos from the western North and South Pacific Ocean. Solid triangle, P. notatus holotype; solid squares, P. notatus paratypes; open triangle, P. triphanos holotype; open diamonds, P. triphanos, North Pacific; open squares, P. triphanos, South Pacific. Linear regression statistics: P. notatus, y = - 0.0211 x + 1.0031, R 2 = 0.1517; P. triphanos, y = 0.0559 x - 0.0666, R 2 = 0.7650.

Tables

TABLE 1. Morphometric character values expressed as percentages of head length (2 to 4) or standard length (all others) for Polyipnus notatus holotype (USNM 361926) and range for 22 paratypes, ASIZP 62376 (10), CAS 56034 (10), and USNM 427221 (2), with overall mean and N for each character.

	Holotype	Paratypes (range)	mean	N
1. Standard length	27.7	17.6 30.7	26.0	23
2. Posttemporal spine length	5.9	4.8 13.1	9.4	23
3. Orbit length	49.1	42.1 57.1	51.9	22
4. Snout length	24.6	18.1 29.4	24.4	23
5. Head length	34.3	31.8 38.8	35.4	23
6. Body depth	59.0	57.2 68.8	61.5	23
7. Caudal peduncle length	13.3	9.6 16.0	13.5	22
8. Caudal peduncle depth	11.3	8.7 13.2	10.8	23
9. Dorsal fin base length	18.9	16.1 21.7	18.7	23
10. Anal fin base length	27.2	25.5 30.5	28.0	22
11. Preanal length	67.7	64.8 74.7	70.0	23
12. Predorsal length	54.5	54.5 60.3	56.7	23
13. Prepelvic length	60.2	60.0 69.6	64.2	23
14. Postdorsal length	55.5	46.5 55.2	52.3	21
15. Postanal length	41.5	38.9 46.0	42.0	23
16. Dorsal-pelvic length	54.4	51.5 61.5	55.7	23
17. ACC length	5.9	6.7 9.9	8.3	23
18. ACB-ACC length	2.4	0.9 5.0	1.9	23
19. OVB 1 height	10.2	10.1 15.3	12.2	22
20. OVB 2 height	5.1	3.5 7.4	5.8	22
21. OVB 3 height	8.1	7.6 10.7	9.1	22
22. ACA 1-AFPS distance	13.8	11.4 14.9	13.2	22
23. ACA 2-AFPS distance	18.1	15.4 19.6	17.4	22

TABLE 2. Frequency distribution of counts of ACB photophores, dorsal-, anal-, and pectoral-fin rays, and total vertebrae. * juvenile specimen (17.6 mm) with 8 left and 7 right ACB photophores. Values reported for P. notatus based on the type series and four non-types. Indo-Philippine refers to oceanic areas through Indonesia, northward to and including the Philippines (North Pacific).

	7	8	9	10
P. notatus		1*	12	14
P. triphanos Indo-Philippine	12	8	1
P. triphanos Coral Sea	4	21	1

ACB photophores

Dorsal-fin Rays

TABLE 3. Frequency distribution of counts of gill rakers for Polyipnus notatus and P. triphanos.

	14	15	16	17	18	19	20	21
P. notatus	6	14
P. triphanos Indo-Philippine	P. triphanos Coral Sea			4	4	5	1	3	5	3	4	3
P. triphanos Coral Sea					1	5	4	3