Leptoderma macrophthalmum, Byrkjedal, Ingvar, Poulsen, Jan Yde & Galbraith, John, 2011

Byrkjedal, Ingvar, Poulsen, Jan Yde & Galbraith, John, 2011, Leptoderma macrophthalmum n. sp., a new species of smooth-head (Otocephala: Alepocephalidae) from the Mid Atlantic Ridge, Zootaxa 2876, pp. 49-56 : 51-54

Leptoderma macrophthalmum sp.n.

( Fig. 2–3 )

Holotype. NORTH ATLANTIC, 42o47’ N – 29o38’ W, 8 July 2004, 2107– 2063 m gear depth, soft bottom, R/V “G. O. Sars”, super station 42, local station 368, ser. 1150, bottom trawl (shrimp trawl). ZMUB 19686.

Diagnosis. The species differs from three of the four other congeneric species ( L. affinis , L. macrops and L. retropinna ) by having a distinct gap between the posterior ends of the dorsal and anal fins and the beginning of procurrent caudal finrays. This gap is absent in the three species mentioned, but present in the fourth ( L. lubricum ), from which L. macrophthalmum differs by having a lack of dermal papillae along the lateral line, pectoral fins lower on body, a larger eye relative to head dimensions, and a shorter pre-dorsal length.

Description. SL 151 mm, fresh weight 16 g. Dimensions as per cent of SL as follows: Pre-dorsal length 49.3, pre-anal length 45.7, pre-pelvic length 39.5, dorsal fin base 31.1, dorsal procurrent caudal fin section 15.5, anal procurrent caudal fin section 15.1, anal fin base 40.7, pectoral fin length (left) 7.3, pelvic fin length (left) 4.8, greatest body depth 12.8, caudal peduncle depth 2.1, maximal head width (behind eyes) 11.3, head length 23.2, snout length 7.0, horizontal orbital diameter 9.3, post-orbital head length 7.2, upper jaw length 7.9. Eye diameter as percent of head length 40.3. Fin-ray counts as follows: D 32, procurrent dorsal fin 21, A 47, procurrent anal fin 20, pectoral fins 8 (left and right), pelvic fins 8 (left and right), caudal fin 16. Number of gillrakers on first arch 19. Five branchiostegal rays on each side. Total number of vertebrae 67 (15 + 52).

No scales present. Body slender and compressed, greatest body depth a distance from the snout of 13.9 % of SL. Eyes large, upper margin protruding above the dorsal profile of the head. The dorsal profile of the forehead in the fresh specimen convex, but straightening over the snout (shrinkage caused by preservation has decreased the convexity of the forehead profile). Pectoral fins are set fairly low, their upper fin-ray in level with dorsal corner of the gill opening.

Pores along the lateral line about 48, difficult to observe. No dermal papillae found along the lateral line, on the head, or along the back. Three supraorbital pores, four suborbital pores, three preopercular pores, and four mandibular pores, all of these large. Nostrils with large longitudinal openings, partly covered by a dermal flap.

Mouth subterminal. Small, well separated conical teeth present in one row on premaxilla and dentary, the latter teeth of minute size. Supramaxilla slender, pear-shaped and curved.

Head and anterior part of body black, turning gradually lighter brownish towards posterior.

Molecular characterization. The mitogenome sequence of the specimen is 16,607 bp long and shows a typical vertebrate gene order with L and H-strand coding of the 13 protein coding genes, 2 rRNA genes and 22 tRNA genes ( Table 2 ). Compared to the other two species of Leptoderma available, the mitochondrial genome in this new species is 6 and 9 bp longer than L. retropinna and L. lubricum , respectively. Mitogenomic p-distances between the new species and congeners show a difference of 5.2% compared to Leptoderma lubricum and 6.1% compared to L. retropinna with polymorphisms distributed fairly equal throughout the genome. Most polymorphisms are found at third codon positions of protein coding genes and in the control region ( Table 2 ).

Etymology. The specific epithet macrophthalmum (from Greek makros, large, and Greek ophthalmos, eye) refers to the large eyes found in this species.

Mitogenome of Leptoderma mac- Number and position of mt polymorphisms between L. macrophthalmum and a

rophthalmum L. lubricum L. retropinna

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Mitogenome of Leptoderma mac- Number and position of mt polymorphisms between L. macrophthalmum and a rophthalmum L. lubricum L. retropinna

a Gaps excluded from the data since only about 20 gaps are present in the alignments (most located in 16S and CR) b Two additional transitions in intervening non-coding regions included

Figures

FIGURE 2. Drawing of Leptoderma macrophthalmum, holotype ZMUB 19686.

FIGURE 3. Leptoderma macrophthalmum, holotype ZMUB 19686, photographed newly caught, A showing specimen and B close-up of head.

Tables

TABLE 2. Mitogenome characterization of Leptoderma macrophthalmum (holotype) and codon positions, type of polymorphisms and genetic distances compared to L. lubricum (BSKU 57837) and L. retropinna (NSMT 66397), respectively. 1, 2 and 3 denote codon position in the 13 protein coding genes. Ts = transitions, Tv = transversions, P-dist. = Patristic distance. All coding region names follow standard mitochondrial nomenclature and genes encoded on the L-strand are shown in bold.

Region	bp	1	2	3	Ts	Tv	P (%)	1	2	3	Ts	Tv	P (%)
Phe	1–69 69				0	2	2.90				2	1	4.3
12S	70–1020 951				19	5	2.52				27	5	3.37
Val	1021–1092 72				0	0	0				1	0	1.39
16S	1093–2774 1682				24	11	2.08				27	12	2.32
Leu UUR	2775–2849 75				3	1	5.33				3	1	5.33
ND1	2850–3824 975	4	0	50	42	12	5.54	5	2	59	51	15	6.77
Ile Gln	3830–3899 70 3899–3969 71				2 0	0 0	2.86 0				3 1	0 0	4.29 1.41
Met	3969–4037 69				0	0	0				1	0	1.45
ND2	4038–5082 1045	14	3	59	60	16	7.27	14	3	65	64	18	7.85
Trp	5083–5152 70				1	0	1.47				2	0	2.94
Ala	5154–5222 69				1	1	2.90				0	1	1.45
Asn O L Cys	5224–5296 73 5297–5329 33 5330–5396 67				0 2 2	0 0 1	0 6.06 4.55				0 3 2	0 0 1	0 9.09 4.55
Tyr	5395–5465 71				2	0	2.82				1	0	1.41
CO1	5467–7017 1551	4	0	78	68	14	5.29	2	0	83	70	15	5.48
Ser UCN	7018–7088 71				6	0	8.45				5	0	7.04
Asp	7094–7164 71				3	0	4.62				4	0	6.25
CO2	7179–7869 691	3	0	29	24	8	4.63	2	0	40	33	9	6.08
Lys	7870–7943 74				0	0	0				0	0	0
ATP8	7945–8112 168	1	0	4	4	1	2.98	1	0	6	7	0	4.17
ATP6	8103–8786 684	8	2	38	33	15	7.02	11	2	41	42	12	7.89
CO3	8786–9571 786	6	1	36	36	7	5.47	7	2	40	42	7	6.23
Gly	9571–9641 71				0	0	0				0	1	1.43
ND3	9642–9990 349	5	0	21	22	4	7.45	7	0	21	23	5	8.02
Arg	9991–10059 69				1	0	1.45				2	0	2.94
ND4L	10060–10356 297	2	0	12	12	2	4.71	4	1	11	16	0	5.39
ND4	10350–11730 1381	16	2	84	87	15	7.39	20	3	101	101	23	8.98
His	11731–11798 68				2	0	2.90				2	0	2.94
Ser AGY	11799–11866 68				2	1	4.41				3	0	4.41