Lamellibrachia sagami, Kobayashi, Genki, Miura, Tomoyuki & Kojima, Shigeaki, 2015

Kobayashi, Genki, Miura, Tomoyuki & Kojima, Shigeaki, 2015, Lamellibrachia sagami sp. nov., a new vestimentiferan tubeworm (Annelida: Siboglinidae) from Sagami Bay and several sites in the northwestern Pacific Ocean, Zootaxa 4018 (1), pp. 97-108 : 99-106

Genus Lamellibrachia Webb, 1969

Lamellibrachia sagami sp. nov. ( Figs. 2−5 )

Lamellibrachia sp. (La-Ld): Kojima et al. 1997, 507–513.

Lamellibrachia sp. L1: Kojima et al. 2000, 7–13; Kojima et al. 2001, 211–219; Kojima et al. 2002, 57–64; Kojima et al. 2003, 625–635; Kojima et al. 2006, 1357–1361; Miura & Kojima 2006, 209–224; Fujikura et al. 2008, 57–80, Figs. 3.10., 3.13., 3.19.; Miura & Fujikura 2008, 153, Fig. 9.3. A–C.

Lamellibrachia sp. ( Sagami Bay, 300 and 1200 m): Andersen et al. 2004, 980–999.

Lamellibrachia sp. (Nankai Trough): Hilário et al. 2011, 200–207.

Lamellibrachia sp. (Nankai Trough, 1200 m): McMullin et al. 2003, 1–41; Gardiner et al. 2001, 694–707.

Lamellibrachia sp. Sagami : Southward et al. 2011, 245–279.

Material examined. Holotype: off Hatsushima, Sagami Bay, female, 39° 0.95′ N, 139° 13.32′ E, 853 m, Hyper- Dolphin Dive HPD #0928 during Natsushima NT08–25 cruise, 17 Dec 2008, NSMT-Pol H-593, JAMSTEC No. 0 79102. Paratypes: off Hatsushima, Sagami Bay during four dives, three males and two females, the same catch as the holotype, NSMT-Pol P-594, NSMT-Pol P-595, JAMSTEC No. 0 79069, 0 79073, respectively, and JAMSTEC No. 0 79098, 0 79100, 079109; two males and a female, 35° 0.00′ N, 139° 13.50′ E, 1170 m, Dolphin 3K Dive 3K#0190 during Natsushima NT94–04 cruise, 22 Sep 1994, NSMT-Pol P-596, JAMSTEC No. 79842; three males and a female, 35° 0.77′ N, 139° 13.65′ E, 937 m, Shinkai 2000 Dive 2K#1203 during Natsushima NT00–08 cruise, 10 Jul 2000, JAMSTEC No. 26480−26483; five females, 35° 0.76′ N, 139° 13.49′ E, 850 m, Shinkai 2000 Dive 2K#1203 during Natsushima NT00–08 cruise, 10 Jul 2000, NSMT-Pol P-597, JAMSTEC No 026501−026507. Non-type specimens: a male, off Hatsushima, Sagami Bay, 35° 00.00′ N, 139° 13.50′ E, 1160 m, Natsushima NT86–02 cruise Shinkai 2000 Dive2K#222, 27 May 1986, JAMSTEC No. 80467; a female, the Daini Tenryu Knoll, the Nankai Trough, 34° 04.61′ N, 137° 47.27′ E, 606 m, Hyper-Dolphin Dive HPD #1655 during Natsushima NT14−07 cruise, 25 Apr 2014, JAMSTEC No. 1140043315.

Description. Tube length 277.0– 661.5 mm (mean= 545.7 mm, n=4); outer width of top funnel opening 9.5– 11.2 mm (n=4); width of basal end 2.8–7.8 mm (mean= 4.5 mm, n=4). All tubes incomplete, lacking considerable parts of basal regions. External characters of tube variable along its length ( Fig. 3 ). Anterior part straight or slightly curved, but not coiled, with many short collars. Inter-collar distance generally small but varying among specimens. Posterior part sinuous, curled, smooth, without collars.

Obturaculum length 5.8–22.5 mm (mean=17.0 mm, n=18); width 4.4–10.8 mm (mean= 8.1 mm, n=18), with bare anterior face, lacking any secreted structure ( Figs. 4 A, B). Lateral surface of obturaculum surrounded by branchial plumes. Three to six pairs of outer sheath lamellae (mean=4.4, n=17) present. Branchial lamellae with ciliated pinnules enclosed by sheath lamellae, number of pairs 19–26 (mean=23.2, n=17). Ratio of number of branchial lamellae pairs to obturaculum width (BL/OW) varying from 2.0−5.5 (mean=3.0, n=17).

Vestimentum length 32.0– 84.5 mm (mean=58.0 mm, n=18); width 3.5–7.3 mm (mean=5.0 mm, n=18). Anterior edge of vestimentum forming centrally split collar-like fold extending outwardly ( Fig. 4 A). Dorsal paired genital ciliated grooves running along most length of vestimentum and flanked by conspicuous narrow epidermal folds in males; without epidermal folds in females. Ventral surface of vestimentum covered by numerous cuticular plaques, with narrow central ciliated field ( Figs 4 C, 5A). Posterior ends of vestimental folds separated centrally and rounded distally with tongue-like extensions.

All specimens lacking considerable posterior trunk parts. Trunk ( Fig. 4 D) filled with fragile tissue; surface covered entirely by cuticular plaques ( Fig. 5 B) except midventral and middorsal seam-like lines. Opisthosome not observed.

Vestimental plaques from 17 specimens ranging in diameter from 59–101µm (mean=77.4 µm; SD=8.3; n=170). Trunk plaques from 17 specimens ranging in diameter 67−130 µm (mean=94.0 µm; SD=11.7; n=170).

Type-locality. Off Hatsushima in Sagami Bay, 853 m deep.

Etymology. The specific epithet sagami , as noun in apposition, refers to the province name of the Edo period for Kanagawa, the coastal area of Sagami Bay, the type locality.

Comparison with specimens from non-type localities. The COI sequence and the morphology of a specimen collected from the Daini Tenryu Knoll (JAMSTEC No. 1140043315) was examined. Its COI sequence (626bp) was identical to the sequence of 22 specimens (Haplotypes A and D) from the type locality of the new species ( Kojima et al. 2001). Judging from the diameter of vestimental and trunk plaques and the number of branchial lamellae and sheath lamellae, it was also thought to be the new species ( Table 1).

Distribution. Based on the COI sequence ( Kojima et al. 2001; Miura & Fujikura 2008), the species is known from cold seep areas off Hatsushima and on the Okinoyama Bank, Sagami Bay, the Kanesu-no-se Bank, the Ryuyo Canyon, the Omaezaki Spur and the Tenryu Knoll, the Nankai Trough, and the Kuroshima Knoll, the Ryukyu Trench between 270–1300 m ( Fig. 1 ). It is also known from hydrothermal vent fields on the Iheya Ridge and the North Iheya Knoll, the Okinawa Trough, and the Sumisu Caldera, the Izu-Bonin arc between 900–1500 m depth ( Kojima et al. 2001; Miura & Fujikura 2008).

Remarks. All species of the genus Lamellibrachia are distinguishable by the sequence data for COI ( Southward et al. 2011) with the exception of L. victori for which sequence data are not available. In this study, we compare morphologically the new species with other congeneric species.

Lamellibrachia sagami sp. nov. differs morphologically from other known congeneric species in the diameter of cuticular plaques, the number of branchial lamellae and sheath lamellae ( Table 1). There was no significant correlation between mean of the vestimental plaques diameters and the body size (the length and width of obturaculum and vestimentum), and between the trunk plaques diameters and the body size in each specimen of L. sagami sp. nov. (Spearman rank correlation, 17 type specimens and two non-type specimens, P>0.05). Also the number of branchial lamellae and sheath lamellae were not correlated with the body size (Spearman rank correlation, 18 type specimens and two non-type specimens, P>0.05). These suggest that in adults, the diameter of plaques, and the number of branchial lamellae and sheath lamellae are independent of the growth and we, therefore used them for morphological comparison in the genus.

specimen n OL OW BL SL VP TP

mm mm plaque diameter plaque diameter n (µm) n (µm)

Lamellibrachia sagami sp. nov.

6 2.7–3.9 17–25

Lamellibrachia juni 8 6.6–12.9 5.2–8.3 22–35 2–3 87 –99*7 80–98*7 Lamellibrachia anaximandri 26 5.5–17 1.8– 6 8–19 3–9 55–70*6 60–95*6 ……continued on the next page BL/OW References

range mean

Lamellibrachia sagami sp. nov.

: obturacular length, OW: obturacular width, BL: number of branchial lamellae, SL: number of sheath lamellae, /TP: vestimental/trunk plaques. Blanks: no data.

: specimen n=16; *2: specimen n=1; *3: specimen n=5; *4: specimen n=53; *5: specimen n=57; *6: specimen n not mentioned in the paper; *7: specimen n=4, referred to the plaque width in the text; *8: calculated in this study.

At the continental margins in the Pacific, L. sagami sp. nov., L. barhami and L. satsuma differ one another in the diameter of vestimental plaques ( Table 1); 59–101 µm in L. sagami sp. nov., 60–150 µm in L. barhami ( Southward et al. 2011) and 35–63 µm in L. satsuma ( Miura et al. 1997) , and in that of the trunk ones; 67–130 µm, 115–160 µm and 51–82 µm, respectively.

In the South Pacific, L. sagami sp. nov., L. columna and L. juni are distinguishable by the number of sheath lamellae ( Table 1); 8–16 pairs in L. columna and two or three pairs in L. juni ( Southward 1991) while three to six pairs in L. sagami sp. nov.. Although some specimens of L. juni and L. sagami sp. nov. have three pairs of sheath lamellae (Miura & Kojima 2006), the new species has a smaller number of branchial lamellae.

Lamellibrachia sagami sp. nov. differs from L. luymesi known from the Atlantic and L. anaximandri found in the Mediterranean in the diameter of plaques ( Table 1). The diameter of vestimental plaques vary 59–101 µm in L. sagami sp. nov., whereas 55–60 µm in L. luymesi and 55–70 µm in L. anaximandri ; that of trunk ones 67–130 µm in L. sagami sp. nov. whereas 75–85 µm in L. luymesi ( Southward et al. 2011) . Lamellibrachia anaximandri has fewer branchial lamellae than L. sagami sp. nov.. Lamellibrachia victori has seven pairs of sheath lamellae (Mañé- Garzón & Montero 1985) and differs from L. sagami sp. nov., in having three to six pairs ( Table 1).

Additionally, the BL/OW ratio significantly differs from each other in ranging 2.0– 5.5 in L. sagami sp. nov., 4.7–7.8 in L. satsuma , 2.7–4.6 in L. juni (Steel-Dwass test, n=17, 6, 8, respectively, P<0.05).

Lamellibrachia sagami sp. nov., has been thus demonstrated to be new to science.

Figures

FIGURE 1. Distribution of Lamellibrachia sagami sp. nov. around Japan. Stars, Lamellibrachia sagami sp. nov. examined in this study; circles, L. sagami sp. nov.; Open symbols stand for cold seep area; closed symbols stand for hydrothermal vent fields (Fujikura et al. 2008).

FIGURE 2. Field photographs of Lamellibrachia sagami sp. nov. with Alaysia sp. in the cold seep area off Hatsushima. A, Taken during the dive when the holotype was collected, NT 08 – 25 cruise of RV Natsushima dive HPD # 0928; B, Many branchial plumes of L. sagami sp. nov. were popping out of tubes. Taken during the NT 06 – 23 cruise of RV Natsushima dive HPD # 636. Anterior tube diameter of L. sagami sp. nov. are approximately 10 mm.

FIGURE 3. Tubes of Lamellibrachia sagami sp. nov., paratypes. Arrow indicates for the anterior end of the tube. JAMSTEC No. 26480 − 26483. Scale bars = 50 mm (A, B, C).

FIGURE 4. Lamellibrachia sagami sp. nov., holotype. A, anterior region, ventral view; B, anterior region, dorsal view; C, vestimental region, ventral view; D, whole specimen, dorsal view. Scale bars = 5 mm (A, B); 10 mm (C, D).

FIGURE 5. A, plaques on vestimentum; B, plaques on trunk of holotype in grey scale. Scale bar = 100 µm (A, B).