Zibrovermilia zibrowii, Kupriyanova, Elena K. & Ippolitov, Alexei P., 2015

Kupriyanova, Elena K. & Ippolitov, Alexei P., 2015, Deep-sea serpulids (Annelida: Polychaeta) in tetragonal tubes: on a tube convergence path from the Mesozoic to Recent, Zootaxa 4044 (2), pp. 151-200 : 182-185

Zibrovermilia zibrowii sp. nov.

Figures 1 G, 13, 14.

Material examined. R/V ALIS, cruise MUSORSTOM 6, Coral Sea: St. CP438: 18.2.1989, 20°23.00'S, 166°20.10'E, 780 m (holotype MNHN POLY TYPE 1565,>30 paratypes MNHN POLY TYPE 1566, including 1 prepared for SEM AM W.46387,> 30 paratypes NBCL ZMA V. P o l 5543,> 30 paratypes SMF 24002, 10 paratypes NHMUK ANEA 2015.902–911,>30 paratypes LACM-AHF Poly 7016,>30 paratypes USNM 1283054, tubes prepared for SEM and X-ray diffraction analysis PIN 5485/17, 5485/32, 5485/33, 5485/45).

R/V CORIOLIS, cruise BIOGEOCAL, Coral Sea: St. CP272, 20.4.1987, 21°00.04'S, 166°56.94'E, 1615–1710 m (2 spec. MNHN PNT 29); St. CP308, 1.5.1987, 20°40.07'S, 166°58.05'E, 510–590 m (1 spec. MNHN PNT 30).

R/V VAUBAN, cruise MUSORSTOM 4, Coral Sea: St. DC168, 16.5.1985, 18°48.2'S, 163°10.8'E, 720 m (5 spec. MNHN PNT 31, 5 spec. AM W.46390, 4 spec. NBCL ZMA V.P O L 5545, 5 spec. SMF 24007, 5 spec. NHMUK ANEA 2015.917–921, 5 spec. LACM-AHF Poly 7018, 4 spec. USNM 1283056).

R/V CORIOLIS, cruise MUSORTSOM 5: St. CP323, 14.10.1986, 21°18.52'S, 157°57.62'E, 970 m (15 spec. SMF 24008).

R/V ALIS, cruise MUSORSTOM 6, Coral Sea: St. DW394, 13.2.1989, 20°49.46'S, 167°09.11'E, 570 m (1 spec. SMF 24003); St. DW410, 15.2.1989, 20°38.05'S, 167°06.65'E, 490 m (9 spec. AM W.46388); St. CP427, 17.2.1989, 20°23.35'S, 166°20.00'E, 800 m (1 old empty tube SMF 24004); St. DW468, 21.2.1989, 21°05.86'S, 167°32.98'E, 600 m (9 spec. NBCL ZMA V.P o l 5544); St. DW469, 21.2.1989, 21° 03.64S, 167°34.67’E, 630 m (1 spec. SMF 24005); St. DW483, 23.2.1989, 21°19.80'S, 167°47.80'E, 600 m (5 spec. MNHN PNT 28, 5 spec. NHMUK ANEA 2015. 912–916, 5 spec. LACM-AHF Poly 7017, 5 spec. USNM 1283055, 3 spec. AM W.46389); DW484, 23.2.1989, 21°20.80'S, 167°50.05'E, 520 m (6 spec. MNHN PNT 27); DW489, 24.2.1989, 20°48.37'S, 167°05.86'E, 700 m (6 spec. SMF 24006).

Description. Tube: white, straight, ostensibly free, quadrangular in cross-section, occasionally and locally pentagonal. Edges may be slightly serrate, especially in younger tube parts. Tube sides slightly concave. Distal part of tube circular in cross-section, smooth, with small peristomes resembling circular rings ( Fig. 14 A, D).

Tube ultrastructure: wall two-layered, inner layer occupying almost entire thickness, with spherulitic irregularly oriented prismatic ultrastructure (SIOP) containing abundant micritic cement. Inner layer made of small 1 Μm or less densely packed spherulites of irregular shape, but more or less isometric. Spherulites appear as aggregates of very small crystals with common crystallization centre, precise shape of spherulites unclear, their size uniform throughout wall ( Fig. 13 A–D), but relatively large near the tube edges, especially in middle part of the wall (compare Fig. 13 I and Fig. 13 J). Outer layer uniformly thin (~5 Μm; corresponding wall thickness 180 Μm), having spherulitic prismatic structure (SPHP), consisting of elongated spherulites with growth direction perpendicular to tube surface ( Fig. 13 B, H).

Tube mineralogy: 100% calcite (I calc=447).

Radiolar crown: 5–7 pairs of radioles arranged pectinately, not joined by inter-anterior membrane. Stylodes absent.

Peduncle: inserted as 2nd dorsal radiole, with about same thickness as other radioles, with pinnules ( Fig. 14 C). Pair of lateral wings proximal to opercular bulb absent.

Operculum: inverted cone covered with flat or slightly concave chitinous endplate, constriction distinct ( Fig. 14 C). Pseudoperculum absent.

Collar and thoracic membranes: collar subdivided into 3 lobes, 2 small latero-dorsal and wide and longer ventral one ( Fig. 14 B). Thoracic membranes relatively wide, about same width throughout, ending between 2nd and 3rd chaetiger.

Thorax: with 7 thoracic chaetigers, 6 of which uncinigerous ( Fig. 14 B). Thoracic tori of similar size along thorax, parallel, not shifted dorso-ventally (no triangular depression). Collar chaetae limbate of two sizes, special chaetae absent ( Fig. 14 E); other thoracic notochaetae limbate of two sizes and Apomatus chaetae ( Fig. 14 F). Uncini rasp-shaped with around 15 teeth in profile view and 4–5 teeth in frontal view, dental formula P:4:5:5:5:5:5:5:5:5:5:4 ( Fig. 14 I); anterior peg rectangular flattened with crenulated edge.

Abdomen: up to 70 segments. Abdominal uncini rasp-shaped, with 12–14 teeth in profile view and 4–5 rows in frontal view, anterior peg rectangular flattened with crenulated edge, dental formula P:3(4):4:4:4:5:5:5:5:5:5 ( Fig. 14 K). Abdominal chaetae flat geniculate with edge made of rounded denticles ( Fig. 14 G, H), replaced by longer limbate capillaries only on very last 10–12 posterior segments ( Fig. 14 J); each chaetiger normally with a single chaeta. Posterior glandular pad absent ( Fig. 14 J).

Size: Total body length up to 18 mm, including up to 6 mm long radioles, width of thorax up to 0.65 mm. Tube total length up to 50 mm, outer diameter up to 0.9 mm, corresponding lumen diameter 0.55 mm. Thickness of tube wall in between angular margins varies in range 1/8–1/4th of outer diameter.

Distribution. Coral Sea, New Caledonia area, including Loyalty Islands, 490–1710 m.

Etymology. Named after Dr Helmut Zibrowius who initiated this study.

Remarks. SIOP tube ultrastructure was reported for a large number of serpulid genera (Vinn et al. 2009), many of which are unrelated. Two species reasonably close to the new species and having reported SIOP structure are Vermiliopsis infundibulum ( Philippi, 1844) and Pseudovermilia madracicola ten Hove, 1989. However, both of them have unilayered tubes, without an external SPHP layer (Vinn et al. 2008) and thus, cannot be confused with Zibrovermilia zibrowii gen. et sp. nov. The differentiation of SIOP structure from a relatively more common IOP structure may be difficult when spherulites are small and irregularly shaped as in the studied species. For example, in Vinn et al. (2008) V. infundibulum is reported to have IOP structure in one paragraph (Vinn et al. 2008: 645), but SIOP structure in another (ibid.: 635, table 2).

Figures

FIGURE 1. External morphology of polygonal serpulid tubes. Recent species: A— Spirodiscus grimaldii, R / V VITYAZ- 2, St. 78. B, C— Bathyditrupa hovei, R / V VITYAZ- 2, St. 79. D— Spirodiscus groenlandicus comb. nov., R / V VITYAZ- 2, St. 79. E— Bathyvermilia gregrousei sp. nov., R / V VITYAZ, St. 5074. F— Hyalopomatus dieteri sp. nov., R / V JEAN CHARCOT, cruise BIOCAL, St. CP 27. G— Zibrovermilia zibrowii gen. et sp. nov., R / V ALIS, cruise MUSORSTOM 6, St. CP 438. Fossil tubes: H, I— Nogrobs cf. vermicularis, PIN 5485 / 23. J – K— Glandifera cf. vertebralis, spirally coiled juvenile tube with median keel running along the lateral tube side, PIN 5485 / 02. L, M— Glandifera cf. vertebralis, a fragment of straight adult tube with regular peristomes, PIN 5485 / 01. N, O— Tetraserpula barremica, PIN 5485 / 06. P, Q— Tetraditrupa canteriata, PIN 5485 / 04. R – T— Tubulostium discoideum, ARI Od 224 / 70 (the specimen figured by Chiplonkar & Tapaswi, 1973, pl. 11, fig. 15).

FIGURE 13. Tube ultrastructures of Zibrovermilia zibrowii gen. et sp. nov. PIN 5485 / 17. A—longitudinal wall section, Benlarged outer part showing outer layer consisting of elongated crystals orientated perpendicular to outer surface, C—enlarged middle wall part consisting of small isometric crystals, D—enlarged inner wall part with smallest isometric crystals, E—tube cross-section, G—enlarged cross-section through edge showing separation of inner wall layer, dark area to the right is an artefact (cutting trace), F—another enlarged cross-section through edge, H—details of outer wall part with clearly visible outer layer, I—details of middle wall part, J—details of inner wall part showing layer consisting of smallest isometric crystals. Abbreviation: o. s. ‒ outer tube surface.

FIGURE 14. Photos and SEM images of Zibrovermilia zibrowii gen. et sp. nov. AM W. 46387. A – C: photos, A—tubes, Blateral view of thorax stained with methyl blue, C—radiolar crown with operculum and pinnulated opercular peduncle similar to other radioles, D – K: SEM images, D—tube fragment with denticulate edges, E—collar chaetae, F—thoracic chaetae, G, Habdominal chaetae, I—thoracic uncini, J—posterior abdomen, K—abdominal uncini.