Bathyditrupa hovei Kupriyanova, 1993a

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 : 158-162

Bathyditrupa hovei Kupriyanova, 1993a

Figures 1 B, C, 2, 3

Bathyditrupa hovei Kupriyanova, 1993a: 22 –23, fig. 1.

Bathyditrupa hovei .—ten Hove & Kupriyanova 2009: 29, fig. 9; Kupriyanova et al. 2011: 46, fig. 2, 3. Spirodiscus grimaldii . — Hartman & Fauchald 1971: 183 [in part, only in R/V CHAIN St. 100, ATLANTIS-II St. 118].? Filogranula spp.— Hartman & Fauchald 1971: 182 [in part, R/V CHAIN St. 85, St. 100, R/V ATLANTIS-II, St. 155].

Material examined. R/V VITYAZ, North Pacific: St. 5620, 44°48'N, 156°33'E, 5070 m (11 spec. SIO, 1 tube used for SEM PIN 5485/08, 5485/09, and X-ray diffraction analysis, sample # 1); St. 5622, 45°14'N, 155°15'E, 5110 m (holotype and 1 paratype SIO); St. 5624, 45°26'N, 154°12'E, 5020 m (2 spec. SIO); St. 4279, 19º46'N, 120º17'W, 4104 m (1 tube SIO); St. 4281, 20º01'3''N, 121º59'W, 4370 m (4 spec. SIO); St. 6015, 26º51′5''N, 165º32′1''E, 5850 m (1 spec. SIO); St. 5074, 10º28′N, 140º01′W, 4833 m (1 tube SIO); St. 7391, 24º08''N, 143º46′1''E, 6330 m (3 spec. SIO); St. 4370, 26°04'2''N, 153°49'3''W, 6050 m (1 spec. ZMA V.Pol. 5325); St. 3151, 44º28'3''N, 170º07'E, 5237 m (3 tubes ZMA V.Pol. 5326).

R/V VITYAZ-2, North Atlantic: St. 79, 34°54.3'N, 45°39'W, 4440 m (2 spec. SIO, 1 tube used for SEM, PIN 5485/14, 5485/15, 5485/34, 5485/40, and X-ray diffraction analysis, sample # 2).

R/V CHAIN, North-West Atlantic: St. CH 85, 37°59.2'N, 69°26.2'W, 3834 m (14 spec. LACM-AHF); St. CH 100, 33°56.8'N, 65°47'W, 4892– 4743 m (1 tube LACM-AHF).

R/V ATLANTIS-II, West Atlantic: St. 118, 32°19.4'N, 64°34.9'W, 1135–1153 m (5 spec. LACM-AHF); St. A155, 0°0.3'S, 27°78.0'W, 3730–3783 m (2 spec. LACM-AHF).

R/V KNORR, cruise 25, North-West Atlantic: St. 288, 25.2.1972, 11°02.2'N, 55°05.5'W, 4417–4429 m (1 spec. MNHN PNT 39).

R/V CRYOS, cruise ABYPLAINE, North-East Atlantic: St. 10-CP17, 11.6.1981, 42°44.5'N, 15°58.5'W, 4480 m (1 broken tube MNHN PNT 43); St. 10-CP18, 11.6.1981, 42°52.3'N, 15°53.1'W, 4330 m (2 spec., including 1 removed from broken into pieces tube MNHN PNT 42); St. 8-DS7, 30.5.1981, 34°06'N, 17°04'W, 4270 m (1 spec. in decalcified tube MNHN PNT 44); St. 12-DS13, 21.7.1983, 44°41.2'N, 17°49.0'W, 4990 m (2 spec. MNHN PNT 45); St. 11-DS11, 12.6.1981, 42°59.7'N, 14°05.4'W, 5260 m (2 spec. in decalcified tubes MNHN PNT 40); St. 12- DS12, 20.7.1983, 44°39.9'N, 17°52.9'W, 4990 m (3 spec. without tubes MNHN PNT 46); St. 11-CP20, 12.6.1981, 42°59.7'N, 14°07.2'W, 5260 m (1 dry specimen in brittle tube MNHN PNT 41); St. 2-DS1, 17.5.1981, 37°18'N, 15°33'W, 4260–4450 m (1 spec. AM W.46391); St. 8-CP11, 30.5.1981, 34°06.1'N, 17°06.3'W, 4270 m (8 spec. AM W.46392, 1 prepared for SEM AM W.46393 and PIN 5485/11); St. 10-DS10, 11.6.1981, 42°51.2'N, 15°55.3'W, 4270–4360 m (10 spec., 1 spec. prepared for SEM AM W.46394, 10 spec. NBCL ZMA V.P o l. 5549, 10 spec. SMF 23989, 5 spec. NHMUK ANEA 2015.927-936, 5 spec. LACM-AHF Poly 7021, 5 spec. USNM 1283058).

R/V JEAN CHARCOT, cruise WALVIS, South Atlantic, Cape Basin and Angola Basin: St. C-Pr44-DS7, 3.1.1979, 26°59.7'S, 1°07.1'E, 5100–5214 m (1 spec. SMF 23983); St. B-Pr37-DS5, 30.12.1978, 33°20.5'S, 2°34.9'E, 4560 m (1 spec. SMF 23982); same, cruise INCAL, SW Ireland - off Brittany: St. 2.4-Pr48-OS3, 4.8.1976, 46°02.5'N, 10°19.5'W, 4798 m (1 spec. SMF 23984); St. 2.3-Pr67-WS8, 9.8.1976, 47°30.5'N, 9°33.7'W, 4287–4301 m (1 spec. in decalcified tube SMF 23986); St. 2.4-Pr48-OS3, 4.8.1976, 46°02.9'N, 10°18.7.1'W, 4798 m (1 spec. SMF 23985); same, cruise DEMERABY: St. A-Pr29-DS2, 14.9.1980, 8°09.23'N, 49°04.37'W, 4430 m (1 spec. in decalcified tube SMF 23987); St. A-Pr51-KG9, 16.9.1980, 8°09.91'N, 49°03.47'W, 4440 m (1 spec. in decalcified tube SMF 23988).

Description. Tube: white opaque, free-lying, slightly curved ( Fig. 1 B, C), open at both ends; quadrangular in cross-section outer part, with flat to slightly concave sides ( Fig. 2 A), entirely opaque. Tube surface with transversal growth lines.

Tube ultrastructure: wall essentially unilayered with irregularly oriented prismatic ultrastructure (IOP sensu Vinn et al. 2008 = “criss-cross” sensu ten Hove & Zibrowius 1986; Sanfilippo 1998a, b; 2009, Fig. 2 A), consisting of elongated cigar-shaped (most common) to isometric crystals. Innermost wall part (~1/5 of total thickness; Fig. 2 D) made of smaller isometric crystals sized 0.5–1 µm consolidated by amorphous cement. Middle part of wall ( Fig. 2 C) with larger elongated rice grain-like crystals (length ~1.5–2 µm, diameter 0.5 µm). In some transverse sections elongated crystals oriented loosely parallel to tube surface ( Fig. 2 E, G). Outer part of wall ( Fig. 2 B) similar to middle one, but with a characteristic thin outer layer of ordered elongated rice grain-like crystals oriented more or less along tube length with their axes (SOIOP structure, see Table 2). No distinct border between inner, middle, and outer wall parts, all structures changing gradually. Crystal shapes and sizes not changing significantly during ontogeny ( Fig. 2 G–I). Parabolic growth lamellae indistinct, with parabolic axis displaced centrally within wall.

Tube mineralogy: sample # 1: 5% calcite (I calc=1); 95% aragonite (I arag=20); sample # 2: 8% calcite (I calc=3); 92% aragonite (I arag=36);

Radiolar crown: arrangement of radioles semi-circular, up to 4–6 pairs of radioles not joined by inter-radiolar membrane. Radiolar eyes not observed. Mouth palps absent.

Peduncle: inserted as 2nd dorsal radiole, three to five times thicker than radioles, slightly flattened, with pinnules ( Fig. 3 C, D).

Operculum: funnel-shaped, covered with concave brown chitinous endplate ( Fig. 3 C); opercular bulb continuing smoothly into peduncle, constriction absent.

Collar and thoracic membranes: collar not subdivided into lobes (entire), slightly shorter laterally than dorsally. Medium-sized incision along the ventral mid-line may be present. Thoracic membranes reaching up to 2nd chaetiger, about same width throughout ( Fig. 3 D).

Thorax: with 5 thoracic chaetigers, 4 of which uncinigerous ( Fig. 3 B). Collar chaetae a few short capillaries ( Fig. 2 F); other thoracic notochaetae limbate, with short slightly bent distal blades; Apomatus chaetae absent ( Fig. 3 J). Thoracic uncini saw-to-rasp-shaped with numerous (12–5) teeth in profile view ( Fig. 3 H); front uncinal view triangular, starting with one tooth posteriorly and ending in up to 5 teeth over wide gouged blunt anterior peg, dental formula P:5:4:3:3:3:2:2:2:1:1:1:1.

Abdomen: abdominal chaetigers 30–40. Uncini similar to thoracic ones, but rasp-shaped ( Fig. 2 I), dental formula P: 5(6):4(5):4:4:4:3:3:3:3:2:?:?. Chaetae short capillaries, slightly longer on posterior segments ( Fig. 2 G); each chaetiger with a single chaeta.

Size: total body length up to 15 mm, including up to 3 mm long radioles, width of thorax up to 0.35 mm. Tube length up to 25 mm. Maximum external tube diameter across angular margins up to 0.65 mm, in between up to 0.5 mm, corresponding lumen diameter 0.35–0.4 mm. Thickness of tube wall in between angular margins about 1/10th of outer diameter.

Distribution. Atlantic Ocean, bathyal—lower abyssal, 1135–5260 m, North and Central Pacific Ocean, 4104– 6330 m.

Remarks. This species, characterised by distinct tusk-shaped quadrangular in cross-section tubes was originally described from depths of 5050–5620 m in the Kuril-Kamchatka Trench ( Kupriyanova 1993a). Recently Kupriyanova et al. (2011) summarised published data and provided new records of this species from the North and Central Pacific Ocean. In this study the distribution range of B. hovei is extended to the bathyal-abyssal of the Atlantic Ocean.

Kupriyanova & Nishi (2011) showed that material reported as Spirodiscus grimaldii from three stations (R/V CHAIN St. 100, R/V ATLANTIS-II St. 118 and 119) in the Western Atlantic by Hartman & Fauchald (1971: 183) was in fact a mixture of several species and that two of these stations ( CH 100 and A118) had included Bathyditrupa hovei . Similarly, animals identified in Hartman & Fauchald (1971: 183) as? Filogranula from stations CH 85 and A155, also partly belonged to B. hovei as it is clear even from the description by Hartman & Fauchald (1971: 182): “ Long, straight tubes, from Sta. Ch 85, are square in cross section, externally smooth and have a cylindrical lumen. The small, slender body measures less than 10 mm long, consists of 5 thoracic and 30 to 40 abdominal setigers; the crown consists of four or five pairs of radioles, of which the dorsalmost is modified as an operculum, with thick, fleshy stalk and sparse numbers of barbules limited to its ventro-basal part. The opercular disk is circular, infundibular, lightly chitinized and minutely crenulated at its margin. The collar segment is the longest; it has simple collar setae, and the last four setigers are uncinigerous. Abdominal segments are short and crowded ”. In addition to Bathyditrupa hovei , station CH 85 also included numerous specimens of Spirodiscus groenlandicus comb. nov. in octagonal tubes (see below).

Kupriyanova et al. (2014) reported Bathyditrupa hovei to have aragonitic tubes with IOP structure, therefore, data herein principally agree with the earlier ones. However, as we used X-ray diffraction (direct quantitative method), precise calcite/aragonite ratios are now available for this species for the first time. Details of crystal arrangement along the outer tube surface were also observed for the first time.

Ten Hove (pers. comm.) noticed 10 oblong eggs, 120–140 µm long and 50–60 µm wide, inside the tube of along the abdomen of the specimen from NBCL ZMA V.Pol. 5325, which suggests that the species is a lecithotrophic intratubular brooder.

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 2. Tube ultrastructures of Bathyditrupa hovei. A – D: PIN 5485 / 08, A—longitudinal wall section, B—enlarged outer wall part, C—enlarged middle wall part consisting of elongated crystals, D—enlarged inner wall part showing a thin layer of smaller isometric crystals. E: PIN 5485 / 09, middle wall part showing loose transverse orientation of crystals (oblique section). F: PIN 5485 / 11, longitudinal wall section. G – I: PIN 5485 / 15, a series of tube fragments of different sizes (may belong to different specimens) showing no principal ultrastructural ontogenetic changes. Arrows indicate direction of tube growth. Abbreviation: o. s. — outer tube surface.

FIGURE 3. SEM images of Bathyditrupa hovei AM W. 46394. A—anterior tube part, B—lateral view of thorax, C—radioles with operculum, D—dorsal view of thorax showing thoracic membranes, E—lateral view of thorax and radioles showing pinnulated peduncle, F—collar chaetae, G—abdominal chaeta, H—thoracic uncini, I—abdominal uncini, J—thoracic chaetae.