Rhamphostomella hincksi Nordgaard, 1906

Grischenko, Andrei V., Gordon, Dennis P., Taylor, Paul D., Kuklinski, Piotr, Denisenko, Nina V., Spencer-Jones, Mary E. & Ostrovsky, Andrew N., 2022, Taxonomy, ecology and zoogeography of the Recent species of Rhamphostomella Lorenz, 1886 and Mixtoscutella n. gen. (Bryozoa, Cheilostomata), Zootaxa 5131 (1), pp. 1-115 : 52-55

Rhamphostomella hincksi Nordgaard, 1906

( Figs 15 , 30G , 32H, I )

? Cellepora plicata Smitt, 1868a, p. 30 , 31 (part), pl. 28, figs 195, 196.

Cellepora plicata: Hincks 1877, p. 106 , pl. 11, figs 3, 4.

Ramphostomella [sic] hincksi Nordgaard, 1906, p. 31 , 41, pl. 4, fig. 51.

Rhamphostomella hincksi: Kluge 1962, p. 541 , fig. 378; 1975, p. 658, fig. 378; Powell 1968a, p. 2311, fig. 10, pl. 13a; Hayami 1970, p. 332, pl. 36, fig. 1.

Additional references. Rhamphostomella hincksi: Osburn 1955, p. 38 ; Hansen 1962, p. 40; Hayami 1975, p. 89; Sakagami et al. 1980, p. 330; Gontar 1980, p. 18; 1990, p. 133; 2010, p. 153; 2013, p. 184; Gontar & Denisenko 1989, p. 357; Denisenko 1990, p. 39; 2008, p. 187; Kuklinski 2002b, p. 203; Denisenko & Kuklinski 2008, p. 48; Foster 2010, p. 57.

Material examined. Neotype: NHMUK 1976.8.6.39pt, three fragments from one colony, RV Ernest Holt , Stn 41, 74°25.0ʹ N, 18°02.0ʹ E (about 22 km westwards from Medvezhii Island, western Barents Sea), depth 128 m.

NHMUK 68.3 .13.46, one colony, 1858, Spitsbergen , collectors O. Sorella and N. Nordenskjold. NHMUK 1877.11 .28.112, two colonies encrusting pieces of the same bivalve shell, A.M. Norman Collection, HMS Valorous, 1875, Davis Strait . NHMUK 1899.5 .1.876, two colony fragments , T. Hincks Collection , Labrador . NHMUK 1963.2 .12.244, three colony fragments, no locality given, Dundee Collection . NHMW 72986 , one colony, 1884, L. Lorenz Collection, II Austro-Hungarian Polar Expedition , 1882–1883, Jan Mayen, depth 160–180 m, collector F. Fischer. NHMW 92534 (=1884.II.48), one colony fragment, L. Lorenz Collection, II Austro-Hungarian Polar Expedition , 1882–1883, Jan Mayen, depth 160–180 m, collector F. Fischer. USNM 11130 , nine colony fragments, Arctic Research Laboratory Collection ,? August 1948, Point Barrow, Alaska, Beaufort Sea, depth 55.5 m, collector G.E. MacGinitie. ZIRAS 7 /50119, two colony fragments detached from broken shells of bivalve mollusc Chlamys sp ., MFRT Rodino , 12 September 1992, about 32 km from Cape Hayryuzova , western Kamchatka shelf, Sea of Okhotsk, 57°36.2ʹ N, 156°09.0ʹ E, depth 78–81 m, crab trap, collector A . V. Grischenko .

Measurements. ZIRAS 7/50119, western Kamchatka, Sea of Okhotsk ( Fig. 15A–G, I, K ). ZL, 0.77–1.35 (1.00 ± 0.14). ZW, 0.37–0.60 (0.50 ± 0.06). ZD, 0.43–0.55 (n = 2). OrL, 0.15–0.28 (0.22 ± 0.03). OrW, 0.22–0.35 (0.29 ± 0.04). OeL, 0.28–0.32 (0.31 ± 0.01). OeW, 0.33–0.40 (0.37 ± 0.02). Av(s)L, 0.15–0.27 (0.20 ± 0.03). P(m)N, 7–13 (10). P(oe)N, 18–26 (25) (n = 10).

Description. Colonies encrusting, multiserial, unilaminar ( Fig. 15A ), more or less circular, attaining 16 mm in maximal dimension, reddish or burgundy when alive, pink when dry. Zooids large, hexagonal ( Fig. 15D ), widest at midlength, arranged in regular, straight rows, packed in quincunx; demarcated by fine, undulating sutures between lateral and transverse walls; sutures visible in both young and old parts of colony.

Frontal shield umbonuloid ( Fig. 15D, E, I ), inflated or moderately convex, smooth to weakly dimpled centrally, with series of deep areolae along zooidal margins ( Fig. 15D–G ) separated by radially arranged interareolar ridges; in younger zooids, ridges relatively short, low, some connecting with cystid of suboral avicularium ( Fig. 15A, D, E ). In older zooids, ridges tall, thickened, elongate, often joining along zooid midline and connecting to peristomial lappet and avicularian cystid, giving strongly costate appearance to frontal shield ( Fig. 15F, G ). Interior of frontal shield ( Fig. 15I ) with discrete ring scar ( Fig. 15K ). Umbonuloid component occupying about 40% of length of frontal shield (44% in one measured zooid), with fine parallel lineation and accretionary banding.

Primary orifice submerged, irregularly round; rounded distally, sinuate or bisinuate ( Fig. 15B ) proximally ( Fig. 15A, B, I ); if bisinuate, with small process ( Fig. 15B ). Distal and lateral margins of primary orifice formed by upper terminal part of distal transverse wall.

Secondary orifice ( Fig. 15C–E ) broadly triangular in outline, cormidial, distally and distolaterally restricted by thickening of vertical walls of distal and distolateral zooids, laterally and proximally formed by avicularian cystid (often with small distal lappet on its rostrum) on one side and high lappet of frontal shield on opposite side; lappet triangular, straight, slightly concave or sinuous in profile, together with avicularium forming proximally broad deep V-shaped pseudosinus in secondary orifice ( Fig. 15C–H ). Distally, lappets connect with lateral walls of distolateral zooids; in ovicellate zooids, lappets not fused with proximolateral corners of ooecium. No oral spines.

Cystid of suboral avicularium ( Fig. 15A–H ) relatively small but distinct, bulbous, strongly elevated, with coarsely dimpled surface, and 1–3 (normally 2) communication pores connecting avicularian and hypostegal coeloms, asymmetrically placed to left or right side of proximal peristomial rim. Inclined frontal surface (rostral/ postmandibular areas) of avicularium converging toward or crossing zooidal midline, facing obliquely frontally. Rostrum oblong-oval, weakly curving inward, with small, hooked tip directed laterally to distolaterally and upwards, extending somewhat over orifice ( Fig. 15C, H ). Palate semielliptical to triangular, with rounded distal end; palatal foramen elongate-oval or triangular, with rounded angles; opesia semicircular. Crossbar complete.

No adventitious avicularia.

Ovicells initially hyperstomial ( Fig. 15H ), but ooecia rapidly becoming subimmersed by peripheral overgrowth of secondarily thickened lateral and proximal walls of distolateral and daughter zooids ( Fig. 15F, G ); thickened lateral walls plugging gaps between distal margins of peristomial lappets and proximal corners of ooecium, thus completing secondary orifice in ovicellate zooids ( Fig. 15F, G ). Ooecium formed by distal autozooid; ooecial fold arises on colony periphery concurrently with frontal shield of distal zooid. Ooecial coelomic cavity connected with visceral coelom via communication canal opening on underside of proximal part of frontal shield as small, curved slit-like communication pore close to transverse wall ( Fig. 15I ). Ooecium with slightly concave proximal margin and numerous small, scattered circular and oval (sometimes irregular) pseudopores.

Zooids interconnecting by two mural pore chambers in each distolateral wall ( Fig. 15L ). Communication pores in basal part of transverse walls arranged either as horizontal “band” or forming two multiporous septula.

Basal wall of zooids ( Figs 15J , 30G ) fully calcified, smooth, slightly convex, with tubular protuberances (up to 0.47 mm long, up to 0.28 mm in diameter). Boundaries between zooids indicated basally by gently sinuous incisions.

Ancestrula and early astogeny not observed.

Remarks. Described and illustrated by Hincks (1877) as Cellepora plicata from Iceland, R. hincksi was recognized and redescribed as a separate species by Nordgaard (1906) based on specimen from the Barents Sea. Still, it is rather possible that figures 195 and 196 of Smitt (1868a, pl. 28) show the same species. Regrettably, only a tiny, poorly preserved fragment of the presumed R. hincksi survived in Nordgaard’s collection in the Natural History Museum, University of Oslo (E. Di Martino, pers. comm., 2020). To correct this situation, we have selected a neotype for this species based on a specimen collected in the Barents Sea from the RV Ernest Holt. Three fragments of one colony are deposited at the Natural History Museum, London.

In having a sinuate, elevated secondary orifice formed by an asymmetrically set avicularian cystid on one side and a high triangular lappet on the opposite side, and spherical ooecia with small, evenly distributed pseudopores, R. hincksi strongly resembles R. plicata (Smitt, 1868) . Historically, this resemblance led to some misidentifications.

The differences between these species are as follows: 1) the frontal shield has a series of deep marginal areolae separated by tall, radially arranged ridges along the entire lateral wall in R. hincksi , but only a few areolae separated by short ridges along the distal half of the zooid in R. plicata ; 2) the palatal foramen of the suboral avicularium is gently curved in R. hincksi but straight in R. plicata ; 3) ooecia are rapidly surrounded by growing and thickening vertical walls of neighbouring zooids in R. hincksi , but not in R. plicata ; 4) the primary orifice lacks a lyrula in R. hincksi but may occasionally bear a very small denticle ( Fig. 15B ) (see also Nordgaard 1906; Osburn 1952; Kluge 1962, 1975), whereas a distinct lyrula is always present in R. plicata .

Ecology. Rhamphostomella hincksi has been recorded from depts of 10–270 m, predominantly on mixed bottoms, including silt, sand and gravel overlain with broken mollusc shells. Colonies encrust mollusc shells and colonies of other bryozoans.

Distribution. This is a boreal-Arctic, circumpolar, sublittoral species. In the Arctic R. hincksi has been recorded in the Barents Sea (? Smitt 1868a; Nordgaard 1896; Bidenkap 1900a; Waters 1900; Andersson 1902; Norman 1903; Kluge 1962, 1975; Denisenko 1990), Kara Sea ( Kluge 1962, 1975; Denisenko 2021), Laptev Sea ( Kluge 1962, 1975; Gontar 1990), Chukchi Sea ( Kluge 1962, 1975; Denisenko 2008; Denisenko & Kuklinski 2008; Gontar 2010), Point Barrow, Alaska, Beaufort Sea ( Osburn 1955), Canadian Arctic Archipelago ( Nordgaard 1906), Baffin Bay ( Hansen 1962), Davis Strait ( Hansen 1962; Kluge 1962, 1975), Hudson Bay ( Gontar & Denisenko 1989), western Greenland ( Norman 1876; Kluge 1908b; Levinsen 1914; Osburn 1919, 1936; Denisenko & Blicher 2021), eastern Greenland ( Levinsen 1916; Denisenko & Blicher 2021), Iceland ( Hincks 1877; Gontar & Denisenko 1989), Jan Mayen Island ( Lorenz 1886), Franz Josef Land ( Denisenko 1990), and Spitsbergen ( Kuklinski 2002b). In the northern Atlantic, it is known from St Lawrence Gulf ( Whiteaves 1901). Northwestern Pacific records are from the Sea of Okhotsk, including the eastern shore of southern Sakhalin Island ( Kluge 1961; Kluge et al. 1959), the western Kamchatka shelf (our data), coastal waters of Iturup and Shikotan Islands and south Kuril Islands ( Kluge 1961; Kluge et al. 1959; Gontar 1980). The only known locality in the northeastern Pacific is Cook Inlet, Gulf of Alaska ( Foster 2010).

R. hincksi has also been reported from Miocene and Neogene deposits in northern Japan ( Hayami 1970, 1975).

Figures

FIGURE 15. Rhamphostomella hincksi Nordgaard, 1906.A–G, I, K. ZIRAS 7/50119 (western Kamchatka, Sea of Okhotsk). H, J, L. USNM 11130 (Point Barrow, Beaufort Sea). A. Colony margin with developing zooids. B. Distal view of marginal zooids, showing primary orifices with small, slender median tooth. C. Orifice with suboral avicularium. D, E. Groups of non-ovicellate zooids in young parts of colony. F. Ovicellate zooids with strongly developed interareolar ridges of frontal shield in older part of colony. G. Ovicellate zooids in older part of colony. H. Ovicellate zooid with suboral avicularium. I. Interior of frontal shield in three zooids, showing ring scars, areolae and ooecial communication slits (arrows). J. Basal colony surface with numerous broken tubular protuberances. K. Frontal shield interior, showing ring scar and exterior wall microstructure of umbonuloid component. L. Lateral view of zooid, showing suboral avicularium and zooidal lateral wall with mural pore chambers. Scale bars: A, D, G, J, 500 μm; B, C, H, I, 100 μm; E, F, 250 μm; K, 50 μm; L, 200 μm.

FIGURE 30. Basal colony surface insome Rhamphostomellaspecies.A. R. scabra, ZIRAS 93/50106 (BeringIsland, Commander Islands, Pacific Ocean), colony fragment developed above irregular substrate, showing broken protuberances and pits formed above sponge spicules. B. R. commandorica, ZIRAS 1/50125 (Medny Island, Commander Islands, Pacific Ocean), colony fragment, showing smooth surface with rare thin protuberances. C. R. cristata, ZIRAS 2/50110 (Medny Island, Commander Islands, Pacific Ocean), colony area growing above crustose coralline algae Lithothamnion sp., showing regular series of columnar protuberances with broad bases. D. R. gigantea, ZIRAS 3/50129 (western Kamchatka shelf, Sea of Okhotsk), colony detached from internal side of broken shell of bivalve mollusc Chlamys sp. E. R. pacifica, ZIRAS 1/50124 (Kronotsky Gulf, eastern Kamchatka, Pacific Ocean), colony developed above irregular substratum. F. R. curvirostrata, NHMUK 1964.1.2.7 (Pacific coast of North America), colony margin with developing zooids, supported by long tubular processes. G. R. hincksi, USNM 11130 (Point Barrow, Alaska, Beaufort Sea), basal surface with long tubular protuberances. H. R. sibirica, ZIRAS 34/50113 (Medny Island, Commander Islands, Bering Sea), basal surface with long tubular protuberances. I. R. multirostrata, ZIRAS 1/50545 (Urup Island, Kuril Islands, Sea of Okhotsk), colony detached from a sponge, showing marginal zooids with regular series of tubular protuberances. Scale bars: 500 μm.

FIGURE 32. Type specimens of Rhamphostomella species. A, B. Rhamphostomella gigantea Osburn, 1952. Holotype, USNM 11033 (Point Barrow, Alaska, Beaufort Sea). C–E. Rhamphostomella alutacea Gontar, 1993. Holotype, ZIRAS 1/44569 (Krabovaya Bight, Shikotan Island, Lesser Kuril Ridge, Pacific Ocean). F, G. Rhamphostomella bilaminata (Hincks, 1877). Neotype, NHMUK 1911.10.1.1580A (Gaspe, Gulf of St Lawrence, Atlantic Ocean). H, I. Rhamphostomella hincksi Nordgaard, 1906. Neotype, NHMUK 1976.8.6.39pt (about 22 km westwards from Medvezhii Island, western Barents Sea). J, K. Rhamphostomella plicata (Smitt, 1868). Lectotype, SMNH-Type-1696 (Waygat Islands, Hinlopen Strait, Svalbard and Jan Mayen). L, M. Rhamphostomella radiatula (Hincks, 1877). Neotype, NHMUK 1911.10.1.1592 (Iceland). Scale bars: A, B, D–G, K, M, 250 µm; C, H, I, J, L, 500 µm.