Rhamphostomella spinigera Lorenz 1886

Rhamphostomella spinigera Lorenz, 1886

(Figs 23, 25C, 33E, F)

Cellepora plicata: Smitt 1868a, p. 30, 31 (part), pl. 28, fig. 192.

Rhamphostomella spinigera Lorenz, 1886, p. 12.

Rhamphostomella spinigera: Nordgaard 1906, p. 32, 41, pl. 4, figs 52–55; Osburn 1952, p. 429, pl. 51, fig. 1; Kluge 1962, p. 542, fig. 379; 1975, p. 659, fig. 379; Hayami 1970, p. 332, pl. 36, fig. 11; 1975, p. 89, pl. 17, fig. 2; Gostilovskaya 1978, p. 228, fig. 144.

Rhamphostomella plicata: Waters 1900, p. 92, pl. 11, figs 28, 29; Nordgaard 1905, p. 171, pl. 5, figs 14, 15.

Additional references. Rhamphostomella spinigera: Kluge 1906, p. 46; 1907, p. 196; 1908b, p. 553; 1915, p. 386; 1964, p. 190; Osburn 1936, p. 542; 1955, p. 38; Gostilovskaya 1957, p. 455; 1964, p. 219; Hansen 1962, p. 42; Sakagami et al. 1980, p. 330; Denisenko 1988, p. 13; 1990, p. 39; 2013, p. 184; Gontar & Denisenko 1989, p. 359; Grischenko 1997, p. 174; 2002, p. 115; 2003b, p. 237; Gontar et al. 2001, p. 195; Shunatova & Ostrovsky 2001, p. 118; Kuklinski 2002b, p. 203; Foster 2010, p. 57; Gontar 2010, p. 153.

Material examined. Lectotype: NHMW 92535 (=1884.II.51), single colony encrusting shell of Chlamys islandica, L. Lorenz Collection, II Austro-Hungarian Polar Expedition, 1882–1883, Jan Mayen, depth 160–180 m, collector F. Fischer. Paralectotype: NHMW 92536 (=1884.II.51), single colony encrusting shell of Chlamys islandica, L. Lorenz Collection, II Austro-Hungarian Polar Expedition, 1882–1883, Jan Mayen, depth 160–180 m, collector F. Fischer.

NHMUK (1911.10.1.1585 NHML), two colonies, ex Vienna Museum Natural History Collection, from L. Lorenz, A.M. Norman Collection, Jan Mayen. SMNH-131116, one colony, Swedish Arctic Expedition, 1858, west Spitsbergen, Svalbard and Jan Mayen. ZIRAS 25 /50111, one colony, KIENM Collection, Stn 208, 22 July 1991, Podutesnaya Bight, coastal waters of Bering Island, Commander Islands, Pacific Ocean, 55°01.3ʹ N, 166°06.2ʹ E, depth 20 m, SCUBA, collector V. V. Oshurkov. ZIRAS 26 /50112, one colony encrusting bivalve shell of Hiatella arctica, KIENM Collection, Stn 91, 16 July 1992, Korabelnaya Bight, coastal waters of Medny Island, Commander Islands, Bering Sea, 54°41.4ʹ N, 167°47.2ʹ E, depth 15 m, SCUBA, collector V.I. Shalukhanov. NHMUK 2013.10.21.7b, one colony encrusting oyster shell, RV Norseman, Stn AST–2, 16 July 2011, reef in middle of Boot Bay, coastal waters of Adak Island, Andreanof Islands, Aleutian Islands, Pacific Ocean, 51°44.4ʹ N, 176°30.3ʹ W, depth 10–12 m, SCUBA, collector P. Kuklinski.

Additional material. 131 specimens. KIENM Collection (1991) Stns 186, 210, 225; (1992) Stns 4, 5, 37, 38, 39, 54, 58, 64, 88, 89, 90, 91, 97, 98, 99, 126, 127, 135, 136, 137, 142, 143, 145, 147, 150, 151; PIBOC Collection (1991) Stns 17, 20; A. V. Grischenko Collection (1991) Stn 17 (see Appendix 1 for details).

Measurements. ZIRAS 26/50112, Medny Island, Commander Islands, Bering Sea (Fig. 23A–F, H, I, L). ZL, 0.52–0.88 (0.67 ± 0.09). ZW, 0.33–0.48 (0.39 ± 0.04). ZD, 0.34–0.40 (n = 2). OrL, 0.12–0.20 (0.16 ± 0.02). OrW, 0.15–0.21 (0.19 ± 0.02). OeL, 0.20–0.33 (0.27 ± 0.04). OeW, 0.30–0.40 (0.35 ± 0.03). Av(s)L, 0.08–0.25 (0.16 ± 0.04). Sp(or)L, 0.24–0.90 (0.51 ± 0.17) (n = 20). P(m)N, 9–13 (10). P(oe)N, 21–29 (25) (n = 10).

NHMUK 2013.10.21.7b, Adak Island, Aleutian Islands, Pacific Ocean. ZL, 0.37–0.72 (0.52 ± 0.07). ZW, 0.20–0.43 (0.33 ± 0.05). ZD, 0.32–0.38 (n = 2). OrL, 0.14–0.20 (0.16 ± 0.01). OrW, 0.14–0.23 (0.19 ± 0.02). OeL, 0.20–0.48 (0.25 ± 0.05) (n = 23). OeW, 0.22–0.56 (0.30 ± 0.06) (n = 25). Av(s)L, 0.11–0.36 (0.18 ± 0.06). Sp(or)L, 0.05–0.10 (0.08 ± 0.01) (n = 16). P(m)N, 6–15 (10) (n = 15). P(oe)N, 12–27 (24) (n = 12).

NHMW 1884.II.51, Jan Mayen (Fig. 25C). AnL, 0.44 (n = 1). AnW, 0.34 (n = 1). AnOpL, 0.30 (n = 1). AnOpW, 0.24 (n = 1).

Description. Colonies encrusting, multiserial, unilaminar (Fig. 23A), small, more or less circular, attaining 11 mm in maximal dimension, red to bright brown when alive, light brown to pale-yellow when dry. Zooids mediumsized, hexagonal to oval, arranged in quincunx, demarcated by fine sutures between transverse and lateral walls; sutures less visible in older colony parts.

Frontal shield umbonuloid (Fig. 23B, I), thin, moderately convex, covered with small pointed tubercles giving reticulate appearance to zooids. Oval and round areolae along zooidal margins separated by low, short interareolar ridges in distal half of marginal zooids (Fig. 23A); these ridges absent or strongly reduced in older parts of colony (Fig. 23D, E). Interior of frontal shield (Fig. 23I) shows relatively small umbonuloid component, occupying about 30% of length of frontal shield (31% in one measured zooid). Ring scar (Fig. 23K) discrete.

Primary orifice (Fig. 23B, C, E) irregularly quadrangular to transversely oval, with gently straight sides and broadly rounded angles; its distal and lateral margins formed by upper part of distal transverse wall (Fig. 23A, E, F). Distal margin of orifice almost straight or shallow rounded, proximal margin bisinuate, with prominent, median lyrula, normally bifurcate, but sometimes trifid or with four tips. Two triangular acute processes lateral to lyrula. Condyles absent. Four articulated oral spines, medial two of smaller diameter, located around distal curvature of orifice in non-ovicellate zooids (Fig. 23B, E). Normally only two lateral spines found in ovicellate zooids, adjoining proximolateral corners of ooecia (Fig. 23F–H); 3–4 spines can be seen in some zooids with developing ooecia (Fig. 23D). Oral spines usually short in young zooids, and strongly elongated and thicker in older zooids.

Secondary orifice transversely oval, cormidial (Fig. 23B–H); its distolateral curvature slightly above primary orifice, being formed by upper terminal part of distal transverse wall (Fig. 23B); laterally and proximally it is constructed by thin-walled low peristome consisting of two roundly triangular flared lappets, one incorporating cystid of suboral avicularium and forming broad, deep U-shaped, asymmetrically placed pseudosinus in secondary orifice (Fig. 23G); distally, lappets mounted to lateral walls of distolateral zooids, not fused with proximolateral corners of ooecia in ovicellate zooids (Fig. 23B–H).

Cystid of suboral avicularium (Fig. 23A, F) small, strongly elevated, with dimpled surface and single communication pore, asymmetrically situated on left or right near orifice margin. Frontal surface (rostral/ postmandibular areas) slightly concave (Fig. 23B, C), crossing zooidal midline, facing proximolaterally. Rostrum oblong oval, tapering distally, or triangular, pointed, occasionally hooked terminally, directed ditstolaterally and frontalwards. Palate semielliptical to triangular, with rounded distal end; foramen triangular with acute tip; opesia semicircular. Crossbar complete.

No adventitious avicularia.

Ovicells hyperstomial (Fig. 23F–H, L), ooecium not overgrown by secondary calcification. Ooecium formed by distal autozooid; ooecial fold developing at colony periphery concurrently with formation of frontal shield of distal zooid (Fig. 23A). Ooecium narrowing at proximolateral corners, with straight or weakly concave proximal margin that may have several minor wrinkles. Ectooecium with scattered small circular pseudopores.

Zooids interconnected by two mural pore chambers (Fig. 23L) in each distolateral wall. Communication pores spread through basal part of transverse walls either as horizontal “band” or form two multiporous septula.

Basal surface of zooids (Fig. 23J) fully calcified, smooth, inflated, lacking white spots and protuberances. Boundaries between zooids indicated basally by deep undulating grooves laterally and indistinct sutures transversely.

Ancestrula tatiform (Fig. 25C), longitudinally oval, with fully calcified basal wall. Opesia longitudinally oval, with eight periopesial spines evenly distributed around opesial margin. Ancestrula budding triplet of periancestrular zooids distally and distolaterally (right zooid undeveloped); periancestrular zooids similar to but smaller than subsequent zooids, bearing four hollow articulated oral spines around distal curvature of orifice.

Remarks. In the constant presence of long oral spines R. spinigera resembles R. echinata n. sp., but differs in having the frontal shield tuberculate vs tessellated in the latter.

Ecology. Rhamphostomella spinigera has been recorded from 7–234 m depth on hard bottoms such as rock faces (including crevices), boulders and blocks, encrusting shells of bivalve molluscs (Hiatella arctica, Monia macrochisma, etc.), gastropods (Cryptonatica jantostoma, and others), barnacles, tubes of serpulid and spirorbid polychaetes, bryozoans (Myriapora orientalis, lichenoporid cyclostomes) and calcareous red algae (Lithothamnion sp.). It is also known as a component of the cryptic community met in the cavities formed by the crustose coralline red alga Clathromorphum nereostratum and has been found on the brown alga Agarum clathratus.

Kluge (1962, 1975) noted that colonies of R. spinigera loosely overgrow the substratum. In contrast, we observed colonies of this species tightly attached to various substrates.

Distribution. This is a high-boreal-Arctic, sublittoral species. Numerous Arctic records were summarized by Kluge (1962, 1975) and Gontar & Denisenko (1989). In the Arctic it has been reported from the Barents Sea (Bidenkap 1900a; Waters 1900; Nordgaard 1905; Kluge 1906, 1962, 1975; Kuznetsov 1941; Denisenko 1988, 1990), White Sea (Kluge 1907; Gostilovskaya 1957, 1978; Shunatova & Ostrovsky 2001), Kara Sea (Nordgaard 1912; Kluge 1962, 1975; Denisenko 2021), Laptev Sea (Gontar & Denisenko 1989), Chukchi Sea (Gontar 2010), Point Barrow, Alaska, Beaufort Sea (Osburn 1952, 1955), Canadian Arctic Archipelago (Nordgaard 1906; Osburn 1932, 1936), Baffin Bay (Hansen 1962), Davis Strait (Kluge 1962, 1975; Hansen 1962), Labrador (Gontar & Denisenko 1989), western Greenland (Henning 1896; Kluge 1908b; Osburn 1936; Denisenko & Blicher 2021), eastern Greenland (Levinsen 1916; Denisenko & Blicher 2021), Greenland Sea (Gontar & Denisenko 1989), Jan Mayen Island (Lorenz 1886), Norwegian Sea (Gontar & Denisenko 1989), Franz Josef Land (Denisenko 1990) and Spitsbergen (Gontar et al. 2001; Kuklinski 2002b). In the northwestern Pacific it has been documented in the Bering Sea from the shelf of the Commander Islands (Grischenko 1997, 2002, 2003b; our data). Northeastern Pacific localities include Canoe Bay (Osburn 1952), Cook Inlet (Foster 2010) and Kodiak Island, Gulf of Alaska (our data).

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