Taxonomy, ecology and zoogeography of the Recent species of Rhamphostomella Lorenz, 1886 and Mixtoscutella n. gen. (Bryozoa, Cheilostomata) Author Grischenko, Andrei V. gat1971@mail.ru Author Gordon, Dennis P. dennis.gordon@niwa.co.nz Author Taylor, Paul D. p.taylor@nhm.ac.uk Author Kuklinski, Piotr kuki@iopan.gda.pl Author Denisenko, Nina V. ndenisenko@zin.ru Author Spencer-Jones, Mary E. m.spencer-jones@nhm.ac.uk Author Ostrovsky, Andrew N. andrei.ostrovsky@univie.ac.at text Zootaxa 2022 2022-05-02 5131 1 1 115 http://dx.doi.org/10.11646/zootaxa.5131.1.1 journal article 54924 10.11646/zootaxa.5131.1.1 1daf4875-bf0f-4fb9-b648-459a83357801 1175-5326 6521113 CF550031-D6A9-48A3-A953-A1BD40C72F5E Rhamphostomella sibirica ( Kluge, 1929 ) ( Figs 19 , 25B , 30H , 33A, B ) Rhamphostomella bilaminata var. sibirica Kluge, 1929 , p. 21 . Rhamphostomella bilaminata var. sibirica : Kluge 1952 , p. 160 ; 1953, p. 178; 1955, p. 108, tab. 23, fig. 6; 1961, p. 142; 1962, p. 546, fig. 383; 1964, p. 190; 1975, p. 664, fig. 383; Gostilovskaya 1957 , p. 455 ; 1978, p. 232, fig. 148; Kluge et al . 1959 , p. 213 ; Kubanin 1976 , p. 34 ; Androsova 1977 , p. 202 ; Gontar 1980 , p. 13 ; 1990, p. 133; Denisenko 1988 , p. 13 ; 1990, p. 39; 2008, p. 187; Gontar & Denisenko 1989 , p. 358 . Rhamphostomella sibirica : Kubanin 1997 , p. 123 ; Grischenko 2002, p. 115; 2003b, p. 237; Grischenko & Ivanyushina 2002 , p. 33 ; Denisenko & Kuklinski 2008 , p. 48 ; Kuklinski 2009, p. 228; Denisenko 2011 , p. 14 ; 2013, p. 184. Rhamphostomella bilaminata : Levinsen 1916 , p. 461 ; Nordgaard 1929 , p. 7 ; Osburn 1933 , p. 55 , pl. 10, fig. 8. Rhamphostomella bilaminata sibirica : Lukin 1979 , p. 37 ; Gontar 1979 , p. 246 ; 1992, p. 197; 1993b, p. 202; 1994a, p. 146; 1996, p. 46; 2010, p. 153; 2013, p. 48; Grischenko 1997 , p. 175 ; Gontar et al . 2001 , p. 194 . Rhamphostomella curvirostrata : Kubanin 1997 , p. 123 . Rhamphostomella sp. : Kubanin 1997 , p. 123 . Material examined. Lectotype : ZIRAS 1 /50730, two fragments from one colony, RV Vega , Stn 71, 23 August 1878 , Laptev Sea, 76°40.0ʹ N , 115°30.0ʹ E , depth 10.9 m , clay . Paralectotype : ZIRAS 2 /50731, single colony , RV Vega , Stn 71, 23 August 1878 , Laptev Sea, 76°40.0ʹ N , 115°30.0ʹ E , depth 10.9 m , clay . P. Kuklinski Collection, one colony encrusting rock, Russian-German Expedition Transdrift 1, RV Ivan Kireev , Stn 48, 18 August 1993 , Laptev Sea , 74°30.0ʹ N , 137°05.0ʹ E , depth 22 m , rock dredge, collectors M.K. Schmid and D. Piepenburg. ZIRAS 2 /155–134, single colony fragment, Russian Polar Expedition , RV Zarya , St 46, 28 August (3 September ) 1901, Laptev Sea , depth 60 m , silt with stones, otter trawl . ZIRAS 6 /155–134, single colony fragment, Russian Polar Expedition , RV Zarya , Stn 15, 18(31) August 1901 , Middendorff Bay , eastern side of Zarya Peninsula , Taymyr Peninsula , Kara Sea , 75°54.0ʹ N , 92°59.0ʹ E , depth 7.9–10.7 m , silted sand, dredge . ZIRAS 34 /50113, nine colony fragments , KIENM Collection , Stn 133, 23 July 1992 , Rock Sivuchy Kamen , coastal waters of Medny Island , Commander Islands , Bering Sea , 54°47.4ʹ N , 167°39.3ʹ E , depth 10 m , SCUBA , collector V .I. Shalukhanov . NHMUK 2013.10 .21.5, one colony encrusting oyster shell , RV Norseman , Stn LT –2, 3 July 2011 , Longshot , East of Square Bay , coastal waters of Amchitka Island , Rat Islands , western Aleutian Islands , Bering Sea , 51°26.6ʹ N , 179°12.2ʹ E , depth 10 m , SCUBA , collector P. Kuklinski. NHMUK 2013.10 .21.6, one colony encrusting oyster shell , RV Norseman , Stn CT –1, 8 July 2011 , Cannikin , White Alice Creek , coastal waters of Amchitka Island , Rat Islands , western Aleutian Islands , Pacific Ocean , 51°28.6ʹ N , 179°07.3ʹ E , depth 10–15 m , SCUBA , collector P. Kuklinski. Additional material. 310 specimens . E.F. Guryanova Collection (1931) Stn 223; IMB Collection (1972) Stns 5/12, 59/167; (1973) Stns 113/302, 113/305, 113/306, 217/558; KIENM Collection (1988) Stn 326; (1991) Stns 196, 197, 198, 199, 203, 208, 215, 217, 225, 227, 228, 229, 230, 236; (1992) Stns 19, 20, 25, 27, 32, 34, 57, 63, 66, 68, 69, 70, 71, 72, 75, 76, 77, 79, 87, 97, 99, 100, 105, 118, 120, 124, 128, 130, 133, 144, 148; A. V . Grischenko Collection (1990) Stns 5, 15; (1992) Stns 1, 7, 8 (see Appendix 1 for details). Measurements. ZIRAS 34/50113, Medny Island, Commander Islands, Bering Sea ( Figs 19A–L , 30H ). ZL, 0.68–1.03 (0.80 ± 0.09). ZW, 0.36–0.51 (0.44 ± 0.04). ZD, 0.49–0.65 ( n = 2). OrL, 0.22–0.36 (0.28 ± 0.03). OrW, 0.24–0.35 (0.29 ± 0.03). OeL, 0.20–0.30 (0.26 ± 0.03). OeW, 0.30–0.38 (0.36 ± 0.02). Av(s)L, 0.15–0.31 (0.22 ± 0.04). P(m)N, 7–15 (12). P(oe)N, 0–9 (6). FIGURE 19. Rhamphostomella sibirica ( Kluge, 1929 ) . ZIRAS 34/50113 (Medny Island, Commander Islands, Bering Sea). A. Colony margin with developing zooids and ooecia. B. Zooids near colony margin showing form of primary orifice with lyrula. C. Suboral avicularium and lyrula. D. Group of non-ovicellate zooids in young part of colony. E. Zooids with developing ooecia. F, G. Ovicellate zooids in older parts of colony. H. Ovicellate zooid in older part of colony. I. Interior of frontal shield, showing lyrula, umbo, ring scar, areolae and ooecial communication pore (arrow). J. Basal surface of colony with tubular protuberances. K. Interior of frontal shield, 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, E, F, 250 μm; C, K, 50 μm; H, I, 100 μm; L, 200 μm. NHMUK 2013.10.21.5, Amchitka Island, Aleutian Islands, Bering Sea. ZL, 0.43–0.88 (0.64 ± 0.07). ZW, 0.28– 0.49 (0.38 ± 0.05). ZD, 0.45–0.54 ( n = 2). OrL, 0.21–0.30 (0.25 ± 0.02) ( n = 21). OrW, 0.23–0.30 (0.27 ± 0.02) ( n = 22). OeL, 0.21–0.31 (0.26 ± 0.02) ( n = 20). OeW, 0.25–0.39 (0.33 ± 0.02) ( n = 23). Av(s)L, 0.18–0.50 (0.28 ± 0.10). P(m)N, 6–12 (10) ( n = 10). P(oe)N, 5–9 (7) ( n = 20). P. Kuklinski Collection, Amchitka Island, Aleutian Islands, Bering Sea ( Fig. 25B ). AnL, 0.36 ( n = 1). AnW, 0.26 ( n = 1). AnOpL, 0.16 ( n = 1). AnOpW, 0.15 ( n = 1). Description. Colonies encrusting, multiserial, unilaminar ( Fig. 19A ), more or less circular, attaining 22 mm in any one direction, bright-orange or red-brown when alive, light-orange to yellowish when dry. Free-growing bilaminate folds or occasionally multilayered zooidal aggregations with free spaces between adjoining zooidal layers developing in some colonies. Zooids of moderate size, irregularly hexagonal, oval or irregular in shape, tapering proximally, packed in quincunx, demarcated by fine sutures between lateral and transverse walls in all parts of colony, young and old. Frontal shield umbonuloid ( Fig. 19A, I ), thin, moderately convex, smooth to gently dimpled on avicularian cystid, with large areolae along zooidal lateral walls, separated by interareolar ridges ( Fig. 19A, D–H ); ridges elongate, relatively low and thin in young zooids ( Fig. 19A, D ), tall and thick in older zooids, conferring to frontal shield a strongly costate appearance ( Fig. 19E–H ). As calcification progresses, ridges join along zooidal midline; some ridges connected to peristomial lappets and cystid of suboral avicularium. Umbonuloid component extensive, occupying about 60% of length of frontal shield (57% in one measured zooid), with parallel lineation and accretionary banding ( Fig. 19I ). Ring scar discrete ( Fig. 19L ). Primary orifice ( Fig. 19A, B ) submerged, subcircular or sometimes oval; distal and lateral rim formed by upper terminal part of distal transverse wall. Distal margin of orifice rounded, proximal margin concave, with median, bifurcate or, sometimes, alate lyrula ( Fig. 19B, C, I ). Condyles absent. Secondary orifice ( Fig. 19D–H ) asymmetrically oval to broadly triangular, cormidial, distolateral curvature formed by extensions of proximal and lateral walls of distal and distolateral zooids ( Fig. 19D ); proximally with deep, V-shaped pseudosinus defined by flared lappets from frontal shield, one of them concurrently fusing with cystid of suboral avicularium ( Fig. 19D–H ). In ovicellate zooids, lappets not fused with proximolateral corners of ooecia; instead, opposing lobes of secondary calcification growing from lateral walls of neighbouring zooids towards each other over proximal part of ectooecium ( Fig. 19F–H ). These lobes together with peristomial lappets and avicularian cystid forming incomplete circle giving tubular, transversely oval to irregularly triangular outline to secondary orifice. No oral spines. Cystid of suboral avicularium ocсupying from one-fifth to one-third of frontal zooidal wall, elevated, broad, with dimpled surface and 2–3 communication pores, asymmetrically situated on the left or right side proximal to orifice ( Fig. 19A–H ). Frontal surface (rostral/postmandibular areas) of avicularium slightly concave, crossing zooidal midline, facing distally or obliquely frontally. Rostrum elongate-triangular, slightly curved laterally, occasionally with hooked tip, directed distolaterally and upwards ( Fig. 19C ). Palate elongate-triangular, with rounded distal end, insignificantly curved laterally, foramen elongate-oval, with distal cryptocystal shelf; opesia semicircular. Crossbar complete. No adventitious avicularia. Ovicells initially hyperstomial, becoming subimmersed in older parts of colony by overgrowth of ooecium by secondary calcification ( Fig. 19F – H ). Ooecium formed by distal autozooid; ooecial fold developing concurrently with frontal shield of distal autozooid at colony periphery. Ooecial coelomic cavity connecting to visceral coelom via communication canal opening on underside of proximal part of frontal shield of distal zooid as straight slit-like communication pore situated near transverse wall ( Fig. 19I ). Ooecium hemispherical, smooth, with weakly concave proximal margin and 4–8 circular to oval pseudopores, sometimes occluded by secondary calcification. Zooids interconnected by 2‒3 mural pore chambers in each distolateral wall ( Fig. 19L ). Communication pores spread through basal part of transverse walls either as wide horizontal “band” or forming two multiporous septula. Basal surface of zooids ( Fig. 19J , 30H ) fully calcified, smooth, thin, with numerous tubular protuberances ( 0.08–0.28 mm in diameter) and occasional fine transverse lineation on surface. Numerous white spots (presumably less-calcified areas) visible in semitransparent basal wall by light microscopy. Boundaries between zooids indicated basally by sinuous incisions. Ancestrula modified tatiform ( Fig. 25B ), oval, basal wall with central uncalcified window; ancestrular opesia longitudinally oval, occupying distal half of cystid; eight spines evenly distributed around opesial margin.Ancestrula budding triplet of periancestrular zooids distally and distolaterally (left distolateral zooid not developed in Fig. 25B ); periancestrular zooids similar to but smaller than subsequent zooids, with distal zooid bearing two hollow, ephemeral oral spines incorporated in lateral peristomial lappets. Remarks. In contrast with early descriptions of an exclusively encrusting colony form in this species, some specimens we examined had erect, free-growing bilaminate folds or occasionally formed a multilayered compound aggregation of zooids. Although Kluge (1962 , 1975 ) mentioned the presence of tiny condyles, we did not observe them, although their presence/absence possibly falls into the range of variation for orificial characters in this species. Rhamphostomella sibirica strongly resembles R . bilaminata , and the species was long considered to be a variety or subspecies of R . bilaminata ( Kluge 1929 , 1952 , 1953 , 1955 , 1961 , 1962 , 1964 , 1975 ; Gostilovskaya 1957 , 1978 ; Kluge et al . 1959 ; Kubanin 1976 ; Androsova 1977 ; Gontar 1979 , 1980 , 1990 , 1993b , 1994a , 1996 ; Denisenko 1988 , 1990 ; Gontar & Denisenko 1989 ; Grischenko 1997 ). However, R . sibirica differs from R . bilaminata in the following characters: 1) zooids are longer in R . sibirica , with the mean length of zooids only just overlapping ( 0.64–0.80 mm in R . sibirica vs 0.55–0.69 mm in R . bilaminata ); 2) the frontal shield is flattened to moderately convex in R . sibirica , whereas most zooids are swollen in the distal half in R . bilaminata ; 3) interareolar ridges are numerous, prominent and long in R . sibirica ( Fig. 19D–H ) but very short, sparse or occasionally lacking in R . bilaminata ( Fig. 12D ); 4) the avicularian cystid has a neatly dimpled surface in R . sibirica but is entirely smooth in R . bilaminata ; 5) the suboral avicularia have an elongate triangular rostrum with a slightly curved distal end in R . sibirica , whereas they are broadly lingulate in R . bilaminata ; 6) the opposing peristomial lappets are generally convergent in R . bilaminata , defining a narrow U-shaped pseudosinus in the secondary orifice ( Fig. 12G, H ), but these are separated and the pseudosinus is V-shaped in R . sibirica ( Fig. 19F–H ). Based on these differences, we consider R . sibirica to represent a distinct species. Ecology. Rhamphostomella sibirica has been recorded at depths of 0–170 m on various bottom types (including silty plateaux, vertical rocky surfaces and crevices) and substrates (boulders, blocks, pebbles, gravel, sand and silt). Colonies encrust holdfasts of brown algae ( Alaria fistulosa , Laminaria dentigera , etc.), red algae ( Constantinea rosa-marina , etc.), and the species also occurs as a component of the crytic communities in the cavities formed by the coralline red alga Clathromorphum nereostratum . Other substrata include sponges, hydroids, bivalve shells, ascidians and other bryozoans ( Tegella aquilirostris , Scrupocellaria elongata , Myriapora orientalis , Phidolopora elongata , Celleporina nordenskjoldi ). Distribution. This is a boreal-Arctic, circumpolar, sublittoral species. Numerous Arctic records include the Barents Sea ( Smitt 1868a ; Kluge 1962 , 1975 ; Denisenko 1988 , 1990 ), White Sea ( Gostilovskaya 1957 , 1978 ), Kara Sea ( Kluge 1929 , 1962 , 1975 ; Denisenko 2021), Laptev Sea ( Kluge 1929 , 1962 , 1975 ; Gontar 1990 , 1996 ), East Siberian Sea ( Nordgaard 1929 ; Kluge 1929 , 1962 , 1975 ; Gontar 1994a ; Denisenko 2011 ), Chukchi Sea ( Kluge 1929 , 1962 , 1975 ; Denisenko 2008; Denisenko & Kuklinski 2008 ; Gontar 2010 ), western Greenland ( Kluge 1962 , 1975 ; Denisenko & Blicher 2021 ), eastern Greenland ( Levinsen 1916 ; Denisenko & Blicher 2021 ), Spitsbergen ( Gontar et al . 2001 ; Kuklinski 2009), and Franz Josef Land ( Denisenko 1990 ). In the northwestern Atlantic, R . sibirica has been reported from St Lawrence Gulf ( Kluge 1962 , 1975 ) and Gulf of Maine ( Osburn 1933 ). In the northwestern Pacific, it has been documented in the northern part of the Bering Sea from St Lawrence Island, Provideniya Bay, Anadyr Gulf, Navarin Cape ( Kluge 1961 ; Grischenko 2002; Gontar 2013 ), along eastern Kamchatka in the Litke Strait (our data), Africa Cape, Avacha Gulf ( Kluge 1961 ; Grischenko 2002), and around the Commander Islands ( Kubanin 1997 ; Grischenko 1997 , 2002, 2003b; Grischenko & Ivanyushina 2002 ); in the Sea of Okhotsk at Zavjalov Island ( Kubanin 1976 ), southwestern Kamchatka, Penzhinskaya, Gizhiginskaya, Yamskaya and Tauyskaya Inlets, Okhotsk, Ayan ( Kubanin 1997 ); eastern coast of southern Sakhalin Island ( Kluge 1961 ; Kluge et al . 1959 ), Sakhalin Gulf, Shantar Archipelago ( Kluge 1961 ), Kuril Islands ( Kluge et al . 1959 ; Kluge 1961 ; Lukin 1979 ; Gontar 1979 , 1980 , 1993b ), and in the Sea of Japan from Tatar Strait ( Kluge 1961 ). The only northeastern Pacific record is from Beringian coastal waters of Amchitka Island, Rat Islands, western Aleutians (our data).