Fatkullina imitata Grischenko & Gordon & Morozov 2018, n. sp.

Fatkullina imitata n. sp. (Figs 1 A–D, 2–6; Table 1) Fatkullina sp.: Grischenko 2015: 39 (table 1). Material examined. Holotype: ZIRAS 1 /50661, colony (18 × 17 mm) encrusting flattened pebble; KamchatNIRO Collection, R.V. Agat, 16 June 2008, Stn 2–S–2, continental slope of western Kamchatka Peninsula, Sea of Okhotsk, 58.03833° N, 155.72028° E, depth 290 m, on pebbles, coll. S.G. Korostylyov. Paratype 1: ZIRAS 2 / 50662, two colonies (23 × 21 mm, 15 × 12 mm) encrusting broken fragment of bivalve shell Chlamys sp.; same data as for holotype. Paratype 2: ZIRAS 3 /50663, 12 fragments of single colony detached from pebble; KamchatNIRO Collection, R.V. Professor Kizevetter, 3 July 2015, Stn 73, shelf of western Kamchatka Peninsula, Sea of Okhotsk, 58.13333° N, 156.01889° E, depth 145 m, on rock and shell, coll. T.B. Morozov. Paratype 3: ZIRAS 4 /50664, seven intact ancestrular colonies; same data as for paratype 2. Paratype 4: ZIRAS 5 /50665, ancestrular colony (4 × 3 mm) encrusting broken fragment of Chlamys sp; same data as for holotype. Paratype 5: ZIRAS 6 /50666, colony (8 × 7 mm) detached from pebble; KamchatNIRO Collection, R.V. Agat, 16 June 2008, Stn 1–K–2, continental slope of western Kamchatka Peninsula, Sea of Okhotsk, 58.01917° N, 155.71667° E, depth 285 m, on pebbles, coll. S.G. Korostylyov. Paratype 6: NHMUK 2017.7.11.7, extensive colony (35 × 29 mm) encrusting cirripede fragment (with adjacent tiny colony—ancestrula and single daughter zooid); same data as for holotype. Paratype 7: NHMUK 2017.7.11.8, colony encrusting fragment of Chlamys sp; KamchatNIRO Collection, R.V. Professor Probatov, 11 August 2013, Stn 82, shelf of western Kamchatka Peninsula, Sea of Okhotsk, 58.15000° N, 156.05000° E, depth 146 m, on gravel from silty sand, coll. T.B. Morozov. Paratype 8: NIWA 127751, colony (33 × 30 mm) encrusting fragment of Chlamys sp., with adjacent colony and tiny ancestrular colonies; same data as for paratype 7. Additional material: KamchatNIRO Collection, R.V. Agat (2008): Stn 2–S–2, one specimen; Stn 3–W–1, two specimens; Stn 3–W–2, six specimens; Stn 4–N–2, one specimen; Stn 5–E–1, one specimen; Stn 5–E–2, three specimens. R.V. Professor Probatov (2013): Stn 62, four specimens; Stn 63, one specimen; Stn 82, 13 specimens. R.V. TINRO (2014): Stn 63, one specimen; Stn 69, one specimen; Stn 82, eight specimens. R.V. Professor Kizevetter (2015): Stn 73, 96 specimens. R.V. TINRO (2016): Stn 74, 43 specimens. Etymology. Latin adjective imitatus (imitated, copied), alluding to the strong resemblance to the type species of the genus, Fatkullina paradoxa. Description. Colony encrusting, multiserial, unilaminar, more or less circular, with undulating margin, attaining c. 40 mm diameter. Colour (when dried) crimson (most typical), pink, dark red, deep purple to black (Fig. 1 A–D); preserved polypides pink. Zooids relatively large, greatly variable in form (Figs 2A, B, 3C, D) including broadly hexagonal, oval, quadrangular, rhombic, pyriform, polygonal or irregular in outline, arranged quincuncially or less orderly, separated by fine undulating sutures between vertical walls; sutures occasionally concealed by secondary calcification. Frontal shield (Figs 3 C–F, 4A–C, 5F, G) lepralioid, thick, convex, most elevated and inflated in distal third of zooid around secondary orifice, moderately convex to evenly flattened centrally and proximally; with finely granular-tubercular surface, uniformly perforated with conspicuous round to elongate oval areolar-septular pores along zooidal margins and numerous smaller, circular frontal pseudopores (Figs 3E, F, 5B, F, G); areolae and pseudopores becoming funnel-shaped with development of secondary calcification, with granulation extending deep inside; some pores occluded. Interior surface of frontal shield (Fig. 5D, E, G) smooth, with numerous openings of pseudopores in center, and openings of tubular areolar pore channels around periphery. Some zooids, especially in elevated older parts of colony, with more-elongated area of calcification distal to orifice, with up to 3– 4 rows of pseudopores (Fig. 4 A–C). Distal margin of secondary orifice can bear a solid, elevated, conical or bulbous umbo (Fig. 4A, B, arrowheads), with orifice shifted proximally to a position about 1/4 to 1/3 zooid length from distal end. Two smaller, conical umbones can additionally flank sinus of secondary orifice, strongly reducing area of secondary orifice and conferring strictly triangular form. Primary orifice (Fig. 5 A–C, E) deeply sunken, wholly visible only at colony margin; transversely oval, with straight or weakly concave proximal margin and short, narrow U-shaped sinus; thin proximal margin lacking granulation. In fully completed zooids, primary orifice tilted proximally at angle of c. 20–40° to frontal plane. Secondary orifice (Figs 3E, 5B) formed by thickening of frontal shield around primary orifice; roughly triangular to drop-shaped in outline, with finely granular tubercular margin; at highest elevation of frontal shield. Distal margin gently convex, arching and overhanging 1/3 to 2/3 of distal part of primary orifice and partially concealing its lateral margins (Fig. 5B, C). Proximolateral margins sloping abruptly within, forming broad to narrowly triangular pseudosinus descending to smooth suboral rim of primary orifice. Lumen of secondary orifice (Figs 3E, F, 5C, E, G) deep, tubular to infundibular, tilted proximally at angle about 30–45° to frontal plane. Some zooids in central colony region secondarily kenozooidal (Fig. 4 D–F), with orifice constricted or closed, often with a cylindrical or mammiform projection over orifice. Operculum dark brown. Oral spines, avicularia and ooecia absent. Larval incubation presumably occurs in internal brood sac. Interzooidal communication via uniporous septula recessed between buttresses (Fig. 3A, B). Basal wall fully calcified (Fig. 5F, G). Zooidal morphogenesis with reversed polarity, i.e. orifice situated at proximal end of zooid relative to colony orientation and directed towards ancestrula. Kenozooids rarely single, distributed among autozooids, more frequently multiple, united into clusters. Ancestrula (Fig. 6 A–H) resembling autozooids in general appearance; roughly hexagonal, convex, with finely granular surface and a few marginal and frontal pores. Ancestrular orifice circular, with deep V-shaped sinus; cormidial, bounded proximally by distal part of frontal shield, distally and laterally by margins of vertical walls of distal and lateral periancestrular zooids; boundaries defined by fine sutures externally (Fig. 6B) and internally (Fig. 6F, arrowheads). Interior of ancestrular frontal shield (Fig. 6 D–F) with mixed (suboral umbonuloid and proximal lepralioid) components; suboral part unequally divided by four radial sutures (Fig. 6F, arrowheads), two of them flanking the sinus, apparently corresponding externally (in part, at least) to sutures seen frontally between other components of ancestrular complex. Ring scar discrete (Fig. 6F), forming very regular boundary between exteriorwall microstructure (planar-spherulitic fabric) of umbonuloid part and extra-umbonuloid calcification. Umbo extensive, occupying about 58% of length of frontal shield. Proximal lepralioid part of shield with smooth interior surface containing scattered tiny, uniformly circular, pseudopores (Fig. 6E). Ancestrula unrecognizable in older region of large colonies owing to secondary calcification that conceals orifices and crosses zooidal boundaries. Ancestrula buds triplet of somewhat spirally arranged periancestrular zooids, integrated into ancestrular complex. First daughter zooid of complex differentiating distally (Fig. 6A, D), perpendicular to ancestrula, slightly curved along long axis, giving T-shaped appearance to initial stage of ancestrular complex (seen in a dozen such newly established colonies), and two periancestrular zooids then differentiating laterally on each side. Orifices of distolateral zooids can be orientated antiparallel to ancestrula (Fig. 6B, C, right zooid; Fig. 6G, left zooid) or same direction as ancestrula (Fig. 6G, right zooid). Weakly spiral budding pattern continued through zone of astogenetic change and visible throughout four to ten or more generations of zooids distant from ancestrula. Remarks. In having zooids with reversed polarity and occasionally possessing deep-purple to black colony colour, Fatkullina imitata n. sp. strongly resembles the type species of the genus, F. paradoxa, and can be confused with it. The two species differ, however, in the following characters: 1 Frontal shield convexity—maximally convex centrally to proximally, with a comparatively depressed orificial area in F. paradoxa; typically most elevated and inflated distally in circumorificial area, and moderately convex proximally in F. imitata n. sp. 2 Umbo(nes)—a prominent solid umbo or 2–3 smaller, scattered mamilliform umbones in the suboral/ subcentral part of the frontal shield in many zooids of F. paradoxa; a conical to bulbous umbo occasionally developing distal to the orifice in some zooids of F. imitata n. sp., particularly in elevated older parts of colony. Further, 2–3 smaller umbones can occasionally replace the single prominent umbo randomly over the whole frontal shield in F. paradoxa, whereas a pair of smaller umbones may flank the sinus proximolaterally in F. imitata n. sp. 3 Shape of the primary orifice—more or less circular in outline (mean length and width 0.20 × 0.21 mm in type material) with a deep, widely V-shaped sinus in F. paradoxa; transversely oval (mean length and width 0.12 × 0.19 mm) with a straight proximal margin and narrowed, shallow U-shaped sinus in F. imitata n. sp. 4 Depth of the primary orifice—little sunken, facing frontally and wholly visible in all zooids at all stages of astogeny in F. paradoxa; deeply sunken, tilted proximally at about 20–40° to frontal plane, and partly concealed by the overhanging distal margin of the secondary orifice for 1/3 to 1/2 of its length, hence wholly visible only in developing zooids near the colony margin in F. imitata n. sp. 5 Relative proportions of the orifice—orifice width and sinus length are very similar and overlapping in F. paradoxa and F. imitata n. sp., respectively 0.19–0.24 mm (0.21 ± 0.02 mm) vs 0.16–0.23 mm (0.19 ± 0.02 mm), and 0.03–0.05 mm (0.04 ± 0.01 mm) vs 0.02–0.05 mm (0.03 ± 0.01 mm), whereas orifice length in F. paradoxa exceeds that in F. imitata n. sp. (0.18–0.25 mm (0.20 ± 0.02 mm) vs 0.10–0.15 mm (0.12 ± 0.02 mm)) and the ranges do not overlap. 6 Ratio of primary orifice length to zooid length—half as great in F. imitata n. sp. (about 14%) compared to F. paradoxa (about 29%). 7 Secondary orifice—the primary and secondary orifices are nearly identical in form and roughly circular in F. paradoxa; the primary orifice is transversely oval and the secondary orifice triangular to drop-shaped in outlines in F. imitata n. sp. 8 The cormidial nature of the primary orifice—cormidial in several generations of periancestrular zooids in F. paradoxa; cormidial only in zooids of the ancestrular complex in F. imitata n. sp. 9 Colour of dried colonies (colour not seen in living colonies)—black in F. paradoxa; mostly dark red/crimson in F. imitata n. sp. (sometimes pink, rarely deep purple to black). Ecology. The new species was documented in areas of mixed hard and soft bottoms, including pebbles and rocks with shell, gravel and sand/silt admixtures. Of the 197 colonies examined, 79.69% were found on pebbles, 10.15% and 1.02% respectively on shell fragments of the bivalves Chlamys sp. and Monia macrochisma, 8.12% on barnacles, 0.51% on tubes of serpulid polychaetes and 0.51% on sponges. Co-occurring invertebrates mostly included the echinoderms Strongylocentrotus pallidus and Ophiura leptoctenia, the sedentary polychaetes Scoloplos armiger and Galathowenia oculata, the gammaridean amphipod Melita dentata and the bivalve Yoldia myalis, as well as hydroids, barnacles, sponges and about 70–90 other bryozoan species, the most abundant being Hippothoa arctica (Kluge, 1906), H. expansa Dawson, 1859, Escharella ventricosa (Hassall, 1842), Ragionula rosacea (Busk, 1856) and Stomacrustula tuberculata (Androsova, 1958). The number of F. imitata colonies/m 2 by collection year was 4–28 (2008), 4–40 (2013), 4–32 (2014), 384 (2015) and 172 (2016). Colonies of F. imitata occasionally cover a considerable area of any particular substratum, appearing as the ‘background’ species at certain sites where shingly bottoms prevail. Distribution. Fatkullina imitata n. sp. is currently known from 16 stations in the depth range 100–361 m, in an area bounded by the coordinates 56.98389– 58.18528° N and 154.93389– 156.05000° E. It can thus be categorized as a high-Boreal, Pacific, Asian, sublittoral to upper bathyal species, endemic to the western Kamchatka shelf and slope, Sea of Okhotsk.Published as part of Grischenko, Andrei V., Gordon, Dennis P. & Morozov, Taras B., 2018, Fatkullina imitata n. sp., second species of a unique cheilostome bryozoan genus with reversed-polarity zooidal budding, and new family Fatkullinidae in Zootaxa 4508 (1), DOI: 10.11646/zootaxa.4508.1.4, http://zenodo.org/record/260685