Fatkullina imitata, Grischenko & Gordon & Morozov, 2018

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, Zootaxa 4508 (1) : -

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.

Figures

FIGURE 1. General view of dried colonies of Fatkullina imitata n. sp. (A–D) and F. paradoxa Grischenko, Gordon & Taylor, 1998 (E). A, B, specimens R.V. Professor Kizevetter 2015, Stn 73; C, D, specimens paratype 8 NIWA 127751; E, specimen R.V. Professor Probatov 2013, Stn 5, 16 June 2013, 57.41694° N, 156.51806° E, 27 m, pebbles, sand, silt. A, B. Colonies encrusting pebbles. C, D. Colonies encrusting external (C), and internal (D) surface of shell fragment of Chlamys sp. E. Colony encrusting internal surface of bivalve shell fragment of Serripes sp., surrounded by other encrusting bryozoan species. Scale bars: 5 mm.

FIGURE 2. Fatkullina imitata n. sp. A, Holotype ZIRAS 1/50661; B, paratype 5 ZIRAS 6/50666; C, paratype 4 ZIRAS 5/ 50665. A. General view of colony encrusting flattened pebble in boundary interactions with Celleporina ventricosa (Lorenz, 1886) (top left), Reussinella arctica (Osburn, 1950) (top right), Hippothoa arctica (Kluge, 1906), H. expansa Dawson, 1859 (bottom left) and Pachyegis princeps (Norman, 1903) (centrally to bottom right). B. General view of a medium-sized colony. C. General view of a young colony demonstrating a gradual shift in geometry of zooidal budding from spiral into reversedpolarity. Asterisks indicate zooids with a sideways (transverse) orientation. Scale bars: 1 mm.

FIGURE 3. Fatkullina imitata n. sp. A, holotype ZIRAS 1/50661; B–D, paratype 5 ZIRAS 6/50666; E, F, paratype 2 ZIRAS 3/50663. A, B. Zooids differentiating at colony margin. C, D. Randomly orientated autozooids in central colony area. E. Three zooids, showing granular-tubercular frontal walls uniformly perforated by large, round, deep infundibuliform pseudopores and drop-shaped secondary orifices with rugged outlines, overhanging distal curvature of primary orifice and slightly covering its sides. F. Distolateral view towards two zooids, showing roughly granular-tubercular, elevated and distended frontal wall around orificial area, evenly perforated with circular to oval deep infundibuliform pseudopores. Scale bars: A–D, 0.25 mm; E, F, 0.1 mm.

FIGURE 4. Fatkullina imitata n. sp. A–C, E, F, paratype 1 ZIRAS 2/50662; D, holotype ZIRAS 1/50661. Intracolonial polymorphism. A. Strongly distended zooids in elevated colony center, with proportionally elongated and elevated distal (preoral) frontal wall terminating with conical and bulbous solid umbones (arrowheads). B. Two neighboring zooids, each bearing distal (preoral) conical knob (arrowheads), with lateral boundary occluded by secondary calcification, indicated by enlarged infundibular pseudopores; note minute shortened distal suture line separating preoral areas. C. Two oppositely orientated zooids with strongly swollen frontal shields and orifices shifted to the top of frontal surface. D. Irregularly hexagonal, flattened, uniformly perforated kenozooid with undulating margins, surrounded by six autozooids. E. Colony area comprising mixed kenozooids and autozooids; note irregular shape of flattened kenozooids possessing strongly reduced orificial areas remaining in form of larger frontal pseudopores (left to central kenozooids) or two minor pseudopores (right kenozooid). F. Colony area fully represented by flattened kenozooids with orifices constricted or closed by calcified cylindrical or mammiform projections with tiny circular to slit-like openings at their apices. Scale bars: 0.25 mm.

FIGURE 5. Fatkullina imitata n. sp. A, paratype 5 ZIRAS 6/50666; B, holotype ZIRAS 1/50661; C–G, paratype 2 ZIRAS 3/ 50663. A. Orificial area of newly formed zooid near colony margin, showing transversely oval primary orifice bordered by thinly calcified smooth narrow rim, and surrounded by granular-tubercular surface with circular pseudopores. B. Orificial area of completed zooid, showing drop-shaped secondary orifice with granular tubercular surface, overhanging distal curvature of deeply submerged primary orifice, leaving visible its proximal thickened smooth shelf with shallow sinus; note circular infundibular pseudopores with finely tuberculated surfaces stretched deep inside. C. Interior of zooidal orificial area, showing transversally oval primary orifice with shallow sinus and deep calcified visor with denticulate margin, covers half of primary orifice length. D. Interior of group of zooids from central colony area, indicating their incoherent orientation, showing transversally oval primary orifices, smaller circular scattered openings of pseudopores in frontal shields, and enlarged circular to oval openings of tubular areolar pore channels encroaching via vertical walls, which connect main coelom with hypostegal coelom. E. Interior of frontal shield, showing scattered smaller openings of pseudopores centrally, enlarged openings of tubular areolar pore channels encroaching via vertical walls, which connect main coelom with hypostegal coelom, and transversally oval primary orifice with distal overhanging visor of secondary calcification covering more than 2/3 of primary orifice length. F. Internal and external view of zooidal lateral wall with basal pore chambers and external openings of tubular areolar pore channels encroaching lateral wall to open into the hypostegal coelom. G. Longitudinal cross-section through zooid, showing remarkable thickness of frontal shield, with deep, proximally tilted lumen between primary and secondary orifices, and lateral to frontal openings of tubular areolar pore channels connecting main coelom with hypostegal coelom. Scale bars: A–C, E–G, 0.1 mm; D, 0.25 mm.

FIGURE 6. Fatkullina imitata n. sp. A–G, paratype 3 ZIRAS 4/50664; H, specimen R.V. TINRO 2016, Stn 74. Early astogeny. A–C, ancestrular complex formation; D–F, ancestrular interior; G, H, colonies at early stages of astogeny, external and internal views. A. Ancestrula with first distally-budded, transversally/spirally arranged postancestrular zooid. B. Ancestrula with two postancestrular zooids (right bud partially damaged) spirally arranged and budded in opposite directions; note cormidial nature of ancestrular orifice, with its distal margin comprises lateral vertical wall of distally budded zooid, and right lateral margin – lateral vertical wall of laterally budded zooid. C. Ancestrula with two postancestrular zooids, spirally arranged and budded in same direction. D. Interior of ancestrula and distally arranged, perpendicularly orientated periancestrular zooid. E. Interior of ancestrular zooid, showing intensive distal umbonuloid area around orifice composed of four lobes separated with fine meandering sutures, ring scar, and proximal pseudoporous (lepralioid) part of the frontal shield. F. Close-up of umbonuloid area including circular orifice possessing deep V-shaped sinus, four uneven lobes separated with fine meandering sutures, discrete ring scar forming regular boundary between exterior-wall microstructure of umbonuloid part and extra-umbonuloid calcification. G. Ancestrular complex comprising ancestrula and three spirally arranged periancestrular zooids plus four developing to fully completed zooids. H. Undersides of ancestrular complex. Scale bars: A–D, G, H, 0.2 mm; E, F, 0.1 mm.