Rhamphostomella cellata ( O’Donoghue & O’Donoghue, 1923 )

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 : 46-49

Rhamphostomella cellata ( O’Donoghue & O’Donoghue, 1923)

( Fig. 13 )

Smittina cellata O’Donoghue & O’Donoghue, 1923, p. 43 , pl. 4, fig. 31.

Smittina cellata: O’Donoghue & O’Donoghue 1926, p. 68 .

Rhamphostomella cellata: Osburn 1952, p. 431 , pl. 52, fig. 9.

Not Rhamphostomella cellata: Hansen 1962, p. 39 .

Smittina torquata O’Donoghue & O’Donoghue, 1923, p. 43 , pl. 4, fig. 32.

Smittina torquata: O’Donoghue & O’Donoghue 1926, p. 68 .

Material examined. Lectotype: NHMUK 1964.1 .2.9, single colony detached from bivalve mollusc shell, fractured into nine fragments (mounted on seven SEM stubs), C.H. O’Donoghue Collection, Pacific coast of North America (presumably Vancouver Island , British Columbia).

Measurements. NHMUK 1964.1.2.9, Pacific coast of North America ( Fig. 13A–L ). ZL, 0.65–1.23 (0.89 ± 0.14). ZW, 0.32–0.55 (0.44 ± 0.06). ZD, 0.30–0.33 (n = 2). OrL, 0.15–0.25 (0.21 ± 0.02). OrW, 0.20–0.28 (0.23 ± 0.02). OeL, 0.25–0.33 (0.29 ± 0.02) (n = 22). OeW, 0.35–0.43 (0.38 ± 0.02) (n = 22). Av(s)L, 0.07–0.16 (0.11 ± 0.02). P(m)N, 17–27 (22).

Description. Colonies encrusting, multiserial, unilaminar ( Fig. 13A ), more or less circular, attaining 22 mm in maximal dimension, light brown when dry. Zooids large, oblong-hexagonal to oval, or pyriform ( Fig. 13A, D, F, G ), arranged in checkered pattern, demarcated by fine sutures between lateral and transverse zooidal walls; sutures visible in both young and old parts of colony.

Frontal shield umbonuloid ( Fig. 13A, D, G, I ), thin, inflated to slightly convex, smooth to dimpled, with reticulate appearance in young zooids( Fig.13A,B,D )and smoothly tuberculate in older zooids( Fig.13E–G );with numerous deep circulartoovalareolaealongmargins,separatedbyshort,narrowinterareolarridges.Umbonuloidcomponentoccupying about40%oflengthoffrontalshield,withparallellineationandaccretionarybanding( Fig.13I,K ).Ringscardiscrete( Fig. 13I,K ),formingregularboundarybetweenumbonuloidexteriorwallandextra-umbonuloidinteriorwallmicrostructure.

Primary orifice ( Fig. 13B, C, E ) broadly circular to transversely oval; distal and lateral margins formed by upper terminal part of distal transverse wall incidentally bearing ill-defined rim ( Fig. 13C ). Distal margin of orifice rounded, proximal margin concave with median bifid lyrula having acute tips directed distolaterally, and distinct triangular process on each side with acute or round tip, occasionally strongly reduced. Condyles and oral spines absent.

Secondary orifice irregularly circular to oval, cormidial ( Fig. 13C–H ), distally and distolaterally restricted by elevated vertical walls of distal and lateral zooids; proximally formed by slightly elevated peristomial outgrowth of frontal shield, incorporating asymmetrically positioned cystid of suboral avicularium. In ovicellate zooids, lateral peristomial lappets connected to proximolateral corners of ooecium ( Fig. 13F–H ), conferring circular or sometimes irregularly triangular (because of avicularium) outline to secondary orifice.

Cystid of suboral avicularium small, low, asymmetrically situated proximolateral to zooidal orifice on left or right side, with dimpled surface and one small communication pore. Frontal surface (rostral/postmandibular areas) of avicularium concave, to one side of zooidal midline, facing obliquely frontally. Rostrum lodged within rim of peristome, slightly curving inward to conform to it, directed obliquely distolaterally and frontally ( Fig. 13C, D, E, H ). Palatal foramen lingulate to semioval and roundly triangular, conforming to shape of rostrum, opesia semioval to lingulate. Crossbar complete.

No adventitious avicularia.

Although all ooecia were broken in material studied, ovicells are clearly hyperstomial, with ooecia free of secondary calcification ( Fig. 13F–H ). Ooecium formed by distal autozooid, its coelomic cavity connected with visceral coelom via communication canal that opens on underside of proximal part of frontal shield of distal zooid as chevron-shaped communication slit about midway between transverse wall and ring scar ( Fig. 13I ). Remnants of ectooecium bear circular pseudopores in one specimen ( Fig. 13F ). Proximal margin of ooecium very weakly concave.

Zooids interconnected by three mural pore chambers in each distolateral wall ( Fig. 13L ) and two multiporous septula in basal half of transverse walls. In some zooids, transverse walls with two shallow recesses separated by medial buttress.

Basal walls of zooids entirely calcified ( Fig. 13J ), smooth, flat, without white spots or protuberances. Boundaries between zooids indicated basally by fine sutures.

Ancestrula and early astogeny not observed.

Remarks. The fragments examined have zooids with partially to fully damaged ovicells. One zooid shows the incomplete roof of an ovicell with two circular pseudopores and the remnants of a third laterally. In their original description, O’Donoghue & O’Donoghue (1923, p. 43) described the surface of ovicells as being “perforated by a series of large irregular pores” (their fig. 31 shows 10–12 oval to irregular pseudopores).

O’Donoghue & O’Donoghue (1923) described Smittina cellata and S. torquata from Vancouver Island. Osburn (1952, p. 431) synonymized these species, treating the former as the senior synonym of the latter and placing it in Rhamphostomella .

The surface of the frontal shield of R. cellata is dimpled, conferring a reticulate appearance similar to that in R. curvirostrata and R. townsendi . The former species clearly differs from the latter two in having the suboral avicularium located within the rim of peristome, slightly curving inwards to conform to it. While the suboral avicularium in the latter two species is connected with the peristome, both the rostrum and frontal surface differ from R. cellata in position, shape and orientation.

The Canadian Museum of Nature contains some material identified by O’Donoghue from British Columbia (24 items), including a dried specimen of R. cellata (Cat. No. – CMNI 1988-0135, Northumberland Channel). Unfortunately, there are no images, and the specimen is not mentioned as a type in the On-line Collection Data of the Museum. Accordingly, we selected a lectotype from C.H. O’Donoghue Collection deposited in the Natural History Museum, London. Although a precise locality was not written on the label, these specimens likely came from the waters around Vancouver Island, British Columbia.

Ecology. Rhamphostomella cellata is known only from the depth range 1.8–9.1 m. Colonies encrust mollusc shells.

Distribution. This little-known species was first described from Northumberland Channel and Gabriola Passage (about 49°52.0ʹ N, 123°72.0ʹ W), Vancouver Island, British Columbia ( O’Donoghue & O’Donoghue 1923). O’Donoghue & O’Donoghue (1926) recorded it from numerous localities in British Columbia (Namu, Port Simpson, off Round Island, Houston Channel, Brotchie Ledge, Victoria, off Point Caution, off Breakwater Island, Cowichan Gap) and near the San Juan Islands in Puget Sound. The specimens examined by Osburn were collected from Middle Bank, Puget Sound ( Osburn 1952). Records of the species from Baffin Bay and Davis Strait ( Hansen 1962) are doubtful. From these distributional data, R. cellata is an Eastern Pacific boreal, sublittoral species.

Figures

FIGURE 13. Rhamphostomella cellata (O’Donoghue & O’Donoghue, 1923). Lectotype, NHMUK 1964.1.2.9 (Pacific coast of North America, presumably Vancouver Island, British Columbia). A. Colony margin with developing zooids. B. Distolateral view of marginal zooids, showing shape of primary orifice and dimpled surface of frontal shield. C. Zooidal orifice with suboral avicularium. D. Group of non-ovicellate zooids in young part of colony. E. Single non-ovicellate zooid in older part of colony. F. Zooids with damaged ooecia in older part of colony. G. Zooids in older part of colony. H. Distal part of zooid with partially broken ooecium, showing form of secondary orifice and suboral avicularium. I. Interior of frontal shield, showing umbo, areolae and ooecial communication slit (arrow). J. Basal surface of colony, showing hardly recognizable boundaries between zooids. K. Interior of frontal shield, showing ring scar and exterior wall microstructure of umbonuloid component. L. Lateral view of zooid, showing peristome, areolae and zooidal lateral wall with mural pore chambers. Scale bars: A, D, J, 500 μm; B, F, G, 250 μm; C, E, H, I, 100 μm; K, 50 μm; L, 200 μm.