Juxtacribrilina pushkini, Dick & Grischenko & Gordon & Ostrovsky, 2021

Dick, Matthew H., Grischenko, Andrei V., Gordon, Dennis P. & Ostrovsky, Andrew N., 2021, The “ Cribrilina annulata " problem and new species of Juxtacribrilina (Bryozoa Cheilostomata: Cribrilinidae) from the North Pacific, Zootaxa 5016 (3), pp. 333-364 : 348-352

Juxtacribrilina pushkini n. sp.

( Figs 9 , 10 ; Table 3)

urn:lsid:zoobank.org:act:CDED1A27-C2BC-4867-9F62-E395036D70F5

Cribrilina annulata: Dick et al. 2005, p. 3718 , fig. 7A, B; Yang et al. 2018, fig. 13.

Diagnosis. Non-ovicellate zooids with 14–19 costae, 3–5 oral spines (usually 3 or 4); intercostal lacunae small, 6–10 in transverse series. One or two frontal pore chambers on proximal gymnocyst of most zooids. Ovicellate zooids (including ooecium) roughly same size as non-ovicellate zooids occurring but uncommon in basal layer. Reduced or dwarf marginal ovicellate zooids occurring; frontal dwarfs often abundant in colony center. Frontal shield of dwarf zooids as large as or larger than ooecial complex, with 5 or 6 costae. Ooecium in zooids in basal layer moderately reduced, cap-like, with several irregular pseudopores; ooecium in dwarf zooids typically with 2 transversely arranged, oval or irregular pseudopores, with additional pair of smaller pseudopores sometimes present. Ancestrula cribriform, with 4 or 5 oral spines.

Etymology. Named for Dr. Alexander Fedorovitch Pushkin (1938–2019), research associate at the Zoological Institute, Russian Academy of Sciences, zoologist and hydrobiologist, working mostly on Arctic and Antarctic benthic invertebrates and a leading world expert on Pycnogonida.

Material examined. Holotype: YPM-IZ-100361, vicinity of Ketchikan , Alaska, 9–12 September 2003, lower rocky intertidal, -0.46 to - 0.49 m relative to mean low water level ( MLWL); on rock, mounted on SEM stub . Paratypes: YPM-IZ-106544, YPM-IZ-106545, YPM-IZ-106546, East Tongass Narrows, Ketchikan, Alaska (55.31657°N, 131.51990°W), 11–12 September 2003, lower rocky intertidal; YPM-IZ-106547, collection information as for holotype, on SEM stub; YPM-IZ-100481, Settlers Cove , Ketchikan vicinity, Alaska (55.51161°N, 131.72517°W), 9 September 2003, lower rocky intertidal, - 0.46 m from MLWL; all on SEM stubs . Other material: YPM-IZ-106548, collection information as for holotype; on SEM stub. All specimens collected by M.H. Dick.

Measurements. See Table 3.

Description. Colonies encrusting, multiserial, unilaminar except for frontal dwarf zooids ( Fig. 9D ). Nonovicellate zooids ( Figs 9A , 10C, D ) typically oval in outline, widest in middle, closely packed; gymnocyst negligible, sometimes wider in proximal corners or tapering proximally as long caudal zone. Ovicellate and non-ovicellate zooids in basal layer each bearing 1 or 2 (exceptionally 3) oval, triangular, or quadrangular frontal pore chambers on proximal gymnocyst ( Fig. 9A–C ); frontal pore chambers multiporous. Frontal shield convex, tumid, sometimes with slight keel. Costae oval or somewhat flattened in cross section, 14–19 in number (average per colony 15.1– 17.1) in non-ovicellate zooids, suboral pair slightly swollen but not wider than rest, sometimes with small, fused tips extending fronto-distally ( Fig. 10C ) to form slight mucro; each costa with minute lumen pseudopore at or near tip. Intercostal lacunae small; circular, oval, or subcircular; 6–10 (usually 8 or 9) in transverse series (average per colony 8.2–9.0). Secondary orifice ( Figs 9A , 10C ) roughly semicircular, markedly wider than long; oral spines 3 or 4 (rarely 5), lateral pair often longer and heavier than those in between; median spine(s) flattened, basally wide, tapering, single or paired, in latter case sometimes fused.

Ovicellate zooids uncommonly present in basal layer ( Fig. 9B, C ), scattered singly and in small groups.Ovicellate zooids in colony interior as large (including ooecium) as non-ovicellate zooids, with 11–15 costae; suboral pair of costae wider, thicker than rest, with part of fused tips often extending fronto-distally to form sharp or blunt, often flattened mucro ( Fig. 9B ) proximal to and overhanging orifice.

Ooecial complex ( Fig. 9B, C ) in zooids in basal layer comprising ooecium and pair of widened, flattened, nonarticulated, modified latero-oral spines meeting at midline to form proximal margin; spines tapering and twisted in distal half to two-thirds to form concave proximal margin of ooecial complex, and sometimes raised and thickened in midline to form low mucro limited by conspicuous "fold" near middle of modified spine on each side (small arrowheads, Fig. 9B ); each spine bearing lumen pseudopore near truncate tip at midline. Proximal margin of ooecial complex and proximal margin of orifice both labiate in appearance. Ooecium moderately reduced, cap-like, roughly twice as wide as long, with 2–3 moderately large, circular to irregular pseudopores; ooecial cap abutting rather than passing underneath pair of modified spines forming proximal margin of complex; cap sometimes with thickened or folded proximal margin (abutting modified pair of spines) bearing additional 2 or 3 small pseudopores ( Fig. 9C ). Ooecium likely kenozooidal, arising from roof of distal pore chamber, which buds next-distal zooid ( Fig. 9B , arrow) or fails to bud, remaining as circular opening ( Fig. 9B , arrowheads); basal ovicellate zooids thus often but not always in columnar series with other zooids.

Dwarf ovicellate zooids typically present in center of colony ( Fig. 9D ), often densely packed, budded from proximal frontal pore chambers of zooids in basal layer; frontal shield ( Fig. 10A, B ) conspicuous, occupying half of zooid length; costae usually 5 or 6 (rarely, 7 or 8); suboral pair thicker than others, similar to suboral pair in basal ovicellate zooids, often forming median mucro; other costae centripetally directed toward midline, forming tight shield, with small, circular intercostal lacunae. Ooecial complex as described above for basal ovicellate zooids; ooecium small, cap-like ( Fig. 10B ), but kenozooidal, terminal, budded from maternal zooid; typically bearing two moderately large, circular or oval, transversely arranged pseudopores; proximal margin of ooecium (abutting modified pair of latero-oral spines) sometimes thickened and bearing additional smaller pseudopores ( Fig. 10B , arrowheads). Dwarf zooids sometimes with up to three basal pore chambers in distal (ooecial), disto-lateral, or lateral positions ( Fig. 10A ). Dwarf zooids occasionally present marginally in basal layer ( Fig. 10C ).

Ancestrula ( Fig. 10D ) cribriform, similar to but smaller than subsequent zooids, with 10 – 13 costae, surrounded by 6 periancestrular zooids (1 distal, 2 disto-lateral, 2 proximolateral, 1 proximal); 4 (n = 2) or 5 (n = 5) oral spines; if 5, distalmost, median spine thinner and shorter than rest.

Remarks. Dick et al. (2005) described this species (as Cribrilina annulata ) from the same locality, Ketchikan, Alaska. The zooidal measurements differ somewhat between that study and this, possibly due to different methods of measurement (light microscopy using an ocular micrometer in the previous study; measurements from SEM images here). The costal count for non-ovicellate zooids also differs (12 – 17 previously; 14 – 19 here), with the lower previous numbers possibly due to inclusion of some zooids in the zone of astogenetic change and a lower sample size. The number of oral spines in the ancestrula was previously given as four, but ancestrulae more often have five spines.

Juxtacribrilina pushkini n. sp. differs from J. annulata in the same ways as does J. ezoensis n. sp. (see above). Juxtacribrilina pushkini n. sp. and J. ezoensis n. sp. are quite similar in most aspects, including zooidal dimensions, the number of oral spines, and the morphology of ovicellate zooids in the basal layer. However, non-ovicellate zooids in J. pushkini n. sp. tend to have more costae (14–19, overall average 16.2) than in J. ezoensis n. sp. (12–18, overall average 14.8); the intercostal lacunae in basal zooids are smaller and more numerous (8 or 9 in transverse series) than in J. ezoensis n. sp. (usually 6–8); the costal shield in dwarf zooids is larger, tighter, and more convex, bearing 5 or 6 costae, compared to J. ezoensis n. sp. (smaller and flatter, typically bearing 3 or 4 costae); and there is a conspicuous angular "fold" ( Fig. 9B , small arrowheads) near the middle of each of the modified latero-oral spines of ovicellate zooids in the basal layer, whereas this fold is lacking in J. ezoensis n. sp.. The ancestrula in J. pushkini n. sp. has four or five oral spines but more commonly five; in J. ezoensis n. sp., only four oral spines were observed. The two species are most readily distinguished by the size and number of the intercostal lacunae in zooids in the basal layer, and by the number of costae and size of the costal shield in dwarf zooids.

Occurrence. At present, J. pushkini n. sp. is known only from Ketchikan, Alaska.

Figures

FIGURE 9. Juxtacribrilina pushkini n. sp., Ketchikan, Alaska; A, D, holotype, YPM-IZ-100361; B, C, paratype, YPM-IZ- 100481. A. Non-ovicellate zooids in basal layer; every zooid bearing one or two frontal pore chambers on proximal gymnocyst. B. Non-ovicellate and three ovicellate zooids in basal layer; large arrowheads, zooids with non-budding distal pore chamber; small arrowheads, “folds” seen in modified latero-oral spines contributing to ooecial complex; arrow, zooid with distal pore chamber contributing to next zooid. C. Reduced ovicellate zooid (center) at colony margin. D. Part of colony, showing densely packed dwarf zooids in colony center. Scale bars: A–C, 250 µm; D, 500 µm.

FIGURE 10. Juxtacribrilina pushkini n. sp., Ketchikan, Alaska; A–C, holotype, YPM-IZ-100361; D, paratype, YPM-IZ- 100481. A. Dwarf zooids overlying non-ovicellate basal zooids. B. Dwarf zooid; arrowheads indicate thickened proximal margin of ooecium bearing pair of small, additional pseudopores. C. Dwarf zooid budded from basal pore chamber at colony margin. D. Ancestrula and periancestrular zooids. Scale bars: A, C, 500 µm; B, 100 µm; D, 250 µm.