Juxtacribrilina dobrovolskii, 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 : 352-355

Juxtacribrilina dobrovolskii n. sp.

( Fig. 11 ; Table 4)

urn:lsid:zoobank.org:act:C88EE938-BEEE-4FD3-B3B4-EBA40EEE38EA

Diagnosis. Non-ovicellate zooids with 12–16 costae, 3 or 4 oral spines (predominantly 3); intercostal lacunae 6–9 in transverse series. Most zooids in basal layer with 1 or 2 frontal pore chambers on proximal gymnocyst. Ovicellate zooids occurring in basal layer, roughly same size (including ooecium) as non-ovicellate zooids; lacuna evident in midline at base of projection formed by suboral costae. Frontally budded dwarf ovicellate zooids occurring profusely in colony center; 4–7 costae (average 4.9); dwarf costal shield variable; tight, with wide, tapering costae and small intercostal lacunae, or reticulate, with narrow costae and very wide intercostal lacunae. Dwarf ooecium moderately reduced, cap-like, with a few irregular pseudopores; typically bearing single slit-like, oval, or ramifying pseudopore in midline.

Etymology. Named for Dr. Andrej Alexandrovitch Dobrovolskij (1939–2019), Head of the Department of Invertebrate Zoology at Saint Petersburg State University, Russia, zoologist, protistologist, and parasitologist, specializing on Digenea.

Material examined. Holotype and paratype: ZIRAS 01 /50733-A and -B, single pebble with one mature colony (holotype, A) and one ancestrular colony (paratype, B), Krabovaya Bay , Cape Severnyy Vkhodnoy , Shikotan Island, Lesser Kuril Chain (43.87722°N, 146.82000°E), collected by A.P. Tsurpalo, 28 August 1996; mid-intertidal, rocky shore; prepared for SEM examination .

Measurements. See Table 4.

Description. Colony ( Fig. 11A ) encrusting, multiserial, unilaminar except for frontally located dwarf zooids. Zooids ( Fig. 11B–D ) oval or spindle shaped, sometimes extended proximally; gymnocyst irregular, present as intermittent narrow band, widest at proximolateral corners ( Fig. 11B, C ), bearing 1 or 2 small, oval frontal pore chambers in most zooids. Frontal shield highly convex, sometimes slightly keeled; non-ovicellate zooids with 12–16 costae (average 14.5); intercostal lacunae circular, oval, irregular, or heart-shaped, 6–9 (average 7.5) in transverse series, each costa with minute lumen pseudopore at or near tip. In non-ovicellate zooids, suboral costae similar to or somewhat wider than others in width; ends of suboral costae often biramous, with more-distal pair of rami extending frontally or fronto-distally, meeting at midline to form projection proximal to orifice. Secondary orifice roughly semicircular, corners relatively sharp; 3–4 (average 3.1) articulated oral spines present; median one or two spines thinner than lateral spines, flattened, wider basally and tapering distally if single, cylindrical if paired.

Ovicellate zooids abundant in basal layer ( Fig. 11A, C ), occurring in broad band five or six zooid generations wide between central region and margin, with ovicellate zooids again giving rise to non-ovicellate zooids at margin. Ovicellate zooids in basal layer with suboral costae markedly wider than rest ( Fig. 11C ), each with terminal lumen pseudopore; bifurcate at end, with more-distal rami meeting at midline to form broad, labiate flange directed fronto-distally and overhanging orifice; median lacuna at base of flange. Ooecial complex ( Fig. 11C ) with broad, thickened, non-articulated, modified latero-oral spines, each with near-terminal lumen pseudopore, arching toward and meeting at midline, twisted and narrower distally, often flattened and elevated, giving rise to wide, blunt, frontodistally directed flange. Secondary orifice of ovicellate zooids wider than long, with appearance of smiling mouth, flanked by proximal (suboral costae) and distal (latero-oral spines) labiate flanges. Ooecium likely kenozooidal, arising from roof of distal pore chamber; cap-shaped, broader than long, proximal edge overlain by modified spines but not visible in frontal view; with one to several irregular or ramifying pseudopores. Basal ovicellate zooids often in columnar series with other zooids.

No. oral spines 3.1 (3–4)

No. costae 14.5 (12–16)

No. intercostal lacunae 1 7.5 (6–9)

Ovicellate zooids, basal n = 7, 1

Zooid length 2 552 (495–685)

Zooid width 294 (258–353)

Orifice length 77 (47–99)

Orifice width 180 (163–199)

Ooecial complex length 146 (116–172)

Ooecial complex width 234 (174–280)

Ooecium length 62 (33–89)

Ooecium width 172 (151–194)

No. costae 12.0 (11–13)

Frontal dwarf zooids n = 13, 1

Zooid length 2 317 (225–577)

Zooid width 227 (178–357)

Orifice length 80 (52–130)

Orifice width 151 (117–231)

Ooecial complex length 143 (95–231)

Ooecial complex width 200 (138–312)

Ooecium length 71 (52–111)

Ooecium width 142 (112–215)

No. costae 4.9 (4–7)

1 Number of lacunae in transverse series between second and third pairs of costae from orifice. 2 Includes the ooecium.

Frontally budded dwarf zooids (11D, E) scattered abundantly in colony center; ooecial complex similar to that of larger, basal ovicellate zooids but with flanges proximal and distal to orifice less prominent; suboral flange comprising blunt or sharp "double" mucro formed from cylindrical, more-distal rami of suboral costae; distal, elevated flange on proximal margin of ooecial complex often lacking. Ooecium of dwarf zooids cap-like, kenozooidal, terminal, variable in size and shape, as wide as or wider than long; with one or two circular or elongate pseudopores in midline, or single ramifying pseudopore. Dwarf zooids with 4–7 costae (including suboral pair; average 4.9); costal shield either nearly flat, with wide, tapering costae and small intercostal lacunae, or markedly convex, inflated, with narrow costae and very wide intercostal lacunae forming a reticulate shield (both types evident in Fig. 11E ). Ooecium sometimes with basal pore chamber distally ( Fig. 11E ). Only one reduced-size ovicellate zooid observed in basal layer—a dwarf zooid closer to colony center than to margin (not illustrated).

One newly settled ancestrula observed ( Fig. 11F ); cribriform; tight shield composed of 14 costae; with 5 oral spines, median spine shorter and thinner than rest.

Remarks. Juxtacribrilina dobrovolskii n. sp. differs from J. annulata in the same ways as do J. pushkini n. sp. and J. ezoensis n. sp.: most basal zooids bear one or two frontal pore chambers on the proximal gymnocyst; frontal dwarf zooids arise from these chambers and are often abundant and closely packed in the colony center; and the ooecium is cap-like and closely integrated with the modified latero-oral spines forming its proximal boundary.

Juxtacribrilina dobrovolskii n. sp. differs most conspicuously from J. pushkini n. sp. and J. ezoensis n. sp. in features of the dwarf zooids. In J. dobrovolskii n. sp., the dwarf ooecium usually has a single irregular (slit-like, elliptical, or ramifying) pseudopore in the midline, and the costal shield bears 4–7 costae and is variable ( Fig. 11E ), either flatter with fewer costae, or more tumid, with the costae forming a reticulate shield. In the latter two species, the dwarf ooecium usually has two transversely arranged pseudopores, and the costal shield is either somewhat tumid, usually with 5 or 6 costae ( J. pushkini n. sp.; Fig. 10A, B ), or flatter, usually with 3 or 4 costae ( J. ezoensi s n. sp.; Figs 4D , 6C ). Basal zooids in both J. dobrovolskii n. sp. ( Fig. 11C ) and J. ezoensis n. sp. ( Fig. 4A ) have larger intercostal lacunae relative to costal width than J. pushkini n. sp. ( Fig. 9A ), and this is reflected in lower average numbers of intercostal lacunae in transverse series: 7.5, 6.9–7.5, and 8.2–9.0, respectively ( Tables 2–4). Likewise, basal ovicellate zooids in both J. dobrovolskii n. sp. ( Fig. 11C ) and J. ezoensis n. sp. ( Fig. 5C, D ) tend to lack the distinct fold, seen in J. pushkini n. sp. ( Fig. 9B ), in each of the modified latero-oral spines contributing to the ooecial complex. Finally, the conspicuous median lacuna at the base of the flange formed by the suboral costae in basal ovicellate zooids in J. dobrovolskii n. sp. ( Fig. 11B, C ) is lacking in J. pushkini n. sp. ( Fig 9B ) and J. ezoensis n. sp. ( Fig. 5B–D ).

Occurrence. Shikotan Island in the Lesser Kuril Chain is the only known locality for J. dobrovolskii n. sp.

Figures

FIGURE 4. Juxtacribrilina ezoensis n. sp., intertidal, Akkeshi Bay, Japan; A, paratype, NHM 2006.2.27.50; B, paratype, YPM- IZ-106553; C, D, F, paratype, YPM-IZ-106554; E, paratype, YPM-IZ-106555.A. Non-ovicellate zooids in basal layer, showing presence of three or four oral spines and one or two frontal pore chambers on proximal gymnocyst. B. Non-ovicellate zooids in basal layer, showing ubiquitous frontal pore chambers highlighted in white due to electron charging. C. Colony with numerous frontally budded and four marginal (arrowheads) dwarf zooids. D. Dwarf zooids, with three (arrowheads) or four (arrows) costae in frontal shield. E. Dwarf zooid arising from frontal pore chamber. F. Colony margin, showing non-ovicellate zooids in basal layer, and frontal and marginal dwarf zooids. Scale bars: A, D, F, 250 µm; B, 500 µm; C, 1 mm; E, 200 µm.

FIGURE 5. Juxtacribrilina ezoensis n. sp., subtidal, Akkeshi Narrows, Japan; paratype, YPM-IZ-106550. A. Part of colony, showing ovicellate and non-ovicellate zooids in basal layer. B. Ovicellate and non-ovicellate zooids in basal layer; arrowheads, ovicellate zooids that have budded next zooid from distal pore chamber; arrow, ovicellate zooid with non-budding distal pore chamber. C. Oblique view of ovicellate zooids in basal layer, showing labiate flanges proximal and distal to orifice. D. Enlargement of ovicellate zooid in basal layer. E. Multiporous frontal pore chamber on tapering zone of proximal gymnocyst. F. Ancestrula and periancestrular zooids; note dwarf zooids beginning to develop from frontal pore chambers (arrowheads). Scale bars: A, 1 mm; B, C, 500 μm; D, 100 μm; E, 50 μm; F, 250 µm.

FIGURE 6. Juxtacribrilina ezoensis n. sp., subtidal, Akkeshi Bay, Japan. A, E, F, holotype, YPM-IZ-106549; B, paratype, YPM-IZ-106551; C, YPM-IZ-106552; D, paratype, YPM-IZ-106550. A. Portion of colony showing narrow marginal zone of reduced ovicellate zooids in basal layer, including several dwarfs. B. Colony with frontal dwarf zooids crowded in center; ovicellate zooid in primary layer at upper right. C. Frontal dwarf zooids with two, three, or four costae in frontal shield. D. Distal pore chamber of ovicellate zooid in basal layer (in distal view), showing pores in transverse wall (arrowheads) and pore in chamber roof leading to ooecial cavity (arrow); asterisk, ooecium. E. Zooid in basal layer showing developing ooecium; arrow, location of distal pore chamber of maternal zooid (out of view below base of ooecium), from which distal zooid is budding. F. Enlargement from E, showing ooecial cavity, with pore (arrow) at bottom leading to basal pore chamber; asterisk, ectooecium; arrowhead, entooecium. Scale bars: A, B, 500 µm; C, 250 µm; D, E, 50 µm; F, 30 µm.

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.

FIGURE 11. Juxtacribrilina dobrovolskii n. sp. (A–E) Holotype, ZIRAS 01/50733-A, Shikotan I., Lesser Kuril Chain. A. Colony, showing high frequency of ovicellate zooids in basal layer and scattered dwarf zooids in colony center. B. Ovicellate and non-ovicellate zooids near colony margin; arrowheads, frontal pore chambers forming in developing zooid. C. Ovicellate and two non-ovicellate zooids; ovicellate zooids with labiate flanges proximal and distal to orifice. D. Central region of colony, with ovicellate and non-ovicellate zooids in basal layer and numerous frontal dwarf zooids; arrowhead, dwarf zooid budding from frontal pore chamber. E. Frontal dwarfs; note variation in ooecial pseudopores and in frontal shield; arrowhead, compact frontal shield with tapering costae and sutures evident between costae; arrow, reticulate frontal shield. F. Paratype, ZIRAS 01/50733-B, ancestrula and periancestrular zooids. Scale bars: A, 1 mm; B, 500 µm; C–F, 250 µm.