Juxtacribrilina tumida, 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 : 355-358

Juxtacribrilina tumida n. sp.

( Fig. 12 ; Table 5)

urn:lsid:zoobank.org:act:CEF34BD6-BE69-40A7-99E0-CE1B69F860D2

Diagnosis. Non-ovicellate zooids with 7–14 costae, 2 or 3 oral spines (predominantly 3), lateral pair long, stout, with enlarged bases. Costae inflated, elliptical in transverse section, separated by relatively deep intercostal grooves; suboral pair often thicker than rest; intercostal lacunae moderately large, 5–7 in transverse series. Most zooids in basal layer with 1 or 2 frontal pore chambers on proximal gymnocyst. Ovicellate zooids not observed in basal layer. Frontally budded dwarf ovicellate zooids with 4 costae. Ooecium in dwarf zooids cap-like, kenozooidal, bearing single large, circular pseudopore in midline.

Etymology. The specific name derives from the Latin adjective tumidus (swollen), referring to the swollen appearance of the costae.

Material examined. Holotype: YPM-IZ-106557, on SEM stub, Eider Island, Narrow Strait, Kodiak, Alaska (57.88560°N, 152.40095°W), collected by M.H. Dick, December 1982, lower rocky intertidal. Similar material of uncertain identity: ZIRAS 01/50737, Ptichy Island, 11 km northwest of Cape Raduzhnyy, western Kamchatka Peninsula, Sea of Okhotsk (57.16361°N, 156.56194°E), collected by A. V. Grischenko, 6 September 1992, colony detached from inner surface of Mya truncata shell, Balanus zone, middle to lower rocky intertidal, on SEM stub. NHM 2006.2.27.51, Akkeshi Bay, Hokkaido, Japan, small, non-ovicellate colony, collected by A. V. Grischenko and M.H. Dick, rocky intertidal, June–July 2004. YPM-IZ-106558, on SEM stub, Higgins Point, Ketchikan, Alaska (55.455183°N, 131.834305°W), collected by M.H. Dick, 9 September 2003, rocky intertidal.

Measurements. See Table 5.

Description (holotype). Colony ( Fig. 12A ) 5 x 2 mm in size; encrusting, multiserial, unilaminar except for frontally budded dwarf zooids. Zooids ( Fig. 12B ) closely appressed, delineated by deep groove; oval, long-oval, or spindle-shaped in outline. Gymnocyst negligible except as narrow zone proximally, bearing one or two frontal pore chambers on most zooids; frontal pore chambers occasionally also occurring on lateral gymnocyst. Frontal shield highly convex, with 7–14 relatively thick, tumid costae; intercostal lacunae moderately large, circular or irregular, 5–7 in transverse series; each costa with lumen pseudopore at or close to tip. Suboral pair of costae usually stouter than rest, sometimes elevated in midline or curving fronto-distally to form raised suboral projection. Secondary orifice approximately semicircular, broader than long, with rounded corners. Non-ovicellate zooids with 2–3 articulated oral spines; disto-lateral pair tall, thick, cylindrical, arising from enlarged bases ( Fig. 12B ), with or without smaller, single, tapering spine between them. No ovicellate zooids observed in basal layer.

Dwarf zooids ( Fig. 12C, D ) with 4 costae, including thickened suboral pair. Proximal border of ooecial complex concave, formed by pair of thickened, tapering, modified latero-oral spines meeting at midline, each with small lumen pseudopore near tip. Ooecium reduced, cap-like, kenozooidal, terminal, with single, large pseudopore in center ( Fig. 12C, D ). No marginal dwarf zooids observed. No ancestrula observed.

Remarks. Juxtacribrilina tumida n. sp. differs from J. annulata in the same ways as do J. ezoensis n. sp., J. pushkini n. sp., and J. dobrovolskii n. sp. (see above). It differs from the latter three species in having fewer costae (average, 10.1, Table 5; range of averages for the latter three, 12.8–17.1, Tables 2–4); fewer intercostal lacunae in transverse series (average, 6.3; range of averages for the other three, 7.1–8.6); the suboral pair of costae markedly thicker than the rest ( Fig. 12B ); and the disto-lateral pair of oral spines thick, with large bases evident in bleached material ( Fig. 12B ). The dwarf zooidal ooecium in J. tumida n. sp. has a single, relatively large, circular pseudopore in the center ( Fig. 12C, D ), whereas those in J. ezoensis n. sp. ( Fig. 6C ) and J. pushkini n. sp. ( Fig. 10A ) typically have two smaller, transversely arranged pseudopores, and that in J. dobrovolskii n. sp. ( Fig. 11D ) has a single slitlike, oval, or ramifying pseudopore.

A single intertidal specimen from Akkeshi Bay, northern Japan ( Fig. 13A ; Table 5) shows non-ovicellate zooids very similar to J. tumida n. sp. and could be this species, although the identification is tentative because no ovicellate zooids were present. A single intertidal specimen from Ptichy Island, Sea of Okhotsk ( Fig. 13B ; Table 5), likewise showed non-ovicellate zooids similar to those in J. tumida n. sp., with relatively few costae and intercostal lacunae, a similar complement of oral spines, and enlarged bases of the disto-lateral oral spines, but differed in having flatter, less tumid costae and markedly larger zooid size. As the Ptichy specimen lacked ovicellate zooids, its identity likewise remained ambiguous.

Specimen YPM-IZ-106558 from Ketchikan ( Fig. 13C–F ) is unusual in showing a band two generations wide of zooids (both ovicellate and non-ovicellate) similar in morphology to J. tumida n. sp. in having fewer costae and fewer, larger intercostal lacunae ( Table 5), and in the somewhat enlarged bases of the disto-lateral oral spines. This zone, however, gives rise to a marginal zone of zooids having the more numerous costae and smaller, more numerous intercostal lacunae characteristic of J. pushkini n. sp. ( Fig. 13D ). The costae in the J. tumida -like zooids in specimen YPM-IZ-106558 are not as inflated as in J. tumida n. sp. In addition, the ooecia in frontal dwarfs are intermediate between the single-pseudopore condition in J. tumida n. sp. and that in J. pushkini n. sp.; in Fig. 13F , one ooecium has a single large pseudopore, three have two smaller pseudopores transversely arranged but closer together than is typical for J. pushkini n. sp., and two have a dumbbell-shaped opening resulting from the incomplete separation of two close pseudopores. The costal shields in dwarf zooids in YPM-IZ-106558 are flatter and composed of four costae, as in J. tumida n. sp.; those in J. pushkini n. sp. typically have five or six costae.

The nature of the J. tumida -like band in the Ketchikan specimen is not clear. This specimen is not clearly either J. tumida n. sp. or J. pushkini n. sp.; none of the many other specimens from Ketchikan identified as J. pushkini n. sp. showed the mixed zooid types. It is noteworthy that another Juxtacribrilina species , J. mutabilis , shows distinct, alternative zooid types, with individual colonies containing one to three of the types ( Ito et al. 2015; Dick et al. 2020), intermingled or occurring in separate zones. One explanation for Ketchikan specimen YPM-IZ-106558 is that it represents a distinct species showing alternative zooid types. Another possibility is that hybridization has occurred between J. tumida n. sp. and J. pushkini n. sp. at Ketchikan, although no J. tumida n. sp. colonies were detected there. Without more material from across the North Pacific, we cannot resolve this issue.

Occurrence. We found J. tumida n. sp. only at Kodiak, although specimens of ambiguous identity from other localities (Ptichy Island, Akkeshi, Ketchikan), if confirmed, would indicate a broader, amphi-Pacific distribution.

Figures

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 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.

FIGURE 12. A–D. Juxtacribrilina tumida n. sp. Holotype, YPM-IZ-106557, Kodiak, Alaska; intertidal.A. View of colony. B. Non-ovicellate zooids at colony margin.C.Two frontally budded dwarf zooids; arrowheads, ooecia, each with single pseudopore. D. Non-ovicellate zooid and frontal dwarf zooid. Scale bars: A, 1 mm; B, 500 µm; C, 300 µm; D, 150 µm.

FIGURE 13. Juxtacribrilina specimens of uncertain identity similar in morphology to J. tumida n. sp. A. NHM 2006.2.27.51, Akkeshi Bay, Japan, intertidal; non-ovicellate zooids. B. ZIRAS 01/50737, Ptichy Island, Sea of Okhotsk, intertidal; nonovicellate zooids. C–F, YPM-IZ-106558, Higgins Point, Ketchikan, Alaska; intertidal. C. View of part of colony, with frontal dwarf zooids in central region. D. Enlargement from previous panel, showing change in zooid morphology from left (thicker, fewer costae; larger, fewer intercostal lacunae; characteristic of Juxtacribrilina tumida n. sp.) to right (thinner, more numerous costae; smaller, more numerous intercostal lacunae; characteristic of J. pushkini n. sp.). E. Non-ovicellate zooid. F. Frontal dwarf ovicellate zooids near center of colony, each with four costae comprising frontal shield; note variation in ooecial pseudopores. Scale bars: A, D, 250 µm; B, C, 500 µm; E, 100 µm; F, 150 µm.