Bugula pacifica Robertson, 1905

Grischenko, Andrei V., Dick, Matthew H. & Mawatari, Shunsuke F., 2007, Diversity and taxonomy of intertidal Bryozoa (Cheilostomata) at Akkeshi Bay, Hokkaido, Japan, Journal of Natural History 41 (17 - 20), pp. 1047-1161 : 1089-1091

Bugula pacifica Robertson, 1905

( Figure 16A, B )

Bugula pacifica Robertson 1905, p 268 , Plate 10, Figure 50, Plate 16, Figure 101.

Bugula pacifica: O’Donoghue and O’Donoghue 1923, p 162 ; 1926, p 91; Osburn 1950, p 155, Plate 22, Figure 6 , Plate 23, Figure 4 ; McCain and Ross 1974, p 13; Soule et al. 1995, p 108, Plate 36; Grischenko 1997, p 167; 2004, p 40; Dick et al. 2005, p 3712, Figure 6A, B .

Bugula purpurotincta Robertson 1900, p 320 , Plate 20, Figures 5 , 6 .

Bugula pacifica pacifica: Kubanin 1997, p 122 .

Not Bugula pacifica: Kubanin 1975, p 114 , Figure 2b–g .

Material examined

KAI, seven fragments of same colony (NHM 2006.2.27.15). Additional material: six specimens.

Description

Colony ( Figure 16A ) erect, flexible, dichotomously branched, spiralled around a central axis with basal sides facing outwards. Our specimens small, up to 5.5 cm high, yellow in colour when alive, attached by a stalk composed of rhizoids originating from zooids at base of colony. Branching dichotomous, with axil at bifurcations formed by inner zooid of each of first pair on either side of branch point (branching pattern type 3; Hayward and Ryland 1998 after Harmer 1923). Zooids ( Figure 16B ) in biserial series, elongate, narrow, 0.50– 1.03 mm long (0.67¡ 0.13 mm), tapering proximally, truncate distally, with thin, flexible, transparent, weakly calcified walls. Opesia occupies nearly entire frontal surface, leaving only a small zone of proximal gymnocyst. One relatively short, spinous projection located on inner distal zooidal margin; two elongate spinous projections on outer distal margin; distalmost projection strongly thickened, pointing distolaterally, curved away from zooid. Avicularia attached by a flexible joint near base of zooid, on lateral wall close to opesial margin, 0.21–0.27 mm long, with hooked rostrum; not occurring on all zooids. Neither ovicells nor ancestrula present in our material.

Remarks

Androsova (1977) described a new subspecies, Bugula pacifica nana , from Aniva Gulf, southern Sakhalin Island, Sea of Okhotsk. In comparison with the nominal subspecies, B. pacifica pacifica , this subspecies forms smaller colonies, zooids, and zooidal structures (see Androsova, 1977, p 795). Kubanin (1984a, 1984b, 1997) reported B. pacifica nana from Primorye, Peter the Great Gulf, southern coast of Sakhalin Island, and concluded that it is distributed only in Low Boreal Asiatic waters. He suggested that B. pacifica pacifica is primarily distributed in the Boreal eastern Pacific, extending to the fringes of the western Pacific, including the Commander Islands. The finding of B. pacifica pacifica in Akkeshi Bay shows that this form has a trans-Pacific distribution, although its occurrence in the western Pacific as a relatively recently introduced population cannot be ruled out.

Distribution

Bugula pacifica is a Boreal Pacific species distributed from the Channel Islands off Southern California ( Soule et al. 1995) northward to Ketchikan, Alaska ( Dick et al. 2005) and the Pribilof Islands, Bering Sea ( Robertson 1905; Osburn 1950). On the Asian side, it has previously been reported from the Commander Islands ( Grischenko 1997); Akkeshi Bay is the southernmost known locality in the western Pacific.

Figures

Figure 2. Dendrogram (below) showing similarity of sampling localities based on species presence/absence, and a map (above) showing the geographical distribution of three groups of sampling localities (circled) that are less than 70% similar in species composition between groups.

Figure 4. Electra arctica Borg, 1931. ZIRAS 36/50535. Colony on rock collected by A. V. Grischenko, 12 September 1992, Sea of Okhotsk, western Kamchatka shelf (57°36.039N, 156°9.009E), depth 78–81 m. (A) Portion of colony showing anastomosing, narrowly multiserial branches; (B) autozooids and kenozooids; (C) enlargement of autozooids and kenozooids; (D) autozooids with operculum in place and kenozooids with nearly completely closed aperture. Specimen lightly bleached. Scale bars: 2 mm (A); 1 mm (B); 0.5 mm (C, D).

Figure 5. Electra asiatica n. sp. (A, G) NHM 2006.2.27.19; (B) NHM 2006.2.27.20; (C, D) NHM 2006.2.27.21; (E, F) NHM 2006.2.27.24. Colony from Ptichiy Island, Sea of Okhotsk (H). (A, B) Colonies radiating in coherent, fan-shaped lobes from the point of origin, unbleached; (C) colony margin with developing zooids, unbleached; (D) astogenetically mature zooids, unbleached; (E) astogenetically mature zooids, bleached; (F) astogenetically mature zooids with a small interzooidal kenozooid (lower right quadrant), bleached; (G) ancestrula and periancestrular zooids; enlargement of ancestrular area seen in panel (A), unbleached; (H) astogenetically mature zooids, bleached. Scale bars: 2 mm (A, B); 0.5 mm (C–H).

Figure 6. Conopeum nakanosum n. sp. (A, F) NHM 2006.2.27.26; (B, D) NHM 2006.2.27.27; (C, E) NHM 2006.2.27.25; (G, H) NHM 2006.2.27.28. (A) Colony margin with differentiating zooids, bleached; (B) zooids with developing angular cone-shaped kenozooids, bleached; (C) mature zooids with erect and curved spines, unbleached; (D) group of mature zooids with granulated cryptocyst, bleached; (E) distally facing triangular avicularia replacing kenozooids, unbleached; (F) distal view of kenozooids, bleached; (G) lateral view of zooids showing multiporous septula, bleached; (H) interior of distal zooidal wall showing developing angular kenozooids and also multiporous septula, bleached. Scale bars: 0.5 mm (A, G); 1 mm (B–D); 0.2 mm (E, F, H).

Figure 16. (A, B) Bugula pacifica Robertson, 1905. NHM 2006.2.27.15. (A) General view of colony fragment, unbleached; (B) zooids, showing distal spinous projections and avicularia, unbleached. (C–F) Tricellaria occidentalis (Trask, 1857). (C) NHM 2006.2.27.48; (D–F) NHM 2006.2.27.49. (C) General view of colony fragment, unbleached; (D) basal surface of branch with kenozooids (rhizoids or radicle fibres), unbleached; (E) internode with immature zooids, unbleached; (F) abraded internode containing mature zooids with ovicells, unbleached. Scale bars: 1 mm (A); 0.5 mm (B, D, F); 2 mm (C); 0.4 mm (E).