Tegella arctica ( d’Orbigny, 1851 )

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 : 1087-1089

Tegella arctica ( d’Orbigny, 1851)

( Figure 15 )

Reptoflustra arctica d’Orbigny 1851, p 352 .

Membranipora arctica: Lorenz 1886, p 85 , Plate 7, Figure 1 ; Nordgaard 1895, p 17; Osburn 1912, p 229, Plate 23, Figures 33 , 34 , Plate 30, Figure 86.

Membranipora conferta: Hincks 1882, p 249 .

Membranipora sophiae: Hincks 1882, p 466 , Plate 20, Figure 2 .

Callopora arctica: Nordgaard 1918, p 41 ; 1923, p 9; 1927, p 4; Osburn 1919, p 608.

Tegella sophiae: Canu and Bassler 1920, p 166 .

Tegella arctica: Osburn 1950, p 82 , Plate 9, Figure 6 ; Kluge 1962, p 280, Figure 163; 1975, p 334, Figure 163; Gontar 1980, p 5; Mawatari and Mawatari 1980, p 94, Figure 33 ; 1981b, p 46; Dick and Ross 1988, p 43, Plate 3B; Kubanin 1997, p 121; Grischenko 1997, p 157; 2004, p 40.

Material examined

ANC, colony on rock (NHM 2006.2.27.43), colony on bivalve shell (NHM 2006.2.27.44), colony on rock (NHM 2006.2.27.45), colony on erect bryozoan Phidolopora elongata (NHM 2006.2.27.46). Additional material: five specimens.

Description

Colony unilaminar, encrusting, coherent, irregularly circular, largest about 2 cm across, yellowish when alive. Zooids ( Figure 15A–D ) oval or oblong, 0.38–0.63 mm long (0.49¡ 0.06 mm), 0.22–0.33 mm wide (0.28¡zz 0.03 mm), separated by a deep, narrow groove. Opesia ( Figure 15B ) oval, elliptical, widest in middle, 0.17–0.31 mm long (0.25¡ 0.04 mm), 0.14–0.20 mm wide (0.17¡ 0.02 mm), occupying 50–70% of zooidal length. Mural rim ( Figure 15B, C ) raised, with a sloping, finely granulated cryptocyst. Gymnocyst smooth, sloping and narrow distally and laterally; tapering proximally, occupying up to 20–30% of zooid length. Around mural rim, six to eight spines ( Figure 15A–D ); distal pair located just proximal to lateral avicularia and in line with orifice, straighter, thicker and more erect than the rest; proximal four to six spines curved, acuminate, arched over opesia. Proximal gymnocyst covered by relatively large frontal avicularium with raised rostrum; mandible triangular, with complete cross-bar, raised at an angle to frontal plane, directed proximally or proximolaterally, not extending laterally around aperture; abutting and covering distal half of ovicell of preceding zooid, in this case pointing distolaterally. Two small paired avicularia located on mural rim lateral to orifice; mandibles triangular, directed distally and raised 45 ° from frontal plane. Ovicells ( Figure 15D ) hyperstomial, hemispherical, imperforate, 0.13–0.19 mm long (0.16¡ 0.02 mm), 0.16–0.21 mm wide (0.19¡ 0.02 mm), with thick transverse rib across top that may be thickened into a blunt median knob. Proximal margin raised, with lunate tabula between margin and ridge. Four pore chambers in each lateral wall and two in basal half of distal wall. Ancestrula not observed.

Distribution

Tegella arctica is a circumpolar, Arctic-Boreal species. Kluge (1962, 1975) and Gontar and Denisenko (1989) summarized a number of previous Arctic records. In North America it is known from Point Barrow southward to Frederic Sound, southeastern Alaska ( Osburn 1950; Dick and Ross 1988). In the western Pacific, there are records from the Bering Sea near St Lawrence Island, along western Kamchatka ( Kluge 1961; Kubanin 1997), the Commander Islands ( Grischenko 1997, 2004), the Shantar Archipelago ( Kluge 1961), and the Kuril Islands ( Gontar 1980) on the Sea of Okhotsk side. In Japan it has previously been found at Akkeshi and Hakodate, Pacific coast of Hokkaido ( Mawatari and Mawatari 1980, 1981b).

Figures

Figure 1. Map of Akkeshi Bay showing the 10 sampling stations (filled squares); 5, 10, and 20 m depth contours are indicated. Inset shows the location of Akkeshi Bay on Hokkaido Island, northern Japan.

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 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 15. Tegella arctica (d’Orbigny, 1851). (A, C) NHM 2006.2.27.44; (B) NHM 2006.2.27.46; (D) NHM 2006.2.27.43. (A) General view of group of autozooids, unbleached; (B) zooids from region near colony margin, bleached; (C) immature zooids with small paired angular and large frontal avicularia, unbleached; (D) mature zooids with ovicells and associated frontal avicularia, unbleached. Scale bars: 1 mm (A); 0.5 mm (B, C); 0.4 mm (D).

Figure 33. Fenestrulina orientalis Liu, Liu, and Sun, 2003. (A–D, F) NHM 2006.2.27.12; (E) NHM 2006.2.27.11. (A) Colony margin with differentiating zooids; (B) immature zooids; (C) distal half of immature zooid, showing orifice with oral spines and ascopore; (D) mature zooids with completed hemispherical ovicells; (E) tatiform ancestrula and periancestrular zooids; (F) modified ancestrula with acquired frontal shield, surrounded by periancestrular zooids. Scale bars: 0.5 mm (A, B, D–F); 0.2 mm (C).

Figure 34. Microporella luellae n. sp. (A, E) NHM 2006.2.27.94; (B–D) NHM 2006.2.27.93; (F) NHM 2006.2.27.52. (A) Colony margin with developing zooids; (B) immature zooids; (C) distal half of immature zooid, showing orifice, ascopore, and avicularium; (D) mature zooids with radially ribbed ovicells; (E) heavily calcified mature zooids; (F) ancestrula and periancestrular zooids. Scale bars: 0.5 mm (A, B, D–F); 0.2 mm (C).