Porella Gray, 1848

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 : 1099-1101

publication ID	https://doi.org/ 10.1080/00222930701391773
persistent identifier	https://treatment.plazi.org/id/877A7251-CC7F-DE0E-FE26-2780D46B19D5
treatment provided by	Felipe
scientific name	Porella Gray, 1848
status

Treatment

Genus Porella Gray, 1848 View in CoL

Porella acutirostris Smitt, 1868

( Figure 20 View Figure 20 ) Porella acutirostris Smitt 1868, p 21 , Plate 26, Figures 106, 108; holotype illustrated by Dick et al. 2005, Figure 14E–H View Figure 14 . Porella acutirostris: O’Donoghue and O’Donoghue 1923, p 183 ; Osburn 1952, p 394, Plate

46, Figure 4 View Figure 4 ; Mawatari 1956, p 129, Figure 10h–k View Figure 10 ; Androsova 1958, p 163, Figure 93;

Kluge 1962, p 453, Figure 300; 1975, p 550, Figure 300; Gontar 1980, p 10; Mawatari and Mawatari 1981b, p 55; Dick and Ross 1988, p 63, Plate 8A; Kubanin 1997, p 123;

Grischenko 1997, p 179; 2004, p 41; Dick et al. 2005, p 3738, Figure 14A–D View Figure 14 .

Material examined

ACW, colony on rock (NHM 2006.2.27.62); BAC, colony fragment detached from bivalve shell ( NHM 2006.2.27.63), three colony fragments on rock ( NHM 2006.2.27.64); NB, two young colonies on bivalve shell ( NHM 2006.2.27.65). Additional material: 325 specimens .

Description

Colony encrusting, unilaminar, coherent, more or less circular, up to 3 cm across, bright yellow, orange, or tan when alive. Zooids ( Figure 20A, B View Figure 20 ) hexagonal, rectangular, or oval, often tapering proximally, 0.47–0.77 mm long (0.58¡ 0.08 mm), 0.20–0.32 mm wide (0.25¡ 0.03 mm), separated by a groove, with a faint suture line between adjacent vertical walls. Frontal wall convex, coarsely granulated, imperforate centrally, with 5–11 conspicuous areolar pores along each lateral margin, separated by short ridges. Primary orifice ( Figure 20C View Figure 20 ) semicircular, broader than long, 0.09–0.12 mm long (0.11¡ 0.01 mm), 0.11– 0.15 mm wide (0.12¡ 0.01 mm); proximal margin varying from slightly concave to straight or slightly convex, with an inconspicuous, low, flattened condyle near each proximal corner. Peristome ( Figure 20B, C View Figure 20 ) cormidial, consisting distally of upturned proximal margin of succeeding zooid; this is confluent with sharp, raised lateral flanges that meet avicularian chamber proximally; in ovicellate zooids lateral flanges are confluent with upturned proximal margin of ovicell. Secondary orifice semicircular, or approaching quadrate in non-ovicellate zooids, often markedly quadrate in ovicellate zooids. A median suboral avicularium ( Figure 20C View Figure 20 ) lies on internal slope of peristomial rim, orientated almost vertically, mandible triangular with rounded apex or almost semicircular, cross-bar complete; avicularian chamber ( Figure 20D, E View Figure 20 ) raised from frontal wall, broad, roughly granulated, often umbonate, occupying up to one-half of frontal surface, developing from an areolar pore on each side. Ovicell ( Figure 20D, E View Figure 20 ) hyperstomial, hemispherical, prominent, 0.19–0.24 mm long (0.21¡ 0.02 mm), 0.20–0.29 mm wide (0.24¡ 0.02 mm), imperforate, surface coarsely granulated like frontal wall, sometimes bearing a small, salient central umbo. Interzooidal communication via two multiporous septula in basal half of distal wall of zooid and a single multiporous septulum in each distolateral wall. Ancestrula ( Figure 20F View Figure 20 ) of uncertain shape, obscured by surrounding zooids, with semicircular orifice bearing eight short, hollow spines along lateral margins; surrounded by triplet of small zooids distally and distolaterally and two larger zooids proximally; periancestrular zooids similar to later autozooids, but have one to three hollow ephemeral spines along distal margin of orifice.

Remarks

Dick et al. (2005) discussed the taxonomic status of P. acutirostris in some detail, concluding that what has been considered a circumpolar, Arctic-Boreal species may comprise a complex of closely related species in the northern hemisphere, including P. major Hincks, 1884 and P. columbiana O’Donoghue and O’Donoghue, 1923 . Until this species complex is better understood, we simply refer the specimens from Akkeshi to P. acutirostris Smitt, 1868 . Compared to zooids of specimens at Ketchikan, Alaska, zooids at Akkeshi are somewhat longer; the frontal wall and ovicell more coarsely granulated and appear more heavily calcified; the low but conspicuous lyrula seen in the Ketchikan population is absent; and both the ovicell and frontal wall tend to be umbonate, which is not the case at Ketchikan. However, the differences in morphology between Alaskan populations ( Dick and Ross 1988; Dick et al. 2005) might represent geographical variation among conspecific populations.

Distribution

Smitt (1868) originally described P. acutirostris from Spitzbergen. Subsequently, it has come to be considered a circumpolar, Arctic-Boreal species (see Kluge 1962, 1975 and Gontar and Denisenko 1989 for many distributional records), extending as far south as Cape Cod in the northwestern Atlantic ( Osburn 1912), the Lofoten Islands in the northeastern Atlantic ( Nordgaard 1918), and southern California in the northeastern Pacific ( Osburn 1952). In the northwestern Pacific, P. acutirostris has been recorded from the southern Chukchi Peninsula, Commander Islands, eastern Kamchatka, Shantar archipelago, Sakhalin Island, Kuril Islands, and Primorye ( Kluge 1961; Gontar 1980; Grischenko 1997; Kubanin 1997); in Japan it is previously known from Akkeshi and Hakodate, Hokkaido, southward to middle Honshu ( Mawatari and Mawatari 1981b).