Hippoporella kurilensis ( Gontar, 1979 )

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 : 1142-1144

Hippoporella kurilensis ( Gontar, 1979)

( Figure 39 )

Hippoponella kurilensis Gontar 1979, p 240 , Figure 3 .

? Hippoponella parva Androsova 1958, p 143 , Figure 69.

? Hippoponella parva: Kluge et al. 1959, p 212 ; Kluge 1961, p 136; Gontar 1978b, p 14; 1980, p 13; 1992, p 191; Grischenko 1997, p 182; 2002, p 116; 2004, p 41.

? Hippoporella parva: Kubanin 1997, p 124 .

Material examined

DIN, six colonies detached from erect ctenostome bryozoan Flustrellidra filispina (NHM 2006.2.27.103); additional material, four specimens; paratype examined, ZIRAS 2 /43720, colony encrusting erect bryozoan Microporina articulata, Simushir Island, Polanskogo Cape, depth 20 m, rocky bottom, collected by V. I. Lukin, 10 September 1970 .

Description

Colony encrusting, unilaminar, coherent, more or less circular, largest observed 1.2 cm across, beige to orange in colour when alive. Zooids ( Figure 39A, B ) hexagonal to oval, rounded distally, 0.35–0.55 mm long (0.45¡ 0.05 mm), 0.27–0.38 mm wide (0.33¡ 0.03 mm); newly budded zooids ( Figure 39A ) demarcated by groove and fine suture line; boundaries indistinct between heavily calcified zooids. Frontal wall moderately to markedly convex, tessellate, dimpled, imperforate except for two or three areolar pores along each lateral margin. Primary orifice ( Figure 39A, C ) elongate-semicircular, occupying about one-third length of frontal wall, 0.12–0.15 mm long (0.13¡ 0.01 mm), 0.10–0.14 mm wide (0.12¡ 0.01 mm), with straight to slightly concave proximal margin; condyles well developed as rounded-triangular projections located about one-third of distance from proximal to distal margin, separating semicircular anter from shorter, broader poster. Five or six long, hollow oral spines ( Figure 39A ) with enlarged bases occupy distal curvature of primary orifice of marginal zooids; with age, three or four distal spines become covered by secondary calcification and only most proximal pair remains lateral to orifice, in mature zooids lying close to proximolateral corners of ovicell. Primary orifice evident only in newly budded zooids, becoming rapidly submerged and surrounded by shallow, sloping peristome. Secondary orifice oval to irregularly circular; cormidial, bounded proximally by avicularian chamber, laterally and distally by contributions of calcification from lateral and distal zooids. A relatively large median suboral avicularium ( Figure 39B, D ) lies within peristome, just below secondary orifice, often orientated slightly obliquely to longitudinal axis and usually tilted proximally; rostrum oval, cross-bar complete, mandible semicircular, rostral margin proximal to hinge bar even or with small prominences. Avicularian chamber fusiform along long axis, evident in young zooids, completely submersed with increased calcification. Some zooids have hypertrophied suboral avicularium ( Figure 39C ), about 0.19 mm long, comparable to orifice in size, with short-spatulate mandible tilted proximally, almost parallel with frontal plane. Oval frontal avicularia ( Figure 39F ) with semicircular mandible sometimes occur in proximal half of strongly calcified zooids; oval adventitious avicularia 0.17–0.21 mm long, with semispatulate mandible ( Figure 39F ), occupy older regions of colony. Ovicell ( Figure 39D, E ) hyperstomial, globose, 0.17–0.21 mm long (0.19¡ 0.01 mm), 0.20–0.25 mm wide (0.22¡ 0.01 mm), proximal margin straight or nearly so; rapidly submerged and often covered with contributions of secondary calcification from distal and lateral zooids, indicated by fine suture lines; with a smooth proximal tabula having a minute median pore near top. Zooids interconnect by multiporous septula. Ancestrula not observed; Ancestrular region with numerous large adventitious avicularia.

Remarks

Gontar (1979) originally described H. kurilensis from subtidal material collected near Cape Polyanskogo, Simushir Island, Kuril Islands, and later reported the species from near Makanrushi, Onekotan, Harimkotan, Ekarma, Raschua, Ketoy, Chiproy, Broutona, Urup, and Shikotan Islands of the Kuril Ridge ( Gontar 1980). Material from Akkeshi Bay is quite similar to the paratype specimen ( ZIRAS 2/43720).

Hippoporella kurilensis shares many characters with its Asian Pacific Boreal congener H. parva ( Androsova 1958) . The latter is known from the northern part of the Sea of Japan, the coastal waters of southwestern Sakhalin Island, near Moneron Island, and Zolotoy and Uspeniya Capes, northern Primorye ( Androsova 1958); Paramushir, Makanrushi, Onekotan, Simushir, Chiproy, Urup, Iturup, Shikotan, and Zelenyy Islands along the Kuril Ridge ( Gontar 1978b, 1980, 1992), and the shelf zone of the Commander Islands ( Grischenko 1997, 2004).

Both H. kurilensis and H. parva have a tessellated, dimpled frontal wall with a few marginal areolae, and a large suboral avicularium with an undulating proximal rostral margin, complete cross-bar, and semicircular mandible orientated obliquely to the longitudinal axis and tilted slightly proximally. Additionally, both species have the orifices of marginal zooids surrounded by long spines with strong bases, the most proximal of which are more heavily calcified. The ovicells are also similar, with a smooth frontal surface rapidly immersed with secondary calcification.

Although Gontar (1979) did not clarify the differences between her new species and H. parva , they evidently include the presence of small adventitious avicularia on the frontal wall of heavily calcified zooids of H. kurilensis ; an often enlarged suboral avicularium tilted proximally to colony plane and variable in size in H. kurilensis ; and five or six oral spines in marginal zooids of H. kurilensis , compared to four to eight in H. parva .

Examination of material of H. parva from the Commander Islands has demonstrated that the size of suboral avicularium may vary significantly in some colonies. Furthermore, the number of oral spines known for H. kurilensis falls within the range for H. parva . The status of H. kurilensis as a species distinct from H. parva is thus unclear, especially considering their overlapping distribution along most of the Kuril Islands. Since we have not been able to examine the type material of H. parva for comparison and thus cannot adequately address this taxonomic problem here, we retain the name H. kurilensis for the Akkeshi specimens, pending further study.

Distribution

Hippoporella kurilensis is known from the majority of the Kuril Islands, and from Akkeshi Bay.

Figures

Figure 3. Electra korobokkura Nikulina, 2006. (A–C) NHM 2006.2.27.1; (D) NHM 2006.2.27.2. (A) Colony fragment with uniserial branches; (B) colony fragment with anastomosing, multiserial branches; (C) zooids without spinous processes; (D) zooids with spinous processes. All unbleached. Scale bars: 2 mm (A, B); 1 mm (C); 0.5 mm (D).

Figure 39. Hippoporella kurilensis (Gontar, 1979). NHM 2006.2.27.103. (A) Colony margin with developing zooids; (B) immature zooids; (C) zooids near colony margin, one with hypertrophied suboral avicularium; (D) zooids with developing ovicells; (E) mature zooids with immersed ovicells; (F) ancestrular region covered with large adventitious avicularia. Scale bars: 0.4 mm (A–C); 0.5 mm (D–F).