Hippoporella multiavicularia ( Androsova, 1958 )

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 : 1144-1147

Hippoporella multiavicularia ( Androsova, 1958)

( Figure 40 )

Hippoponella multiavicularia Androsova 1958, p 143 , Figure 68.

Hippoponella multiavicularia: Kluge et al. 1959, p 212 ; Kluge 1961, p 136; Gontar 1980, p 13; 1992, p 191.

Material examined

ANC, colony on rock (NHM 2006.2.27.104), colony on rock (NHM 2006.2.27.105), ancestrular colony on rock (NHM 2006.2.27.106). Additional material: 118 specimens.

Description

Colony encrusting, unilaminar, coherent, more or less circular; largest observed 1.4 cm in maximum dimension; bright orange to pink when alive. Zooids ( Figure 40A, B ) hexagonal, rhombic, or irregularly oval, rounded distally, 0.32–0.53 mm long (0.45¡ 0.06 mm), 0.27– 0.45 mm wide (0.36¡ 0.04 mm), demarcated by shallow groove with fine suture line. Frontal wall moderately to markedly convex, translucent, smooth, imperforate except for three or four areolar pores along each lateral margin, rising distally to suboral umbo that varies from a small, low nodule to a tall, conical projection, sometimes rounded in mature zooids. Primary orifice ( Figure 40A ) hat-shaped, slightly longer than broad, 0.10–0.14 mm long (0.12¡ 0.01 mm), 0.10–0.13 mm wide (0.11¡ 0.01 mm), with straight to slightly concave proximal margin; blunt condyles are swellings in internal rim around anter, separating long-semicircular anter from short, broad poster. Four hollow ephemeral oral spines ( Figure 40A ), more proximal pair with enlarged bases, located along distal margin of orifice of marginal zooids. Primary orifice evident only in developing zooids near colony margin; with development of secondary calcification, it becomes submerged and surrounded by shallow, sloping peristome. Secondary orifice ( Figure 40B ) similar in shape to primary orifice, long-semicircular in outline; cormidial, bounded proximally by avicularian chamber, distally and laterally with contributions of calcification from distal and lateral zooids. A circular suboral avicularium ( Figure 40B, C ) lies within peristome, below secondary orifice, orientated perpendicularly to colony surface or tilted slightly proximally; mandible semicircular, cross-bar complete; avicularian chamber small, broader than long, smooth, inflated in young zooids and submersed by umbo in older zooids. One to five small, circular adventitious avicularia ( Figure 40E ) with semicircular mandible occupy frontal surface of many zooids; these tend to occur on proximal half of frontal wall in immature zooids and lateral slopes of suboral umbo in ovicellate zooids; often interzooidal in position, surrounding secondary orifices. Ovicell ( Figure 40C–E ) hyperstomial, globose, broad, smooth, 0.15–0.20 mm long (0.17¡ 0.01 mm), 0.16–0.23 mm wide (0.19¡ 0.01 mm), with a large, circular pore close to slightly concave proximal margin of ectooecium; rapidly submerged ( Figure 40D, E ), with contributions of secondary calcification from frontal walls of distal and lateral zooids delineated by fine sutures. Zooids interconnect by multiporous septula. Ancestrula ( Figure 40F ) 0.07 mm long, 0.10 mm wide, orifice semicircular with straight proximal margin, surrounded by 10 spines; ancestrula buds three zooids distally and distolaterally, with another three larger zooids proximolaterally and proximally; periancestrular zooids with suboral avicularia only, and with five or six spines around distal curvature of orifice.

Remarks

The hat-shaped primary orifice surrounded by four spines with strong bases, the vertically orientated suboral avicularium, and the presence of numerous adventitious avicularia characterize this species. Specimens from Akkeshi Bay agree well with the original description of H. multiavicularia , except for fewer and differently arranged adventitious avicularia, which occasionally cover the entire frontal surface and number up to 10 per zooid in the type material. Androsova (1958) also did not mention a pore near the proximal margin of the ovicell; however, this is difficult to observe without SEM .

This species is close to H. fastigatoavicularis ( Kluge, 1955) , which is common subtidally in Akkeshi Bay ( Mawatari and Mawatari 1981b) in having a similarly shaped secondary orifice, and in the presence of suboral and numerous adventitious avicularia. However, all avicularia, including the suboral avicularium, of H. fastigatoavicularis are very small and lie in the plane of the frontal wall. Hippoporella fastigatoavicularis also has more regularly hexagonal zooids, with small umbones flanking the orifice laterally, in addition to the conical suboral umbo.

Another congener, H. kurilensis ( Gontar, 1979) , has marginal zooids with very similar morphology. In contrast to four spines in H. multiavicularia , H. kurilensis has five or six oral spines, with a pair of them remaining in ovicellate zooids. The frontal wall in H. kurilensis is convex and tessellated; adventitious avicularia are normally lacking, only occasionally present in heavily calcified zooids from the central region of the colony; and the relatively large suboral avicularium is orientated slightly obliquely to the longitudinal axis and usually tilted proximally. Complete ovicells of H. kurilensis are often not entirely covered by secondary calcification.

Distribution

This species was originally described from coastal waters off southern Sakhalin Island in the northern part of the Sea of Japan; it has also been recorded from Primorye ( Androsova 1958; Kluge et al. 1959; Kluge 1961). Gontar (1980, 1992) reported it from Paramushir, Shikotan, and Zelenyy among the Kuril Islands. Hippoporella multiavicularia also occurs in the shelf zone of the Commander Islands (A. V. Grischenko, unpublished data).

Figures

Figure 40. Hippoporella multiavicularia (Androsova, 1958). (A–D) NHM 2006.2.27.104; (E) NHM 2006.2.27.105; (F) NHM 2006.2.27.106. (A) Colony margin with developing zooids; (B) immature zooids; (C) zooids with developing ovicells; (D) zooids with submerging ovicells possessing central pore in ectooecium; (E) heavily calcified mature zooids with numerous small avicularia; (F) ancestrula and periancestrular zooids. Scale bars: 0.5 mm.