Microporella ketchikanensis, Dick & Grischenko & Mawatari, 2005

Dick, Matthew H., Grischenko, Andrei V. & Mawatari, Shunsuke F., 2005, Intertidal Bryozoa (Cheilostomata) of Ketchikan, Alaska, Journal of Natural History 39 (43), pp. 3687-3784 : 3755-3758

Microporella ketchikanensis , new species

( Figure 20A–F )

Diagnosis

Frontal wall uniform, non-rugose, with unusually small pores widely and uniformly spaced; zooids with zero to two avicularia, but most (83%) with only one; avicularium situated along lateral margin proximal to level of ascopore, as far back as middle of zooid, mandible directed laterally; rays in ascopore thick, with openings V-shaped or elongate; two to four (mode54) distal spines on marginal zooids; a small umbo proximal to ascopore and often a heavy, conical umbo on ovicell; ovicell imperforate centrally, with marginal ribbing slight or absent.

Type material

Holotype: ETN, specimen KE-28 bleached and coated for SEM ( YPM 35843) . Paratype 1: HP, specimen KE-15 bleached and coated for SEM ( YPM 35844) . Paratype 2: HP, specimen KE-101, bleached and coated for SEM (NHM 2005.7.11.8).

Etymology

The species name derives from the town of Ketchikan, place name of the type locality.

Description

Colony. Unilaminar, forming tightly encrusting, circular or irregular patches on rocks; off-white in colour; covered with glistening ectocyst when alive; largest observed 1 cm across.

Zooids. Roughly hexagonal, barrel-shaped, or oval; distinct at all stages, separated by a groove; 0.40–0.70 mm long (average 50.523 mm, n 520, 4) by 0.23–0.45 mm wide (average50.340, n 530, 4). Zooids interconnect by an elongate pore chamber occupying a third to half the length of each distolateral wall and two to three pore chambers in basal half of distal wall.

Frontal wall. Markedly convex, inflated, margins rising steeply; five to eight circular areolae along each lateral margin; frontal wall with tiny, evenly and widely spaced pores over the entirety; pores do not become infundibular with frontal thickening; surface between pores finely granulate. Immediately proximal to ascopore, most zooids have a low, knob-like umbo that is often covered by the smooth calcification surrounding the ascopore.

Orifice ( Figure 20C ). Semicircular, broader than long, 0.08–0.10 mm long (average50.086, n 515, 3) by 0.09–0.12 mm wide (average 50.110 mm, n 515, 3); proximal margin straight, serrated, each corner with a conspicuous condyle that is shelf-like or triangular in outline.

Ascopore ( Figure 20C–E ). Sometimes circular, usually transversely elliptical; distance from proximal margin of orifice less than or equal to ascopore width; distal ascopore margin usually with vestige of a median projection, connected to remaining circumference of ascopore by thick rays covered with minute spinules, with width of rays almost as great as width of openings; openings in sieve plate elongate, V-shaped, or irregular.

Spines ( Figure 20A–C ). Marginal zooids have two to four (rarely five) long, erect distal spines (frequencies: two520%, three527%, four553%, n 549, 3), two of them lateral to orifice, the other one or two centred between; spines lost with age.

Avicularia ( Figure 20A–C, F ). Zooids have zero to two avicularia (frequencies per zooid: zero516.7%, one582.8%, two50.5%; n 5198, 3), situated close to lateral zooidal margin, just proximal to level of ascopore, the mandible pointing perpendicularly to margin; rostrum raised from colony surface; mandible long-triangular, with a setose tip as long as the mandible proper.

Ovicell ( Figure 20F ). Globose, 0.25–0.33 mm long (average 50.285 mm, n 513, 3) by 0.25– 0.33 mm wide (average 50.301 mm, n 513, 3); raised at first but becoming subimmersed in frontal calcification of succeeding zooid; marginal ribbing weakly developed or absent; surface granulate like surrounding frontal wall; imperforate except for a few minute pores around margin; often with a thick, blunt umbo on top.

Ancestrula . Not observed.

Remarks

Microporella ketchikanensis was rare at Ketchikan; we identified only three colonies among numerous Microporella specimens examined. This species is superficially similar to M. neocribroides ; both have predominantly a single avicularium positioned along the lateral margin proximal to the ascopore and pointing laterally. However, there are several diagnostic differences. M. ketchikanensis has a high frequency (80%) of zooids with three or four spines, whereas M. neocribroides has predominantly two spines (87%). The orifice of M. ketchikanensis has sharp proximal corners with prominent condyles, and a serrated proximal margin, like that of M. germana ; in contrast, the orifice of M. neocribroides has rounded corners with condyles weak or lacking, and a smooth proximal margin. The ascopore sieve plates of the two species are different. Finally, at all stages of calcification, the frontal wall of M. ketchikanensis remains even in appearance and finely granulate, and the pores remain small; that of M. neocribroides is more rugose with larger pores at all stages, but especially with advanced calcification.

Microporella ketchikanensis is also similar to M. germana in having a high frequency of zooids with only one avicularium (83% and 70%, respectively). However, the latter has a much higher frequency of zooids with two avicularia (28% compared to 0.5% in M. ketchikanensis ), and the orientation of the avicularia is different. Those in M. ketchikanensis tend to be orientated with the long axis nearly perpendicular to the lateral margin and are set farther proximally, in some cases as far back as the middle of the zooid. Those in M. germana tend to point distolaterally, and at slightly different angles if there are two of them; they are generally closer to the orifice. The rays in the ascopore are complete and much coarser in M. ketchikanensis than in M. germana , which has fine, often incomplete rays. Finally, M. germana has larger pores and the frontal wall becomes more rugose with age compared to M. ketchikanensis .

Distribution

Ketchikan is the only known locality.

Figures

Figure 20. Microporella ketchikanensis n. sp.: (A) group of marginal zooids with four to five distal spines per zooid; (B) group of marginal zooids with three distal spines per zooid; (C) enlargement of orifice, ascopore, and marginal avicularium; (D) enlargement of proximal orificial margin and ascopore; (E) enlargement of ascopore; (F) group of zooids, two forming ovicells and two with complete, unribbed, umbonate ovicells; note zooid with rare complement of two marginal avicularia. All specimens bleached. Scale bars: 500 Mm (A, B, F); 100 Mm (C); 50 Mm (D); 20 Mm (E).