Microporella neocribroides Dick and Ross, 1988

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 : 3753-3755

Microporella neocribroides Dick and Ross, 1988

( Figure 19A–D )

Microporella neocribroides Dick and Ross 1988, p 76 , Plate 12C.

Microporella neocribroides: Suwa and Mawatari 1998, p 899 , Figure 2.

Microporella ciliata: Dick and Ross 1986, p 89 (in part).

Description

Colony. Unilaminar, encrusting, white with glistening ectocyst, forming circular or irregular patches; largest collected 2 cm across.

Zooids. Vitreous when young, chalky with age; hexagonal to barrel-shaped; varying from elongate to nearly as wide as long; 0.43–0.63 mm long (average 50.553 mm, n 520, 3) by 0.28–0.45 mm wide (average 50.361 mm, n 520, 3).

Frontal wall. Inflated, quite convex; with 6–10 areolar pores along each lateral margin and perforated over entire surface with smaller pores; surface coarsely granulate between pores; becoming thick and rugose with age, sometimes with a conical umbo proximal to ascopore.

Orifice ( Figure 19B ). Distinctly broader than long, 0.08–0.11 mm long (average 50.089 mm, n 520, 3) by 0.11–0.15 mm wide (average 50.124 mm, n 520, 3); proximal margin straight and smooth; proximal corners rounded; condyles slight or lacking.

Ascopore ( Figure 19B, D ). Transversely elliptical; covered with a cribriform sieve plate; separated from orificial margin by distance approximately equal to or less than ascopore width.

Avicularia ( Figure 19A–C ). Zooids either lack an avicularium, or have a single one on one side (frequencies: 0562%, 1538%), situated anywhere along lateral margin, at or proximal to level of ascopore, with mandible pointing toward margin.

Spines ( Figure 19A, B ). Marginal zooids usually either lack spines or have a pair of short, weak spines widely separated at distolateral margins of orifice (frequencies: 0513%, 2587%; n 5111, 3); rarely a zooid can have three to four spines.

Ovicell ( Figure 19C ). Raised, globose, 0.20–0.38 mm long (average 50.291 mm; n 520, 3) by 0.28–0.33 mm wide (average50.301, n 520, 3); imperforate except for minute marginal pores; surface granulate like frontal wall; marginal ribbing variable, ranging from absent to moderately developed and converging near proximal margin.

Ancestrula . Not observed.

Discussion

We found this species at all three collecting sites at Ketchikan, but it was most common at Higgins Point, a relatively exposed shore of cobbles and boulders. A similar preference for exposed sites was noted at Kodiak ( Dick and Ross 1988). The Ketchikan material is similar in all respects to that originally described at Kodiak ( Dick and Ross 1988). Key characters are the cribriform ascopore placed close to the orificial margin; zooids with no more than one avicularium, which on at least some zooids is located near the middle of the lateral margin; marginal zooids usually with no or two orificial spines; and the orifice with proximal corners rounded, a smooth proximal margin, and condyles weak or lacking. The species has been reported from Hokkaido, Japan ( Suwa and Mawatari 1998); there, avicularia tend to be closer to the orifice than is typical for specimens from the eastern Pacific and are also occasionally paired, but other characters indicate M. neocribroides .

Distribution

The species has an amphi-Pacific, northern boreal distribution. Other records include Katalla and Kodiak, Alaska ( Dick and Ross 1988) and Muroran, Hokkaido, Japan ( Suwa and Mawatari 1998). Ketchikan is the southernmost extent of the known range in the north-eastern Pacific.

Figures

Figure 19. (A–D) Microporella neocribroides Dick and Ross: (A) two marginal autozooids; note unusual proximal position of marginal avicularium of zooid at left; (B) enlargement of orifice, ascopore, and marginal avicularium; (C) two ovicellate zooids, each showing a marginal avicularium in typical position; (D) enlargement of ascopore. All specimens bleached. Scale bars: 400 Mm (A); 200 Mm (B); 500 Mm (C); 50 Mm (D).