Microporella neocribroides Dick & Ross, 1988

Chowdhury, Ismael A., Martino, Emanuela Di, Lee, Hannah, Windecker, Claire C. & Craig, Sean, 2024, Diversity and distribution of intertidal Microporella (Bryozoa: Cheilostomatida) from California, European Journal of Taxonomy 932, pp. 34-68 : 55-57

Microporella neocribroides Dick & Ross, 1988

Fig. 8 , Table 2

Microporella neocribroides Dick & Ross, 1988: 76 , pl. 12 fig. c.

Microporella neocribroides – Dick et al. 2005: 3753 , fig. 19a–d.

Microporella cribrosa – Suwa & Mawatari 1998: 899, fig. 2.

Material examined

USA • 1 colony of 60 zooids, two ovicellate, on rock; California, Greenwood; 39°7′45.0582″ N, 123°43′9.192″ W; 22 Jun. 2020; I.A. Chowdhury and H. Lee leg.; SBMNH 704691 • 1 colony of 40 zooids, none ovicellate, on rock; California, Stengel Beach; 38°42′55.6884″ N, 123°27′34.7616″ W; 23 Jun. 2020; I.A. Chowdhury and H. Lee leg.; SBMNH 704692a • 1 colony of 30 zooids, 13 ovicellate, on rock; California, Stengel Beach ; 38°42′55.6884″ N, 123°27′34.7616″ W; 23 Jun. 2020; I.A. Chowdhury and H. Lee leg.; SBMNH 704692b • 1 colony of 20 zooids, 11 ovicellate, on rock; California, Stengel Beach ; 38°42′55.6884″ N, 123°27′34.7616″ W; 23 Jun 2020; I.A. Chowdhury and H. Lee leg.; SBMNH 704692c .

Description

Colony encrusting, multiserial, unilaminar, forming subcircular patches, typically inhabiting rocks of various size and bivalve shells (mussels and clams).

Autozooids hexagonal, rectangular, or irregularly polygonal, ZL = 377–540 µm (470±48 µm, N = 20), ZW = 272–439 µm (348±45 µm, N = 20), mean L/W = 1.30; boundaries marked by grooves between slightly raised vertical walls. Frontal shield flat to convex centrally, often ribbed, finely granular, with reduced number of sparse, circular pseudopores (D = 9–15 µm), and 6–14 circular to elliptical, marginal areolae clearly distinguishable due to their larger size (D = 25–45 µm) ( Fig. 8A–D ).

Primary orifice transversely D-shaped, OL = 55–116 µm (82±16 µm, N = 20), OW = 100–136 µm (113±10 µm, N = 20), mean OL/OW = 0.73; mean ZL/OL = 5.73; hinge-line straight, smooth, without condyles or denticles ( Fig. 8E ). Two oral spines observed in some zooids, absent or obscured by secondary calcification in some others ( Fig. 8A ).

Ascopore depressed relative to adjacent frontal shield, within one ascopore width or less from orifice, outlined proximally by rim of gymnocystal calcification that is confluent with lateral peristomial flanges; ascopore circular or transversely elliptical, opening 21–37 µm in width, cribrate ( Fig. 8E ).

Avicularium single but often absent, AvL = 54–72 µm (54±8 µm, N = 17), AvW = 30–52 µm (40±6 µm, N = 17), mean AvL/AvW = 1.35; located at zooidal mid-length, always proximal to ascopore, on either left or right side of zooid; crossbar complete; rostrum rounded-triangular, directed laterally or slightly distolaterally, rostrum tip only slightly raised ( Fig. 8C ). Mandible not observed.

Ovicell prominent, round ( Fig. 8B–C ); OvL = 198–269 µm (224±15 µm, N = 20), OvW = 242–354 µm (298±29 µm, N = 20), mean OvL/OvW = 0.75; continuous with frontal shield of next distal zooid, sometimes obscuring distal margin of maternal orifice; calcification finely granular, smoother than that of the frontal shield, sometimes with marked ribs when developing, imperforate except for peripheral row of elliptical marginal areolae, 5–34 µm in maximum dimension.

Ancestrula not observed.

Remarks

Our material conforms very well to the original description of Microporella neocribroides Dick & Ross, 1988 , from Alaska, sharing all the main diagnostic characters, including zooid size, the cribrate ascopore close to the orifice, the smooth proximal margin of the orifice, condyles slight or lacking, two oral spines (though absent in most zooids), the imperforate ovicell, and the shape, location and direction of the avicularium, which is often lacking. Dick & Ross (1988) observed that the calcification of the frontal shield and ovicell becomes thicker and rugose with age, which we likewise observed in the Californian colonies.

Distribution and ecology

The species has been described as amphi-Pacific, with a northern boreal distribution ( Dick et al. 2005). It has been previously reported from Katalla and Kodiak, Alaska, USA ( Dick & Ross 1988); Ketchikan, Alaska ( Dick et al. 2005); and Muroran, Hokkaido, Japan ( Suwa & Mawatari 1998). The southernmost record is from Mill Creek, California (this study).

Figures

Fig. 8. Microporella neocribroides Dick & Ross, 1988 (SBMNH 704692), Stengel Beach, California, USA. A. Group of autozooids lacking avicularia and showing two distolateral oral spines. B. Group of zooids lacking avicularia, with ovicells in various stages of development. C. Group of zooids, mostly ovicellate, and some with avicularia. D. Group of zooids, some in formation, at colony growing edge. E. Close-up of the orifice and reticulate ascopore. Scale bars: A–D = 500 µm; E = 50 µm.