Microporella rota Chowdhury & Di Martino, 2024

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 : 44-49

Microporella rota Chowdhury & Di Martino sp. nov.

urn:lsid:zoobank.org:act:15D7C5BF-B963-4A75-96F7-64413ED6A0EE

Fig. 4 , Table 2

Diagnosis

Encrusting Microporella with interzooidal communications through multiporous septula; zooids with single, large, distolaterally directed adventitious avicularium, with crossbar at same level as ascopore, or lacking avicularium; primary orifice with smooth proximal margin lacking condyles; 2–5 oral spines, obscured in ovicellate zooids; frontal shield tubercular, granular, with reticulate, wheel-like pseudopores and distinct, elliptical marginal areolae; ascopore cribrate without distal projection, lunate in periancestrular zooids, close to orifice, with umbo developing proximally; ovicells globular, granular, radially ribbed, with pseudopores in radial rows between ribs extending from ovicell periphery but not reaching centre.

Etymology

Latin ‘ rota ’, wheel, alluding to the wheel-like pattern of the pseudopores in the frontal shield of this species. Used as a name in apposition.

Type material

Holotype USA • colony of 70 zooids, 45 ovicellate, on rock; California, Shelter Cove; 40°1′17.6952″ N, 124°4′4.8684″ W; 17 Oct. 2020; I.A. Chowdhury and H. Lee leg.; SBMNH 704766 .

Paratypes USA • 1 colony of 40 zooids, none ovicellate, on rock; California, Mill Creek; 35°58′59.0586″ N, 121°29′32.0598″ W; 22 Jul. 2020; I.A. Chowdhury and H. Lee leg.; SBMNH 704767a • 1 colony of 50 zooids, none ovicellate, on rock; California, Mill Creek ; 35°58′59.0586″ N, 121°29′32.0598″ W; 22 Jul. 2020; I.A. Chowdhury and H. Lee leg.; SBMNH 704767b • 1 colony of 60 zooids, none ovicellate, on rock; California, Mill Creek ; 37°29′42.306″ N, 122°29′45.6354″ W; 24 Jul. 2020; I.A. Chowdhury and H. Lee leg.; SBMNH 704769 • 1 colony of 30 zooids, none ovicellate, on rock; California, Marshall Gulch; 38°22′8.4″ N, 123°4′32.52″ W; 17 Mar. 2020; A. Chowdhury and H. Lee leg.; SBMNH 706126 .

Additional material

USA • California, Monterey County, Carmel ; 36°31′59. 998169″ N, 121°56′59.989014″ W; unknown leg.; SBMNH 666548 • California, Monterey County, Carmel ; 36°31′59. 998169″ N, 121°56′59.989014″ W; 16 Nov. 1948; R.J Menzies leg.; SBMNH 693359 .

Description

Colony encrusting, multiserial, unilaminar, forming circular patches, typically found encrusting on rocks of various sizes; elliptical pore chamber windows observed along lateral and distal walls; interzooidal communications through multiporous septula ( Fig. 4E ).

Autozooids hexagonal, ZL = 345–543 µm (450±55 µm, N = 15), ZW = 241–463 µm (354±76 µm, N = 15), mean L/W = 1.27, boundaries marked by grooves and slightly raised vertical walls. Frontal shield convex centrally, tubercular, finely to coarsely granular, with narrowly elliptical marginal areolae (70–110 µm long) at zooidal corners usually distinguishable from much smaller, circular pseudopores; pseudopores reticulate, with wheel-like pattern ( Fig. 4C , see insert for a close-up, E), rarely elliptical, D = 10–30 µm, numbering 21–53, evenly distributed on frontal shield proximal to ascopore ( Fig. 4A ).

Primary orifice transversely D-shaped ( Fig. 4C ); OL = 64–106 µm (88±14 µm, N = 15), OW = 116– 170 µm (138±14 µm, N = 15), mean OL/OW = 0.64, mean ZL/OL = 5.11; hinge-line straight or slightly concave, smooth, lacking condyles. Two to five articulated oral spines, more commonly three or four, visible in non-ovicellate zooids ( Fig. 4A, C, F ), but obscured in those with ovicells ( Fig. 4B ).

Ascopore moderately depressed relative to adjacent frontal shield, transversely elliptical to subcircular, D = 27–79 µm, less than one to roughly one ascopore width from orifice; in some zooids, ascopore outlined by band of gymnocystal calcification; ascopore opening cribrate ( Fig. 4C ) without any distal projection except in periancestrular zooids in which ascopore is C-shaped ( Fig. 4D ); pores of ascopore plate circular. In some zooids, low, knobby, rounded or pointed umbo develops proximally to ascopore and becomes robust, rounded, and sometimes ribbed with age and increasing calcification ( Fig. 4A–B ). Avicularium usually single ( Fig. 4A, C ) or absent ( Fig. 4H ); relatively large, AvL = 85–141 µm (112±17 µm, N = 20), AvW = 45–89 µm (62±12 µm, N = 20), mean AvL/AvW = 1.81; located laterally in zooidal distal half, on either side, with complete crossbar usually at same level as ascopore; rostrum acutely triangular, narrowly channelled distally, mostly directed distolaterally, sometimes laterally or distally, often distally raised. Mandible with setose end ( Fig. 4H ).

Ovicell globular, prominent ( Fig. 4B ), OvL = 201–309 µm (256±32 µm, N = 13), OvW = 61–365 µm (313±29 µm, N = 13), mean OvL/OvW = 0.82; overlying frontal shield of next distal zooid, secondary covering confluent with that of shield, obscuring distal part of maternal orifice; calcification finely granular, radially ribbed, with 8–15 circular pseudopores, D = 7–21 µm, arranged in radial rows between ribs extending from ovicell periphery but not reaching centre, which appears imperforate.

Ancestrula tatiform, elliptical, 271 µm long by 180 µm wide ( Fig. 4D ); opesia surrounded by at least eight spines; first zooid budded distally from ancestrula, similar in appearance to later autozooids but smaller, with most-proximal oral spines at same level as proximal margin of orifice, lacking avicularium, with C-shaped rather than cribrate ascopore ( Fig. 4D ).

Remarks

Microporella rota Chowdhury & Di Martino sp. nov. is superficially similar to M. cribrosa ( Fig. 5 ). Both species share radially ribbed ovicells with pseudopores arranged in radial rows between ribs, extending from ovicell periphery but leaving the centre imperforate. Additionally, they both display a variably developed umbo proximal to the ascopore. Despite these similarities, M. rota differs in a sufficiently large number of characters to justify the recognition as a separate species.

In contrast to the holotype of M. cribrosa ( Fig. 5 ), colonies of M. rota Chowdhury & Di Martino sp. nov. differ in the number of oral spines, ranging from two to five within the same colony ( Fig. 4A, F ). In the holotype of M. cribrosa , spines vary from five to seven and are more robust ( Fig. 5B, F ) than those in M. rota . The proximalmost pair of spines is obscured in ovicellate zooids of M. rota ( Fig. 4B ) but consistently retained in those of M. cribrosa ( Fig. 5A–B ). Ovicellate zooids of M. cribrosa also show the development of two wings of calcification proximolateral to the orifice below the proximalmost pair of spines ( Fig. 5D ), feature absent in M. rota .

Further differences lie in the number of avicularia, the morphology of pseudopores, and the ascopore. Paired avicularia are consistently seen in M. cribrosa ( Fig. 5A ), while a single avicularium is typical of M. rota Chowdhury & Di Martino sp. nov. In some instances, M. rota lacked avicularia, and the corresponding zooids were smaller than those bearing avicularia. Pseudopores exhibit a reticulate, wheel-like pattern in M. rota ( Fig. 4C ), while they are non-reticulate in M. cribrosa ( Fig. 5C ). Moreover, the ascopore in M. rota ( Fig. 4C ) lacks the robust, distal projection observed in the ascopores of M. cribrosa ( Fig. 5D–E ).

Upon SEM examination, two specimens (SBMNH 666548 and SBMNH 693359) identified as M. cribrosa by R.C. Osburn were reconfirmed as the new species M. rota Chowdhury & Di Martino sp. nov. Two more specimens (SBMNH 668407 and SBMNH 668408) appeared conspecific with M. cribrosa sensu Soule et al. (1995) . Despite some similarities with both M. rota and M. cribrosa , these specimens have distinct characters that warrant the description of a new species (see below M. similis Chowdhury & Di Martino sp. nov.).

The presence of a variably developed umbo proximal to the ascopore, becoming robust and pointed with age, has been observed in other species of Microporella including some of the species described here. The development of the umbo has been interpreted either as a protection for the ascopore from obliteration by secondary calcification or as an environmental effect to protect the colony from sediment deposition and consequent abrasion ( Soule et al. 1995; Di Martino & Rosso 2021).

Aberrant features were evident in some zooids, such as the presence of two avicularia budded on the same side of the zooid ( Fig. 4G ). This condition is previously known in Microporella but quite uncommon. Taylor & Mawatari (2005: fig. 4G) documented an instance in Microporella sp. that appeared to have resulted from damage and regeneration; Dick et al. (2005: fig. 21E–F) documented several zooids with two avicularia on the same side in a single unidentified colony, with no signs of damage and regeneration, as was the case for our specimen.

Another aberrant feature was zooids lacking an opening but bearing an avicularium and one or more malformed ascopores at the edge of encounter between two colonies ( Fig. 4F ).

Distribution and ecology

We detected Microporella rota Chowdhury & Di Martino sp. nov. at ten sites, spanning from Cape Flattery to Monterey Bay. Colonies were found encrusting on boulders and shells (e.g., red abalone, clam, and mussel). Furthermore, upon examining some museum specimens previously identified as M. cribrosa by Osburn (specifically, specimens SBMNH 666548 and SBMNH 693359), the presence of this species was confirmed at an additional site in Carmel Bay.

Figures

Fig. 4. Microporella rota Chowdhury & Di Martino sp. nov., all California, USA. A, D, F. Paratype (SBMNH 704769), Pillar Point. B–C. Holotype (SBMNH 704766), Shelter Cove. E, G. Paratype (SBMNH 704767), Mill Creek.H. Paratype (SBMNH 706126), Marshall Gulch.A. Group of autozooids with umbonate frontal shield. B. Group of ovicellate zooids. C. Close-up of the ascopore, reticulate pseudopores (see also insert), and orifice. D. Partially overgrown tatiform ancestrula and first budded autozooid lacking an avicularium. E. Close-up of multiporous septula. F. Aberrant zooids, lacking an orifice but with avicularium and ascopore (seemingly triple in the aberrant zooid at the bottom), formed at the edge of encounter between two colonies. G. Autozooid with two avicularia on the same side. H. Autozooids having avicularia with preserved mandibles. Scale bars: A–B, F, H = 500 µm; C = 200 µm; D = 150 µm; E = 50 µm; G = 250 µm.

Fig. 5. Microporella cribrosa Osburn, 1952, holotype (SBMNH 668403) (previously AHF 80), Corona del Mar (36°31′59.998169″ N, 121°56′59.989014″ W), Newport Harbor, Orange County, California, USA. A. Group of ovicellate zooids with two oral spines visible and paired avicularia with setiform mandibles. B. Group of zooids, most ovicellate, with umbones hiding the ascopore; one zooid showing five robust oral spines. C. Close-up of frontal shield and ovicells showing the simple (i.e., nonreticulate) pseudopores. D–E. Close-ups of ascopore showing well-developed distal projections and radial denticulations converging towards the centre giving to the lunate aperture a reticulate appearance. F. Tatiform ancestrula, seemingly regenerated as a kenozooid with adventitious avicularium, and early astogeny with zooids showing up to 7 oral spines. Scale bars: A–B, F = 500 µm; C = 200 µm; D = 100 µm; E = 50 µm.