Microporella sp. A

Martino, Emanuela Di & Rosso, Antonietta, 2021, Seek and ye shall find: new species and new records of Microporella (Bryozoa, Cheilostomatida) in the Mediterranean, ZooKeys 1053, pp. 1-42 : 1

Microporella sp. A

Fig. 9

Examined material.

Italy • 1 dead colony fragment consisting of ca. 14 zooids (some incomplete), none fertile; Tyrrhenian Sea , Palinuro Cape, Scaletta submarine cave; sediment sample; 40°1'35"N, 15°16'7"E; 46 m; 14 Sep. 2009; R. Leonardi leg.; scuba diving; PMC Rosso Collection I. H. B. 88a .

Description.

Colony encrusting, multiserial, unilaminar.

Autozooids irregularly polygonal, rounded, 435-676 (510 ± 80, N = 7) × 255-427 µm (342 ± 68, N = 7) (mean L/W = 1.49), distinct, with interzooidal boundaries marked by a narrow, raised, gymnocystal rim (Fig. 9A ). Frontal shield nearly flat to slightly convex, densely and coarsely granular and irregularly pseudoporous; granules 5-25 µm in diameter; 20-30 pseudopores, circular (5-12 μm in diameter), sparse in the proximal two-thirds of the zooid; 4-6 marginal areolae, usually visible at zooidal corners, circular to elliptical (10-40 µm long).

Orifice transversely D-shaped, 90-107 (94 ± 5, N = 10) × 118-143 (132 ± 9, N = 10) µm (mean OL/OW = 0.71; mean ZL/OL = 5.43); hinge-line straight, smooth to slightly crenulated; in each corner a short, blunt, triangular condyle directed distally (Fig. 9B ). Oral spine bases four or five, 10-18 µm in diameter, evenly spaced, the proximalmost pair at about one-third of orifice length (Fig. 9B ).

Ascopore field a narrow, elliptical area of smooth gymnocystal calcification (33-44 × 39-55 μm), placed 22-30 μm below the orifice, slightly depressed relative to the adjacent frontal shield; ascopore opening divided by thin radial septa, usually with a distinct tongue extending proximally from the distal edge (Fig. 9B ).

Avicularium single, sometimes absent (two out of 14 zooids without avicularium in the fragment available), 93-123 (107 ± 12, N = 9) × 70-87 (79 ± 6, N = 9) μm (mean AvL/AvW = 1.36), located distolaterally, on either side; crossbar complete; rostrum short, triangular, not channelled, directed distolaterally, sometimes slightly raised distally (Fig. 9A, B ). Mandible, ovicells and ancestrula not observed. Subsequent intramural budding observed in avicularia.

Remarks.

This species differs from its Mediterranean congeners in having a finely reticulate ascopore but it is left in open nomenclature owing to the availability of a single, infertile colony fragment. Similar ascopores can be found in M. arctica Norman, 1903 from Norway, M. ketchikanensis Dick, Grischenko & Mawatari, 2005 from Alaska, M. santabarbarensis Soule, Chaney & Morris, 2004 from southern California, and M. stellata (Verril, 1879) from Maine, USA. Microporella arctica differs from Microporella sp. A in having a finely granular frontal shield pierced by a greater number of marginal areolae that are always very distinct from pseudopores, in the lack of oral spines, and in having a smooth gymnocystal area laterally and proximally to the orifice that is continuous with the gymnocyst of the ascopore field ( Kukliński and Taylor 2008). The ascopores of both M. ketchikanensis and M. santabarbarensis have a similar, delicate cribrate aspect but lack the distal tongue extending from the distal edge ( Dick et al. 2005; Soule et al. 2004). Microporella stellata differs in having only two oral spines and a proximal orifice margin with broad, rectangular condyles ( Winston et al. 2000).

Distribution and ecology.

Presently known only from the Palinuro Peninsula, along the Tyrrhenian coast of Campania (southern Italy). A dead colony was collected from the biogenic muddy sediment covering the floor of a completely dark sector of the Scaletta submarine cave, at 46 m depth where the colony presumably lived.

Figures

Figure 9. Microporella sp. A from Palinuro Cape, Scaletta cave PMC Rosso Collection I. H. B. 88 a A irregularly shaped autozooids with inconstant avicularia B close-up of two zooids with details of the orifice, the lateral condyles on the hinge-line, four or five thin oral spines and the ascopore divided by thin radial septa. Scale bars: 500 µm (A); 100 µm (B).