Exechonella reniporosa, Cáceres-Chamizo & Sanner & Tilbrook & Ostrovsky, 2017

Cáceres-Chamizo, Julia P., Sanner, Joann, Tilbrook, Kevin J. & Ostrovsky, Andrew N., 2017, Revision of the Recent species of Exechonella Canu & Bassler in Duvergier, 1924 and Actisecos Canu & Bassler, 1927 (Bryozoa, Cheilostomata): systematics, biogeography and evolutionary trends in skeletal morphology, Zootaxa 4305 (1), pp. 1-79 : 12-14

Exechonella reniporosa n. sp.

( Fig. 3 , Table 3)

Material examined. Holotype: MTQ G 100215, on coral (mounted on SEM stub and coated with gold). Coral Sea , Great Barrier Reef , Lizard Island, Watson’s Bay, depth 6.5 m, 4 October 2012.

Etymology. The name reflects the kidney-like shape of the frontal foramina that is commonly met in younger zooids in this species. Derived from the Latin word “ren” (kidney).

Description. Colonies encrusting, unilaminar, multiserial. Autozooids bottle-like: convex, oval-elongated, separated by deep grooves and pits in the ‘corners’ between zooids. Primary orifice oval, wider than long, with the proximal edge straight or slightly concave. Anter wall underlain by an inner lamina (only visible in oblique view) ending in distolateral condyles seen as narrow, flat or roundish elongated plates. Condyles are often associated with a small opening (‘pocket’) on the internal surface of the peristome. Long tubular peristome is pustulose externally and with shallow longitudinal grooves on its internal surface, the rim is slightly flared. Frontal shield pustulose, with 13‒45 foramina (also counted in ancestrula and early generations of zooids). The lumen of each foramen has vertical gymnocystal walls, whereas an area around is a slightly elevated wide ring with an inner wall surface. In older zooids foramina are predominantly oval and sometimes round. In younger peripherical zooids they are predominantly kidney-shaped because of a short blunt projection developing asymmetrically on the foraminal ring and, thus, changing the originally oval/round shape of the foramen. In younger zooids the oval/round foramina are predominantly placed along the mid-line of the zooid whereas kidney-shaped ones are curved towards their closest lateral side of zooid or proximally. The proximal part of the frontal shield is ‘reduced’ in some zooids making a sort of ‘gap’ in the ‘corner’ between zooids. Marginal pores small and rounded, well seen in peripherical zooids, but hidden in those of the center of the colony. No avicularia. Adventitious kenozooids with 3‒6 pores, each having centrally perforated cuticular plate. Vertical zooidal walls narrow, represented by multiporous mural septula with communication pores arranged in two rows. Ancestrula autozooidal, smaller than the rest of zooids, with less frontal foramina.

Lizard Island, Great Barrier Reef Remarks. Exechonella reniporosa n. sp. is characterized by the kidney-like shape of its foramina in younger, peripherical zooids. The specific shape of the foramina is explained by the development of the associated blunt projection that changes the original oval or round shape of the foramen. For instance, similar blunt projections are sometimes met in the E. variperforata n. sp. (see below), but their development does not affect the foraminal shape.

Tilbrook (2006, p. 116) mentioned a specimen NHM 1964.3 .20.15 from Zanzibar (assigned to E. discoidea ) in which “the numerous reniform frontal foramina radiating in concentric arcs from the proximal of the peristome. This specimen should be further restudied to compare it with our material that also has these characters.

Distribution. Exechonella reniporosa n. sp. has been found only at the Lizard Island, Great Barrier Reef, Coral Sea, south Pacific Ocean.

Figures

FIGURE 3. Exechonella reniporosa n. sp. Great Barrier Reef, Lizard Island (A ‒ F: holotype MTQ G 100215). A, general view of the colony from above. B, central part of the colony showing multiporous mural septulum in left autozooid. C, proximal part of the colony with ancestrula. D, peripheral autozooid showing typical foraminal shape. E, primary orifice with condyles shown by arrows (lower part of the ‘ pocket’ seen above the right condyle). F, close-up of adventitious kenozooid (k) with five pores, three of them having a tiny central pore. Scale bars: A = 1 mm; B ‒ E = 100 µm; F = 10 µm.