Exechonella maldiviensis, 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 : 19-21

Exechonella maldiviensis n. sp.

( Fig. 6 , Table 6)

Material examined. Holotype: DPUV 2013-0002-0001 , on coral rubble (mounted on SEM stub and coated with gold). Indian Ocean, Maldive Islands, North Male Atoll, Vabbinfaru Island, House Reef , depth 5–19 m, 12–13 January 2008 . Paratypes: DPUV 2013-0002-0002 , DPUV 2013-0002-0003, on coral rubble. Indian Ocean , Maldive Islands, North Male Atoll, Vabbinfaru Island, depth 10 m, 3 August 2009 ; DPUV 2013-0002-0004 , DPUV 2013-0002-0005 , DPUV 2013-0002-0006 , DPUV 2013-0002-0007 (mounted on SEM stub and coated with gold), on coral rubble. Indian Ocean, Maldive Islands, North Male Atoll, Angsana Ihuru Island, House Reef , depth 8 m, 28 July 2009 ; DPUV 2013-0002-0008 (mounted on SEM stub and coated with gold), on coral rubble. Indian Ocean, Maldive Islands, North Male Atoll, Vabbinfaru Island, House Reef , depth 5–19 m, 12–13 January 2008 . Other material examined: IPUW 7025 , on coral rubble. Indian Ocean , Maldive Islands, North Male Atoll, Vabbinfaru Island, depth 10 m, 3 August 2009 .

Etymology. Named after the Maldive Islands, where the species has been found.

Description. Colonies encrusting, unilaminar, multiserial, patch-like or dichotomously branching. Autozooids bottle-like: convex, oval-elongated, separated by deep grooves and pits in the ‘corners’ between zooids. Primary orifice oval, wider than long, anter wall underlain by an inner lamina (only visible in oblique view) ending in distolateral condyles seen as narrow elongated plates slightly widening distally. Condyles are associated with a ‘pocket’ of unknown function in some zooids. Long tubular peristome is pustulose externally and with longitudinal grooves on its internal surface, the rim is slightly flared. Frontal shield pustulose, with 13–37 foramina of various shapes, mostly round and oval, but often irregular in some colonies. 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 some zooids from one to four foramina bear high flattened pointed process (sometimes ‘curved’ around a half of the foraminal opening). Each process has a gymnocystal surface faced to the foraminal lumen and connected with its gymnocystal walls. The process ‘back-side’ has an inner wall surface. Marginal pores small and rounded, with centrally perforated cuticular plate, only seen in the marginal zooids. No avicularia. Adventitious kenozooids with 2–4 pores, each having centrally perforated cuticular plate. Vertical zooidal walls narrow, represented by multiporous mural septula with communication pores arranged in 1–2 rows. Ancestrula unknown.

Maldive Islands, Indian Ocean Remarks. Exechonella maldiviensis n. sp. is characterized by its flattened and pointed frontal processes that sometimes ‘curved’ around the foramen in some zooids.

E. maldiviensis n. sp. in several respects reminiscent of E. variperfotara n. sp. In both species zooids are often characterized by the frontal shield with foramina of various shapes. The differences between these species are the wide ( E. maldiviensis n. sp.) and narrow ( E. variperfotara n. sp.) rim around the foraminal lumen, and the shape and size of the foramen-associated projections that are rather long, flattened and pointed in E. maldiviensis n. sp., sometimes ‘curved’ around a half of the foraminal opening, and short, pointed or blunt in E. variperforata n. sp. (although tips were all broken in them).

Distribution. Exechonella maldiviensis n. sp. is known at present only from Vabbinfaru Island and Angsana Ihuru Island, North Male Atoll, Maldive Islands, Indian Ocean.

Figures

FIGURE 6. Exechonella maldiviensis n. sp. Indian Ocean, Maldive Islands (A ‒ D: holotype DPUV 2013 - 0002 - 0001; E: paratype DPUV 2013 - 0002 - 0008; F: paratype DPUV 2013 - 0002 - 0007). A, general view of holotype from above. Ancestrular zone is broken. B, central part of the same colony. C, peripheral part of the same colony showing typical frontal processes, some ‘ curved’ around foramina. D, primary orifice with condyles (right condyle with a ‘ pocket’ shown by arrow). E, general view of the dichotomously branching paratype colony from above (one zooid shows partially broken peristome with flared edge, intrazooidal budding is seen in another zooid (arrow )). Ancestrular zone is overgrown by calcareous algae. F, lateral view of the peripheral part of the colony showing zooidal frontal shields with pointed processes associated with foramina, marginal pores and lateral multiporous septulum. Scale bars: A, E = 1 mm; B ‒ D, F = 100 µm.