Exechonella variperforata, 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 : 14-16

Exechonella variperforata n. sp.

( Fig. 4 , Table 4)

? Exechonella tuberculata: Scholz & Cusi 1991 , p. 412, 428, pl. 4, fig. 1.

Material examined. Holotype: MTQ G 100217 (mounted on SEM stub and coated with gold), on coral. Coral Sea , Great Barrier Reef , Lizard Island, Pigeon Point, depth 8–10 m, 9 October 2012 . Paratype: MTQ G 100218, two fragments (mounted on SEM stub and coated with gold). Coral Sea , Great Barrier Reef , Lizard Island, Pigeon Point, depth 8–10 m, 9 October 2012 . Other material studied: MTQ G 100220 (mounted on SEM stub and coated with gold). CReefs Heron Island 2010. Coral Sea , Great Barrier Reef, Heron Island, Site HI 10-051, 23° 27’ 37.764’’ S, 151° 55’ 45.444’’ E, depth 16 m, 24 November 2010, collected by K.J. Tilbrook, G. Cranitch.

Etymology. The name was given because of the variations in shape and size of the frontal foramina in comparison with the other species of this complex. Derived from the Latin word “variis” (various).

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, anter wall underlain by an inner lamina (only visible in oblique view) ending in small rounded distolateral condyles. Long tubular peristome is pustulose externally and with longitudinal grooves on its internal surface, the rim is flared often with short pointed spikes. Frontal shield pustulose, with 8‒20 foramina of various shapes: from round and oval to irregular. In some zooids from one to six foramina bear the short triangular, blunt or pointed, process. Each process has mostly gymnocystal surface connected with vertical gymnocystal walls of its foramen. The area around a foramen is a slightly elevated narrow ring with an internal wall surface. Gymnocystal walls of neighbour lateralmost foramina often confluent with each other thus making the edge of frontal shield zigzag-like in outline. In this case the areas between foraminal luminae are closely apposed to the frontal shield of the neighbour zooid. The proximal part of the frontal shield is ‘reduced’ in some zooids making a sort of ‘gap’ in the ‘corner’ between zooids. 1‒2 rows of small, rounded marginal pores are seen mainly in the peripheral zooids. The distalmost part of zooid below peristome can be bear up to three rows of such pores. In the central part of the colony zooids are closely appressed and the marginal pores are not seen. No avicularia. Adventitious kenozooids with 2‒4 pores, each having cuticular plate. Vertical zooidal walls narrow or wide, represented by multiporous mural septula with communication pores arranged in two or several rows. Ancestrula unknown.

Lizard Island, Great Barrier Reef Remarks. Exechonella variperforata n. sp. is characterized by its comparatively fewer foramina with narrow rim, by the irregular shape of some of them and by small rounded condyles.

Most of the species of this complex are characterized by relatively high number of frontal foramina (16–41 in E. ampullacea , 13–45 in E. reniporosa n. sp., 23–46 (Safaga) and 30–58 (Jeddah) in E. safagaensis n. sp., and 13– 37 in E. maldiviensis n. sp.) (see below). E. variperforata n. sp. is the only species with 8–20 foramina per zooid. The variability of the foraminal shape is rather prominent character of this species that is also met (though in lesser degree) in E. maldiviensis n. sp.

Apart of our material from the Lizard Island, north part of the Great Barrier Reef, an additional colony of E. variperforata n. sp. has been collected at the Heron Island, south part of the Great Barrier Reef. Scholz and Cusi (1991), described and illustrated a colony from Leyte, Philippines, identified as E. tuberculata , but it shows all the major characters of E. variperforata n. sp., including shape of the peristome margin, and reduced number of foramina and their shape.

Distribution. Despite of the above suspicions, the current distribution of E. variperforata n. sp. is restricted to the Great Barrier Reef.

Figures

FIGURE 4. Exechonella variperforata n. sp. Great Barrier Reef, Lizard Island (A, B: holotype MTQ G 100217; C ‒ F: paratype MTQ G 100218). A, general view of the colony from above. Ancestrular zone is overgrown by calcareous algae. B, autozooid showing various foraminal shapes. C, general view of the colony fragment from above (‘ gaps’ between zooids are clearly seen; peristome of left zooid bears two spikes). D, lateral view of the same fragment showing marginal pores arranged in 2 ‒ 3 rows and multiporous septula. E, primary orifice with condyles (arrows) visible. F, distolateral view of the frontal shield with foramina, two of which bear short pointed process. Scale bars: A = 1 mm; B ‒ F = 100 µm.