Atlantisina inarmata, Berning & Harmelin & Bader & Cibio, 2017

Berning, Björn, Harmelin, Jean-Georges & Bader, Beate, 2017, New Cheilostomata (Bryozoa) from NE Atlantic seamounts, islands, and the continental slope: evidence for deep-sea endemism, European Journal of Taxonomy 347, pp. 1-51 : 14-16

Atlantisina inarmata gen. et sp. nov.

urn:lsid:zoobank.org:act:BDF79949-1519-48E1-81DF-12B922AE7D25

Fig. 4 A–F, Table 4

Diagnosis

Frontal shield porcelain white, markedly convex, surface densely covered by large flattened nodules, up to eight tiny marginal pores; lateral walls well developed, septular pores large, round to transversely oval; orifice margin with six oral spines, condyles short and narrow, occasionally slightly thickened distally, operculum yellowish; no suboral mucro. Ooecium as long as wide; ectooecium covering slightly more than the lower half of ooecium; exposed endooecium relatively large and hemispherical, surface densely covered by numerous closely spaced and deep pits separated by thickened ridges. Ancestrula with nine spines separated into two groups of five widely spaced proximal and four closely spaced distal spines, opesia pyriform, cryptocyst a narrow proximal band thinning distally.

Etymology

The name refers to the absence of a protective suboral mucro, in contrast to the other species occurring in the nearshore seamounts and the continental slope.

Material examined

Holotype

CANARY ISLANDS: 1 large colony (> 50 autozooids), on rock, Stn 10 ( MNHN-IB-2014-53 ).

Paratypes

CANARY ISLANDS: 7 colonies on skeleton, Stn 9 (MNHN-IB- 2014-54); 1 ovicellate colony on biogenic substrate, Stn 9 (MNHN-IB- 2014-55); 1 young colony with ancestrula, on echinid test, Stn 9 ( OLL 2016/140); 1 colony on rock, Stn 11 (MNHN-IB- 2014-56).

Other material examined

CANARY ISLANDS: 10 colonies on small rocks, shells and other biogenic substrata, Stn 9 (unregistered MNHN material); 7 colonies on small rocks, Stn 9 ( OLL 2016/141); 3 colonies on rock, Stn 11 ( OLL 2016/142); 1 small colony with ancestrula on limestone, unbleached, Stn 11 ( OLL 2016/143).

Description

Colony encrusting, unilaminar, forming small irregular patches or biserial to triserial branching ribbons ( Fig. 4A ). Zooecia oval to polygonal, with proximal ends tapering and wedged in between proximal zooecia ( Fig. 4B ). Frontal shield translucent, very convex, densely covered by relatively large, closelyspaced, flattened nodules (Fig. D, F), imperforate except for up to eight minute marginal pores that may be difficult to detect in frontal view or in older zooecia; lateral walls well developed, septular pores large and surrounded by a distinct cryptocystal area, lateral ones usually transversely oval, slightly raised distal pore suborbicular ( Fig. 4E ).

Orifice a little longer than wide, with a rounded and broader anter and a fairly straight and narrower proximal margin delimited by a pair of very short, blunt and occasionally distally thickened condyles directing proximomedially ( Fig. 4C ); distolateral orifice margins with six closely-spaced spines with thick bases, arranged in two groups of three with a distinct distal gap ( Fig. 4E ).

Ovicell hyperstomial, ooecium barely resting on frontal shield of distal zooid, globular with a short tubular proximal peristome wedged in between distalmost pair of spines and terminating at distal orifice margin, about as long as wide; ectooecium smooth, encompassing slightly more than lower half of ooecium; exposed endooecium relatively large, hemispherical, densely covered by numerous deep pits that give it a perforate appearance ( Fig. 4C ); ooecial aperture about as tall as wide.

Ancestrula tatiform, broadly oval (ca 320 µm long, 260 µm wide), widest at about mid-distance, gymnocyst relatively well developed all around, gently sloping all around, becoming slightly narrower and steeper distally, cryptocyst forming only a very narrow rim around proximal half of opesia, opesia extensive (ca 215 µm long, 150 µm wide), pyriform, distinctly constricted in distal third, surrounded by

nine spines arranged in four closely positioned distal spines and five more widely spaced proximal ones; a single first-generation autozooid budded distally or distolaterally ( Fig. 4D ).

Remarks

The autozooids of Atlantisina inarmata gen. et sp. nov. are very similar to those of A. atlantis gen. et sp. nov. when observed under the SEM. When observed under a binocular microscope, however, the frontal shield of the former is porcelain-white while that of the latter is rather translucent. Moreover, the ovicells are distinctly different, with A. inarmata gen. et sp. nov. having a deeply and densely pitted endooecial surface structure, while it is rather faint and irregular in A. atlantis gen. et sp. nov. The zooids, orifices and ovicells are also larger in A. inarmata gen. et sp. nov. than in A. atlantis gen. et sp. nov. (see Table 1 ). Nevertheless, the similarity in autozooidal morphology is remarkable given the distance of ca 1500 km between Atlantis Smt and the Canary Islands.

Ecology

The bi- to triserial colonies of A. inarmata gen. et sp. nov. encrust empty shells, dead skeletons and small rocks at depths between 345 and 485 m. Some zooidal frontal shields show bevelled boreholes ( Fig. 4F ), which were presumably drilled by predatory microgastropods, while others are damaged around the orifice, and intramural buds occur in damaged or undamaged zooecia (cf. Berning 2008). The relatively high percentage of damaged and repaired zooids may be related to the lack of defensive structures around the orifice apart from oral spines, which characterise all other species from nearshore seamounts and the continental slope described below.

Distribution

Restricted to the island of Gran Canaria (Canary Islands).

Figures

Fig. 4. Atlantisina inarmata gen. et sp. nov. Canary Islands. A. Overview of holotype, optical image (MNHN-IB-2014-53). B. Several autozooids and ovicellate zooids (paratype MNHN-IB-2014-55). C. Close-up of the orifice and the deeply pitted ooecium (paratype MNHN-IB-2014-55). D. Periancestrular region (paratype OLL 2016/140). E. An autozooid at the colony growth margin (paratype MNHN-IB-2014-54). F. An autozooid with a borehole in the frontal shield (centre), and one with an intramural bud (at right), indicated by the presence of a secondary orifice rim (paratype MNHN- IB-2014-54). Scale bars: A = 500 µm; B = 300 µm; C = 50 µm; D = 200 µm; E, F = 100 µm.