Atlantisina meteor, 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 : 11-13

Atlantisina meteor gen. et sp. nov.

urn:lsid:zoobank.org:act:F9928F6E-D74B-47B5-B985-CAC2BB62ED51

Figs 1B , 3 A–F, Table 3

Diagnosis

Frontal shield densely covered by relatively small, irregularly shaped nodules with flattened tips; lateral walls very well developed, septular pores very large, round to elongate transversely oval; distolateral margin of orifice with eight (or rarely nine) slender oral spines, condyles short, blunt and thickened, no suboral mucro. Ectooecium covering more or less the lower half of ooecium; exposed endooecium relatively large and hemispherical, surface topography generally as frontal shield but nodular pattern not as pronounced. Ancestrula presumably with nine spines grouped in five widely spaced proximal ones and four closely spaced distal ones, opesia slightly constricted in distal third, cryptocyst practically absent.

Etymology

Named after its type locality, the Great Meteor Bank; used as a noun in apposition.

Holotype

GREAT METEOR BANK: 2 colonies on limestone, the larger one with eight ovicells is the holotype ( OLL 2016/130a ), the smaller colony without ovicells is the paratype ( OLL 2016/130b ), bleached, Stn 20.

Paratypes

GREAT METEOR BANK: 4 colonies on limestone (2 with ovicells, 1 with ancestrula), unbleached, Stn 20 (MNHN-IB- 2014-50); 2 colonies on limestone (1 with ancestrula, 1 with ovicells), unbleached, Stn 20 (MNHN-IB- 2014-51); 1 colony with ancestrula on limestone, unbleached, Stn 20 (MNHN- IB- 2014-52); 1 colony on Cladocora debilis Milne Edwards & Haime, 1849 , mounted on stub and sputter-coated, Stn 21 (OLL 2016/131); 1 colony with ancestrula and ovicells on coral base, unbleached, Stn 20 (OLL 2016/132); 2 colonies on limestone, unbleached, Stn 20 (OLL2016/133); 1 colony on bioclast, mounted on stub and sputter-coated, Stn 20 (SMF 40.039); 4 colonies (2 with ancestrula) on limestone, unbleached, Stn 20 (SMF 40.040); 1 colony with ovicells on limestone, bleached, Stn 20 (SMF 40.041).

Other material examined

GREAT METEOR BANK: 10 colonies on Anomocora fecunda (Pourtalès, 1871) , Stn 19 (unregistered MNHN material); 1 tiny colony on biogenic debris, sputter-coated, Stn 23 (unregistered MNHN material); 1 colony on C. debilis , mounted on stub and sputter-coated, Stn 21 (OLL 2015/10); 1 colony on C. debilis , mounted on stub and sputter-coated, Stn 19 (OLL 2016/134); 3 zooids (interior frontal shield), mounted on stub and sputter-coated, Stn 20 (OLL 2016/135); several colonies on C. debilis skeletons, unbleached, Stn 21 (OLL 2016/136); numerous colonies on limestone, unbleached, Stn 20 (OLL 2016/137).

IRVING SMT: 2 colonies on small rocks, 3 colonies on Flabellum chunii Marenzeller, 1904 , Stn 31 (unregistered MNHN material); 5 colonies on small rocks, Stn 32 (unregistered MNHN material); 12 colonies on small rocks (1 sputter-coated) plus 4 colonies on F. chunii, Stn 33 (unregistered MNHN material); 1 colony on stylasterid skeleton, Stn 34 (unregistered MNHN material).

HYÈRES SMT: 3 colonies on F. chunii, Stn 26 (unregistered MNHN material); 1 small colony on old shell, Stn 27 (unregistered MNHN material); 1 colony on F. chunii and 5 small colonies on shell fragments (one sputter-coated), Stn 28 (unregistered MNHN material); 1 colony on F. chunii, Stn 29 (unregistered MNHN material); 3 colonies on F. chunii, Stn 30 (unregistered MNHN material); 1 colony on rock fragment, Stn 25 (unregistered MNHN material); 1 colony on bioclast, mounted on stub and sputter-coated, Stn 28 (OLL 2016/138); 1 colony on bioclast, mounted on stub and sputter-coated, Stn 28 (OLL 2016/139).

Description

Colony encrusting, unilaminar, forming small patches and bi- to triserial ribbons ( Fig. 3A ). Zooecia oval to polygonal, with tapering proximal end wedged in between proximal zooecia, separated by deep grooves ( Fig. 3B ). Frontal shield matted vitreous, convex, surface densely covered with relatively small irregular and flattened nodules, imperforate except for some six to eight very small marginal pores, invisible in frontal view or in older zooecia; lateral walls particularly well developed, septular pores in

lateral walls very large and transversely oval, surrounded by a broad area of nodular cryptocyst, distal pore suborbicular, slightly raised relative to lateral ones ( Fig. 1B ).

Orifice almost as wide as long, broadest in distal third, proximal and lateral margins fairly straight, proximal third delimited by a pair of very short and thick, blunt condyles oriented proximomedially ( Fig. 3C ); lateral and distolateral margins with eight (very rarely nine) closely-spaced, slender, tapering and slightly curved spines with thick cylindrical bases ( Fig. 3C, F ), arranged in two groups of four with a distinct distal gap (in case there are nine spines, one group consists of five); all eight spines present in ovicellate zooids, with the distalmost pair thinner and tightly pressed against the ooecial peristome ( Fig. 3D ).

Ovicell hyperstomial, ooecium barely resting on distal zooid’s frontal shield ( Fig. 3B, D ), globular, about as long as wide, with a short tubular peristome wedged in between distalmost pair of spines and terminating at distal orifice margin; ectooecium smooth, encompassing approximately lower half of ooecium; exposed endooecium relatively large, hemispherical, surface covered by flattened irregular nodules similar to frontal shield ( Fig. 3D ); ooecial aperture suborbicular, about as tall as wide, acleithral.

Ancestrula oval (ca 280 µm long, 210 µm wide), tatiform, gymnocyst well-developed and gently sloping proximally, becoming steeper and narrower distally; cryptocyst practically absent; opesia oval (ca 185 µm long, 140 µm wide), slightly constricted in distal third; presumably nine mural spines, with five proximal ones widely spaced and four distal ones situated closer together; a single first-generation autozooid budded distally or distolaterally ( Fig. 3E ).

Remarks

Atlantisina meteor gen. et sp. nov. is the only species in the genus with eight or occasionally even nine spines surrounding the orifice (all other species have six), and in which the number of spines may occasionally vary. The additional spine is usually thinner and wedged in between the four others on one side of the orifice. Besides this difference in spine number, A. meteor gen. et sp. nov. is very similar to A. atlantis gen. et sp. nov., which occurs on the relatively closely located Atlantis Smt (ca 150 km north of the Great Meteor Bank-Hyères-Irving seamount complex), and also to A. inarmata gen. et sp. nov. from the Canary Islands (see below). However, the nodules on the frontal shield in A. meteor gen. et sp. nov. are slightly smaller and more irregular in outline. Moreover, the surface structure of the endooecium is similar to that of the frontal shield, while it is more indistinctly and variably sculptured in A. atlantis gen. et sp. nov., and deeply pitted in A. inarmata gen. et sp. nov.

Besides the Great Meteor Bank, A. meteor gen. et sp. nov. has also been recorded from the relatively closely located Irving and Hyères seamounts. These three discrete populations differ slightly in the size of their frontal shield nodules, and also in the nodular pattern on the endooecial surface, which may be variably pronounced. However, these differences are very subtle and may also occur within colonies. We thus regard these differences as representing intraspecific variability until genetic analyses can be carried out.

Ecology

The bi- to triserial colonies of this species encrust coral and stylasterid skeletons, shells and pebbles at depths between 270 and 750 m.

Distribution

Atlantisina meteor gen. et sp. nov. occurs on the central Atlantic Great Meteor Bank and probably also on Irving Smt and Hyères Smt.

Figures

Fig. 1. Morphological characteristics of Atlantisina gen. nov. A. The kenozooidal ooecium of Atlantisina lionensis gen. et sp. nov. in lateral view (paratype MNHN-IB-2014-67), showing the broad band of ectooecium and the centrally exposed endooecium; note that the suboral crest is formed by smooth gymnocyst whereas the remaining frontal shield is cryptocystidean. B. Distal view of an autozooid of Atlantisina meteor gen. et sp. nov. showing two distolateral communication pores and the slightly raised central pore from which the ooecium is budded (paratype MNHN-IB-2014-50); note the broad band of cryptocyst bounding the septular pores, and that the remaining parts of the distolateral vertical walls and orifice are entirely gymnocystal. C. Oral region of an ovicellate zooid of Atlantisina atlantis gen. et sp. nov. (paratype MNHN-IB-2014-49), showing the contact between the cryptocystidean frontal shield and the gymnocystal distal part of the zooecium; note that the frontal shield is superpositioned on the condyles (white arrow) and meets the distolateral vertical walls in a sinusoidal suture (black arrow). D. Initial stages of zooid formation with the lateral walls being partly broken, showing the large basal pore chambers in Atlantisina atlantis gen. et sp. nov. (paratype OLL 2016/123). E. Slightly oblique view of the ancestrula of Atlantisina tricornis gen. et sp. nov. (paratype MNHN-IB-2014-64); note the simple tatiform morphology, the absence of a cryptocyst, and the slightly restricted oral region (top). Scale bars: A–B, D = 100 µm; C, E = 50 µm.

Fig. 3. Atlantisina meteor gen. et sp. nov., Great Meteor Bank A. Overview of holotype (OLL 2016/130a). B. Several autozooids and ovicellate zooids (holotype OLL 2016/130a). C. Orifice (paratype MNHN- IB-2014-50). D. Ooecium (holotype OLL 2016/130a). E. Periancestrular region (SMF 40.040). F. Unbleached autozooids with typical whip-like spines (paratype OLL 2016/133a). Scale bars: A = 1 mm; B = 300 µm; C = 50 µm; D = 100 µm; E–F = 200 µm.