Cellaria gracillima, Achilleos & Gordon & Smith, 2020

Achilleos, Katerina, Gordon, Dennis P. & Smith, Abigail M., 2020, Cellaria (Bryozoa, Cheilostomata) from the deep: new species from the southern Zealandian region, Zootaxa 4801 (2), pp. 201-236 : 207-209

Cellaria gracillima n. sp.

( Fig. 4 )

Cellaria sp. 9: Achilleos et al. 2019: [4–8].

Material examined. Holotype: NIWA 128674 , cruise TAN0104, Stn 150, 42.7156º S, 179.9061º W, Chatham Rise, 1004–1181 m, collected 18 April 2001. No paratypes.

Etymology. Latin superlative of gracilis, thin, alluding to the stem, which is proportionally very long and thin.

Diagnosis. Colony unbranched. Autozooids arranged back to back in pairs (whorls of two), tending to face more on one aspect so stem presents a continuous series of lateral walls. Opesia wider than long with smooth rim; proximal rim with upturned knob-like condyles. Small interzooidal avicularia with triangular rostrum slit-like distally. Halfmoon-shaped ooecial opening with tiny slits in corners.

Description. Colony erect, stems proportionally very long and slender, not> 10 mm in length, tapering proximally (W, 99–411 μm). Zooids arranged back to back in pairs (i.e. whorls of 2), tending to face more on one aspect such that, from one angle the stem presents a continuous series of lateral walls; up to 23 whorls along stem. Actual branching not seen.

Zooidal outline hexagonal, longer than wide (ZL, 539–606 μm; ZW, 272–308 μm; ratio 1.5). Cryptocyst mi- nutely and evenly granular-tubercular, the cryptocyst ridges continuous, surrounding sunken oval area. Opesia wider than long (OpL, 61–85 μm; OpW, 94–137 μm; ratio 0.6), rim smooth, slightly elevated, the convex proximal margin flanked by small upturned knob-like. Typically a small hole between distal opesial rim and margin of cystid.

Avicularia common, small, interzooidal, always situated distal to parent zooid. Cystid outline oval, tapered at both ends. Rostrum occupying c. half cystid length, triangular overall but somewhat pagoda-shaped in outline, with steep smooth sides, directed distally; rostral foramen circular. Mandibular pivots horizontal, raised, their tips converging and bent distal to form a small ligula-like process. Avicularian opesia tiny, slit-like, proximal to ligula. Cryptocystal area inversely triangular, granular, with smooth rim inside cystid boundary (AvCL, 123–186 μm; AvCW, 85–115 μm; ATL, 60–73 μm; ATW, 64– 7 μm; RL, 60–73 μm; RW, 64–87 μm).

Ovicell with granular proximofrontal face between opesia and ooecial opening, which is halfmoon-shaped with proximally taped corners (OvApL, 21–53 μm; OvApW, 50–87 μm; ratio 0.4).

Ancestrula resembling autozooids but proportionally shorter (AnL, 356 μm; AnOpL, 61 μm).

Remarks. Cellaria gracillima n. sp. shares with C. curiosa n. sp. the tendency for zooid pairs to face more on one aspect, thus presenting mainly lateral walls on the opposite aspect. Similar zooid arrangement is observed in some Euginoma species, such as E. vermiformis (see Souto et al. 2011) but E. vermiformis lacks avicularia, the opesia and opesia rim is different and the cryptocyst is coarsely granular. The ovicell is slightly different with distolateral oval pores, which are absent from Cellaria gracillima n. sp.

Like C. calculosa n. sp., C. gracillima n. sp. has triangular interzooidal avicularia, but these are smaller and the rostrum has the outline of a truncate pagoda. The avicularia resemble those in Paracellaria wandeli ( Calvet, 1909) , which, however, are non-ligulate and the zooids in this species completely lack cryptocyst ridges.

Distribution. Endemic; Chatham Rise, New Zealand, 1004–1181 m depth.

Figures

FIGURE 4. Cellaria gracillima n. sp., TAN0104/150.A. Internode with autozooid pairs facing to one side of the stem, leaving a continuous surface of zooidal lateral walls and their boundary lines. B. Close up of part of (A). C. Non-ovicellate zooids and an avicularium. D. Ovicellate zooids and avicularia. E. Close-up of an opesia and avicularium. F.Ancestrula, with foramen distal to opesia and a proximal rootlet pore. G. Abfrontal side of a proximal zooid (ancestrula?) with small rootlet pores; daughter zooid with rootlet pore faces on opposite aspect. Scale bars: A, 500 μm; B, E, F, G, 100 μm; C, 200 μm; D, 250 μm.