Cellaria curiosa, 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 : 205-207

Cellaria curiosa n. sp.

( Fig. 3 )

Cellaria sp. 7: Achilleos et al. 2019: [4, 7, 8].

Material examined. Holotype: NIWA 128670 , cruise TAN9912, Stn DR 3, 28.1455º S, 175.448º E, South Fiji Basin, 460–590 m, collected 20 October 1999 . Paratypes: NIWA 128671 , cruise TAN9912, Stn DR 3, 28.1455º S, 175.448º E, South Fiji Basin, 460–590 m, collected 20 October 1999 .

Etymology. Latin, curiosus, odd, strange, alluding to the unusual method of producing lateral branches.

Diagnosis. Colony unbranched. Autozooids arranged back to back in pairs (whorls of two), facing obliquely frontally, with distinct abfrontal colony surface. Opesia as long as wide with smooth rim; convex proximal rim with upturned knob-like condyles. Occasional zooids with duplicated opesiae, elevated frontalwards with rootlet pores in the distal wall. Vicarious abfrontal avicularia with lingulate rostrum and rounded tip; transversely oval opesial foramen.

Description. Colony erect, jointed, flexible. Stem fragments not> 5 mm in length; slender (W, 100–230 μm) and tapered at node. Zooids arranged back to back in alternating pairs (i.e. whorls of 2 zooids) in main part of stem, with each pair facing a little more on one aspect such that the basal walls present an abfrontal face. Proximally, zooids are more overlapping and not in strict whorls; up to 16 transverse series along stem.

Zooid outline not wholly visible in frontal view, the lateral walls being vertically disposed; longer than wide (ZL, 370–450 μm; ZW, 150–180 μm; ratio 2.5). Paired cryptocyst ridges continuous distally, converging without meeting proximally, enclosing a drop-shaped sunken cryptocystal shelf in which the opesia is set. Cryptocyst mostly smooth with faint lineations frontally. Opesia as long as wide (OpL, 50–70 μm; OpW, 50–80 μm; ratio 0.95), set at distal end with deep furrow between it and distal zooid margin; rim raised, smooth, the proximal convexity flanked by slender upturned knob-like condyles.

Avicularia vicarious, rare, situated abfrontally. Rostrum lingulate with more-or-less parallel sides and round- ed tip, directed distally. Palate concave, extensive, arching around conspicuous palatal foramen. Mandibular pivots horizontal, raised, delimiting rostral foramen from transversely oval opesia. Avicularian cryptocyst extensive, smooth; proximal opesial margin with a few denticulations (AvCL, 320 μm; AvCW, 136 μm; ATL, 240 μm; ATW, 68 μm; AopL, 79 μm; AopW, 49 μm; RL, 166 μm; RW, 66 μm).

Ovicells not seen.

Ancestrula not seen with certainty. Proximal-most zooids resembling autozooids but shorter, each with three conspicuous rootlet pores at proximal end.

Remarks. Actual colony branching was not seen; but several zooids had an unusual, highly distinctive feature, namely a frontally duplicated opesia. These regrow from existing opesiae but in such a way as to be elevated frontalwards at an oblique angle. When thus elevated, an area of wall is created that faces distally, perforated by 3–4 holes that appear to be typical rootlet pores. Whereas the initial colony is supported by rootlets at the proximal end of the stem, the longest stems may lie somewhat horizontal to the substratum, supported by the rootlets that come from these pores.

This interpretation is supported by a similar arrangement in Euginoma vermiformis Jullien, 1883 . Hayward (1978, fig. 4C, D) described how lateral branches might arise from specially modified zooids in which the distal wall is elevated above the branch surface and bears three tubular structures that look like rootlet pores. Although actual branching was not seen, the conclusion was that these structures were branch sites. The parallel between E. vermiformis and Cellaria curiosa n. sp. raises the question of relatedness. Euginoma vermifomis lacks avicularia and its granular-tubercular cryptocyst is unlike the smooth surface in C. curiosa n. sp. (see also Souto et al. 2011).

Cellaria curiosa n. sp. is similar to Euginoma species (see Lagaaij 1963; d’Hondt & Schopf 1985) in regard to zooid arrangement and the consequent presence of an abfrontal colony surface. However, the type species of Euginoma lacks avicularia and condyles—key characteristics of Cellaria .

Among Cellaria species, C. curiosa n. sp. most resembles Cellaria praelonga Harmer, 1926 from 1158 m depth off North Sulawesi, Indonesia. This species has autozooids that are even more elongate than in C. curiosa n. sp., and the elongate-triangular avicularian rostrum and small semicircular opesia take up proportionately less of the cystid. Cellaria curiosa n. sp. is the first Cellaria species in which the avicularium appears solely abfrontally.

Distribution. South Fiji Basin, 460–590 m depth.

Figures

FIGURE 3. Cellaria curiosa n. sp., TAN9912/DR3. A. Internode with autozooids. B. Distal part of the colony with duplicated opesiae; note the rootlet pores. C. Lateral view of a duplicated opesia. D. Opesia with condyles; note the deep furrow distal to the opesial rim. E. Abfrontal avicularium. F. Close-up of an avicularium. G. Proximal end of the colony with well-developed rootlet pores. Scale bars: A, 500 μm; B, E, 200 μm; C, D, F, 50 μm; G, 100 μm.