Opaeophora triangula, Matsuyama, Kei, Janssen, Annika, Arbizu, Pedro Martínez, Martha, Silviu O. & Freiwald, André, 2014

Matsuyama, Kei, Janssen, Annika, Arbizu, Pedro Martínez, Martha, Silviu O. & Freiwald, André, 2014, Bryozoans from RV Sonne deep-sea cruises SO 167 ‘ Louisville’ and SO 205 ‘ Mangan’, Zootaxa 3856 (1), pp. 100-116 : 105-107

Opaeophora triangula n. sp.

( Fig. 4 , A–F)

Material examined. Holotype: SMF 15002, SO 167 Stn 23, 22.06150° S – 22.06167° S, 176.22350° W – 176.21633° W, South Tonga Arc, 356–510 m, collected 18 October 2002. Bleached.

Etymology. From Latin triangulus, triangular, alluding to the overall triangular shape of the autozooids.

Description. Colony encrusting, unilamellar ( Fig. 4 , A). Zooids pyriform, subtriangular. Cryptocyst extensive, granular, concave, with a low rim that is narrow laterally and broader proximally; depressed part of the cryptocyst with a very broad median convexity separating a pair of shallow, lateral depressions, each with a small, round opesiule ( Fig. 4 , B); cryptocyst smooth in the area immediately around opesiules. Opesia-orifice transversely Dshaped with low peristomial rim, with a distal arc of 3–6 (mostly 4–5) oral spines. Fertile zooids with only 2 oral spines at distolateral corners. Operculum with granular surface, similar to cryptocyst. Avicularia interzooidal, large, able to attain same length as autozooid; rostrum scimitar- or dagger-shaped with incomplete pivot bar ( Fig. 4 , C–E); mandibular pivots forming prominent ridges, constricting claviform opesia that is surrounded by a subcircular, granular cryptocyst. Occasionally 2–3 tiny spine bases located on edge of zooidal rims. Ooecia hyperstomial, prominent, globular; entooecium calcified, granular like cryptocyst, ectooecium presumably membranous. Distal transverse wall of autozooid and avicularium with large, shallow pore-chambers, typically 1 mid-distal uniporous chamber, flanked by a longer biporous chamber on either side ( Fig. 2 , D, F). Ancestrula not observed.

Measurements.

Zooid length 654–737 µm, σ = 33 µm, N = 10; width 401–498 µm, σ = 37 µm, N = 10

Orifice length 74–122 µm, σ = 15 µm, N = 10; width 124–154 µm, σ = 10 µm, N = 10

Ovicell diameter 220–257 µm, σ = 20 µm, N = 5

Avicularium length 261–573 µm, σ = 118 µm, N = 10; width 92–145 µm, σ = 20 µm, N = 10.

Remarks. This species closely resembles Opaeophora monopia Brown, 1952 , illustrated and reported from the Kermadec Ridge by Gordon (1984) as Manzonella monopia . Opaeophora triangula n. sp., however, has more spines than O. monopia , which only has two oral and no lateral spines. The cryptocyst also differs in having a much broader, less well-defined median convexity. Owing to larger zooidal dimensions, the opesiules appear proportionately smaller in the new species. The proximal rim of the peristome is also less well developed in O. triangula than in O. monopia . Interzooidal avicularia differ in their length/width ratio, which is greater in the new species. Autozooids have a more triangular shape and are larger than those of O. monopia .

Opaeophora occulta Moyano, 2002 , reported from the eastern Pacific ( Sala y Gomez Island 400 km east of Easter Island) also resembles O. triangula . Both share a single pair of opesiules and more than three oral spines, O. occulta having four. The shape of the ooecium is also quite similar. Opaeophora occulta differs, however, in having a more circular orifice and, most significantly, a broader, less well-defined zooidal rim.

Opaeophora browni Moyano, 1983 , from Chilean coastal waters, has also four oral spines, but differs significantly in having proportionately larger opesiules, an ooecium with a smooth surface and linguiform avicularia.

The type species of the genus, Opaeophora lepida ( Hincks, 1881) , is least similar. It is readily distinguished by having two to five pairs of opesiules, arranged in rows parallel to the lateral margins, the distal pair being usually the largest. Oral spines are absent. Zooids are regularly hexagonal. Both O. monopia and O. lepida are reported from the EEZ (Exclusive Economic Zone) of New Zealand ( Gordon et al. 2009).

We consider the sum of the characters of O. triangula n. sp., especially oral-spine number, as sufficient to erect a new species; molecular analysis, now a common tool in investigating intra- and interspecific variation, will shed further light on the relationships of O. triangula . Because this species is recorded from one site only, an estimate of its geographical extent is not possible.

Figures

FIGURE 2. German license areas for the exploration of polymetallic nodules (in yellow) with station locality (arrow).

FIGURE 4. Opaeophora triangula n. sp. A, small colony. B, a single zooid; note the five oral-spine bases. C, a dagger-shaped avicularium. D, autozooid with opercular closure plate and two scimitar-shaped interzooidal avicularia. E, ovicellate zooid with interzooidal avicularium. F, zooid at the growing edge; note the spine bases on the mural rim and the flattened pore-chambers with simple communication pores. Scale bars: A, 1 mm; B – D, F, 100 µm; E, 300 Μm.