Hippothyris cf. aganactete Gordon, 1984

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 : 111-112

Hippothyris cf. aganactete Gordon, 1984

( Fig. 7 , A–F)

Material examined. SMF 15007, SO 167 Stn 23, 22.06150° S – 22.06167° S, 176.22350° W – 176.21633° W, South Tonga Volcanic Arc, 356–510 m, collected 18 October 2002. Bleached.

Description. Colony encrusting, multilamellar. Zooids slightly convex, about as wide as long with distinct boundaries ( Fig. 7 , A). Periancestrular zooids rounded, later becoming pentagonal. Frontal shield with 2–3 rows of pores at periphery, central area imperforate and relatively smooth ( Fig. 7 , B). Orifice subquadrate with small, proximally situated condyles ( Fig. 7 , C); poster shallow and wide. Avicularium single, situated at either proximal corner of orifice, laterally orientated, with a thin, complete pivot-bar; most avicularia small and oval but, at edge of colony, huge, elongate avicularia can be observed, directed transversely towards zooid midline ( Fig. 7 , C–D). Ooecium hyperstomial, globular, thin with numerous frontal pores ( Fig. 7 , B, E). Ancestrula like adult zooids, but much smaller; no spines present.

Measurements.

Zooid length 652–1035 µm, σ = 97 µm, N = 10; width 705–1155 µm, σ = 127 µm, N = 10

Orifice length 126–188 µm, σ = 17 µm, N = 10; width 138–178 µm, σ = 17 µm, N = 10

Ooecium diameter 405–483 µm, σ =31 µm, N = 10

Small avicularium length 69–87 µm, σ = 6 µm, N = 10; width 35–48 µm, σ = 4 µm, N = 10

Large avicularium length 323–391 µm, σ = 28 µm, N = 3; width 116–126 µm, σ = 3 µm, N = 3

Ancestrula length 615 Μm; width 386 Μm

Ancestrular orifice length 158 µm; width 149 µm.

Remarks. The sole colony is very similar to H. aganactete from the Kermadec Ridge but differs from the description by Gordon (1984) in the smaller zooid size, which might be due to its youthfulness. However, this does not explain the absence of ancestrular spines. Another difference is the presence of large avicularia at the rim of the colony.

Figures

FIGURE 7. A – F, Hippothyris cf. aganactete Gordon, 1984. A, ancestrular area. B, two marginal zooids, one with a broken ooecium. C, marginal zooids with large Avicularia. D, close-up of a large avicularium. E, ooecium and partly concealed orifice. F, orifice with small avicularium. G – H, Haswelliporina? quinaria. G, stem fragment. H, autozooidal peristome. Scale bars: A, G, 1 mm; B, C, 300 Μm; D – F, H, 100 Μm.