Disporella minicamera, Gordon & Taylor, 2010

Gordon, Dennis P. & Taylor, Paul D., 2010, New seamount- and ridge-associated cyclostome Bryozoa from New Zealand, Zootaxa 2533 (1), pp. 43-68 : 61-63

Disporella minicamera n. sp.

( Fig. 11 A–D )

Material examined. Holotype: NIWA 61256 , from cruise TAN0104, Stn 3, 42°45.48– 42°45.18’S, 179°59.47– 179°59.54’ W, “Graveyard” Seamount, Chatham Rise, 943–1097 m depth, collected 15 April 2001 . Paratypes: NIWA 61257 , same locality as holotype . Other material: TAN0104 Stns 43, 116, 149, 150, 153, 194, 288, 289, 333, 336, 337, 389, 399.

Distribution. “Graveyard Seamount Complex”, north-central Chatham Rise, New Zealand, 750–1181 m.

Etymology. Latin minus, small + camera, chamber.

Description. Colony small, circular, generally with a single macular centre, but a secondary macula can develop in fertile colonies. Maximum diameter 1.9 mm. Completely adnate, with entire basal surface affixed to substratum. Frontal surface granular-tubercular.

Fertile colonies with only 15–16 autozooidal peristomes in 1–2 cycles around the colony periphery, radiating outwards, the apertural rims coarsely fimbriated. Colony centre hummocky, with small openings (kenozooidal?) in the depressions. Autozooidal peristomes up to 0.19 mm in external diameter; apertures 0.08 mm in internal diameter.

Gonozooid comprising a subglobular sac-like brood chamber, 0.38 mm wide, 0.44–0.47 mm long, prominent on the colony surface near the periphery, not embedded; exterior surface calcification granulartubercular like the rest of the colony, the ooeciopore very broad, wider (0.12–0.16 mm) than long, set low on the side facing the colony margin, the narrow rim of the ooeciostome very thin with little granulation. Ancestrula not seen.

Remarks. Gordon & Taylor (2001) described the known species of Lichenoporidae from New Zealand, comprising five species of Disporella and one of Doliocoitis . Two of the Disporella species are quite small — D. humilis , from 107 mm on Puysegur Bank, has a maximum diameter of 2.5 mm; D. sacculus , from 972– 1350 m at the Norfolk and Kermadec Ridges and the Bay of Plenty, achieves 5 mm diameter — but both of these species have concealed brood chambers, although D. sacculus has 1–3 sequentially functional brood chambers that are somewhat saccate. The closest species in morphology to D. minicamera is Disporella minima Moyano, 1991 ; it is equally tiny (not exceeding 2 mm diameter) and has an inflated sac-like gonozooid that is not concealed by kenozooids and secondary calcification. Its brood chamber is located entirely in the macular centre of the colony. Moyano (1991) noted some apparent differences between D. minima and other species of Disporella , suggesting that D. minima could represent a new genus. This possibility occurred to the present authors but we think that D. minima and D. minicamera can be accommodated within Disporella on the grounds that:

1. The small size and saccular nature of the brood chamber is probably no more than a consequence of small colony size: large colonies, large chambers; small colonies, small chambers.

2. The occurrence of the brood chamber on the surface of the colony instead of being embedded in it is probably also associated with small colony size and limited growth; large species have the capacity for increase in colony thickness, such that frontal growth of kenozooidal chambers can be achieved relatively quickly, partially or wholly concealing brood-chamber surfaces.

3. Schäfer (1991) showed that the brood chamber in Disporella species has a definite floor, unlike the situation in Patinella ( Lichenopora auctt.); the floor of the brood chamber in D. minicamera conforms to that of other Disporella species.

Figures

FIGURE 11. A–D. Disporella minicamera n. sp. (TAN0104 Stn 3). A, B, whole colonies with globular brood chambers; C, infertile colony; D, brood chamber with broad transverse ooeciostome. E, F. Disporella minutissima n. sp. (TAN0104 Stn 3); E, close-up of ooeciostome; F, whole colony with short, smooth base and central brood chamber with ooeciostome.