Electra oligopora, Gordon, 2009

Gordon, Dennis P., 2009, New bryozoan taxa from a new marine conservation area in New Zealand, with a checklist of Bryozoa from Greater Cook Strait, Zootaxa 1987, pp. 39-60 : 41-42

Electra oligopora n. sp.

( Figs 2–6 )

Electra pilosa: Uttley 1951: 18 (part); Macken 1958: 104 (part); Uttley & Bullivant 1972: 15 (part); Gordon 1986: 26 (part), pl. 1 E-F. Non Linnaeus 1767.

Material examined. Holotype: NIWA 46351 . Paratypes: NIWA 46352 , 4653 . All types from the same locality on an unidentified brown alga, Lyttelton Harbour, collected 11 February 2004 .

Etymology. Alluding to the paucity of gymnocystal pores.

Description. Colony algal-encrusting, exceeding 25–30 mm in length or spread depending on space availability on algal substratum; pluriserial to multiserial, tending to form lineal runners several zooids wide, along growth axis of alga, from which parallel rows of zooids bud obliquely to left and right at angle of 55–65°; or colonies much broader with fewer side branches. Zooids monomorphic, elongate-rectangular, 0.49–1.25 mm long and 0.25–0.39 mm wide in zone of astogenetic repetition, longest in lineal runners. Proximal gymnocyst variable in extent, generally very short to vestigial, occupying as little as 4% of zooidal length, with 4–8 small pores in each proximolateral corner, or, even in same colony; gymnocyst occupying up to 28% of zooidal length, with up to 30 gymnocystal pores present, these covered by thin cuticularised epithelium in life; typically short, thorn-like spine borne on the gymnocyst, calcified at base and grading to cuticularised spine tip; a pair of similar spines distolaterally. Some colonies lacking midproximal spine on some or most zooids and adjacent gymnocyst more vestigial with only 1 or 2 pores; distal pair of spines present in these zooids. A very thin, smooth cryptocystal rim inset on inner margin of gymnocyst; this a little wide distally where it appears as a narrow shelf. Operculum constituting a D-shaped flap of membranous frontal wall; entire distolateral border strengthened by a cuticularised sclerite.

Remarks. Species of the genus Electra include those, like the type species (by synonymy) E. pilosa ( Linnaeus, 1767) , which have pores in the gymnocyst and those that do not. In New Zealand waters, only one, variable, porous species has been recognised in the literature and universally attributed to E. pilosa . The typical “long-spined” form that is common around New Zealand’s coasts, especially on red algae ( Nikulina et al. 2007), conforms to the description of Electra lesueuri d’Hondt, 1979 , discriminated on the basis of material collected in Western Australian waters on seaweeds. It differs from E. pilosa in having more thickly cuticularised spines of larger basal diameter (up to 0.1 mm compared to 0.06 mm in E. pilosa ) and smaller, shorter zooids.

Electra oligopora may be unique among the species with porous gymnocysts in the extent of the reduction in the gymnocyst. This character and the lack of lateral spines are consistent in populations known so far with certainty only from the coast of Wellington, Tasman Bay in the Nelson region, and Lyttelton. Notwithstanding, short to vestigial gymnocysts typify colonies from off the coast of Waimate, South Canterbury (33 m water depth) on a thin brown algal stipe (possibly of Carpophyllum sp. ) that have smaller zooids, 1 or 2 pairs of proximal gymnocystal spines and 1–2 pairs of lateral spines, all of which have darkly sclerotised tips. In zooids from another colony with short gymnocysts, collected from the coast at Clifton, southern Hawke Bay, the gymnocystal spine is extremely elongated with a very broad base. It is not certain if these forms represent E. oligopora or further undescribed species. More material and a detailed morphomolecular study are required for porous Electra species in New Zealand. The only other species of Electra reported in New Zealand waters is E. angulata Levinsen, 1909 (misidentified as E. tenella ( Hincks, 1880) in Gordon & Mawatari 1992), found occasionally on drifting or beach-stranded plastic along northern coasts ( Stevens et al. 1996) or as small colonies on the hulls of pleasure craft plying tropical and subtropical waters. Electra angulata has an imperforate gymnocyst.

Figures

FIGURES 2–6. Electra oligopora n. sp. 2, Part of cleaned encrusting colony showing general disposition of runner-andbranch zooidal series. 3, Zooids with membranous frontal walls and spine tips intact. 4, An autozooid in quincuncial arrangement with its neighbours. 5, Proximal and distal ends of zooids in a lineal series showing the small area of porous gymnocyst. 6, The operculum fully folded back proximally, showing the marginal sclerite that supports it. Scale bars: Fig. 2 = 1 mm; Figs 3–5 = 100 µm; Fig. 6 = 30 µm.