Steginoporella neozelanica ( Busk, 1861 )

Gordon, Dennis P., Voje, Kjetil L. & Taylor, Paul D., 2017, Living and fossil Steginoporellidae (Bryozoa: Cheilostomata) from New Zealand, Zootaxa 4350 (2), pp. 345-362 : 347-348

Steginoporella neozelanica ( Busk, 1861)

( Figs 1A , 2 , 6–9 , 28 )

Vincularia neozelanica Busk, 1861: 155 , pl. 34, fig. 5; Hutton 1880: 189.

Steganoporella neozelanica: Hincks 1882: 119 ; Hincks 1893: 175; Waters 1888: 14, pl. 2, fig. 32; Hutton 1891: 104; Harmer 1900: 259, pl. 12, fig. 4, pl. 13, fig. 25; Hutton 1904: 296; Levinsen 1909: 168, pl. 5, fig. 3a–d.

Steganoporella neo-zealandica: Hamilton 1898: 195, 198.

Steganoporella neozelanica f. typica Livingstone, 1929: 65 , text-fig 2a, pl. 1, fig. 10.

Steginoporella neozelanica: Pouyet & David 1979a: 571 , fig. 4; Pouyet & David 1979b: 788, pl. 1, fig. 4; Gordon 1984: 56, pl. 17B; Gordon et al. 2009: 290.

Material examined. Syntype: NHMUK 99.7.1.1530, Busk Collection, ‘New Zealand’.

Other: NHMUK: 98.6.5.2, Napier. NIWA 73096, Stn TAN1105/27; NIWA 75121, Stn TAN1108/179; NIWA 75193, Stn TAN1108/197; NIWA 75364, Stn TAN1108/213; NIWA 75401, Stn TAN1108/217; NIWA 75479, Stn TAN1108/233; NIWA 75496, Stn TAN1108/239; NIWA 101415, Stn Z15924 ; NIWA 107197, Stn E268; NIWA 107200, no data; NIWA 107201, C.A.J. Duffy donation; NIWA 119897, Stn T254. Plus unregistered (nonseparated) specimens in multispecies samples from NIWA Stations K796, K820, K849, K851, K856, K857, Z15598 , Z15904 , Z15924 , Z1595, Z9665, Z9674, Z9680, Z9681, Z9682, Z9685, Z9686, Z9688, Z9689, Z9694, Z9698, Z9701, Z9702, Z9704, Z9713, Z9714, Z9715, TAN0906/21.

Redescription. Colony erect, comprising cluster of unbranched columnar stems of varying lengths up to 80 mm, mostly in the range 40–60 mm, attached to hard substratum by basal tangle of rootlets. Rootlets forming as prolongations of the frontal cuticle of autozooids no longer possessing opercula; no rootlet pores. Colour in life brownish-orange. Zooids monomorphic, roundly subhexagonal but longer than wide (mean L/W = 1.37), widest at level of median process. Cryptocyst occupying about half length of frontal surface, shelf depressed, flat, densely porous, with a pair of recesses in proximal corners. Opercular opening delimited proximally by acutely triangular opercular pivots and median process, with distolateral ‘wings’ that do not meet pivots but have narrow, delicate calcareous extension on each side meeting the lateral margin and delineating an irregular transverse opesiule; proximomedial pore longitudinally elongate. Operculum reinforced by distinctive pattern of sclerites, generally comprising a transverse strip (straight or irregular) from which an oblique pair of strips connect to the proximal margin; an I- or H-shaped sclerite occurs between these, sometimes with the crossbar and the top half of the H lacking; a short median vertical sclerite may pass from the mid-distal margin to the transverse sclerite or part or all of it is lacking or is paired. Thickness of sclerites may increase with age of zooid. Polypide with 22–24 tentacles. Ancestrula and early astogeny not seen.

Measurements. ZL 864±36, 778–894 (1, 10); ZW 632±26, 578–667 (1, 10); OpL 238±30, 198–278 (1, 10); OpW 462±34, 411–500 (1, 10).

Remarks. Steginoporella neozelanica was the first steginoporellid to be described for New Zealand. Its colonies are large, distinctive and common enough on underwater rock faces to be noticed and photographed by divers, who refer to it as the ‘finger bryozoan’ ( Fig. 1A ). The number of stems in a clump can exceed 60; whether or not these are all part of the same genetic individual is not known. It seems likely, insofar as clumps are discrete, but the variation in stem length within a clump suggests the possibility of larval recruitment to established colonies, a hypothesis that needs to be tested genetically. In colonial morphology it is closest to Steginoporella marcusi Livingstone, 1929 (see below), which, however, comprises single stems, not clusters, often has a single bifurcation, and a different pattern of opercular sclerites. Out of the many samples of S. neozelanica that have been examined, only a single branch bifurcation has ever been seen, and it was very short and only at the base of a stem near the rootlets, unlike the distal branching in S. marcusi . Zooids of S. marcusi are, on average, larger than those of S. neozelanica and the median process, while very similar, consistently differs in detail. The reticular sclerites of the operculum of S. marcusi form somewhat of a honeycomb pattern that is closer to that in S. perplexa than to S. neozelanica . Nevertheless, it seems that S. neozelanica and S. marcusi are closely related.

Distribution. Endemic to New Zealand: Three Kings Islands, Spirits Bay, northeast coast of North Island from North Cape to Bare Island off the coast of central Hawke’s Bay at depths of 6–76 m on rock faces. Harmer (1900) reported the species [the ‘Vincularian form’] from Wanganui, on the West Coast of the lower North Island, but it has never been seen in any of the many NIWA samples from this region, which suggests a possible local extinction.

Waters (1887) cited Steganoporella [sic] neozelanica as a fossil in the Hawke’s Bay region of eastern North Island but, since he stated that colonies comprised “ S. neozelanica in the Lepralia -stage”, it is apparent that he was referring to S. magnifica (see below), of which we also have seen fossil material from this area.

Figures

FIGURE 1. Six species of Recent New Zealand Steginoporella (NIWA stations in parentheses). A, S. neozelanica (TAN 1105 / 27); B, S. marcusi (respectively from three localities, left to right, D 896, TAN 1105 / 42, TAN 1105 / 60); C, S. perplexa (small colony from Z 15617); D, S. discors n. sp. (TAN 0906); E, S. modesta n. sp. (TAN 0413 / 109); F, S. lineata n. sp. (TAN 0205 / 64). All to same scale (scalebar 25 mm).

FIGURES 2 – 5. Autozooids of New Zealand Steginoporella (NIWA stations in parentheses). 2, S. neozelanica (TAN 1105 / 27); 3, S. marcusi (D 896); 4, S. perplexa (Z 8662); 5, S. magnifica (M 797). All to same scale (scalebar 1 mm).

FIGURES 6 – 9. Steginoporella neozelanica, Napier, NHMUK 98.6. 5.2. 6, distal zooids; 7, incompletely bleached zooids showing median process and polypide tube; 8, rootlets at proximal end of the colony; 9, origin of rootlets as prolongations of the frontal cuticularised wall. Scalebars: 6, 8, 1 mm; 7, 9, 0.5 mm.

FIGURES 28 – 36. Opercula of New Zealand Steginoporella species showing presence and absence of sclerites on the inner face of the outer layer (localities in parentheses). 28, S. neozelanica (non-NIWA locality, Bare Island, Hawke’s Bay); 29, S. marcusi (D 896); 30, S. perplexa (Stn Z 8662); 31 – 33, S. magnifica, showing variation in sclerites from the same colony (Stn M 797); 34, S. discors n. sp. (Stn Z 9743); 35 – 36, S. lineata n. sp., showing opercula of smaller autozooid and larger avicularian B-zooid (Stn TAN 0205 / 64). All to same scale (scalebar 0.2 mm).