Conopeum oretiensis Uttley 1951

Conopeum oretiensis Uttley, 1951: 21, fig. 2; Gordon et al. 2009: 289.

Material examined

NIWA 92728, NIWA Stn Z18615, 39.8622° S, 174.7040° E, 0 m, W of Waiinu Beach, Wanganui, 20 January 2014; NIWA 132862, Stn Z18616, 41.2790° S, 173.2487° E, on beach-cast shell, Tahunanui Beach, Nelson, coll. G.H. Uttley, no date (late 1940s?); NIWA 132863, Stn Z18617, 43.5035° S, 172.7305° E, on beach-cast shell, New Brighton, Christchurch, coll. G.H. Uttley, no date (late 1940s?); NIWA 132866, Stn Z18620, 46.4379° S, 168.2302° E, on beach-cast shell, Oreti Beach, Southland, coll. G.H.Uttley, no date (late 1940s?). MITS 16147, KPR363, 36.2978° S, 174.1872° E, 9 m, Kaipara Harbour, 28 September 2006; MITS 16171, KPR1004, 36.4849° S, 174.3295° E, 18 m, Kaipara Harbour, 9 October 2006; MITS 16172, KPR1006, 36.4961° S, 174,3233° E, 25 m, Kaipara Harbour, 9 October 2006; MITS 19665, 1 MNK234, 36.9411° S, 174,7076° E, no depth data, Manukau Harbour, 1 June 2006; MITS 19666, 1 MNK567, 37.0373° S, 174.7290° E, no depth data, Manukau Harbour, 1 June 2006; MITS 19671, 1 MNK442, 37.0401° S, 174.5732° E, no depth data, Manukau Harbour, 1 June 2006; MITS 19673, 1 MNK566, 37.0373° S, 174.7290° E, no depth data, Manukau Harbour, 1 June 2006; MITS 19674, 1 MNK347, 36.9645° S, 174.7191° E, no depth data, Manukau Harbour, 1 June 1006; MITS 19684, 1 MNK419, 37.0508° S, 174.6689° E, no depth data, Manukau Harbour, 1 June 2006; MITS 28186, 1 MNK271, 36.9571° S, 174.6658° E, no depth data, Manukau Harbour, 1 June 2006; MITS 28192, 1 MNK288, 36.9695° S, 174.6501° E, no depth data, Manukau Harbour, 1 June 2006; MITS 28195, 1 MNK323, 37.0056° S, 174.6522° E, no depth data, Manukau Harbour; 1 June 2006; MITS 28211, 1 MNK420, 37.0508° S, 174.6689° E, no depth data, Manukau Harbour, 1 June 2006; MITS 28224, 1 MNK528, 37.0367° S, 174.8278° E,no depth data,Manukau Harbour, 1 June 2006; MITS 30939,KPR451, 36.2600° S, 174.2525° E, 9 m, Kaipara Harbour, 28 September 2006.Also, SEM micrograph of specimen from Napier, no longer extant, coll. D.P. Gordon 1970s.

Description

Colony encrusting, typically unilamellar but self-overgrowing when large, multiserial, up to ~ 65 mm maximum spread, whitish. By light microscopy, zooid walls are white, the membranous frontal wall transparent and the operculum very pale brown.

Mature autozooids in zone of astogenetic repetition arranged quincuncially, about twice as long as wide, suboval; each autozooid initially separated from neighbours by a narrow furrow.

Opesia elongate-oval, surrounded by narrowly sloping cryptocyst (Figure 5 (a,c)) that is of equal width throughout, its surface with conspicuous tubercular granules that may be much reduced or lacking on vertical thin distal margin. Gymnocyst conspicuous (Figure 5 (a)) in several autozooidal generations from the ancestrula, occupying a third or more of zooid length proximally and narrowing around steeply sloping margins; of more-variable length in zooids in the zone of astogenetic repetition, generally concealed by adventitious kenozooids of varying size in proximolateral corners and often along interzooidal margins. Periopesial spines 8–12 (Figure 5 (b)), the most distolateral pair and a midproximal spine typically stoutest, remaining spines mostly acicular, all leaning across opesia.

Fully formed kenozooids (Figure 5 (b–d)) with round to oval opesia at bottom of steeply sloping granular (initially smooth) cryptocyst with elevated rim; cystid gymnocystal, smooth, sometimes extended along interzooidal boundary.

Interzooidal communications via small oligoporous septula low on lateral walls.

Ancestrula subpyriform (Figure 6 (a, b)), with gymnocyst occupying more than onethird zooid length. Opesia near-circular, distal rim slightly extended distad. Very narrow cryptocystal rim unevenly granular. Opesial spines five, comprising a distolateral pair, a somewhat proximolateral pair, and a midproximal spine. Distal daughter zooid budded slightly obliquely in mid-distal position, with eight spines; slightly larger additional zooid later budded midproximally, also with eight spines. This pattern establishes an initially linear colony form, widening at each end into pluriserial then multiserial growth.

Measurements

Ancestrulate colony (MITS 28211) from Manukau Harbour, Auckland:

ZL 335–518 (424) [N = 20]; ZW 161–302 (240) [N = 20]; OpL 148–307 (258) [N = 20]; OpW 101–221 (169) [N = 20]; PCrL 15–44 (26) [N = 10]; KL 174–303 (227) [N = 10]; KW 82–136 (115) [N = 10]; AnL 262 [N = 1]; AnW 181 [N = 1]

Remarks

Conopeum oretiensis has not been formally reported from any new localities since its first discovery until now. Zooidal characters are very variable. For instance, when the articulated spines are limited to a conspicuous midproximal one and a smaller distolateral pair, the species can appear somewhat ‘electriform’ (Figure 5 (a)). With the development of additional spines and numerous adventitious kenozooids, the species more obviously conforms to Conopeum. Uttley (1951) noted that a fossil specimen of this species was also in the collection of the Canterbury Museum, in which case it would likely have been Pleistocene in age; no data were given as to its provenance in Napier.

One mollusc shell bore a colony from which some autozooids had flaked off, revealing deeply etched traces in the shell surface (Figure 6 (c)), representing the incipient ichnofossil Finichnus.

Distribution: Endemic – sporadically distributed at the present day from Kaipara Harbour to Foveaux Strait, 0–9 m, on hard substrata.