Conopeum antipodum, Gordon & Sutherland & Perez & Waeschenbach & Taylor & Di Martino, 2020

Gordon, Dennis P., Sutherland, Judy E., Perez, Brenda A., Waeschenbach, Andrea, Taylor, Paul D. & Di Martino, Emanuela, 2020, The bryozoan genus Conopeum (Electridae) in New Zealand, with description of a new species and discussion of the morphological and genetic characters of Conopeum seurati (Canu, 1928), Journal of Natural History (J. Nat. Hist.) 54 (15 - 16), pp. 947-970 : 950-955

Conopeum antipodum n. sp. ( Figures 1 , 2 )

Membranipora cf. arcifera: Gordon 1967: 50 , fig. 10. Non Membranipora arcifera Canu and Bassler, 1929 .

Conopeum seurati: Gordon 1986: 24 , pl. 1A–D; Gordon and Mawatari 1992: 17 (part), pls 2B, C, 4A; Cranfield et al. 1998: 25 (part); Scholz 2001: 173; Gordon 2009: 55; Gordon et al. 2009: 289 (part). Non Nitscheina seurati Canu, 1928 .

Material examined

Holotype: NIWA 92729 , NIWA Stn Z18073, 37.1547° S, 175.3098° E, 0 m, on stone, Taramaire creek mouth, Miranda , Firth of Thames , Auckland, 24 February 2013.

Paratype: NIWA 98824 , Stn Z18215, 36.8329° S, 174.7961° E, 0 m, on Perna canaliculus, Devonport Wharf, Waitemata Harbour , coll . D .P. Gordon, March 1967.

Other material: NIWA 98812, Stn Z18080, ~ 36.2339° S, 174.2742° E, 0 m, on Spirobranchus cariniferus , E of Tinopai, Kaipara Harbour, coll. P.D. Taylor 15 March 1996; NIWA 98813, Stn Z18076, 43.8272° S, 176.4768° W, 0 m, on Mytilus galloprovincialis, Zeacumantus subcarinatus and Irus largillierti, Te Whanga Lagoon , Chatham Island, coll. D.P. Gordon, 20 December 1996; NIWA 134511, Stn Z18075, 36.8764° S, 175.0215° E,0 m, on rock, Omana Beach,Maraetai,coll. D.P. Gordon, 8 October 2015; NIWA 134514, 134515, 134516, Stn Z18216, 43.5540° S, 172.7209° E, 0 m, on Micrelenchus tenebrosus, Avon-Heathcote estuary, coll. Travis Foster, 22 June 2016; NIWA 132864, Stn Z18618, 41.2790° S, 173.2487° E, 0 m, beach-cast on shell, Tahunanui Beach, Nelson, coll. G.H. Uttley, no date (early 1950s?); NIWA 132865, Stn Z18619, 43.5035° S, 172.7305° E, 0 m, beach-cast on shell, New Brighton, Christchurch, coll. G.H. Uttley, no date (early 1950s?). MITS 14129, MNK 408, 37.0176° S, 174.5622° E, no depth data, Manukau Harbour, 1 June 2006; MNK 408, Manukau Harbour, MITS 16145, KPR012, 36.1369° S, 174.0154° E, 7 m, Kaipara Harbour, 27 September 2009; MITS 16174, KPR1150, 36.5708° S, 174.3804° E, 3 m, Kaipara Harbour, 10 October 2006; MITS 19690, MNK 366, 36.9768° S, 174.7063° E,no depth data,Manukau Harbour, 1 June 2006; MITS 28216, MNK 498, 37.0369° S, 174.8281° E,no depth data,Manukau Harbour, 1 June 2006; MITS 28228, MNK 598, 36.9332° S, 174.7849° E, no depth data, Manukau Harbour, 1 June 2006; MITS 30957, KPR657, 36.1566° S, 174.2397° E, 8 m, Kaipara Harbour, 28 September 2006; MITS 42926, 2LYT116, 43.6056° S, 172.7155° E, no depth data, Lyttelton, 4 November 2004; MITS 57159, LY 038, 43.6093° S, 172.7267° E, 3 m, Lyttelton, 19 March 2002; MITS 58217, NE001, 41.2584° S, 173.2749° E, 1 m, Nelson, 22 December 2001; MITS 58318, NE014, 41.2606° S, 173.2703° S, 3 m, Nelson, 22 January 2002; MITS 58672, NE060, 41.2561, 173.2771, 2 m, Nelson, 24 January 2002; MITS 58732, NE065, 41.2561° S, 173.2771° E, 1 m, Nelson, 24 January 2002; MITS 70071, BNZ2750, 37.5300° S, 175.9800° E, barge hull, Tauranga Harbour; MITS 70611, BNZ( REW) 2799_Galeos, no coordinates, vessel hull, Bluff, April 2013.

Description

Colony encrusting, unilamellar, multiserial, up to 80 mm maximum spread. Greyish-white in the field, browning in older parts of colony. By light microscopy, zooid walls are white, the membranous frontal wall transparent and the operculum brown; retracted tentacle crown of polypide whitish, stomach brown; tentacles 15–16.

Mature autozooids in zone of astogenetic repetition arranged quincuncially, almost twice as long as wide, subrectangular,truncated distally and proximally with lateral margins bulging outwards slightly, but shape variable depending on place in colony; each autozooid separated from neighbours by a narrow furrow.Basal wall wholly calcified,no window.Entire frontal area covered by smooth cuticularised frontal membrane ( Figure 1 (a)) except for very narrow smooth gymnocystal margin laterally (often not visible) and a variable proximal transverse strip, or traces of gymnocyst just in proximolateral and distolateral corners.

A pair of fairly prominent hollow spines typically present ( Figure 1 (b)), occasionally lacking, one at each distolateral corner, thicker at base, tapering, each curved slightly proximad and with very thin cuticular joint basally, such that the spines are separated from their bases in bleach or when dead. Spine bases more or less flush with gymnocystal surface. Articulated lateral spines, when present, shorter and thinner than distolateral spines ( Figure 1 (c,d)), variable in number from 0 to 4 along each margin, always from the gymnocyst, even when this is not visible in frontal view, arching over the frontal membrane.

Operculum at distal end of frontal wall, differentiated within it as a distally rounded flap a little longer than semicircular, with cuticular thickening (sclerite) around curved inner margin only ( Figure 2 (a)), hinged along straight proximal margin with frontal wall.

Opesia elongate-oval, entirely surrounded by narrowly sloping cryptocyst that is of equal width throughout ( Figure 1 (b)), its surface with conspicuous rounded granules in mostly 3–4 discontinuous series. Edge of gymnocyst minutely crinkled at margin with cryptocyst. Where autozooids have regenerated within the cystid cavity of existing such zooids, their cryptocystal margins narrower than in the original zooid.

Kenozooids sporadic, adventitious, typically inserted in corners between autozooids, small, of irregular shape ( Figure 2 (b)), with relatively large opesia unevenly surrounded by granular sloping cryptocyst and a smaller area of gymnocyst (mostly proximally). One of the distolateral spines may be lacking when a kenozooid present.

Ancestrula longitudinally oval to subcircular, single (i.e. not twinned), with very large opesia ( Figure 1 (d)). Cryptocyst extremely narrow, more or less smooth, surrounded by smooth gymnocystal wall that slopes to substratum. A single pair of spines at distolateral corners, each like that in mature autozooids. Ancestrula budding a short uniserial series of about three daughter zooids before first daughter zooid itself begins to bud a daughter from a basal pore-chamber at each distolateral corner.

First daughter zooid with a pair of long proximolateral spines as well as the distolateral pair. An additional shorter, less-robust acicular spine produced from each lateral gymnocystal margin, generally curving over frontal wall. Cryptocyst wider than in ancestrula, with single series of granules. Succeeding autozooids continue to have both proximolateral and distolateral spines for several zooidal series, as well as up to three shorter spines on each lateral margin; eventually, the proximolateral and lateral spines cease to be produced and only the distolateral ones remain.

Interzooidal communications via multiporous septula ( Figure 2 (c–d)) in transverse walls (16–26 pores) ( Figure 2 (d)) and round mural septula in lateral walls (7–13 pores) ( Figure 2 (c–e)). Budding of some zooids from 1 to 2 midlateral pore-chambers intermediate in form between basal and mural in early stages ( Figure 1 (c,d)); these less evident in later colony stages, in which zooids all have conventional mural septula.

Measurements

Separate measurements were made of specimens from Kaipara Harbour, Auckland (Waitemata Harbour), Christchurch (Avon-Heathcote Estuary) and Chatham Island (Te Whanga Lagoon):

Kaipara: ZL 297–524 (423) [N = 36]; ZW 109–337 (254) [N = 43]; OpL 249–422 (342) [N = 33]; OpW 134–287 (185) [N = 38]; PCrL 15–60 (42) [N = 19]

Auckland (holotype): ZL 415–572 (494) [N = 35]; ZW 215–289 (250) [N = 34]; OpL 326–424 (382) [N = 33]; OpW 152–224 (181) [N = 34]; PCrL 28–68 (41) [N = 9]

Christchurch: ZL 363–531 (469) [N = 33]; ZW 266–330 (292) [N = 32]; OpL 252–379 (338) [N = 30]; OpW 165–229 (194) [N = 33]; PCrL 34–47 (41) [N = 4]

Chatham: ZL 428–640 (571) [N = 41]; ZW 247–394 (341) [N = 52]; OpL 355–514 (440) [N = 31]; OpW 192–271 (241) [N = 32]; PCrL 27–73 (52) [N = 15]

All localities: ZL 297–640 (493) [N = 145]; ZW 109–394 (283) [N = 161]; OpL 249–514 (377) [N = 127]; OpW 134–287 (237) [N = 137]; PCrL 15–73 (45) [N = 47]; ZD 97–152 (122) [N = 25]; KL 169–314 (216) [N = 5]; KW 78–168 (114) [N = 6]; AnL 192–256 (218) [N = 7]; AnW 131–183 (163) [N = 7]

Remarks

Specimens of Conopeum antipodum n. sp. have been found in Kaipara, Waitemata, Manukau and Tauranga Harbours, Patea River mouth, at the ports of Nelson, Lyttelton and Bluff, and in Te Whanga Lagoon, Chatham Island, in very shallow water on hard substrata – pilings, shells, rock. Across the geographic range of the species in New Zealand, mean zooid size is greatest in Te Whanga Lagoon on Chatham Island. The earliest known record of C. antipodum is of a specimen on Perna canaliculus collected from Devonport, Waitemata Harbour in 1967 ( Gordon 1967). Having not been discovered or recorded earlier, it begs the question whether the species may be invasive. Mediating against this possibility is its apparent absence in any other part of the world, the presence of a similar undescribed Recent species in southern Australia ( Bock 2009) and a related endemic Pleistocene species, Conopeum ongleyi ( Brown, 1952) n. comb., in New Zealand (redescribed below). Conopeum antipodum n. sp. also resembles Conopeum aciculatum ( MacGillivray, 1891) from New South Wales and South Australia, which differs in having proportionally less gymnocyst and stouter tuberculation.

Conopeum seurati , though naturalised, is much rarer, having been found only at Opua, Whangarei, Whanganui Inlet (northwest South Island) and Lyttelton. The Whanganui Inlet specimens were found on shells of Xenostrobus securis in 1963, which constitutes the earliest known record of the species in New Zealand. SEM examination of its skeletal morphology ( Figure 4 (a)), and that of specimens from the other localities, unequivocally confirm its identity. The morphology of topotypic C. seurati is described below for comparison.

Distribution: Endemic – Kaipara Harbour to Bluff and Chatham Island, 0–8 m on hard substrata.

Figures

Figure 1. (a–d). Conopeum antipodum n. sp.: NIWA 98813, Te Whanga Lagoon, Chatham Island, New Zealand. (a), Autozooids with membranous frontal walls and opercula in situ. (b), Autozooids with stout distolateral spines. (c), Post-ancestrular autozooids with stout distolateral spines and smaller lateral spines. (d), Ancestrula and daughter zooids. Arrows in (c) and (d) indicate communication-pore areas in lateral walls. Scalebars: All 200 μm.

Figure 2. (a–e). Conopeum antipodum n. sp.: (a, b), NIWA 98813, Te Whanga Lagoon, Chatham Island; (c, e), NIWA 16174, Kaipara Harbour; (d), NIWA 98824,Waitemata Harbour,Auckland, New Zealand. (a), Inner face of operculum showing the form of the marginal sclerite. (b), Two kenozooids flanking a repaired autozooid. (c), Lateral view of an autozooid with mural septula and stumpy spine bases on each side midlaterally. Arrows indicate raised distal zooid rims in profile. (d), Distal end on an autozooid showing a dense pore cluster in the transverse wall and (arrowed), inner (left) and outer (right) multiporous mural septula. (e), Close-up of the interior face of a multiporous mural septulum. Scalebars: (a, d), 50 μm; (b), 200 μm; (c), 100 μm; (e), 20 μm.

Figure 4. Conopeum seurati (Canu, 1928): (a, c), NIWA 98946, Whanganui Inlet, South Island, New Zealand; (b), NIWA 134508, Piombino, Tuscany, Italy. (a), Autozooids showing the peripheral cryptocystal groove,and a small kenozooid. (b), Lateral view of the cryptocystal rim of an autozooid, showing part of the peripheral grove, granules, minute pores (in the groove and lateral interior wall, and multiporous septula). (c), Lateral view of an autozooid and its proximal neighbour with mural septula. Scalebars: (a, c), 200 μm; (b), 100 μm.