Bathymarginaster patriciae ( McKnight, 2006 )

Mah, Christopher L., 2023, New occurrence of Poraniidae (Valvatacea, Asteroidea) in Australia with a new genus and species from deep-sea settings, Memoirs of Museum Victoria 82, pp. 119-131 : 122-124

Bathymarginaster patriciae ( McKnight, 2006) nov. gen, nov. comb.

Figure 1a–f

Diagnosis. Body weakly stellate to stellate (R/r=1.6–2.1) ( Fig. 1a ). Body surface, including abactinal, marginal, actinal surface all covered by dermis. Abactinal surface reticulate to imbricate, with coarse granulation/spination on each plate ( Fig. 1a, b ), single papulae present. Marginal plates lateral facing, approximately 16 per interradius ( Fig. 1c ), each plate bearing an upper and lower series, each with 2–3 spinelets present, the lower series approximately 2–3 times as large as the upper and present around the actinolateral fringe. Distinct actinolateral edge ( Fig. 1e ) formed by the inferomarginal plates and the actinal surface. Actinal intermediate region with approximately 16 segments, each with a spine forming a transverse series across each interradius ( Fig. 1f ). Furrow spines, two covered in dermis ( Fig. 1d, f ); no other adambulacral spination evident.

Comments. Examination of M. patriciae specimens relative to other Marginaster species, including the holotype of Marginaster paucispinus , led to the conclusion that M. patriciae is significantly different from other species assigned to Marginaster . ‘ Marginaster’ patriciae shows a much more stellate body shape, has a much denser and heavier abactinal skeleton that is weakly fenestrate. This contrasts with the skeleton in more typological Marginaster species, which show a more openly arranged mesh with a variably developed dermal covering ( Fig. 2). Marginaster patriciae has laterally oriented marginal plates that form a distinct ventrolateral edge with the actinal surface, whereas the marginals, especially the inferomarginal plates, of other Marginaster species are extended from the superomarginals to form a distinct flattened lateral “ledge” or platform with spines.

Marginaster patriciae was originally described from New Zealand waters from near Chatham Rise at 900–1130 m.

Among poraniids, Bathymarginaster nov. gen. is perhaps closest to Poraniomorpha , which shows a fenestrate skeleton. The abactinal skeleton of the former shows a skeleton with a granular/spinose covering, rather than the more open reticulate skeleton observed in true Marginaster species (e.g. Fig. 2a–d). Bathymarginaster displays a much heavier dermal overlay ( Fig. 1b ) than Poraniomorpha that obscures the marginal and actinal plate boundaries in the former. Bathyporania similarly displays a granular overlay but possesses a more open, reticulate skeleton.

Occurrence. Chatham Rise, central New Zealand, 900–1130 m. Note that McKnight (2006: 107) confused the depth range of M. patriciae with that of M. paucispinus (518–554 m).

Australian waters. J1 Seamount near Tasmania, Great Australian Bight. 850–1650 m.

Description. Body thick, strongly arched weakly stellate to stellate (R/r=1.6–2.1), arms triangular in shape, cylindrical to triangular in cross-section, actinal surface flat with distinct actinolateral edge. Plates, spines, accessories all covered by dermis ( Fig. 1a, b ). Arm tips upturned.

Abactinal surface fenestrate to imbricate, skeletal plates individually wide, fully enclosed over disk but forming wider, open spaces distally on arms. Individual plates ranging from larger, more irregular in shape proximally, becoming more crescentic along arms. Each plate with short, blunt spines or granules (4–15, but mostly 7–10), widely spaced, number decreasing distally along arm ( Fig. 1b ). Single papular pores present irregularly scattered on arms and disk on abactinal and lateral surfaces. Madreporite round, flat, adjacent to abactinal plates and slightly overlaid with tissue around edges.

Marginal plate boundaries largely obscured by dermis, but approximately 16 per interradius, eight per arm side at R=1.0 cm ( Fig. 1c, e ). At arm tip dermis sufficiently translucent as to reveal elongate plates, edges rounded, decreasing in width adjacent to arm terminus.

Superomarginal and inferomarginal plates each with spines (tips conical and pointed) in upper and lower series, approximately 2–3 in each row. Inferomarginal spines approximately twice as large as those on the superomarginal series, especially those spines on the lower series adjacent to the contact with the actinal plates. Terminal plate quadrate with a circular edge, bearing two small spines.

Actinal plates covered by dermis that shows distinct channels ( Fig. 1d, f ), forming segments that track from the abactinal-lateral surface via the marginal plates to the underside of the actinal surface around the marginals to each adambulacral plate ( Fig. 3e ). Actinal surface smooth, dermal tissue continuous from marginal plates. Each actinal intermediate segment has approximately 16 dermis-covered cone-like spines. These are single proximally, becoming double adjacent to the spines on the inferomarginal plates. These spines are in three lateral series across the actinal intermediate region.

Two furrow spines ( Fig. 1d, f ), covered by dermis in transverse series. No subambulacrals or other accessory adambulacral structures. Oral plate with two furrow spines, a single prominent spine projecting into mouth ( Fig. 1f ).

Material examined. NMV F84961 84 km SSE of South East Cape, J1 Seamount , Tasmania. - 44.27° S, 147.33° E, 1300–1450 m, Coll . T. Stranks et al . CSIRO, 27 Jan 1997. 1 wet spec . R=1.3, r=0.6.

NMV F159299 Hill U. top west, Tasmania, Australia. - 44.3257° S, 147.175° E, 1100–1160 m. Coll . CMBAR SS02 , April 2 2007 . 3 wet specs. R=1.3, r=0.7; R=1.0, r=0.5; R=1.4, r=0.6.

NMV F159300 Pedra West , south of Tasmania, - 44.2585° S, 147.092° E, 850–1000 m, Coll. O’Hara et al , CMAR, 2 April 2007, 1 wet specs . R=1.3, r=0.8.

NMV F159301 Mini Matt SSW, Australia.- 44.2447°S, 146.164° E, 1120–1136 m. Coll. O’Hara et al, 4 April 2007 , CMAR SS02 . 3 wet specs. R=1.1, r=0.6; R=1.2, r=0.7; R=1.2, r=0.6.

NMV F159302 Mini Matt site, S. of Tasmania, - 44.2439° S, 146.165° E, 1120–1310 m, Coll. O’Hara et al , CMAR 4 April , 2007, 2 wet specs . R=1.1, r=0.6; R=1.3, r=0.7.

NMV F159303 Pedra West, - 44.1322° S, 146.144° E, 1140– 1180 m, Coll. O’Hara et al . CMAR 5 April 2007, 1 wet spec . R=0.9, r=0.5.

NMV F240386 , Great Australian Bight - 33.3366° S, 130.257° E, 188–191 m, Coll. IN 2015_C02 GAB BP Expedition – Ichthyology Team, IN 2015_C02 GAB BP Expedition – Marine Invertebrates Team, 15 Dec 2015. 1 wet spec . R=0.6, r=0.4.

NMV F240376 , 82.6 km SSE of South East Cape, J1 Seamount , Tasmania, - 44.24° S, 147.36° E, 1200–1450 m, Coll . T. Stranks et al . CSIRO, 27 Jan 1997 . 4 wet specs. R=1.1, r=0.6; R=1.2, r=0.7; R=1.1, r=0.6; R=1.1, r=0.6.

NMV F 241095 , 85.8 km SSE of South East Cape,“B1” seamount, -4431° S, 147.27° E, 1150–1550 m, Coll . T. Stranks et al . CSIRO, 28 Jan 1997 . 3 wet specs. R=1.2 r=0.5 R=1.1 r=0.5 R=0.9 r=0.6.

NMV F241096 , 87.8 km SSE of South East Cape, “A1” seamount, - 44.33° S, 147.27° E, 1200–1300 m, Coll . T. Stranks et al . CSIRO, 30 Jan 1997, 1 wet spec . R=1.1 r=0.5.

NMV F241097 , 94.5 km SSE of South East Cape , “ V ” Seamount, - 44.4° S, 147.15° E, 1400–1650 m, Coll . T. Stranks et al . CSIRO, 31 Jan 1997. 1 wet spec . R=1.0 r=0.6

NMV F241098 , K1 seamount, 89.5 km SSE of South East Cape , Tasmania, Australia, - 44.29° S, 147.41° E, 1225 m, Coll. Tim N. Stranks , CSIRO aboard RV Southern Surveyor , 25 Jan 1997. 4 wet specs . R=1.0, r=0.7; R=1.0, r=0.5; R=0.9, r=0.4; R=0.7, r=0.3.

NMV F241099 , 81.6 km SSE of South East Cape, “38” seamount, Tasmania. - 44.23° S, 147.38° E, 1200–1400 m, Coll . T. Stranks et al . CSIRO 30 Jan 1997, 1 wet spec . R=1.2, r=0.6.

NMV F241100 “ Sister 1” seamount, 82.9 km SSE of South East Cape, - 44.27° S, 147.29° E, 1100–1122 m, Coll . T. Stranks et al . CSIRO, 23 Jan 1997 , 2 wet specs. R=1.1, r=0.5; R=1.0, r=0.6.

NMV F241101 “ Sister 1” seamount, 82.9 km SSE of South East Cape, - 44.27° S, 147.29° E, 1100–1122 m, Coll . T. Stranks et al . CSIRO, 1 wet spec. R=1.0, r=0.4

NMV F241102 Mongrel seamount, Tasmania. - 44.2554° S, 147.114° E, 898 m. Coll . R. Thrasher and D. Staples, 23 Dec 2008. 1 wet spec . R=1.0, r=0.5.

NMV F241103 Mongrel seamount, Tasmania. - 44.2554° S, 147.114° E, 899 m. Coll . R. Thrasher and D. Staples, 13 Oct 2008. 1 wet spec . R=0.4 r=0.2.

NMV F241573 Patience seamount, Huon Commonwealth Marine Reserve, Tasmania, Australia, - 44.1206° S, 147.377° E, 1087 m, Coll. D. Bray , RV Investigator 12 April 2015. 2 wet specs . R=1.0, r=0.3; R=1.2, r=0.4.

NMV F270826 Punch’s Hill, Tasmanian seamounts, Tasmania, - 44.185556° S, 147.188333° E, 919–1085 m. Coll. A. Williams, A.A. Weber and R-L. Erickson, 13 Dec 2018. 2 wet specs . R=0.9, r=0.6; R=0.9, r=0.4.

Figures

Figure 1. Bathymarginaster patriciae nov. gen. nov. comb. NMV F240376: a, abactinal; b, abactinal surface showing granules; c, abactinal-lateral view showing lateral surface, marginal series; d, actinolateral view showing edge and actinal surface; e, actinal view; f, closeup of actinal view showing adambulacral spination, oral view. Scale bars a=3.5 mm, b=1.5 mm, c, f=2 mm, d=2.5 mm, e=3.5 mm.

Figure 3. Poraniomorpha tartarus n. sp., holotype. NMV F 241811: a, abactinal; b, abactinal surface showing madreporite, surface texture; c, actinal view; d, actinal intermediate region and inferomarginals; e, actinal view furrow spines, oral region. Scale bars a=9.0 mm, b=5.0 mm, c=9.0 mm, d, e=2.0 mm.