Nullarbora heptaxia, Ekins & Erpenbeck & Goudie & Hooper, 2020

Ekins, Merrick, Erpenbeck, Dirk, Goudie, Lisa & Hooper, John N. A., 2020, New carnivorous sponges and allied species from the Great Australian Bight, Zootaxa 4878 (2), pp. 240-266 : 244-247

publication ID	https://doi.org/ 10.11646/zootaxa.4878.2.2
publication LSID	lsid:zoobank.org:pub:111A9D05-860F-4917-A466-A44847B2D650
DOI	https://doi.org/10.5281/zenodo.4570951
persistent identifier	https://treatment.plazi.org/id/A10BF9A8-86E4-48BA-8D8D-D2E9CB76BA25
taxon LSID	lsid:zoobank.org:act:A10BF9A8-86E4-48BA-8D8D-D2E9CB76BA25
treatment provided by	Plazi
scientific name	Nullarbora heptaxia
status	sp. nov.

Treatment

Nullarbora heptaxia View in CoL sp. nov.

Figures. 2–3 View FIGURE 2 View FIGURE 3 , Table 1 View TABLE 1

urn:lsid:zoobank.org:act:A10BF9A8-86E4-48BA-8D8D-D2E9CB76BA25

Cladorhiza sp. 1, Ekins, Erpenbeck & Hooper, 2020: Table 5 View TABLE 5

Material examined: Holotype: SAMA S2592 About SAMA , Nullarbor Canyon, Great Australian Bight , South Australia, OR 26, 35 o 2’34.2” S 130 o 54’48” E, 3007.91 m, ROV, Coll. CSIRO on RV Rem Etive Cruise IN 2017_C01, sample RE2017_C01_OR26A_061_102, 23 March 2017 . Paratype: SAMA, S2593 About SAMA , Nullarbor Canyon, Great Australian Bight , South Australia, OR 26, 35 o 2’31.2” S 130 o 54’13.2” E, 3048.42 m, ROV, Coll . CSIRO on RV Rem Etive, Cruise IN 2017_C01, sample RE2017_C01_OR26A_141_101, 23 March 2017 . Paratype: SAMA S2594 About SAMA , Nullarbor Canyon, Great Australian Bight , South Australia, OR26, 35 2’31.2” S 130 o 54’9.6” E, 3038.52 m, ROV, Coll GoogleMaps . CSIRO on RV Rem Etive, Cruise IN 2017_C01, sample RE2017_C01_OR26A_144_101, 24 March 2017 .

Etymology: Gr. hepta, seven; axon, Gr. axle.

Distribution: This species is presently known only from the type locality in the Great Australian Bight, South Australia, from bathyal depths.

Description: Growth form: Stipitate, erect, unbranched, tall, bottle-brush shaped sponge adorned with copious fragile horizontal filaments ( Figure 2 A View FIGURE 2 ). The holotype is 405 mm in length and the stem is 6 mm in width. There are seven columns of filaments up to 25 mm in length This species also has basal root like processes up to 54 mm in length and usually 0.2 mm in width. Both paratypes are smaller and thinner of 275 and 205 mm in length and only 2.9 mm width of the stem, and the filaments only reach a maximum of 10–13 mm.

Colour: Pale brown on-deck. Creamy gold when preserved.

Ectosomal skeleton: Ectosomal skeleton is membranous and contains the abundant large sigmas and smaller anisochelae. This ectosome is clearly seen on the filaments ( Figure 3 F View FIGURE 3 ). The anisochelae are absent in the ectosome of the root like processes ( Figure 3 E View FIGURE 3 ). In the stem of the sponge the mycalostyles echinate the endosomal columns of styles and the ectosome ( Figure 3 C View FIGURE 3 )

Endosomal skeleton: In cross-section the stem has a radial skeleton, with a very small core. Around the nucleus seven arms radiate outwards ( Figure 3 A View FIGURE 3 ). These arms are composed of flattened bundles of longitudinal mycalostyles, providing support to the sponge. In between these radiating arms and at right angles to them, there are also seven radiating wedges containing sigmas, anisochelae ( Figure 3 B View FIGURE 3 ) and styles both longitudinally and radially orientated ( Figure 3 C View FIGURE 3 ). From within these wedges the mycalostyles give rise to and support the filaments (lower Figure 3 D View FIGURE 3 ).

Megascleres: The large mycalostyles (1510–3110 x 22–56 µm) are fusiform, with an abruptly sharp tip and slightly tapering base, and the greatest width at the centre of the spicule ( Figure 2 D, E View FIGURE 2 , Table 1 View TABLE 1 ). The less common smaller styles (426– 1690 x 6–24 µm) are more regular style shape but are slightly thicker in the centre of the spicule ( Figure 2 F, G View FIGURE 2 , Table 1 View TABLE 1 ). Very rarely the mycalostyles have some central or basal swelling, appearing as subtylostyles. Both styles occur in the stem, filaments and root-like processes of the sponge.

mens of Nullarbora heptaxia sp. nov.

Microscleres: Microscleres consist of two different types of anisochelae, and three different types of sigmas (see Figure 2 View FIGURE 2 and Table 1 View TABLE 1 ). The larger anisochelae (size range 42–69 x 1.5–4 µm) have five upper alae, the three frontal alae being nearly completely detached and the two lateral alae completely fused to the shaft; whereas the five lower alae are unguiferate anchorate. The smaller unguiferate anchorate anisochelae (size range 21–31 x 1–3 µm) have both upper and lower alae, with five teeth on the upper alae, and three teeth on the lower alae. Both the larger sigmas and thinner sigmas are c-shaped, the large sigmas are slightly contort, whilst the thin sigmas have a 90 o bend. The size ranges of the large and thin sigmas are 58–229 x 3.5–12 µm, and 61–106 x 1–3.5 µm, respectively. There are also uncommon sigmancistras of 31–46 x 2–4 µm.

Molecular data: 28S see Figure 1 View FIGURE 1 .

Remarks: This species is unique amongst the Cladorhizdae having stipitate bottle-brush growth form and having two very different anisochelae morphologies, the larger with palmate upper and unguiferate lower alae, and the smaller with unguiferate upper and lower alae. Morphology is not well known for many species as they are often damaged on collection. These anisochelae differentiate N. heptaxia sp. nov. from four morphologically similar species. Nullarbora rectangularis ( Ridley & Dendy, 1887) , N. evae ( Lundsten, Reiswig & Austin, 2014) (both have a single size category of multidentate unguiferate anchorate anisochelae), N. caillieti ( Lundsten, Reiswig & Austin, 2014) and N. investigator ( Ekins, Erpenbeck & Hooper, 2020) have two size categories of anisochelae but have unguiferate anchorate (see Table 5 View TABLE 5 in Ekins, Erpenbeck & Hooper 2020).