Three new species of deep-sea Gromia (Protista, Rhizaria) from the bathyal and abyssal Weddell Sea, Antarctica Author Rothe, Nina Author Gooday, Andrew J. Author Cedhagen, Tomas Author Fahrni, José Author Hughes, J. Alan Author Page, Anton Author Pearce, Richard B. Author Pawlowski, Jan text Zoological Journal of the Linnean Society 2009 2009-10-26 157 3 451 469 https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2009.00540.x journal article 10.1111/j.1096-3642.2009.00540.x 0024-4082 10114782 GROMIA MARMOREA SP. NOV. ( FIGS 2–4 ) Diagnosis: species of Gromia with a rounded test, which is spherical, to droplet-shaped, to ovoid in shape; diameter 1.0– 3.4 mm , length: width ratio 0.6– 1.9. Overall colour in fresh specimens, greenish with silvery patches, giving marble-like mottling of wall; preserved specimens, brown. Single, prominent, mound-like oral capsule. Type material and locality: The holotype and paratypes are from an EBS deployment at RV Polarstern station 133#2, 62°46.95 ′ S , 53°1.72 ′ W , 1584 m water depth, 16th March 2005 ( Table 1 ). They are deposited at the Research Institute and Natural History Museum Senckenberg , Frankfurt am Main. The holotype is catalogued under reg. no. SMF XXVII 7398 . The paratypes are catalogued under reg. no. SMF XXVII 7399 . The type specimens were extracted from > 300-Mm residue and are preserved in 4% formaldehyde solution buffered with borax . Figure 2. Gromia marmorea sp. nov. A–D, reflected-light photographs of preserved specimens, from station 133#2, 1584-m depth. Photographed in water. A, holotype, reg. no. SMF XXVII 7398, spherical morphotype. B, paratype, reg. no. SMF XXVII 7399, droplet-shaped morphotype. C, paratype, reg. no. SMF XXVII 7399, oval morphotype. D, detail of oral capsule. E, scanning electron microscope (SEM) photograph of oral capsule. F, unfixed specimens. Figure 3. Gromia marmorea sp. nov. A, B, scanning electron microscope (SEM) photographs of wall consisting of multiple layers. C, transmission electron microscope (TEM) photograph of ‘honeycomb membrane’ layer. D, detail of (C). Additional material: Station 133#2: approximately 130 specimens . Derivation of name: From the Latin marmoreus , meaning ‘like marble’, alluding to the marbled pattern of the test surface. Overall appearance: The 130 specimens range in length from 1.0 to 3.4 mm (mean 1.9 ± 0.4 mm ), and range from 0.8 to 3.7 mm in width (mean 1.7 ± 0.4 mm ). The length: width ratio varies from 0.6 to 1.9 (mean 1.1 ± 1.0). They vary from nearly spherical, to droplet-shaped, to ovoid in lateral outline. Ovoid specimens are widest behind the midpoint, with a rounded posterior end, and a narrower anterior end terminating in the oral capsule. The degree to which the test narrows towards the aperture varies between specimens, giving rise to the different morphologies. Freshly collected, unfixed specimens were greenish-grey, sometimes with silvery, shiny patches giving the test a mottled appearance. After formalin fixation, specimens were predominantly brown in colour, although the mottling persisted ( Fig. 2 ). Oral capsule: The single oral capsule is a very distinct, golden brownish-coloured structure, and is roughly circular in plan view ( Figs 2E , 4A ). In lateral view it appears as a broad, mound-like structure, and is penetrated by a central canal ( Fig. 2D ). In the ovoid- and droplet-shaped specimens, the oral capsule is located at the narrower end of the test ( Fig. 2B ). Sediment data from Howe (2006) , Howe, Shimmield & Diaz (2004) , and Diaz (2004) . Figure 4. Gromia marmorea sp. nov. scanning electron microscope (SEM) photographs. A, oral capsule (the arrow indicates the direction of the photograph sequence shown in panels Ci–Civ). B, perforations of the test surface. Ci–Civ, sequence of photographs over a distance of 250 Mm showing test pores (each pore is highlighted by a white circle), with the number of pores increasing with increasing distance from the aperture (from left to right); 4000¥ magnification. D, E, interior of broken specimen showing stercomata and other structures. Table 1. Weddell Sea sample stations, gear, depth, number of examined specimens, position, and environmental data

Approx.
Number of	bottom
Station	Sample	Depth	specimens	temperature	Bottom
No.	gear	(m)	per species	°S	°W	(°C)	salinity	Sediment type
133#2	EBS	1584	~700	69°46.49 ′	53°3.50 ′	0.00	34.67	Greenish grey silty sand,
G. marmorea	moderate bioturbation,
scattered Mn-coated
dropstones, poorly sorted clay
80#9	EBS	3103	15	70°39.07 ′	14°43.36 ′	-0.50	34.66	Olive-grey sandy mud,
G. melinus	hemipelagite, intensely
bioturbated, foraminiferal-rich
81#8	EBS	4392	1	70°32.02 ′	14°35.05 ′	-0.70	34.66	Olive-grey sandy mud, very
G. melinus	poorly sorted, abundant
Mn-coated clasts,
hemipelagite, and contourites
121#7	EBS,	~2600	36	63°37.43 ′	50°45.11 ′	0.00	34.67	Greenish grey silty sand,
AGT	G. winnetoui	moderate bioturbation,
scattered Mn-coated
dropstones, poorly sorted clay

The height of the oral capsule (i.e. the distance it protrudes from the test surface) ranges from 100 to 600 Mm (mean 140 ± 100 Mm, N = 129), and the diameter ranges from 200 to 800 Mm (mean 400 ± 100 Mm, N = 129). In 18 specimens , a flaccid extension (up to a maximum length of 200 Mm), composed of organic material, protrudes from the central canal through the aperture opening ( Fig. 2D ). Test wall: The test is delicate and tears easily. The organic wall appears featureless and smooth when viewed under a binocular microscope. It is usually partially translucent, sometimes with a milky appearance, and displays a characteristic marble-like pattern ( Fig. 2A–C ). Viewed using SEM, the wall is composed of multiple layers, and each layer is a fraction of a micron thick ( Fig. 3A, B ); TEM revealed the existence of an inner layer of honeycomb membranes ( Fig. 3C, D ). In cross section, the membranes appear as a series of very regular lines. The pores form openings on the test surface, ranging in diameter from ~0.3 to 3.1 Mm ( N = 14; only clearly defined pores were measured; Fig. 4B ). They occur across the entire surface, but are usually less frequent around the aperture. In the illustrated specimen, their density increases from about one pore per 10 Mm 2 , within 40 Mm of the aperture, to about 12 pores per 10 Mm 2 , at ~250 Mm from the aperture ( Fig. 4C, i –iv). Concurrently, the pore diameter tends to increase from ~0.3 Mm close to the oral capsule to about 3.1 Mm at a distance of ~250 Mm from the capsule. However, the density of pores also varies between specimens. In one of the four individuals investigated by SEM, the pores were smaller and less frequent than in the other specimens, and did not display the decrease in size described above. Test contents: The test contents are visible through the translucent test wall, and consist mainly of a densely packed mass of small, oval, and brownish stercomata ( Fig. 4D ). These range from 6 to 22 Mm ( N = 140) in length, and from 3.7 to 20 Mm in width ( N = 140), and are characterized by a very smooth surface. Additional particles visible in SEM include possible mineral grains and sponge spicules ( Fig. 4E ). Distribution: Powell Basin, east of the tip of the Antarctic Peninsula, 1584-m depth ( Fig. 1 ). Remarks: Gromia marmorea sp. nov. is by far the most abundant gromiid in the ANDEEP-III material. The new species encompasses a range of shapes, from spherical, to ovoid, to droplet-shaped, which are also exhibited by G. oviformis ( Jepps, 1926 ) . However, it differs from the latter in the mottled appearance of the test wall and the dark-greenish, rather than lightbrownish, colour of fresh, live specimens. In addition, the organic test wall of G. marmorea sp. nov. is very delicate, and tears easily. Gromia marmorea sp. nov. ranges in length from 1.0 to 3.4 mm , and is therefore larger than G. pyriformis ( < 1-mm long; Gooday & Bowser, 2005) and smaller than G. schulzei (8–9-mm long; Schulze, 1875 ), as well as being smaller than G. sphaerica (maximum length 38 mm ; Gooday et al. , 2000 ). Like most other gromiids, this new species has a single, large oral capsule rather than many small capsules scattered across the test, as in G. sphaerica ( Gooday et al. , 2000 ) . The capsule is a prominent, relatively low, broad, mound-like structure, and is larger (200–800 Mm in diameter) than in other Weddell Sea species. The test is perforated by numerous pores that have a minimum diameter of 0.3 Mm ( 300 nm ), compared with 73 nm in G. pyriformis (Gooday & Bowser, 2005) .