Nodellum aculeata, Gooday & Todo & Uematsu & Kitazato, 2008

Gooday, A. J., Todo, Y., Uematsu, K. & Kitazato, H., 2008, New organic-walled Foraminifera (Protista) from the ocean’s deepest point, the Challenger Deep (western Pacific Ocean), Zoological Journal of the Linnean Society 153 (3), pp. 399-423 : 401-405

publication ID	https://doi.org/ 10.1111/j.1096-3642.2008.00393.x
persistent identifier	https://treatment.plazi.org/id/03BE87EC-982E-FF96-3603-FC5CDBC5FA0B
treatment provided by	Felipe
scientific name	Nodellum aculeata
status	sp. nov.

Treatment

NODELLUM ACULEATA View in CoL SP. NOV. FIGS 1–7 View Figure 1 View Figure 2 View Figure 3 View Figure 4 View Figure 5 View Figure 6 View Figure 7

‘Needle-shaped, organic-walled allogromiid resembling Chitinosiphon ’. Todo, Kitazato, Hashimoto, Gooday, 2005, fig. 1A

Derivation of name: Latin aculeolus, a small needle, referring to the needle-like test morphology.

Diagnosis: Small, delicate species of Nodellum , <500 Mm in length with maximum width 5–9% of length. Test wall mainly organic, usually yellowish and several micrometres thick. Proloculus with closed proximal (basal) end that is usually pointed. Surface of proloculus strewn with minute rod-shaped particles, typically 0.4–0.7 Mm long and ~0.1 Mm wide. Main part of test tubular, usually gently curved. At submicrometre scale most areas covered in short, branching, finger-like projections of organic wall, in some areas interrupted by flake-like patches (probably clay particles).

Types: The type specimens are deposited in Tokyo and London under reg. nos MPC-02705 (holotype), MPC- 02706-02709 (four paratypes) and ZF 5169 (six paratypes)

Other material examined: 42 specimens.

Description

Test morphology: The test is 230–426 Mm long ( Table 1) and forms a very narrow tube that follows a slightly to gently curved, occasionally almost straight course ( Fig. 1 View Figure 1 ). The proximal part consists of an elongate proloculus, 27–44 Mm long and 11.0–15.5 Mm wide and occupying 7.9–17.3% (usually 9–14%) of the total length of the test. The end is usually pointed ( Figs 1 View Figure 1 , 2A View Figure 2 ) but in a few cases narrowly rounded ( Figs 1K View Figure 1 , 3B View Figure 3 ). The proloculus gives rise to a long, tubular section that gradually increases in width from around 10 Mm just in front of the proloculus to

The figure in parentheses is an outlier.

SE = standard error, N = number of specimens. about 20 Mm near the distal end. The final section of the tube usually tapers towards the aperture. The outline of the test is fairly smooth but there are sometimes slight irregularities and discontinuities in width ( Figs 3F View Figure 3 , 4A View Figure 4 ). Occasional specimens exhibit an abrupt decrease in width ( Fig. 1M View Figure 1 ), possibly reflecting a growth interruption.

Aperture: The aperture is a simple opening, 6–8 Mm in diameter, usually with a somewhat puckered rim ( Figs 3E View Figure 3 , 5C, D View Figure 5 ). Occasionally, the apertural end is sharply truncated ( Figs 1M View Figure 1 , 3F View Figure 3 , 5B View Figure 5 ). An aperture is never developed at the proximal end.

Wall structure and composition: The test wall is transparent, smooth, with a slight brownish tinge and composed mainly of organic material. Viewed in the SEM, the surface of the proloculus is strewn with submicrometre-sized particles, many of which are more or less rod shaped, typically 0.30–0.70 Mm long and 0.08–0.10 Mm wide ( Figs 2B–F View Figure 2 , 3C, D View Figure 3 ). Some more equidimensional grains, 0.10–0.15 Mm in diameter, occur between these elongate particles.

The tubular part of the test beyond the proloculus is devoid of rod-shaped agglutinated particles. The surface has a complex appearance in the SEM. At magnifications of ~15 000¥, it often appears lumpy ( Figs 4E View Figure 4 , 6B, D View Figure 6 ). At higher magnifications, the lumps resolve into a complex mass of short, branching, finger-like projections ( Figs 4F View Figure 4 , 6C, E View Figure 6 ) that appear to be elaborations of the underlying organic wall. Flat, scale-like patches with free edges around a part of their circumference ( Fig. 7F, G View Figure 7 ) are interpreted as clay particles (see below). Along the border between the proloculus and the tubular part of the test, the two types of surfaces tend to interdigitate, with V-shaped, agglutinated areas penetrating into areas devoid of obvious grains ( Fig. 4B, D View Figure 4 ).

When damaged mechanically, the test wall shatters into fragments, sometimes with curved edges ( Fig. 7B View Figure 7 ), indicating that the wall is brittle rather than soft. Broken sections viewed by SEM are ~0.10– 0.12 Mm thick. The complex surface structure is visible on the outer margin of these sections, but the wall exhibits no obvious internal structure ( Fig. 7C, D View Figure 7 ).

EDS analyses of the grains covering the proloculus reveal strong peaks for Fe and Si with secondary peaks for Mg and Al. Areas of test beyond the proloculus devoid of rod-like particles show a strong Fe peak and secondary peaks for Al and Si. These analyses suggest that the rod-like particles on the proloculus are composed of clay minerals, that other kinds of clay particles (presumably the flake-like patches referred to above) are also present on the tubular part of the test, and that the organic wall contains iron.

Test interior: The inner surface of the test is smooth. At very high magnifications (100 000¥), however, it resolves into closely packed lumps, 0.02–0.05 Mm in diameter, which impart a granular appearance at a submicrometre scale ( Fig. 7E View Figure 7 ). The lumen of the tube is usually uninterrupted, but occasionally is divided by a transverse partition. It contains brownish stercomata that occupy a greater or lesser proportion of the cavity. Sometimes, most of the interior is filled with stercomata while in other cases only part of the test, usually towards the distal end, is occupied ( Fig. 1 View Figure 1 ). Sometimes there are empty gaps, possibly artifactual, between stercomata-filled sections. In specimens that appear to be dead, the stercomata have lost their identity and decayed into a greyish powder. Distinct areas of cytoplasm are occasionally observed adjacent to the aperture ( Fig. 1F View Figure 1 ).

Remarks: This ‘ Chitinosiphon- like’ species resembles Nodellum rufescens in the general shape of the test, but is much smaller (maximum test length ~500 Mm), and more delicately constructed. The wall is also considerably thinner and only slightly tinged with brown rather than being deep, brownish-red in colour, as in the type specimens of N. rufescens . Another difference is the frequent presence of a small aperture at the pointed end of the proloculus in N. rufescens . A similar structure is never present in N. aculeata . The new species is much smaller and more slender than Xenothekella elongata .

Needle-like, organic-walled Foraminifera resembling Nodellum aculeata are fairly widespread across a considerable bathymetric range in the Pacific and Atlantic oceans. There are published records of these ‘ Chitinosiphon -like’ forms from 1345 m water depth in the Porcupine Seabight (north-east Atlantic) and at abyssal depths on the Porcupine Abyssal Plain (north-east Atlantic, 4850 m), the central Weddell Sea (4975 m), the North Pacific (4263–5289 m), the western Equatorial Pacific (5300–5570 m), the eastern Equatorial Pacific (4032–4089 m) and 7800 m in the Atacama Trench, south-east Pacific ( Gooday, 1986; Gooday et al., 2001, 2004; Sabbatini et al., 2002; Cornelius & Gooday, 2004; Nozawa, 2005). Slight differences in the shape of the proloculus and the relative width of the tubular part of the test suggest that several species are represented amongst this material. The Challenger Deep specimens are smaller than any of those previously illustrated (length <500 Mm compared with> 700 Mm). They resemble most closely specimens from the Atacama Trench ( Sabbatini et al., 2002: pl. 1, fig. 4) in having a rather inflated proloculus and in the relative width of the tubular part of the test.