Psammina contorta, Gooday & Ishitani & Chen & Holzmann & Richirt & Seike & Yamashita & Tsuchiya & Nomaki, 2025

Gooday, Andrew J., Ishitani, Yoshiyuki, Chen, Chong, Holzmann, Maria, Richirt, Julien, Seike, Koji, Yamashita, Momo, Tsuchiya, Masashi & Nomaki, Hidetaka, 2025, Integrative taxonomy of new xenophyophores (Rhizaria, Foraminifera) from the abyssal northwest Pacific, European Journal of Taxonomy 1004, pp. 144-189 : 159-163

Psammina contorta sp. nov.

urn:lsid:zoobank.org:act:E698FACF-6DE6-461F-95F3-EA971F1F8695

Figs 2C–D , 5A–C , 8F–G , 9–10 , 22B ; Supp. file 2: Figs S4C–D, S 5C–F ; Supp. file 4: µCT video 2

Diagnosis

Species of Psammina with free, epifaunal test comprising complex, irregular system of variously shaped, often crookedly curved, plate-like elements up to ~ 60 mm in overall extent with no clear growth pattern or symmetry. Obvious apertures absent. Concentric zones sometimes present. Micro-CT scans reveal irregularly shaped, cell-like internal compartments. Test wall friable, comprising mixture of mineral grains of different sizes and colours. Stercomare forms branching and anastomosing strings of variable width that occupy internal spaces with no clear pattern. Granellare strands yellowish-brown, branching, thread-like (width ~14 to 40 µm), in places attached to grain surfaces; barite crystals not observed.

Etymology

From the Latin ‘ contortus ’, referring to the crooked and irregular appearance of different parts of the test.

Material examined

Holotype NW PACIFIC OCEAN – 32.5° N (west of Kuroshio Extension Observatory (KEO)) • 32°34.81′ N, 143°46.24′ E; depth 5509 m; 22 Oct. 2022; H. Nomaki leg.; Dive 1659 of HOV Shinkai 6500, core Red#8; GenBank accession nos: PP662678 , PP662679 ; National Museum of Nature and Science, Tsukuba, Japan, reg. no. TNS Pr695 . The specimen is preserved in a core in 10% buffered formalin.

Paratype

NW PACIFIC OCEAN – 32.5° N (west of KEO) • 1 spec.; same data as for holotype; Dive 1659 of HOV Shinkai 6500, core Red#7; National Museum of Nature and Science, Tsukuba, Japan, reg. no. TNS Pr694 . The specimen is preserved in a core in 10% buffered formalin .

Description

Overall test morphology

Holotype (TNS Pr695). In the seabed photograph, the holotype ( Fig. 2D ) appears as an apparently unstructured cluster of plate-like elements of various shapes and sizes, including one that is fairly large and fan-shaped and others that are more elongate. Most of the main elements are orientated in the same general direction. Shipboard photographs (Supp. file 2: Fig. S4D ) show a crooked, elongate, branched structure extending upwards with a small fan-shaped extremity, in addition to plate-like elements, most of which lean outwards away from the centre of the core.

The preserved specimen includes a main cluster of plate-like elements on one side, and on the other side, a smaller group of plates (not clearly visible in the seafloor image), part of which is attached to a stone (Supp. file 4: µCT video 2; Fig. 9A ). A pebble-shaped xenophyophore, described below, partially separates these two groups. The overall appearance is confused and devoid of any obvious pattern. Many of the plates seem rather isolated, possibly because connections are obscured by resedimented material. A μCT render showing the view from above reveals that the main cluster (length 59 mm, width 40 mm), at least, forms a single, complex, inter-connected structure lacking any obvious organisation ( Fig. 9A ). The other smaller group of plates (length 40 mm, width 15 mm) also seems to have some connection to the main cluster, although this is not entirely clear in the μCT render. The plates have complicated, irregular shapes and are either curved, sometimes strongly, or undulating ( Fig. 9B–E ; Supp. file 2: Fig. S5E–F ; Supp. file 4: µCT video 2). In a few places they are punctuated by one or two small open spaces. The margins are typically lobate, and may give rise to more elongated, rounded, prong-like projections. Other crooked, elongate processes are also developed. The plates are about 1.0– 1.7 mm (mean 1.33 ± 0.20 mm, n = 15) thick.

Paratype (TNS Pr694). The in situ photograph shows a complex, confusing mass of irregular, poorlyresolved, and apparently plate-like elements, which is difficult to make sense of ( Fig. 2C ). Shadows suggest that some parts are upstanding. In the shipboard photograph, the most prominent part of the test is a large erect plate with vague concentric zones and an open space at its base (Supp. file 2: Fig. S4C ). Adjacent to it is a recumbent plate that is curved into a trough-like structure, behind which two rounded lobes are visible. There is no sign of any symmetry or organisational pattern in either image.

By the time the paratype was examined in the shore-based lab, much of the test had collapsed. Some parts still projected upwards, but others that were originally upstanding lay flat on the surface of the preserved core ( Fig. 10 ). These collapsed remnants measure 3.9 × 2.5 cm in maximum extent. The main features that remain in what appear to be their original positions are the trough-like plate, which is visible in the µCT renders and shipboard image, and the two rounded lobes ( Fig. 10C–F ; Supp. file 2: Fig. S5C–D ), also seen in the shipboard photograph (Supp. file 2: Fig. S4C–D ). These lobes arise from a plate that lies in a vertical plane; they are orientated more of less at right-angles to each other, one projecting vertically, the other horizontally. Some of the other structures visible in the light photographs and µCT scans probably represent parts of the large collapsed plate.

Surface ornamentation, test structure and composition

In light photographs, some of the plates display rather irregular concentric zones; these are most apparent on parts of the holotype ( Fig. 9D–E ) but also visible on the paratype ( Fig. 10E ; Supp. file 2: Fig. S5C ). Radial features, however, have not been observed. Concentric zones with irregular boundaries can be seen in some μCT scans, which show that the internal space within the zones appears to be subdivided further into irregular spaces of different sizes and shapes ( Fig. 9B ). Micro-CT scans of the surface structure also reveal a rather faint pattern of shallow, cell-like depressions, some of them elongate, across parts of the test surface ( Fig. 10B ). These features are difficult to interpret. They cannot be seen in light photographs and whether they have any connection with the internal spaces is unclear.

The test wall is greyish, friable, 210 – 340 µm (mean 295 ± 0.04 µm, n =15) thick and similar to that of Psammina yokosukae sp. nov. When viewed through the wall of the core tube, the test surface in areas not covered in redeposited sediment includes a scattering of larger grains (Supp. file 2: Fig. S5C ). Seen under a stereo microscope, the wall is composed of mineral grains of various sizes ( Fig. 5A–C ). The larger grains are often dark, with a smaller proportion that are whitish and orange.

Stercomare and granellare

The stercomare resembles that of Psammina yokosukae sp. nov. in consisting of branches and more irregular masses with varying dimensions that occupy spaces between internal particles and do not conform to any particular trend or pattern. Similarly, the granellare forms narrow strings with a width of 14–40 µm (usually 20–30 µm, mean 24.8 ± 7.26 µm, n = 46). They are closely associated with the internal agglutinated particles and in places are attached to them. The granellare was not observed using SEM, but a strand examined using transmitted light under a high-power microscope did not contain any obvious barite crystals ( Fig. 8F–G ).

Molecular characterisation

Psammina contorta sp. nov. is strongly supported by the BV (98%) and branches at the base of P. tenuis and P. yokosukae sp. nov. The group is supported by 99% BV. The sequenced 18S barcoding fragment of P. contorta sp. nov. contains 1036 nucleotides and the GC content is 36%. The obtained sequences are identical.

Remarks

Psammina contorta sp. nov. resembles P. yokosukae sp. nov. in many respects, notably the test structure, the size and composition of the agglutinated grains, and the organisation of the stercomare and granellare systems. However, there are two main morphological differences. First, the test of P. contorta is a highly irregular structure made up of plates of various sizes and shapes that appear somewhat disconnected, in contrast to the more coherent system of fairly well-formed branching plates that characterise the holotype of P. yokosukae . Second, although concentric zones are visible in both light photographs and µCT scans of P. contorta , there is no evidence for internal radial structures running between the zones. Instead, µCT renders appear to show the interior occupied by the irregularly shaped spaces. These rather different morphological characteristics, together with the genetic data, support the recognition of two distinct species.

As in the case of Psammina yokosukae sp. nov., our phylogenetic reconstruction shows that P. contorta sp. nov. is a close relative of P. tenuis and has similarly narrow granellare branches that are, to some extent, attached to internal test particles. Moreover, the disorganised test is morphologically quite different from the simple curved plate of P. tenuis . As also noted above for P. yokosukae , a particularly striking difference is that the test of P. tenuis is composed largely of radiolarian tests, whereas that of P. contorta consists of mineral grains.

Figures

Fig. 2. Seafloor images. A–B. Psammina yokosukae sp. nov. A. Holotype, reg. no. TNS Pr691. B. Paratype, reg. no. TNS Pr693. C–D. Psammina contorta sp. nov. C. Paratype, reg. no. TNS Pr694. D. Holotype, reg. no. TNS Pr695; the rounded object on the left side is the ‘Pebble-shaped, honeycombed xenophyophore’ informally described below. The arrowhead (A) indicates the chimney-like feature referred to in the text.

Fig. 5. Stereo microscope images. A–C. Psammina contorta sp. nov. A. Fragment of holotype, reg. no. TNS Pr695.B. Fragment of paratype, reg. no. TNS Pr694.C. Detail of holotype surface.D–G. Psammina yokosukae sp. nov., fragments of holotype, reg. no. TNS Pr691. D. Outer surface of fragment. E. View of broken test edge showing wall and interior with dark stercomare. F. Closer view of test wall. G. Interior of fragment showing dark stercomare mass comprising accumulation of stercomata (tiny waste pellets) and two thin granellare branches (arrowed). A–D, F taken in Geneva; E, G taken at JAMSTEC.

Fig. 8. Light microscope images. A–E. Psammina yokosukae sp. nov., fragments of holotype, reg. no. TNS Pr691. A. Test interior showing damaged stercomare; fine granellare strands also visible. B. Granellare fragments dissected from test for molecular analyses. C. Closer view of granellare fragments. D–E. Granellare fragments immersed in glycerol on a glass slide and viewed with transmitted light in compound microscope. F–G. Psammina contorta sp. nov., granellare fragments from paratype, reg. no. TNS Pr694, viewed in glycerol, as described for D–E. Images A–C were taken in Geneva, D–G in Southampton.

Fig. 9. Psammina contorta sp. nov., holotype, reg. no. TNS Pr695. A. Micro-CT render showing exterior surface of complete test, as seen from above; the rounded object is the ‘pebble-shaped, honeycombed xenophyophore’ (TNS Pr696) informally described below.B. Micro-CT render showing interior features of part of the test, viewed obliquely; note the apparent compartmentalization of the test interior. Note that both images include parallel stripes that are obviously artifacts. C–E. Light photographs of parts of the test seen through the curved wall of the core tube, which causes some optical distortion.

Fig. 10. Psammina contorta sp. nov. paratype, reg. no. TNS Pr694. A–D. Micro-CT renders showing exterior surface of test. A. Complete test as seen from above. B. Oblique view of part of the test; note the cell-like pattern on the surface. C–D. Slightly oblique side views of the complete test. E–F. Light photographs of views similar to those shown in C–D, as seen through the curved wall of the core tube, which causes some optical distortion.

Fig. 22. Associations between xenophyophores within two cores from the 32.5° N, as seen in µCT renders (views from above), showing exterior surfaces. A. Core with Laminarena variabilis gen. et sp. nov., 32.5N form, reg. no. TNS Pr697 and undescribed smooth-walled xenophyophore. B. Core with Psammina contorta sp. nov., paratype, reg. no. TNS Pr694 and undescribed pebble-like xenophyophore (TNS Pr696).

Fig. 4. Psammina yokosukae sp. nov., holotype, reg. no. TNS Pr691. A–B, E–F. Micro-CT renders of complete test from different angles, showing surface structure. C–D, G–H. Corresponding light photographs taken through the side of the plastic core tube; note optical distortion due to curvature of tube wall.