Laminarena variabilis, 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 : 164-178

Laminarena variabilis gen. et sp. nov.

urn:lsid:zoobank.org:act:A7159F47-DD82-4C93-A3A4-D26481268FF2

Figs 11–19 , 21A–E , 22A ; Supp. file 2: Figs S6–S 14 ; Supp. files 5, 6; µCT videos 3–4

‘ Xenophyophores ’ – Tsuchiya & Nomaki 2021: figs 1–3.

Diagnosis

As for genus.

Etymology

Latin, ‘ variō ’ (‘diverse or variable’) + suffix ‘- bilis ’, adjective, referring to the variable morphology.

Material examined

Holotype NW PACIFIC OCEAN – 30° N • 30°09.2′ N, 143°35.1′ E; depth 5366 m; 23 Oct. 2022; H. Nomaki leg.; Dive 1660 of HOV Shinkai 6500, core Blue#2; GenBank accession no.: PP662670 ; National Museum of Nature and Science, Tsukuba, Japan, reg. no. TNS Pr700 . The specimen is preserved in a core in 10% buffered formalin.

Paratype

NW PACIFIC OCEAN – 30° N • 1 spec.; same data as for holotype; Dive 1660 of HOV Shinkai 6500, core Blue#1; National Museum of Nature and Science, Tsukuba, Japan, reg. no. TNS Pr699 . The specimen is preserved in a core in 10% buffered formalin .

Other material examined

NW PACIFIC OCEAN – 30° N • 1 spec.; same data as for holotype; Dive 1660 of HOV Shinkai 6500, core Blue#6; National Museum of Nature and Science, Tsukuba, Japan, reg. no. TNS Pr702 • 1 spec.; same data as for holotype; Dive 1660 of HOV Shinkai 6500, core Blue#7; National Museum of Nature and Science, Tsukuba, Japan, reg. no. TNS Pr703 • 1 spec.; same data as for holotype; Dive 1660 of HOV Shinkai 6500, core Red#4; National Museum of Nature and Science, Tsukuba, Japan, reg. no. TNS Pr705 . – 32.5 °N • 1 spec.; 32°34.8′ N, 143°46.2′ E, depth 5505 m; 22 Oct. 2022; H. Nomaki leg.; Dive 1659 of HOV Shinkai 6500, core Red#9; National Museum of Nature and Science, Tsukuba, Japan, reg. no. TNS Pr697 • 1 spec.; 32°34.7′ N, 143°46.1′ E; depth 5505 m; 24 May 2022; H. Nomaki leg.; Dive 1633 of HOV Shinkai 6500, core Blue#1; National Museum of Nature and Science, Tsukuba, Japan, reg. no. TNS Pr690 • 1 spec.; 32°34.9′ N, 143°45.9′ E; depth 5505 m; 27 May 2023; H. Nomaki leg.; Dive 1691 of HOV Shinkai 6500, core Blue#0; National Museum of Nature and Science, Tsukuba, Japan, reg. no. TNS Pr714 . Specimens are preserved in cores in 10% buffered formalin .

Description of the typical 30° N form

Overall test morphology

The test comprises a more or less complex, asymmetrical system of thin, interconnected plates that follow a curved, or undulating course. Although the plates may appear to some extent separate, in fact they are either parts of one longer, highly sinuous plate or linked to other plates at branching points. There is considerable variation in test morphology and each specimen is different. Micro-µCT scans show that the tests do not penetrate the sediment to any extent and there is no evidence for root-like structures.

Holotype (TNS Pr700). The seabed photograph of the holotype (Supp. file 2: Fig. S6A ) shows two relatively simple, curved plates with the concave sides facing outwards, and another more complex branching plate, all of them displaying concentric zones. In µCT renders, the recovered specimen measures 49 mm by 39 mm in maximum extent and projects to a height of 24 mm above the sediment surface ( Fig. 11A, D, F, H ). The view from above shows the three main plate-like components that are visible in the seafloor image ( Fig. 11A ). The plates are thin and delicate, ranging in thickness from 1.2–1.5 mm (mean 1.35 ± 0.12 mm, n = 15). They appear somewhat separated but the μCT video (Supp. file 5) shows that all three arise from a common basal area. Two are relatively simple plates facing at approximately 90 degrees to each other. The largest is strongly curved and forms an almost complete circuit, the second less strongly curved. The third main element branches to create a more complex undulating structure with a sinuous upper margin when viewed from above ( Fig. 11A ). One part is attached for a short distance to a stone ( Fig. 11C–F ) and Supp. file 5 appears to show that the largest plate is also attached to a stone. It is possible that the part of the test immediately adjacent the former stone represents the base from which the rest of the test developed.

Paratype (TNS Pr699). The seabed image (Supp. file 2: Fig. S6B ) is dominated by a large, unevenly curved plate with the concave side facing outwards, behind which several additional sinuously curved plates are visible. The recovered specimen is contained within a roughly hemispherical envelope. In µCT renders ( Figs 12A, C, E , 13A–C ) it measures 63 mm by 58 mm in maximum extent and projects to a height of 42 mm above the sediment surface, making it the largest of the six specimens. The plates range in thickness from 0.60 to 0.85 mm (mean 0.72± 0.09 mm, n = 13). The test appears to lie directly on the sediment surface with no obvious structures penetrating the sediment (Supp. file 6: µCT video 4). The view from directly above ( Fig. 13A ) reveals a strongly asymmetrical morphology. The plates are located mainly on one side of an open space through which the sediment is visible, with the largest plate dominating the view and partly obscuring the rest of the test. Other µCT renders and light images ( Figs 12 , 13B–C ) show a series of smaller, often strongly curved plates with sinuous rims. Several small, curved plates near the base of the test form tunnel-like features at or just above the sediment surface. There are no reticulations, although the video (Supp. file 6) clearly shows several points at which the plates branch (see also Fig. 12A, C–D ). It is also clear from the video that large sections of the test, including the largest plate and others that appear separate from it in some views, in fact comprise a single continuous and highly sinuous plate ( Fig. 13B ).

The test has no current connection with several small stones that lie nearby in the core ( Fig. 13A ). However, careful examination of the µCT renders ( Fig. 13A ) suggests that a short broken section of the margin near the base of the largest plate was probably originally attached to one of the stones, which still retains a small fragment of the plate on its surface. As in the holotype, it seems likely that this region near the base of the largest plate represents the initial part of the test.

Additional specimen reg. no. TNS Pr705. In µCT scans the specimen measures 50 mm by 48 mm in maximum extent and projects to a height of 40 mm above the sediment surface. The seafloor image (Supp. file 2: Fig. S6C ), together with laboratory photographs and µCT renders (Supp. file 2: Fig. S7 ), all show what appears to be one continuous main plate that makes several sinuous, sweeping loops in different planes. The largest loop is directed vertically, creating a broad, funnel-like structure that opens in an upward direction, while in the lower part of the test the loops are orientated horizontally (see particularly Supp. file 2: Fig. S7A, E ). There are also several additional curved plates near the base of the structure that possibly arise as branches of the main plate, although obvious branching points cannot be seen.

Additional specimen reg. no. TNS Pr702. The test appears simpler than others in seafloor images. A strongly curved upper plate creates a funnel-like structure through which the sediment surface is visible (Supp. file 2: Fig. S6D ). At least one additional plate can be seen beneath the upper plate. The recovered specimen is located to one side of the core and seems to have slumped slightly. It measures 51 mm by 50 mm in maximum extent, projects to a height of 44 mm, and has a distinctly asymmetrical appearance. The µCT top view render shows two strongly concave plates that face in different directions but are linked together to create a single large plate with a strongly sinuous, S-shaped margin (Supp. file 2: Fig. S8A ). In side view, another large plate that is strongly curved on a horizontal plane appears to be continuous with the sinuous upper plate (Supp. file 2: Fig. S8B ). On one side it branches to give rise to a smaller plate that is curved in the same direction and at one point is attached to a stone (Supp. file 2: Fig. S8B–D ). Both these elements merge together into a gently undulating plate near the base of the test.

Additional specimen reg. no. TNS Pr703. In the seafloor and shipboard images this large specimen is clearly more complex than others and gives the impression of being made up of a larger number of smaller plates (Supp. file 2: Fig. S6E–F ). The recovered specimen measures 60 mm by 55 mm in maximum extent and projects to a height of 35 mm. As in the shipboard image, the test appears to comprise numerous curved plates that are orientated in different directions, but with no clear pattern or obvious reticulations (Supp. file 2: Fig. S9 ). These elements are all interconnected and it is clear from Supp. file 2: Fig. S9A (top view), that many plates that appear distinct from some angles are actually parts of at least two larger plates. One of these is sinuously folded into an S shape, the other follows a straighter course. In places, the plates clearly branch or give rise to side plates. Many parts of the plate system extend upwards but near the base of the test some are more horizontal with their concave sides facing downwards.

Surface ornamentation, test structure and composition

The test surfaces of all specimens display a distinctive pattern of concentric zones that follow the shape of the plate margin and are traversed at right angles by low radial ridges separated by shallow furrows ( Figs 12 , 14A ). These features create a distinctive pattern that in places is strongly developed (Supp. file 2: Fig. S7F ). In the holotype, the zones are 1.8–5.6 mm (mean 3.23 ± 1.28 mm, n = 7) wide and the radial ridges spaced 0.46–0.70 mm (mean 0.57 ± 0.07 mm, n = 14) apart. In the paratype, the zones also measure between 1.8 and 5.6 mm (usually 2.3–3.9 mm; mean 3.11 ± 0.84 mm, n = 21) wide and the radial ridges are spaced 0.46–0.74 mm (mean 0.57 ± 0.08 mm, n = 16) apart. One of the plates of additional specimen TNS Pr703 features a number of dome-like surface pustules that can be seen in the µCT render (Supp. file 2: Fig. S9B ).

The test plates are 250–320 µm (mean 0.28 ±0.02 µm, n = 16) thick and comprise two more or less parallel walls. Sections that have broken across the concentric zones (i.e., at right angles to the test margin) show that the walls of later (younger) zones overlap those of the preceding zones ( Fig. 14C–D ), rather than being a simple continuation of the wall. Sections of the test that have broken across the radial ridges (i.e., parallel to the concentric zones and to the test margin) often show that the interior is interrupted by transverse partitions that define compartments ( Fig. 14E ). Micro-CT scans ( Figs 11–13 ; Supp. file 2: Figs S7–S 9 ) confirm that the surface pattern of radial ridges and furrows corresponds to these internal partitions. When test fragments are broken to expose the interior, the partitions can be seen as low, parallel structures composed of agglutinated particles arising from the inner surface of the wall ( Fig. 14F ). Otherwise, the test interior appears largely devoid of internal particles.

The wall is greyish in overall colour when dried and composed of a mixture of mineral grains of varying sizes ( Figs 14A–B , 15 ). Most of the larger particles are dark but a few are transparent or whitish, although the density of darker grains is higher in some fragments than in others. SEM images show a jumble of particles, mainly of mineral origin and many resembling fragments of volcanic glass ( Fig. 15E–F ). There is also a tendency for the grain size to increase from the inner to the outer part of a zone ( Fig. 15A–C ), thereby creating a contrast in grain size across zone boundaries ( Fig. 15C–D ).

Granellare and stercomare

The granellare strands are generally located between the internal partitions ( Fig. 16A ). They are whitish to pale yellow, branch occasionally, and 45–97 µm wide (mean 67.4 ± 12.8 µm, n = 34). In the fragments examined, the spaces between the partitions are also occupied by masses of loose stercomata or their degraded remnants. In µCT scans of the paratype, the granellare strands appear as bright threads that correspond to the radial lineations ( Fig. 13E–F ). They are present throughout much of the test but less well developed near the base and more strongly developed towards one side of the upper part ( Fig. 13D ). The threads branch to some extent. In places near the margin, they appear to be discontinuous across the boundary between the two outer concentric zones ( Fig. 13F ). In addition to the main radial trend of the granellare, strands running horizontally are visible near the base of some of the concentric zones. Viewed by SEM, fragments of granellare are packed with crystals, a few microns (<5 µm) in size and identical to the barite particles (‘granellae’) that are typical of xenophyophores ( Fig. 16C–D ). Some crystals are marked by deep, sometimes rectangular depressions.

Description of 32.5° N form

This form is represented by two specimens from which we obtained molecular sequences, one collected in 2022 during dive 1659 (TNS Pr697) and the other in 2023 during dive 1691 (TNS Pr714). A third morphologically similar specimen was collected in 2022 during dive 1633 (TNS Pr690) but was immediately preserved in formalin and could not be sequenced.

Overall test morphology

Specimen reg. no. TNS Pr697. The test comprises a complex system of irregularly shaped but generally plate-like elements that are often somewhat curved ( Fig. 17A–F ; Supp. file 2: Fig. S10A–B ). In µCT scans, the specimen has an overall extent of ~ 4.3 cm and rises ~ 1.8 cm above the sediment surface. The central part seems to be generally flat lying, but around the periphery, a series of complicated, elongate elements, some of which branch, project upwards to varying extents and at various angles. Four or five of these elements are particularly conspicuous. They project mainly to one side, giving the test an asymmetrical appearance, and tend to widen upwards, sometimes with a vaguely fan-like termination. The plates range in thickness from 0.9 to 1.3 mm (mean 1.08± 0.12 mm, n = 15) and are punctuated by a few open spaces. One section of the periphery forms an undulating margin that rises only slightly from the surface. Concentric zones can be seen across many parts of the test surface ( Fig. 17F ).

Specimen reg. no. TNS Pr714. This specimen is similar in overall appearance to TNS Pr697. It forms a delicate structure that includes several fan-shaped plates, one of which is larger than the others ( Fig. 17G ; Supp. file 2: Figs S10D, S 11 ). The larger plate is connected to two smaller plates; and one of these merges with a fourth plate that develops from a separate stem. This cluster of plates is linked, in turn, to an irregular formation that includes several bar-like components and irregular excrescences; this part cannot be seen clearly through the core tube because it lies on the edge of the core and is partly obscured by redeposited sediment. The largest plate displays concentric zones and indistinct radial ridges ( Fig. 17H ), features that are clearly evident in the fragment illustrated in Fig. 18C .

Specimen reg. no. TNS Pr690. The seabed photograph shows a compact cluster of irregular elements, some of them plate-like (Supp. file 2: Fig. S10E ). In the shipboard photograph, the largest element terminates in a distinct fan, punctuated by two elongate open spaces, while bar-like structures project out to one side (Supp. file 2: Fig. S10F ). In the µCT render showing the top view, the test appears as a chaotic jumble of relatively small, irregular plate-like elements (Supp. file 2: Fig. S12A ). It measures 6.1 cm by 5.9 cm in maximum extent and projects 3.1 cm above the sediment surface. The test structure is clearer in side view renders that show a number of elongate processes that widen to varying extents towards their extremities (Supp. file 2: Fig. S12B–C ). These include the fan visible in the shipboard photograph. This and many of the other test parts are orientated upwards at an angle of 40° or more, and are clustered around a prominent, straight, chimney-like tube. However, there are also some narrow structures near the base of the test that extend outwards at a lower angle. In a few places, the plates are perforated by open spaces. The chimney-like tube is probably that of a polychaete. In the shipboard photograph, the upper part of this tube is obscured by a mass of detritus (Supp. file 2: Fig. S10F ).

Surface ornamentation, test structure and composition.

Although the surface ornamentation that is a feature of the 30° N specimens is less evident in the 32.5° N form, corresponding internal features are obvious in the µCT images of specimen TNS Pr697 ( Fig. 17B– C ) and particularly specimen TNS Pr690 (Supp. file 2: Fig. S12B–E ). These show a distinct pattern of concentric zones and radial structures, presumably internal partitions. The zones are 1.5–4.1 mm (mean 2.88 ± 0.81 mm) wide and the radial features spaced 0.50–1.22 mm (mean 0.87 ± 0.19 mm, n = 17) apart. Partitions are seen in broken cross sections of the specimen TNS Pr714 fragment viewed under a stereo microscope but their development is variable, ranging from vaguely defined to well defined ( Fig. 18D–E ). Partitions appeared weakly developed on inner test surfaces when this fragment was broken open and viewed under a light microscope ( Fig. 18F–G ) but were rather more obvious in an SEM image ( Fig. 19A ).

In specimens TNS Pr697 and particularly Pr714, the test wall resembles that of the holotype and paratype ( Fig. 18A–C ; Supp. file 2: Fig. S13A ). It is composed of mineral particles of varying sizes, with a matrix of small grains intermingled with a subordinate number of larger grains, mainly whitish and black but occasionally orange. Many of the whitish ones are probably volcanic glass (Supp. file 2: Fig. S13B ). The largest are a few hundred microns in size but most are much smaller.

Granellare and stercomare

The dissected fragment of specimen TNS Pr714 contained stercomare and granellare, both in good condition ( Fig. 18F–G ). The stercomare formed several discrete, dark-grey, sausage-shaped masses situated between indistinct ridges that would have formed incomplete radial partitions when the specimen was intact. The masses have the following dimensions: lengths 0.63–2.20 mm (mean 1.23 ± 0.65 mm, n = 6), width 0.20–0.45 mm (mean 0.35 ± 0.07 mm, n = 10), with one longer, branched strand (length at least 3.9 mm), the broken end of which extends beyond the edge of the fragment. The individual stercomata are generally between 8 and 20 µm (mean 14.1 ± 3.24 µm, n = 10) in size (Supp. file 2: Fig. S13C–D ). The granellare branches are whitish and lay alongside the stercomare for much of their length ( Fig. 18F–G ). The main branches are 40–98 µm (mean 65.8 ± 14.9 µm, n = 18) wide; in places, they appear to be closely associated with the stercomare ( Fig. 18H ). Stercomare masses and granellare branches with similar characteristics were present in a partially dissected fragment of specimen TNS Pr697 ( Fig. 18I ).

SEM images of granellare from specimen TNS Pr714 show that intracellular barite crystals are present ( Fig. 19C–F ). They have a generally oval, sometimes hexagonal morphology and resemble the crystals seen in the 30° N form. Their abundance appears to be quite variable along a granellare strand, with dense concentrations in a few places, sparser numbers or a virtual absence of crystals elsewhere. The dense concentrations are associated with areas where the granellare tube had apparently ruptured. In contrast, only a few could be seen where the tube appeared intact and was strongly crinkled, presumably an artifact of drying ( Fig. 19E ). However, the crystals probably appear to be sparse in such areas only because our view of the cytoplasm is obscured by the granellare tube wall.

Granellare fragments from specimens TNS Pr697 were also observed by SEM ( Fig. 19G–H ). Unfortunately, because they had not been washed adequately, many parts were obscured by salt crystals. Where the granellare surface could be seen clearly, there was no sign of obvious barite crystals within the cytoplasm, although it was not possible to establish whether they were absent or present but obscured by the granellare tube.

Molecular characterisation

Laminarena variabilis gen. et sp. nov. is supported by 89% BV and branches as sister to a clade containing representatives of the genera Aschemonella , Abyssalia Gooday & Holzmann, 2020 , Psammina , Galatheammina Tendal, 1972 and Moanammina Gooday & Holzmann, 2020 . The branching of the latter clade with L. variabilis is not supported by BV. The sequenced 18S barcoding fragment of L. variabilis contains 1013–1015 nucleotides and the GC content ranges from 36% to 37%.

Remarks

The undescribed xenophyophore specimens that were the subject of Tsuchiya & Nomaki’s (2021) feeding experiments came from the same 30° N site as the typical form of Laminarena variabilis gen. et sp. nov. described here and clearly belong to the same morphospecies. A remarkably similar morphotype was photographed (but not collected) in the western CCZ, 7362 km to the southeast of our sampling site ( Gooday et al. 2020b: fig. 1f therein). Kamenskaya et al. (2013: fig. 5c, f therein) published in situ photographs of similar specimens from the central CCZ. Probably the morphologically closest described species is Reticulammina plicata Gooday, 1996 from 4613 m depth on the Cape Verde abyssal plain in the NE Atlantic ( Gooday 1996). The unique specimen consists of the thin, undulating plates with sinuous margins and several branches although unlike those of the new species, a few wide reticulations are also present. Concentric zones are visible and broken plate edges show signs of partitions that traverse the zones at right angles, although these appear to have no surface expression. Some rather similar but undescribed xenophyophores have been collected on east Pacific seamounts (e.g., Levin et al. 1986: fig. 1e therein; Levin & Thomas 1988: fig. 2c therein).

In terms of test morphology, the 32.5° N form has a more disorganised appearance compared to the rather elegant typical form from 30° N. Instead of broad, sinuous plates, the test comprises much slenderer elements that radiate outwards, widening to varying extents but mainly towards their upper ends. They sometimes branch and a few are punctuated by open spaces. The surface pattern of concentric zones and radial lineations is much less obvious than in the typical form. However, to some extent, specimen TNS Pr703 from 30° N bridges the morphological gap between the two morphotypes. This specimen has a more complicated test than others from the type locality and appears rather more similar to the 32.5° N form, particularly when the seafloor photographs (Supp. file 2: Figs S6E, S 10A, C, E ) are compared.

Despite their morphological differences, genetic data support the placement of the two forms in the same species. The molecular distance of partial 18S rRNA sequences between specimens from 30° N and 32.5° N is <0.0089 in the Jukes-Cantor model ( Jukes & Cantor 1969), and the foraminifera-specific 37f hypervariable regions are almost identical (>99 %), categorizing them as the same species according to the criteria for foraminiferal meta-18S that classifies sequences diverging by less than 1% as conspecifics ( Nguyen et al. 2023). Since there has been some diversification, we conducted an Approximately Unbiased test for phylogenetic tree selection ( Shimodaira 2002). However, with only three sequenced specimens available to analyse, this failed to reveal any evolutionary scenario (data not shown). More information is clearly required in order to resolve phylogenetic relationships within this species.

It is not obvious why the 30° N and 32.5° N forms have diverged so much in terms of morphology, or whether there are any environmental drivers that are responsible for the differences between them. As noted above, bottom topography is similar between the two areas, but some environmental differences have been detected (Nomaki unpubl. data). At the 30° N site, CN ratios were higher, and carbon isotopic compositions (δ 13 C) were lower than at 32.5° N, suggesting that the sedimentary organic matter was probably more refractory and may have originated from a different source. This may explain the lower prokaryotic cell numbers and porewater [NH] + concentrations at 30° N compared to 32.5° N, despite TOC concentrations being comparable or even higher. If food is of lower quality at the more southerly site, this would be consistent with the test morphology of the typical form of Laminarena variabilis gen. et sp. nov., which seems better adapted for particle trapping than the more northerly form. Further analysis is needed in order to understand the factors responsible for the striking morphological differences between these two genetically similar xenophyophore populations.

There are precedents for morphological differences between genetically similar populations of xenophyophores that are separated geographically. Two species from the western CCZ, Aschemonella monilis Gooday & Holzmann, 2017 and Moanammina semicircularis Gooday & Holzmann, 2017 , yielded sequences identical to those obtained from specimens collected in the eastern CCZ ( Gooday et al. 2020a), although in these cases the geographical separation was 3800 km, compared to only 270 km between the two forms of Laminarena variabilis gen. et sp. nov.

Figures

Fig. 11.Laminarena variabilis gen. et sp. nov., typical 30° N form, holotype, reg. no.TNS Pr700.A. Micro- CT render showing internal features of complete test, as seen from above. B. Light photograph showing side view of test as seen in through the core tube wall. C–H. Light photographs and corresponding µCT renders showing different side views of test. The light photographs are somewhat distorted as a result of being photographed through the curved core-tube wall, whereas the µCT renders show the true shape.

Fig. 12. Laminarena variabilis gen. et sp. nov., paratype, typical 30° N form, reg. no. TNS Pr699. Micro- CT renders showing exterior surface of test from different angles, and corresponding light photographs taken through the curved wall of the core tube. Note that the light photographs are somewhat distorted whereas the µCT renders show the true shape of the test.

Fig. 13. Laminarena variabilis gen. et sp. nov., typical 30° N form, paratype, reg. no. TNS Pr699. A–C. Micro-CT renders showing exterior surface of test; note surface expression of internal structure. A. View from directly above. B. Oblique top view showing the other side of the test. C. Oblique side view. D. 3D µCT reconstruction of X-ray dense internal features interpreted as granellare strands filled with barite crystals; orientation of the specimens was similar to that shown in Fig. C. E–F. Micro-CT renders showing details of the test interior. The white roughly linear, radial structures are interpreted as granellare strands; note also, particularly in Fig. F, the presence of some strands running horizontally, parallel to the base of the concentric zones.

Fig. 14. Laminarena variabilis gen. et sp. nov., typical 30° N form, stereo microscope photographs of fragments of two additional specimens. A–D. Additional specimen reg. no. TNS Pr705. A. Fragment of test showing parts of several concentric zones, one of them with low radial ridges. The direction of growth is from top to bottom. B. Detail of boundary between two concentric zones. C–D. Broken cross sections across concentric zones; note the overlap between successive zones. The direction of growth is from left to right. E–F. Additional specimen reg. no. TNS Pr702. E. Broken section across radial features showing internal partitions. F. Internal surface of test wall showing partitions.

Fig. 15. Laminarena variabilis gen. et sp. nov., typical 30° N form, SEM images (secondary electron mode) of two fragments of additional specimen reg. no. TNS Pr705. A. First fragment. B. Second fragment. C–D. Details of the second fragment showing boundary between concentric zones (direction of growth from right to left); note the increase in grain size of the agglutinated particles at the base of the new zone. E. Detail of agglutinated surface of the younger zone. F. Detail of agglutinated surface of the older zone.

Fig. 16. Laminarena variabilis gen. et sp. nov., typical 30° N form, paratype, reg. no. TNS Pr699. A–B. Stereo microscope images. A. Test interior showing damaged stercomare and granellare strands running between the internal partitions. B. Granellare strands dissected for genetic analysis. C–D. SEM images (low vacuum, backscatter mode) of granellare strand. C. Overview to show large numbers of barite crystals, clearly seen where the granellare tube has disintergrated; remnants of the flimsy tube remain in places. D. Detail of crystals; note that some are interrupted by deep, sometimes rectangular, depressions. A–B taken in Geneva.

Fig. 17. Laminarena variabilis gen. et sp. nov., 32.5° N form. A–F. Specimen reg. no. TNS Pr697. A–D. Micro-CT renders. A. Oblique view of test from above showing surface features. B. Side view showing internal features. C. Detail of internal features of text extremities. D. Detail of test surface. E–F. Light photographs showing side views of test as seen through the core tube wall. E. Complete test. F. Detail showing concentric zones. G–H. Specimen reg. no. TNS Pr714. G. Complete specimen. H. Large fan-shaped extremity showing concentric zones and radial ridges. Note that the lightphotographs are somewhat distorted by the curvature of the tube wall.

Fig. 18. Laminarena variabilis gen. et sp. nov., 32.5° N form; stereo microscope images. A–B. Specimen reg. no. TNS Pr697. A. Entire fragment; this is the same part of the test as that illustrated in Fig. 17B. B. Detail of test surface. C–H. Specimen reg. no. TNS Pr714. C. Entire fragment showing concentric zones and low radial ridges. D. Broken edge of fragment with poorly developed partitions. E. Another broken edge of the same fragment with clearly developed partitions. F. Fragment broken open to show dark stercomare and pale granellare strands. G. Detail of granellare and stercomare. H. Detail showing stercomare and granellare in close proximity. I. Fragment of specimen reg. no. TNS Pr697 broken open to show stercomare and granellare, similar to those of specimen TNS Pr714. All images taken at JAMSTEC.

Fig. 19. Laminarena variabilis gen. et sp. nov., 32.5° N form. SEM images (low vacuum, backscatter mode). A–E. Specimen reg. no. TNS Pr714. A. Inner surface of fragment with partitions and stercomare. B–E. Granellare strand. B. Overview of strand. C–D. closer view of surface of granellare with areas of exposed barite crystals, apparently where the thin granellare tube has ruptured. E. Detail of granellare surface; the organic-walled tube appears crinkled but intact, obscuring any crystals that might be present beneath. F. Detail of barite crystals; note that a few have deep shadowed depressions. G–H. Specimen reg. no. TNS Pr697. G. Overview, including granellare strand. H. Detail of surface with the granellare tube apparently intact.

Fig. 21. Associated organisms. A. Laminarena variabilis gen. et sp. nov., 32.5° N form, specimen reg. no. TNS Pr697; amphipod sheltering beneath a plate. B–E. Laminarena variabilis, typical 30° N form, specimen reg. no. TNS Pr705. B. Polychaete tube. C. Calcareous polychaete (serpulid) tube. D. Cocoon of the platyhelminth Fecampia abyssicola Christensen, 1981; the neat hole was possibly made by a gastropod. E. Indeterminate ‘polyp’.

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. 6. Psammina yokosukae sp. nov., SEM images (secondary electron mode) of fragment of paratype, reg. no. TNS Pr693. A. Entire test fragment showing outer surface with interior exposed at the edge. B–D. Progressively closer views of test surface. E. Detail showing outer surface of test and coarsergrained internal surface. F. Internal surface showing stercomare (arrowed). G. Broken showing vague internal partitions. H. Detail of stercomare showing stercomata and enclosing membrane.

Fig. 7. Psammina yokosukae sp. nov., SEM images (secondary electron mode) of fragment of paratype, reg. no. TNS Pr693. A. Entire test fragment showing inner surface. B. Closer views of inner surface. C–D. Closer views of two other fragments. E–H. Granellare. E. Surface of granellare showing crinkled surface of organic tube. F. Fragment with ruptured part indicated by arrowhead. G. Detail of ruptured granellare showing thin organic tube and heterogeneous contents. H. Detail of ruptured granellare showing interior with inclusions, including a crystal (arrowed) that yielded an EDX peak for Ba. Arrowheads in B–D indicate granellare strands.

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.