Ipoa, TENDAL & HESSLER, 1977

Gooday, Andrew J., Kamenskaya, Olga E. & Cedhagen, Tomas, 2007, New and little-known Komokiacea (Foraminifera) from the bathyal and abyssal Weddell Sea and adjacent areas, Zoological Journal of the Linnean Society 151 (2), pp. 219-251 : 234-240

publication ID	https://doi.org/ 10.1111/j.1096-3642.2007.00326.x
DOI	https://doi.org/10.5281/zenodo.10544909
persistent identifier	https://treatment.plazi.org/id/CC41BE6E-FFE1-3A77-5BB3-FE7B2ACDFBA7
treatment provided by	Felipe
scientific name	Ipoa
status

Treatment

GENUS IPOA TENDAL & HESSLER, 1977 View in CoL

Type species: Ipoa fragila Tendal & Hessler, 1977

IPOA FRAGILA TENDAL & HESSLER, 1977 View in CoL

( FIGS 10 View Figure 10 , 11 View Figure 11 )

Ipoa fragila Tendal & Hessler, 1977, p. 181 View in CoL , pl. 9 fig. D, pl. 11, fig. C–D

Ipoa fragilis Tendal & Hessler. Schröder, Medioli & Scott, 1989, p. 24 , 28; pl. 1, fig. 1–3; pl. 8, fig. 4; textfig. 7

Ipoa fragila Tendal & Hessler. Kamenskaya, 1993, p. 79 View in CoL

Diagnosis: Test periphery contained within a rounded, often oval, slightly flattened envelope. Central tubule often discernible; irregular in width, and typically constricted where it gives rise to a relatively small number of primary branches. These main trunks radiate from central part and break up into burst of tightly spaced peripheral branches, giving them tree-like appearance. Diameter of tubules decreases markedly with each branching. Tubules non-septate. (Modified after Tendal & Hessler, 1977.)

Holotype: Argo H-30, central North Pacific , epibenthic sledge sample: 30°05′N, 156°12′W; 6065–6079 m water depth. Zoological Museum, Copenhagen; preserved in alcohol. GoogleMaps

ANDEEP material: Stn 59#9, 1 small fragment; Stn 59#11, 2 fragments; Stn 88#5, 1 specimen; Stn 88#7, 1 specimen; Stn 88#8, 4 complete, 10 fragments; Stn 94#5, 1 specimen; Stn 94#11 4 larger?complete, 18 fragments; Stn 94#14, 4 complete specimens, 2 fragments; Stn 102#10, 1 small piece; Stn 102#13, 1 specimen; Stn 110#8, 12 complete, 3 fragments.

Description of holotype

The holotype is light brownish in colour and consists of one large and numerous tiny fragments ( Fig. 10 View Figure 10 ). It is much less complete than shown in the photograph of Tendal & Hessler (1977: pl. 9, fig. D). The large piece measures 1.67 × 1.33 mm and consists mainly of the inner branches that are 120–140 µm in diameter. These main branches give rise to narrow tubules, end- ing in twig-like branches 40–50 µm in diameter. Many of the branches are broken.

Description of ANDEEP material

A number of specimens from Stns 88, 94 and 110 appear to be complete. They have a generally rounded, sometimes oval and usually more or less flattened shape ( Fig. 11A–F View Figure 11 ). The largest is 3.1 mm long, 2.5 mm wide and 2.0 mm high. Other specimens that we judge to be more or less complete measure 1.7– 2.5 mm long, 1.0– 2.5 mm wide and 0.8–1.6 mm high. The central tubule is irregular in width (100–140 µm), and often constricted one or more times where it gives rise to the relatively small number of primary branches, typically ∼80 µm in diameter. It is not always possible to distinguish clearly between the cen- tral and the primary tubules. In one complete specimen, the central tubule has a closed end, presumably the initial part. The broader inner tubules branch repeatedly into a profusion of narrow outer branches, 30–60 µm in diameter. The walls of the tubules are composed of fine-grained particles studded with small, often angular quartz grains (20–40 µm in diameter). Some specimens incorporate a few large mineral grains or planktonic foraminiferal tests.

Remarks

The ANDEEP material includes a larger number of complete individuals than were available to Tendal & Hessler (1977). In the largest holotype fragment, the inner primary branches are prominent and rather wider than in typical ANDEEP specimens. Tendal & Hessler give diameters of 150–190 µm for these primary branches compared with 100–140 µm in our specimens. In other respects, however, our specimens conform closely to Tendal & Hessler’s (1977) description.

Distribution

First described from the Central North Pacific ( Tendal & Hessler, 1977), subsequently from ∼ 5770 m water depth on the Nares Abyssal Plain, north-west Atlantic ( Schröder et al., 1989) and at two stations (2790 and 4912 m) in the Cape Basin ( Kamenskaya, 1993). In our material it occurs in the eastern and central Weddell Sea (4649–4934 m).

IPOA PENNATA SP. NOV.

( FIGS 12 View Figure 12 , 13 View Figure 13 )

Diagnosis: Test bush-like; inner part consists of wide primary tubules that divide into narrower peripheral branches. These outer branches follow a more or less crooked course and give rise to short side branches, usually either more or less tubular or, less commonly, bead-like in shape. Tubules non-septate.

Type material and locality: The holotype and two paratypes were collected from Stn 88#7 using a large boxcorer (Grosskastengreifer); 68°3.61′S, 20°27.99′W; 4934 m water depth. They are preserved in 4% buffered formalin and deposited in the ForschungsInstitut Senckenberg, Frankfurt am Main, under reg. nos. SMF XXVII 7531 (holotype) and XVII 7532 (two paratypes) GoogleMaps .

Other material examined: Stn 88#8, 24 specimens; Stn 94#7, 1 specimen; Stn 102#8, 2 specimens; Stn 102#13, 26 larger specimens and 15 obvious fragments.

Derivation of name: Latin pennatus = with feathers, alluding to the sometimes feathery appearance of the test branches.

Description of type specimens.

Holotype: The test measures 1.80 × 1.30 mm and is rather flattened ( Fig. 12B View Figure 12 ). It forms a bush-like structure with branches radiating out from a central region. Individual tubules can be seen clearly only around the periphery of the test. The inner part consists of a compact cluster of branches that obscures the central structure. The individual branches become clearer in the outer half of the test. They have an irregular and complex form in which a more or less tubular shaft, 60–80 µm in diameter, gives rise to short, unevenly spaced side branches. Many of these are also tubular in form but the shorter ones are more beadlike. On one branch, short, paired, forward-pointing side tubules create two arrowhead-like sections joined by a narrow neck ( Fig. 12D View Figure 12 ).

Paratype 1: The test measures approximately 2.0 × 1.7 mm and is somewhat flattened and rather less compact than the holotype ( Fig. 12A, B View Figure 12 ). The structure of the branches is similar to that seen in the holotype. Neck-like constrictions between some sections of the branches create chain-like formations.

Paratype 2: The second paratype measures 1.95 × 1.45 mm and is distinctly flattened ( Fig. 12E View Figure 12 ). The structure is more open than that of other two type specimens. The inner part of the test has several short, thick branches, 100–160 µm in diameter, which merges into the narrower, peripheral branches. These outer branches are crooked with short, mainly tubular side branches ( Fig. 12F View Figure 12 ).

In all three type specimens, the wall is off-white in colour. It is opaque, soft, fine grained but with scattered small quartz grains (usually no more than 20 µm in size) which glint in reflected light, and small dark grains. Large agglutinated particles are not present. The test interior is occupied by large, oval stercomata, most of them 25–40 µm in maximum dimension. There are no septa.

Description of other material.

Stn 88#8: Specimens range in size from 1.20 × 1.00 mm to 1.30 × 1.80 mm. In many cases, the thicker central branches are clearly developed. These sometimes consist of several lobate sections separated by constrictions ( Fig. 13B View Figure 13 ). The branching pattern of the narrower peripheral branches is often difficult to discern but seems to be largely dichotomous. The available material exhibits some variation, particularly in the development and form of the side branches of the main peripheral branches ( Fig. 13C, D View Figure 13 ). The side branches are often more or less tubular (cylindrical) but some of the shorter ones taper and are more conical in shape. In places, the branches are interrupted by necks to create one or more irregularly shaped segments. One specimen has a compact test and distinctly thicker side branches which give it a less delicate appearance than typical specimens.

Stn 102: Specimens measure from 1.20 × 1.30 mm to 1.80 × 2.00 mm. The thicker central branches are often clearly developed and rather irregular in width (80–140 µm) ( Fig. 13A, E, F View Figure 13 ). The side branches are usually 40–60 µm in diameter and similar in shape to those of the type specimens. However, in one case, they form rather elongate, finger-like projections while in another they are rounded and bead-like in form. The test wall is ∼15–30 µm thick and similar in colour to specimens from Stn 88. The wall incorporates a few fairly large particles (100–200 µm), in addition to numerous tiny quartz grains.

Remarks

We place this species in the genus Ipoa based on the presence of thick, radiating, basal branches which occupy the inner part of the test and divide to form narrower, peripheral branches. A distinctive feature of the new species, which distinguishes it from Ipoa fragila , is that the peripheral branches give rise to short, irregularly developed lateral processes, tubular, conical, or less commonly bead-like in form. The branches are also sometimes interrupted by narrow constrictions that divide them into one or more short, distinct sections. Interestingly, these sections resemble parts of some chain-like komokiaceans, notably Arbor multiplex , as illustrated by Schröder et al. (1989), as well as the chambers of Edgertonia floccula , as illustrated by Shires, Gooday & Jones (1994). However, the fine ‘fibres’ present in these species have not been observed in specimens of Ipoa pennata .

Distribution

The new species occurs in the central Weddell Sea (4803–4934 m water depth).