Tuatara: Volume 21, Issue 3, April 1975
The Xenophyophores of New Zealand (Rhizopodea, Protozoa)
The Xenophyophores of New Zealand (Rhizopodea, Protozoa)
The Xenophyophores are a group of marine, giant protozoans (Schulze, 1907) recently established as a sub-class of the Rhizopodea (Tendal, 1972). They are known to live on the seabed at depths ranging from 1 m. to 7,000 m. but have been reported commonly only from abyssal depths. In this paper I wish to draw attention to their presence in New Zealand waters in the hope that they be recognised more commonly in the future.
Xenophyophores were first reported from New Zealand by Lewis (1966) who described a new species of Syringammina, a genus then regarded as belonging to the arenaceous foraminifera. Subsequently several specimens that appeared to be allied to Syringammina were sorted from trawl samples by Mr. W. de L. Main of the New Zealand Oceanographic Institute. These were kindly loaned to me for identification. For a full description of these and all other known xenophyophores, together with a review of their biology and taxonomy, the reader is referred to the report by Tendal (1972).
Recognition of Xenophyophores
Xenophyophores are by far the largest protozoans known; they range in size from 1 mm. to 25 cm. Nevertheless, they are frequently overlooked. Most of them have an external test which is composed of agglutinated grains termed xenophyae. The xenophyae, which may be mineral grains, sponge spicules, foraminiferal tests or radiolarian tests, are only loosely cemented so that the test is fragile. Depending on the abundance of xenophyae, the test may feel like a friable sandstone, a doughy lump or a wet rag. The form of the test may be spherical, plate-like, irregular or a ball of anastomosing walls or tubes. Xenophyophores may easily be mistaken either for broken and decayed parts of other animals such as sponges, foraminifera, coelenterates, bryozoans and ascidians or for inorganic concrements. Such dubious material is generally handled and investigated with care only where other biological material is scarce. This lack of care may be the reason for by far the largest number of xenophyophores being recorded from abyssal depths. However, the New Zealand material was recognised in biologically rich environments on the upper part of the continental slope despite the fact that it is amongst the most fragile ever found.
Much of the internal structure of the xenophyophores can be investigated with a common dissecting microscope, the specimen being page 93 immersed in alcohol or water. Their cytology can be viewed in stained sections but good sections are difficult to obtain because the xenophyae are difficult to cut and tend to cause displacement of other structures.
Biology of Xenophyophores
The xenophyophores are protozoans whose protoplasm is contained largely in branched, transparent, organic tubes. The tubes, which are filled with plasma, are called granellare. The plasma includes nuclei of several different types as well as flat, rounded or spindle-shaped crystals of barium sulphate known as granellae. Part of the plasma protrudes from open ends of the tubes as branching pseudopodia which spread out over the surrounding substrate.
Most of any xenophyophore is dead matter. This includes large, membrane-covered masses of faecal pellets, known as stercomare, which are retained outside the tubes, perhaps as protection and support for the tubes. The stercomare are characteristic of the xenophyophores. Tubes and stercomare are generally enclosed by an exterior wall of xenophyae, which are loosely cemented by a mucopolysaccharid.
Xenophyophores probably feed on bacteria that live on the surrounding substrate. Food is collected by the pseudopodia which also collect xenophyae and may move the animal along. Pseudopodial fans have been seen in photographs of xenophyophores living on the abyssal ocean floor near New Britain (Western Pacific) (Lemche et al.). Because xenophyophores are commonly recorded from areas of high surface production or from close to land, it is thought that they require a relatively large food supply.
A few shallow-water species have biflagellate gametes and therefore must reproduce by gametogamy. Amoeba-like stages occur in the life cycle, but their role is not definitely decided. Some deep-sea species appear to have amoeboid gametes and therefore may also reproduce by gamontogamy. In a number of species, for instance within the genus Syringammina, the juvenile stages have a test morphology that is different from the adult.
Classification and Description of the New Zealand Xenophyophoria
Phylum PROTOZOA * von Siebold, 1845
Subphylum SARCOMASTIGOPHORA Honigberg and Balamuth, 1963
Superclass SARCODINA Hertwig and Lesser, 1874
Class RHIZOPODEA von Siebold, 1845
Subclass XENOPHYOPHORA Tendel, 1972
Rhizopodea with plasma in strongly branched tubes, granellae in the plasma, and voluminous masses of faecal pellets (stercomare) retained outside the tubes.
The subclass Xenophyophoria has two orders. All known New Zealand specimens belong to the order Psamminida which contains xenophyophores of page 94 very different appearance and is divided into four families, two of which are represented in the New Zealand material.
Family Psamminidae Haeckel, 1889
Genus Reticulammina Tendal. 1972
Test lumpy with numerous anastomosing branches. The texture is friable, The branches have two layers: a thin, hard exterior layer of cemented fine granular matter with some xenophyae and a thick interior layer containing xenophyae loosely associated with granellare and stercomare.
Reticulammina novazealandica Tendal, 1972
Fig. 1—middle left, middle right
R. novazealandica n. sp., Tendal 1972, p. 29, pl. III, E-G
R. novazealandica is the type species for the genus.
Description: Two specimens and a fragment are known. The body is rounded, somewhat flattened on one side, and measures up to about 60 mm. in diameter. It consists of anastomosing, lamella-like branches measuring 3-7 mm. in width, most of them about 5 mm. The open spaces in the network are circular or oval, and are 2-10 mm. wide. The colour is light grey. The internal xenophyae are foraminiferan tests. The thin surface layer consists of wellcemented calcareous matter with only a few foraminiferan tests.
The reddish-brown granellare are 40-60 mic. in diameter. Granellae seem to be scarce; they are rounded, elongate, and measure 1-3 mic. in length. Nuclei are spherical to ellipsoidal and measure 3-5 mic. in diameter. The stercomare anastomose and are 40-150 mic. in diameter.
Localities: NZOI Sta. E903 a, b: 37° 33′ S., 172° 05′ E.; top of Aotea Seamount; depth—a, 960 m., b, 984 m.; bottom—volcanic rock with thin covering of foraminiferal sand; temperature§—about 5° C. 2 specimens.
NZOI Sta. F913, 34° 43.5′ S., 174° 31.5′ E.: continental slope off Bay of Islands; depth 743 m.; bottom—foraminiferal sand with detrital mud; temperature—about 7° C. 1 fragment.
Reticulammina labyrinthica Tendal, 1972
Fig. 1—upper right
R. labyrinthica n. sp., Tendal 1972, p. 30. pl. III, H; IV, A
Description: Two specimens are known. The body is rounded, somewhat flattened on one side, and measures up to about 23 mm. in diameter. It consists of anastomosing branches that are circular or flattened in cross-section, and measure 1-2 mm. in diameter. The open spaces in the network are circular or oval, and are 1-8 mm. wide. The colour is whitish. The internal xenophyae are foraminiferan tests. The surface is covered by a well-cemented thin layer of fine, granular calcareous and silicious material.
The granellare measure 25-60 mic. in diameter. Granellae are rare; they are rounded and measure up to 5 mic. in diameter. Nuclei are spherical to slightly ellipsoidal and measure 3-5 mic. in diameter. The stercomare measure 25-160 mic. in diameter.
Fig. 1—Upper left: Reticulammina lamellata, top view; X 1.5. Upper right: R. labyrinthica, top view; X 2.2. Middle left: R. novazealandica, top view; X 1.5. Middle right: R. novazealandica, side view; X 0.8. Lower left: Syringammina fragilissima fragment, side view; X 3.2. Lower right: S. tasmanensis, side view of sectioned paratype; X 1.8.
Reticulammina lamellata Tendal, 1972
Fig. 1—upper left
R. lamellata n. sp., Hendal 1972, p. 31, pl. IV, B-C
Description: One specimen is known. The body is lumpy and somewhat flattened, measuring 32 mm. in diameter and 15 mm. in height. Most of the anastomosing branches are lamellate, 1-2 mm. wide; a few are nearly circular in cross-section and measure about 1 mm. in diameter. Large irregular cavities occur between the branches. The colour is greyish. The internal xenophyae are sand grains. The surface is covered by a thin layer of sand grains and fine granular matter.
The yellow-brown grannellare measure 12-90 mic. in diameter. Granellae are up to 5 mic. in length. The stercomare measure 50-120 mic. in diameter.
Locality: NZOI Sta. F881, 37° 07.8′ S., 177° 14′ E.; continental slope off Bay of Plenty; depth—1253 m.; bottom—foraminiferal sand with sand and glauconite; temperature—about 4° C. 1 specimen.
Family Syringamminidae Tendal, 1972
Genus Syringammina Brady, 1883
The test is constructed by numerous tubes of tightly cemented xenophyae. The tubes are arranged in a radiating manner, single tubes being connected with other tubes by side branches. The xenophyae are restricted to the tube walls, and only granellare and stercomare are found in the interior.
Syringammina fragilissima Brady, 1883
Fig. 1—lower left
S. fragilissima n. sp., Brady 1883, p. 158, pl. 2: 1-5; 3: 6-8
S. fragilissima, Tendal 1972, p. 36, pl. VI, A-E
Description: The single New Zealand specimen is a nearly spherical fragment about 9 mm. in diameter. The colour is grey, and the test is very fragile. The anastomosing lateral radial tube branches are arranged in relatively conspicuous layers 0.9-2.8 mm. apart. The tube diameter ranges from 0.5-1.6 mm. and tubes with different diameters are intermingled. The xenophyae are sand grains, mineral particles, and fine grained material.
Each tube contains three to six peripheral longitudinally extending head branches of granellare and one centrally placed, thick stercomare mass. The granellare measure 20-140 mic. in diameter. Granellae are oval or rounded, most of them less than 1 mic. in diameter. The stercomare measure 200-540 mic. in diameter.
Locality: NZOI Sta. E417, 45° 12′ S., 171° 49′ E.; continental slope off Otago; depth—860 m.; bottom—detrital sandy mud with shells and foraminifers; temperature—about 5.5° C. 1 fragment.
Syringammina tasmanensis Lewis, 1966
Fig. 1—lower right
S. tasmanensis, n. sp., Lewis 1966, p. 114, fig. 1-8
S. tasmanensis, Hedley 1966, p. 114, fig. 1
S. tasmanensis, Tendal 1972, p. 38, pl. V, D-E; XVI, F
Description: Six specimens are known. The body is roughly hemispherical and up to 44 mm. in diameter. The colour is light grey, and the test is extremely friable. The radial tubes anastomose irregularly in the centre, and more regularly in the periphery where the lateral tube branches form concentrically arranged consecutive layers mostly 0-0.6 mm. apart. The tubes are mostly 1.1-1.5 mm. in diameter. The xenophyae are predominantly foraminiferan tests and fine-grained calcareous matter.
Each tube contains one central granellare branch and 2-4 peripheral stercomare masses. The granellare measure 115-193 mic. in diameter. Granellae measure up to 5 mic. in length. Nuclei are spherical to almost ellipsoidal and 2-3 mic. in diameter. The stercomare measure 77-460 mic. in diameter.page 97
Localities: NZOI Sta. D227, 39° 50′ S., 169° 43′ E.; on the Challenger Plateau; depth — 711 m.; bottom — globigerina ooze; temperature — about 6.5° C. 4 specimens.
NZOI Sta. D228, 39° 08′ S., 170° 17′ E.; on the Challenger Plateau; depth — 664 m.; bottom — globigerina ooze; temperature — about 8° C. 2 specimens.
* High-level classification according to Honigberg et al. (1964).
§ The temperatures are from Garner and Ridgway (1965).