Campascus minutus, from Microworld.

Belongs within: Euglyphida.

The Psammonobiotidae is a family of shelled amoeboids that live in the interstitial habitat between sand grains. Most genera in the family are marine, though the majority of Campascus species inhabit fresh water (Nicholls 2003).

Tinned psammon
Published 3 May 2018
Psammonobiotus communis, copyright Hugh MacIsaac.

In several previous posts on this site, I have discussed representatives of the remarkable group of organisms that are the Foraminifera. However, forams are not the only group of unicellular amoeboids to encase themselves in a shell. Today, I want to consider another such group, the Psammonobiotidae.

Psammonobiotids are a group of testate amoeboids forming part of (as their name suggests) the psammon, the community of organisms inhabiting the interstitial spaces between sand grains along the edge of the sea. Until the 1960s and ’70s, most authors who encountered amoebae tests in marine samples assumed that they were the remains of freshwater organisms washed downstream (Golemansky 2008). Eventually, though, it was realised that there is quite a diversity of amoeboids that not only tolerate salty conditions, they prefer it. The Psammonobiotidae was recognised in the 1970s for a number such organisms. They produce a proteinaceous test without regular scales, the test structure being amorphous or composed of irregular plates. The test is generally more or less flattend to help the organism fit into the narrow spaces between grains. An aperture at one end of the test allows the organism access to the outside world; in many cases, this aperture may be bent to one side to allow the test to lie close to its substrate.

Many psammonobiotids inhabit the supralittoral zone, just above the high tide mark. Groundwater in this region forms the contact zone between fresh water flowing out from under the land and salt water coming in from the sea. As a result, psammonobiotids and other inhabitants of this region need to be able to handle constantly shifting salinity levels. Many interstitial amoeboids can handle variations from 2% salinity in merely brackish waters to 37% in warm tropical seas (Golemansky 2008). Some normally marine psammonobiotids have even been recorded from entirely freshwater streams (Golemansky & Todorov 2007) though I personally suspect misidentifications may be involved.

The relationships of psammonobiotids to other testate amoeboids requires research (Adl et al. 2012). They possess filose rather than lobose pseudopodia, indicating relationships with other testate amoeboid groups in the Cercozoa. A leading possibility is a relation to the Euglyphida, which resemble psammonobiotids in many features but have tests with distinct scales. I haven’t found any references to any psammonobiotids being covered by molecular analyses which may reveal where they really come from.

Systematics of Psammonobiotidae

Characters (from Nicholls 2003): Test covered with irregularly-shaped, flat particles, apparently of exogenous origin. Flared collar present surrounding oral aperture.

    |--Alepiella Golemansky 1970N03, G86
    |    `--A. tricornuta Golemansky 1970G86
    |--Chardezia Golemansky 1970G86
    |    `--C. caudata Golemansky 1970G86
    |--Corythionelloides Sudzuki 1979G86
    |    `--C. fumiana Sudzuki 1979G86
    |--Micropsammella Golemansky 1970N03, G86
    |    |--M. minima Chardez & Thomas 1980G86
    |    `--M. retorta Golemansky 1970 [incl. M. retorta var. japonica Sudzuki 1979]G86
    |--Psammonobiotus Golemansky 1967G86
    |    |--P. balticus Golemansky 1973G86
    |    |--P. communis Golemansky 1967G86
    |    |--P. golemanskyi Chardez 1971G86
    |    |--P. linearis Golemansky 1970G86
    |    |--P. minutus Golemansky 1970G86
    |    |--P. plana Chardez 1971G86
    |    `--P. septentrionalis Chardez 1977G86
    |--Campascus Leidy 1877N03
    |    |--*C. cornutus Leidy 1877N03
    |    |--C. bidens Krascheninnikov 1923N03
    |    |--C. cyphoderiformis Chardez & Gaspar 1984N03
    |    |--C. dentatus Edmondson & Kingman 1913N03
    |    |--C. interstitialis Golemansky 1981N03
    |    |--C. minutus Penard 1899N03
    |    |--C. simcoei Nicholls 2003N03
    |    |--C. triqueter Penard 1891N03
    |    `--C. vulgaris Valkanov 1936N03
    |--Feuerbornia Jung 1942AS12, LT64
    |    `--*F. lobophora Jung 1942 [=Cyphoderia lobophora]LT64
    |--Frenzelina Penard 1902AS12, LT64
    |    `--*F. reniformis Penard 1902LT64
    |--Lesquerella Chardez & Thomas 1980AS12, G86
    |    `--L. mesopsammophila Chardez & Thomas 1980G86
    |--Micramphora Valkanov 1970AS12, G86
    |    |--M. amphoriformis Chardez & Thomas 1980G86
    |    |--M. atlantica Chardez & Thomas 1980G86
    |    |--M. hellebauti Chardez 1971G86
    |    |--M. pontica Valkanov 1970G86
    |    `--M. tokioensis Sudzuki 1979G86
    |--Nadinella Penard 1899AS12, LT64
    |    `--*N. tenella Penard 1899LT64
    |--Ogdeniella Golemansky 1970AS12, G86
    |    |--O. carinata (Chardez 1977)G86
    |    |--O. conica (Golemanski 1979)G86
    |    |--O. elegans (Golemansky 1970)G86
    |    |--O. lucida (Golemansky 1970)G86
    |    |--O. maxima (Golemansky 1970)G86
    |    |--O. pusilla (Chardez 1977)G86
    |    `--O. taschevi (Golemansky 1970)G86
    `--Rhumbleriella Golemansky 1970AS12, G86
         |--R. coreana Golemansky 1979G86
         `--R. filosa Golemansky 1970G86

*Type species of generic name indicated


[AS12] Adl, S. M., A. G. B. Simpson, C. E. Lane, J. Lukeš, D. Bass, S. S. Bowser, M. W. Brown, F. Burki, M. Dunthorn, V. Hampl, A. Heiss, M. Hoppenrath, E. Lara, E. Le Gall, D. H. Lynn, H. McManus, E. A. D. Mitchell, S. E. Mozley-Stanridge, L. W. Parfrey, J. Pawlowski, S. Rueckert, L. Shadwick, C. L. Schoch, A. Smirnov & F. W. Spiegel. 2012. The revised classification of eukaryotes. Journal of Eukaryotic Microbiology 59 (5): 429–493.

[G86] Golemansky, V. G. 1986. Rhizopoda: Testacea. In: Botosaneanu, L. (ed.) Stygofauna Mundi: A Faunistic, Distributional, and Ecological Synthesis of the World Fauna inhabiting Subterranean Waters (including the Marine Interstitial) pp. 5–16. E. J. Brill/Dr W. Backhuys: Leiden.

Golemansky, V. 2008. Origin, phylogenetic relations, and adaptations of the marine interstitial testate amoebae (Rhizopoda: Lobosea, Filosea, and Granuloreticulsea). In: Makarov, S. E., & R. N. Dimitrijević. Advances in Arachnology and Developmental Biology. Papers dedicated to Prof. Dr. Božidar Ćurčić pp. 87–100. Inst. Zool, Belgrade; BAS, Sofia; Fac. Life Sci., Vienna; SASA, Belgrade & UNESCO MAB Serbia.

Golemansky, V., & M. Todorov. 2007. Taxonomic review of the genus Centropyxiella (Rhizopoda: Filosea) with data on its biology and geographical distribution. Acta Zoologica Bulgarica 59 (3): 227–240.

[LT64] Loeblich, A. R., Jr & H. Tappan. 1964. Sarcodina: chiefly “thecamoebians” and Foraminiferida. In Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt C. Protista 2 vol. 1. The Geological Society of America and The University of Kansas Press.

[N03] Nicholls, K. H. 2003. Form variation in Campascus minutus and a description of Campascus simcoei sp. n. (Testaceafilosea, Psammonobiotidae). European Journal of Protistology 39 (1): 103–112.

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