Centropyxis Stein 1857

Introduction

More than 130 species and many varieties have been described. Many of these descriptions are incomplete. Type species: Centropyxis aculeata (Ehrenberg, 1838).

Characteristics

In this genus we find two different shell types:

1. Test bilaterally symmetrical, rounded, flattened more at front than at rear; ventral face flat; often spines at sides and rear. Pseudostome: ventral, anterior, roundish, dorsal and ventral lips recurved, invaginated, often bridged (see title illustration, br and Fig. 1) from ventral margin to dorsal face of the test. Shell can be organic or constructed with mineral particles or diatoms. Shape, number of spines and size extremely variable. These species prefer freshwater habitats. Typical representativea are C. aculeata or C. discoides (title illustration and Fig. 1).
   

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   Fig. 1: Centropyxis discoides in frontal side view showing the internal bridges by which the apertural rim is connected to the dorsal part of the test. © Ralf Meisterfeld

2. Shell circular or elongated in ventral view, in lateral view oral region slightly flattened, aperture subterminal, only ventral lip incurved, no bridges from ventral to dorsal face. Although some are common in freshwater habitats and sphagnum, most species of this group are found in drier mosses and humus. Typical species C. orbicularis (title illustration), Centropyxis sphagnicola or C. aerophila.

All Centropyxis have an ovular nucleus. Feeding: all types of microbiota.

References

Deflandre, G. 1929. Le genre Centropyxis Stein. Arch. Protistenk., 67:322-375.

Bonnet, L. 1989a. Données écologiques sur quelques Centropyxidae (Thécamoebiens) des sols. Bull. Soc Hist. Nat, Toulouse, 125:7-16.

Bonnet, L. & Thomas, R. 1960. Faune terrestre et d'eau douce des Pyrénées-Orientales. Thécamoebiens du sol. Vie et Milieu, 11:suppl.,1-103.

Decloitre, L. 1978. Le genre Centropyxis I. Compléments à jour au 31.12.1974 de la monographie du genre parue en 1929. Arch. Protistenk., 120:63-85.

Decloitre, L. 1979a. Le genre Centropyxis II. Compléments à jour au 31. Décembre 1974 de la monographie du genre parue en 1929. Arch. Protistenk., 121:162-192.

Decloitre, L. 1979b. Mises à jour au 31.12.1978 des mises à jour au 31.12.1974 concernant les genres Arcella, Centropyxis; Cyclopyxis; Euglypha et Nebela. Arch. Protistenk., 122:387-397.

Decloitre, L. 1982. Compléments aux publications précédentes. Mise à jour au 31.XII. 1981 des genres Arcella, Centropyxis, Cyclopyxis, Euglypha, Nebela et Trinema. Arch. Pro¬tistenk., 126:393-407.

Decloitre, L. 1986. Compléments aux publications précédentes. Mise à jour au 31. XII. 1984 des genres Arcella, Centropyxis, Cyclopyxis, Euglypha et Nebela. Arch. Protistenk., 132:131-136.

Lüftenegger, G., Petz, W., Berger, H., Foissner, W. & Adam, H. 1988. Morphologic and Biometric Characterization of Twenty-four Soil Testate Amoebae (Protozoa, Rhizopoda). Arch. Protistenk., 136:153-189.

Ogden, C. G. & Hedley, R. H. 1980. An Atlas of Freshwater Testate Amoebae. Oxford University Press, Oxford.