Centropyxis Stein, 1859

Samant, Bandana, Kumar, Arun, Mohabey, D. M., Humane, Sumedh, Kumar, Deepesh, Dhoble, Anup & Pizal, Priya, 2020, Centropyxis aculeata (testate lobose amoebae) and associated diatoms from the intertrappean lacustrine sediments (Maastrichtian) of central India: Implications in understanding paleolake ecology, Palaeontologia Electronica (a 60) 23 (3), pp. 1-18 : 6

Genus Centropyxis Stein, 1859 (ref. Patterson, R. T. and Kumar, A. 2002, Palaeo 3, 180:225-251)

Type Species. Centropyxis aculeata (Ehrenberg, 1832) ( Figures 5 , 6.1 )

Description. Test bilaterally symmetrical, outline subcircular to ovoid; shell composed of proteinaceous matrix with agglutinated mineral grains and diatom frustules; aperture sub-terminal or eccentric, invaginated, with multiple spines (Ellison and Ogden, 1987). In the present assemblage, some spines are intact but many are often broken, vary between two to five or sometimes more, and test size varies between 60 µm to 75 µm.

Diatoms

Many well-preserved frustules of pennate and centric diatoms were found attached on the Centropyxis aculeata tests . Diatoms could be identified only to the genus level because the central area, valve face or margins were often difficult to observe ( Figure 6 ). Therefore, identification was assigned to the generic level, and species names are tentative and presented in parentheses with a question mark. The observed centric diatoms are Cyclotella sp. , Aulacoseira sp. , and Pantocsekiella sp. ; pennate diatoms include Achnanthes sp. Diadesmis sp. , and Oricymba sp.

Figures

FIGURE 5. (Scale bar for figures 1-6 is 10 µm; EF is England Finder Reading). 1-3. LM photograph of Centropyxis aculeata (Ehrenberg, 1832); 1. Slide no. 1A6, EF H48; 2. 1A3, EF K 40/2; 3. 1A4, EF K40/3. 4. LM photograph of Centropyxis aculeata (Ehrenberg, 1832) with big xenosomes of silica; Slide no 1A4, EF O61/2. 5-6. LM photograph of Centropyxis aculeata (Ehrenberg, 1832) showing presence of xenosomes of variety of diatoms as well as silica grains on the test; 5. Slide no 1A3, EF U38; 6. 1A1, EF E56/1. 7. SEM photograph of Centropyxis aculeata (Ehrenberg, 1832) showing presence of xenosomes of silica. 8. SEM showing magnified view of the same as 7. 9. SEM photograph of Centropyxis aculeata (Ehrenberg, 1832) showing presence of xenosomes of diatoms on the test. 10. SEM photograph of Centropyxis aculeata (Ehrenberg, 1832) showing presence of xenosomes of centric diatoms and silica grains on the test. 11-12 and 15 Centric diatom Cyclotella sp. on the test of Centropyxis aculeata (Ehrenberg, 1832). 13,14. SEM photographs of Centropyxis aculeata (Ehrenberg, 1832).

FIGURE 6. 1. SEM photograph of Centropyxis aculeata (Ehrenberg, 1832). 2. SEM photographs of the centric diatom Pantocsekiella sp. (internal valve view) on the test of Centropyxis aculeata (Ehrenberg, 1832). 3 and 5. SEM photographs of the pennate diatom Achnanthes sp. on the test of Centropyxis aculeata (Ehrenberg, 1832). 4. SEM photograph of the pennate diatom Oricymba sp. on the wall of Centropyxis aculeata (Ehrenberg, 1832). 6. SEM photograph of the pennate diatom Diadesmis sp. on the wall of Centropyxis aculeata (Ehrenberg, 1832).