Studies on the heavy spherical (refractive) bodies of freshwater Amoebae. I. Morphology and regeneration of HSBS in Chaos carolinense

Abstract

*Supported by The Carlsberg FoundationThe heavy spherical bodies of Amoeba and Chaos are refractive organelles, varying in size from ca. 10 ~tm in diameter, down to the limit of resolution of the light microscope. These inclusions have many characteristics in common with the phosphate-rich, Jvolutin~ granules of other unicellular organisms, but differ from the latter in being constantly present in healthy growing amoebae, while in other organisms they appear only under conditions of nutritional imbalance. The fine structure of the HSBs of Amoeba and Chaos show that the organelles are membrane-bound, with an electron translucent periphery, and an electron dense inner core which sublimes in the electron beam, but which is stabilized by lead staining. During centrifugation in vivo, the HSBs collect at the centrifugal pole of the amoebae; under favourable conditions, a HSB-sack is formed at the heavy pole, and can be excised, leaving amoebae, normal in other respects, but containing only ca. 5% of the normal complement of HSBs. Using this method for obtaining practically HSB-free amoebae, the regeneration of HSBs was studied in Chaos carolinense, by determining the number and size distribution of HSBs in a standard volume in fixed, whole mounts by phase contrast microscopy. It was found that although the number of HSBs per standard volume in both fed and starved amoebae returned to that found in control, unoperated, Chaos by 7 days after operation, the size distribution did not return to normal until ca. 50 days after excision of the HSBs, indicating that HSBs originate from precursors in the cytoplasm. Operated amoebae showed normal feeding and locomotory behaviour, and their division rate was similar to that of control amoebae. However, HSB-free amoebae were more prone to rupture at an air-water interface, presumably owing to their lower specific gravity.

Effect of body deformability on microswimming

“…In nature, this class of microswimmers is predominant. [26][27][28][29][30] For artificial swimmers, chemically driven mechanisms are as popular as mechanical ones. [31][32][33][34][35][36][37] An important consideration in mechanical microswimming is the way elastic forces interact with the fluid and any external forces present in determining the motion.…”