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Sex and the single Amoeba

Page updated 14/8/02

Amoeba are notoriously celibate.  This is one of the first things that we learn about amoeba at school.  However, there are indications that amoeba do in fact take part in sexual or at least parasexual activities.  Parasex seems to occur sporadically through many unconnected genera of amoeba.  This may reflect sex being "invented" (or lost) at various times throughout amoeboid lineages. Perhaps a testament to the utility of sex?

Acrasis.  Now strongly suspected of being a member of the Heterolobosea , Acrasis produces spores like slime moulds in a parasexual process.

Heteramoeba clara.  I confess that I do not understand the crossing experiments undertaken by Droop (Droop, 1962) to determine evidence for a sexual cycle in this amoeba.

Sapinia diploidia Suggested of carrying out nuclear exchange in the binuclear cyst (Goodfellow et al, 1974).

Flabellula baltica.  Cell fusion has been observed between individuals in population of the marine amoeba Flabellula baltica (Smirnov, 1999).  There may of course be a number of explanations for this behaviour, this could for example be a method by which benificial symbioitc bacteria are passed around but a more obvious interpretation is that this is a sexual process.  If this process is more widespread amongst other amoebal species then this would have worrying repercussions on the validity of mitochondrial DNA lineage analysis and the great new hope that SSUrDNA anaysis promises!!  This would if it happened even at low levels then horizontal transmission of these genes may occur frequently, especially in the percolozoa amoeba and the entamoebida which have there ribosomal DNA genes on multicopy plasmids!,

References:-

Droop, M. R. (1962) Heteramoeba clara n.gen, n.sp., a sexual biphasic amoeba. Archiv Für Mikrobiol. 42, 254-266.

Goodfellow, L. P., Belcher, J. H. & Page, F. C. (1974) A light and electron-microscopical study of Sappinia diploidea a sexual amoeba. Protistologica. 10, 207-216.

Smirnov, A. V. (1999) An illustrated survey of gymnamoebae isolated from anaerobic sediments of the Niva bay (the Sound). Ophelia. 50, 113-148.

 
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