Vol. 47 No. 2, 2008

Fine Structure and Differentiation of the Midgut Epithelium of Allacma fusca (Insecta: Collembola: Symphypleona)

Magdalena Maria Rost-Roszkowska* and Agnieszka Undrul

Silesian University, Department of Animal Histology and Embryology, Bankowa 9, 40-007 Katowice, Poland

Magdalena Maria Rost-Roszkowska and Agnieszka Undrul (2008) Allacma fusca  belongs to a less well known, primitive, wingless insect group.  The aim of our study was to describe all changes which accompany midgut epithelium differentiation of adult specimens of A. fusca.  The midgut epithelium of A. fusca is composed of columnar cells with an epithelial character.  No regenerative cells, which are commonly responsible for midgut epithelium regeneration, were observed.  Therefore the growth of the entire epithelium depends on an increase in the dimensions of epithelial cells.  Epithelial cells are not able to proliferate, as was earlier suggested, in the 1st larval stage of this species.  The characteristic regionalization in the organelle arrangement was observed like in all epithelia responsible for secretion, transport, and excretion.  However during the insect's lifespan, distinct differences appear between all epithelial cells.  Allacma fusca does not have Malpighian tubules; thus the midgut epithelium is also responsible for excretion.  This process is connected with urospherites which accumulate in epithelial cells.  Their structure suggests that they might be identified with type A granules described for many Pterygota insects.

Key words: Midgut epithelium, Differentiation, Stem cells, Urospherites.

*Correspondence: Tel: 48-32-3591376.  E-mail:mrost@us.edu.pl