Distribution, abundance, and size of rhabdoids in Dugesia polychroa. (Turbellaria: Tricladida)

Abstract

The ontogenetic changes in the distribution, abundance, and size of rhabdoids were examined in an undisturbed laboratory population of Dugesia polychroa. Irrespective of triclad age, rhabdoids in the epidermis and parenchyma were more abundant on the dorsal than the ventral side of the body. No significant differences were found in the abundance of epidermal or parenchymal rhabdoids among the anterior, medial, and posterior regions of the body. Rhabdoid number and size changed significantly with triclad age, with a marked depression coinciding with the onset of cocoon production . Rhabdoid discharge was correlated with physical and/or physiological disturbance and occurred in the absence of any overt environmental disturbance. Simple allometric relationships were observed between rhabdoid size and number on one hand and body plan area on the other. Different allometric trends were observed from field-collected individuals compared to the undisturbed laboratory population . The potential function of rhabdoids in the Tricladida is discussed in light of these findings .

The Effect of Aluminium on the Planarian Polycelis felina (Daly.)

“…Histological analysis of non treated planarian (Polycelis felina) tissue showed typical structure as it is found in other planarian species. They are covered with simple one-layer epidermis which includes defense glandular structures called rhabdites (Wrona 1986). Under epidermis basal membrane and muscular layer are placed.…”

“…Therefore, the next body layer, the muscular layer, was found at the very surface of the planarian body, covered with the thick mucus layer. Due to the damaged epithelial layer that contains rabdites, which on chemical stimulation starts to decompose on acid mucopolysaccharides for a protection (Wrona 1986), we assumed that the muscular layer is next to be damaged. Morphometric analyses showed the same: the thickness of the muscular layer decreased with the increasing concentration.…”