A Study of the Microstructure of Tubifex Species with a Reference to Heavy Metal Pollution

The microstructure of the somatic and generative tissues of the freshwater tubificid oligochaete, Tubifex tubifex Müller, is reported. Descriptions, for the majority of tissues, are based on ultrastructural studies. The morphological account is supplemented by histochemical analyses of protein, carbohydrate and lipid moieties within selected tissue components. These include the cuticle, the chloragosome granules within chloragogen cells, oocytic yolk granules and the secretory material within the gland cells of the clitellum, atrium, prostrate gland and spermatheca.
The order of increasing toxicity of four heavy metals to T. tubifex was iron < zinc < copper < cadmium with 48 hour LC50 values of >10, 9.25, 0.22 and 0.13 mg/l respectively.
The accumulation of zinc-65 by the organism was essentially linear throughout 20 days, Uptake of the radioisotope was greater at 5 mg/1 Zn than at 1 mg/1 Zn but was suppressed by the presence of an antibiotic.
The cytochemical location of specific and non-specific heavy metals occurred within chloragosomes, cuticle, chaetal sacs and, to a lesser extent, intestine, epidermis and blood plasma. Ultrastructural sites of heavy metals were principally within areas of low metabolic activity.
The somatic tissue most sensitive to zinc-induced pathology was the body wall musculature followed by the epidermis, intestine and chloragogen tissues. The fine structural degenerative changes within these tissues following zinc pollution are described and equated with those resulting from non-chemical stress (heated medium).
Cytolocation of zinc occurred within the lumen of nephridia following incubation in zinc-rich medium.