Crinoid Regeneration and Endocrine Disrupters

On the basis of their spectacular regenerative capabilities, crinoid echino-derms are prime candidates for this ecotoxicological approach. In particular, as previously explained, in the common feather star, A. mediterranea, arm regeneration is a common phenomenon which can be easily studied under laboratory conditions thanks to the favourable possibility of inducing experimentally arm autotomy and subsequent regeneration (Fig. 1 c,d), and following the complete regrowth of the lost arm in a relatively short period of time (about 3 weeks). A. mediterranea is a widespread species in the Mediterranean Sea, representative of the benthic fauna and easily found. It is a microsuspension-feeding organism on which persistent sediment-bound pollutants have an immediate impact: it can, in fact, concentrate persistent and hydrophobic pollutants directly by primary uptake from water and from suspended matter and sediment, and secondarily from food, thus giving rise to significant biomagnification phenomena. These animals can be maintained in the laboratory for many months and, due to their remarkable capacity for survival, are particularly amenable to the experimental approach. For all these reasons, A. mediterranea should be considered as a suitable ecotoxico-logical model to test endocrine-disrupting activity of selected compounds on a typical marine species. This idea has been recently confirmed by a series of preliminary results obtained with specimens exposed to specific contami nants belonging to the ED class, which have clearly shown a wide range of interesting potential effects of the exposure to these pollutants on the regenerative processes at all levels,macroscopic and microscopic (Candia Carnevali et al. 2001a,b, 2003).

In this chapter, we analyse and compare the effects of exposure to different classes of ED compounds on the process of arm regeneration in A. mediterranea. The selected types of test compounds are: polychlorinated biphenyls (PCBs), nonylphenols (4-NP) and tripheniltin (TPT-Cl) (Fig. 3). PCBs are commercial products widely used as heat transfer fluids, hydraulic fluids, flame retardants and dielectric fluids because of their unique properties, including resistance to biological and chemical oxidation and nonflammabil-ity. Nonylphenols are products of the slow and incomplete biodegradation of nonylphenol polyethoxylates which are widely employed for domestic and industrial uses. TPT-Cl is a typical organotin compound, extensively used in agriculture and in antifouling paints, which tends to accumulate in the soil and sediments.

The widespread use of these different compounds coupled with improper disposal has led to significant global environmental contamination. Although acute and chronic toxicity tests with benthic freshwater animals have being developed for these contaminants, they have to be still definitely established for marine organisms. These three classes of chemicals have widely documented endocrine-disrupting activities which can be expressed by contrasting effects on the exposed animal models. The first two com-

4-NP

Fig. 3. The tested molecules: typical endocrine disrupter compounds

Fig. 3. The tested molecules: typical endocrine disrupter compounds

TPT-Cl pounds (PCBs, 4-NP) are included in the category of contaminant with estrogenic effects (anti-estrogenic or estrogenic, respectively) (Granmo 1991; Arnold et al. 1996; Dickey 1997; Depledge and Billinghurst 1999; ); the third (TPT-Cl) is a typical compound with androgenic effect (Fait et al. 1994; Matthiessen and Gibbs 1998). The aim of this study is (1) to offer a comparative account of the possible insidious effects of exposure to ED contaminants on developmental physiology of typical marine animals, with particular reference to mechanism(s) of action of EDs on growth, differentiation, and repair/regeneration processes at the whole organism, tissue and cellular level in the model species, and to possible homeostatic mechanisms through which the organism can interact and adapt to adverse environmental conditions; and (2) to assess the validity of the regenerative response for bioassay. A relevant point is that in our experiments, exposure to EDs was performed in seawater at concentration ranges reproducing those of moderately polluted coastal areas. The idea was to simulate realistic exposure conditions for wildlife marine fauna.

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