Comparative avoidance behaviour of the earthworm Eisenia fetida towards chloride, nitrate and sulphate salts of Cd, Cu and Zn using filter paper and extruded water agar gels as exposure media.

We studied the avoidance behaviour of the earthworm Eisenia fetida towards Cd, Cu, and Zn, trace elements (TEs) tested as chloride, nitrate and sulphate salts. Sub adults were exposed individually using dual-cell chambers at 20+2°C in the dark. Recordings were realised at different dates from 2h to 32h. We used filter paper and extruded water agar gel as exposure media to evaluate the contribution of the dermal and the digestive exposure routes on the avoidance reactions. Exposures to Cu or Cd (10mgmetal ionL(-1)) resulted in highly significant avoidance reactions through the exposure duration. Worms avoided Zn poorly and reactions towards Zn salts varied along the exposure. Worm sensitivity towards TEs differed between salts and this could result from differential toxicity or accessibility of these TE salts to earthworms. The anion in itself was not the determinant of the avoidance reactions since exposures to similar concentrations of these anions using calcium salts did not result in significant avoidance worm behaviour. Avoidance responses towards TEs were higher in the case of water agar exposures than in filter paper exposures. Thus, dermal contacts with TE solutions would elicit worm avoidance but signals from receptors located inside the digestive tract could reinforce this behaviour. The use of extruded water agar gels as the substrate allows checking the real sensitivity of earthworm species towards TEs since the TE concentrations leading to significant avoidance reactions were below those reported in the literature when using TE-spiked soils.

Centrosomal CAP350 protein stabilises microtubules associated with the Golgi complex.

A comprehensive model of how the centrosome organises the microtubule network in animal cells has not yet been elucidated. Here we show that the centrosomal large CAP-Gly protein CAP350 is not only present at the centrosome, but is also present as numerous dots in the pericentrosomal area. Using in vitro and in vivo expression of partial constructs, we demonstrated that CAP350 binds microtubules through an N-terminal basic region rather than through its CAP-Gly domain. CAP-Gly-containing domains of CAP350 are targeted not only to the centrosome but also to a Golgi-like network. Interestingly, full-length GFP-tagged CAP350 bound preferentially to microtubules in the pericentrosomal area. These results indicate that the large CAP350 protein has a dual binding ability. Overexpression of CAP350 promoted an increase in the stability of the whole microtubule network, as judged by a significant decrease in the number of EB1 comets and by an enhanced microtubule resistance to Nocodazole treatment. In support of this, CAP350 depletion decreased microtubule stability. Moreover, both depletion and overexpression of CAP350 induced specific fragmentation of the Golgi complex while maintaining a juxtanuclear localisation. We propose that CAP350 specifically stabilises Golgi-associated microtubules and in this way participates in the maintenance of a continuous pericentrosomal Golgi ribbon.