Chaetognaths: a useful model for studying heat shock proteins. Effect of wound healing

The pattern of expression of Heat Shock Protein 70 (Hsp70), a highly conserved cellular protein chaperone, was investigated in Chaetognatha, a very important phylum of marine worms, which play a major role in marine food webs. The in toto distribution of Hsp70-like immunoreactivity was assessed in both intact and experimentally wounded specimens of Spadella cephaloptera Busch, 1851 that have been cut transversally just above the seminal vesicles. In intact animals, the ciliary organs, the corona ciliata, the coronal nerve and the spermatocytes express Hsp70 proteins. The kinetic of the expression pattern has been followed during the wound healing from the lesion to 5 days after. The Hsp70 immunoreactivity was observed according to time in the cerebral and suboesophageal ganglia and in the plexuses of the hood, the mouth, the neck and the tail region. At the wound level, the time-dependent Hsp70 expression was detected in the epidermal cells and along numerous muscle fibres of the tail region. Five days after the tail section, two Hsp70 immunoreactive areas were observed on both sides of the healed wound that correspond to the sites of formation of two new seminal vesicles. It is suggested that, in Chaetognaths, Hsp70 may be implicated in the regulation of several cellular processes especially at the level of the spermatocytes in intact and wounded specimens, and of the nervous system and muscular apparatus during the wound healing. It appears that chaetognaths are a good model as indicator of stress responses for experimental studies at the level of a whole organism.