The "Cnidoblast" as an Excitable System

Abstract

It seems established by now that nettling response as it is given normally by cnidarian nematocysts belongs to a rather standard type of physiological excitation event, though there is still some question about the functional significance of the morphological "cnidoblasts". It is instructive to consider this subject in comparison with that of muscle contraction response provided that one adopts the view of "post-energization' rather than that of "pre-energization". One of the centers of interest is at present in identification of coupler agent that mediates between the external excitation event and internal explosion event. For this problem, the experimentation with isolated nematocysts are of critical role. It was shown that apparently inconsistent situations are to be found even among the same type of cnida from closely related species, and it is interesting to see how one can negotiate such diversions to bring them into fundamental uniformity. Efforts so far made revealed us that there is still need for studying somewhat intricated interrelationship between, water, anions, and cations as to triggering of the isolated cnidae. Such study may lead to an understanding of the mode of operation of cnidae in situ in the normal response system. The discussion extends further to include the problem of remote control of nematocyst discharge.

Calcium Dependence of Settlement and Nematocyst Discharge in Actinulae of the Hydroid Tubularia mesembryanthemum

“…The necessity of external Ca 2+ ions for nematocyst discharge has been demonstrated in Aiptasia mutabilis (Santoro and Salleo, 1991b), Pelagia noctiluca (Salleo et al, 1994a), Calliactis parasitica (Salleo et al. 1994b), Chaiybdea rastonii (Yanagita. 1973), and Anihopleura elegantissima (McKay and Anderson, 1988).…”

Discharge characteristics of nematocysts isolated from acontia ofCalliactis parasitica

“…These nematocysts retained their discharging capacity, however, since treatment with 1% trypsin (Yanagita andWada 1954, Salleo et al 1983) induced a prompt and complete eversion of the tubule in all capsules. Noticeable differences, however, were encountered in the response of nematocysts (isolated by different methods) to 50 mM thioglycolate.…”

“…The microbasic mastigophores of Aiptasia pallida are discharged by treatment of the acontia with 1 M glycerol (Blanquet 1970), as are those (Yanagita 1973) and A. mutabilis (Salleo et al 1988 b) are extruded undischarged in glycerol solutions. The microbasic mastigophores of Aiptasia pallida are discharged by treatment of the acontia with 1 M glycerol (Blanquet 1970), as are those (Yanagita 1973) and A. mutabilis (Salleo et al 1988 b) are extruded undischarged in glycerol solutions.…”

Effects of controlled treatment with trypsin on the functional characteristics of isolated nematocysts of Calliactis parasitica and Aiptasia mutabilis (Cnidaria, Actiniaria)

“…This subject is complicated by the different responsiveness of capsules isolated by different methods. In a previous investigation (Salleo et al, 1990) it was observed that basitrichous isorhiza nematocysts isolated from acontia of Calliactis parasitica (Couch) by suspending the acontial tissue in 1 M glycerol (Yanagita, 1973) are discharged by 50 mM Na-thioglycolate. On the other hand, the same capsules isolated either with 0.5 % Triton X100 or by freezing the tissue were completely unresponsive to this discharging agent.…”