Acetylcholinesterase activity in embryonic and larval development of Artemia salina leach (crustacea phyllopoda)

Abstract

AbstractAcetylcholinesterase (AChE) activity has been studied in Artemia salina embryos and larvae by quantitative, histochemical, and electrophoretic methods. An AChE activity is present in dehydrated encysted gastrulae and remains low in rehydrated developing embryos, showing at hatching an increase that becomes faster during the nauplius stages (twice the gastrula activity at the nauplius II stage), and continues linearly in the first metanauplius stages. The histochemical staining, faint and diffuse in dehydrated gastrulae, in more advanced embryos becomes localized in cell membranes and stronger in differentiating tissues; most AChE activity is localized in the nervous and muscular cells, and a fainter one in the differentiating metanauplius segments. Dehydrated cysts show one electrophoretic AChE band, that is no longer detectable in rehydrated embryos and larvae, while two other bands appear, that migrate more slowly; in advanced larval stages, the more cathodic band is predominant. In dehydrated cysts, isoelectric focusing separates three AChE bands with isoelectric points (IP) at pH 5.0, 5.7, and 5.9; in hydrated embryos and larvae, the band at pH 5.0 is absent and another is seen at pH 5.5. Eserine, DFP, and BW284c51 inhibit the enzyme activity strongly and cause paralysis of larvae; also tubocurarine blocks the motility. These results are discussed in relation to the differentiation of the neuromuscular system and to the development of motility. As a hypothesis, in early embryonic stages, before any neuromuscular differentiation is evident, a cholinergic‐like system might regulate non‐neural cell activities and interactions, associated with embryogenetic events.