Behaviour and cytology ofActinocoryne contractilis, nov. gen., nov. sp., a new stalked heliozoan (Centrohelidia): comparison with the other related genera

Abstract

Actinocoryne contractilis is a new marine, benthic and stalked member of the Centrohelidia (Heliozoa) whose biology, motile behaviour and cytology are described. Preliminary results concerning the life cycle are given. The stalked form emits small subspherical planktonic heliozoans which settle and give rise to the stalked stage again.

Axopodial Contraction in the Heliozoon Raphidiophrys contractilis Requires Extracellular Ca2+

“…In R. contractilis the axopodial contraction took place within one frame of the video recording and the velocity of the contraction was calculated to be more than 3.0 mm/sec, within which the microtubule-containing axopodia completely disappear. Similar phenomena have been described in other heliozoon species such as Echinosphaerium nucleofilum , Actinophrys sol and Actinocoryne contractilis (Febvre-Chevalier, 1980;Febvre-Chevalier and Febvre, 1992;Suzaki et al ., 1992;Kinoshita et al ., 2001). Also in these species, axopodia or the axopodium-like stalk show contraction at similarly rapid rates (1-10 mm/sec).…”

Protists: An exceptional source of cell models

“…The spasmoneme is composed of filaments of about 3 nm in diameter, in which many endoplasmic reticulum vesicles are interconnected and in their vicinity large mitochondria are disposed [51,52]. Other similar spasmoneme-like structures were also described in the dinoflagellate Et3,thropsidimium where a very active appendage called 'piston' could extend from 25 to 1000/.tm long for 0.125 s [741 or in the marine heliozoan Actinocor),ne contractilis where stimula-tion in sea water elicits an extremely fast contraction at the millisecond range, accompanied by an almost complete microtubule dissociation [53,55]. The spasmins are at the origin of the contraction.…”

Protists: An exceptional source of cell models

“…The velocity of contraction is higher than that of the fastened striated muscles, and ATP is required not for the contraction but for the release of the spasmoneme [5,6]. Other similar spasmoneme-like structures were also described in the dinoflagellate Et3,thropsidimium where a very active appendage called 'piston' could extend from 25 to 1000/.tm long for 0.125 s [741 or in the marine heliozoan Actinocor),ne contractilis where stimula-tion in sea water elicits an extremely fast contraction at the millisecond range, accompanied by an almost complete microtubule dissociation [53,55].…”