Cholinesterase activities in the Antarctic scallop Adamussium colbecki: tissue expression and effect of ZnCl2 exposure.

Biochemical characterization of cholinesterase activity (ChE) was carried out on the Antarctic scallop Adamussium colbecki collected in winter 2000 from Campo Icaro (Ross Sea, Antarctica) in order to increase its suitability as a sentinel organism for monitoring the Antarctic environment. The digestive gland, gills and adductor muscle were investigated for substrate specificity and inhibitors sensitivity using acetylthiocholine iodide (ASCh) and butyrylthiocholine iodide (BSCh) as substrates and tetra (monoisopropyl)pyrophosphor-tetramide (Iso-OMPA), 1,5-bis(4-allyldimethylammoniumphenyl)-penthan-3-one dibromide (BW284c51) and the insecticide chlorpyrifos as inhibitors. Effect of in vivo exposure to ZnCl(2) was also investigated. All the tissues expressed ChE activity (gill > adductor muscle > digestive gland) and low substrates specificity throughout the hydrolysis of both ASCh and BSCh substrates. Partial (25-29%) and total inhibition (100%) of ChE activity in gills was demonstrated following in vitro incubation with Iso-OMPA and BW284c51 (3 mM), respectively. Concentration-dependent inhibition was also evident with chlorpyrifos in the range 10(-4)-10(-10) M (IC(50) 10(-6)) while in vivo exposure to ZnCl(2) did not seem to affect ChE activity in the scallop. The potential use of ChE in the A. colbecki as biomarker for monitoring water contamination in the marine Antarctic environment is discussed.

[Experimental research on the biological cycle of Phyllodistomum elongatum Nybelin, 1926 (Digenea: Gorgoderidae Looss, 1901)]. / Ricerche sperimentali sul ciclo biologico di Phyllodistomum elongatum Nybelin, 1926 (Digenea: Gorgoderidae Looss, 1901)

Experimental infection of Tinca tinca and Carassius auratus have demonstrated that Cercaria duplicata von Baer, 1827 is the larval form of Phyllodistomum elongatum Nybelin, 1926 and that the life-cycle occurs between Anodonta cygnea (intermediate host) and Tinca tinca or Carassius auratus (final host) without a second intermediate host. The life-history experimentally completed in the laboratory occurs in the following way: -- adult in the ureters of Tinca tinca and Carassius auratus; -- mother sporocyst and daughter sporocyst of Phyllodistorum elongatum in Anodonta cygnea give rise to the large-tailed rhopalocercous cercaria; -- metacercaria encysted within transformed tail in water.