Les transferts d'eau en fonction de la salinité du milieu chez deux isopodes Cymothoidae: Meinertia oestroides (Risso, 1826) et Anilocra physodes (L, 1758) (parasites de Poissons marins)

Abstract

Meinertia oestroides and Anilocra physodes (lsopoda Cymothoidae) respectively buccal and skin parasites of the teleostean Fish Boops hoops are isosmotic with the surrounding medium in sea water (SW), hyperosmotic and hyperionic in diluted media.

The drinking rate of Meinertia is 0.73 μl in SW and 5.30 μl h⁻¹ g⁻¹ wet weight in 5/10 SW; Anilocra shows 0.31 μl in SW and 0.21 μl h⁻¹ g⁻¹ wet weight in 6/10 SW.

The distribution space of [⁵¹Cr] EDTA in Meinertia reaches 32.7 % in SW and 28.9 % of wet weight in 5/10 SW; Anilocra indicates 29.6 % in full SW and 19.2 % of wet weight in 6/10 SW.

The rate of primary urine production in Meinertia evaluated from the biological period of [⁵¹Cr] EDTA is 130 mg in SW and 338 mg 24 h⁻¹ g⁻¹ wet weight in 5/10 SW, while Anilocra exhibits 118 mg in full SW and 224 mg 24 h⁻¹ g⁻¹ wet weight in 6/10 SW.

The area of pleopoda is 826 mm² for Anilocra, 336 mm² for Meinertia and 277 mm²/g wet weight for Emetha audouini (another buccal parasite); 92.6 % for Anilocra, 84.1 % for Meinertia and 81.8 % for Emetha of the apparent water diffusion outflux take place through the pleopoda.

The apparent permeability diffusion coefficient Pd in SW is 1.63 × 10⁻⁴ cm/sec for Anilocra, 2.80 × 10⁻⁴ cm/sec for Meinertia and 3.31 × 10⁻⁴ cm/sec for Emetha. In dilute media Pd is 1.30 × 10⁻⁴ cm/sec for Anilocra and 3.44 × 10⁻⁴ cm/sec in Meinertia.

The results are compared with those already obtained for other non parasitic Crustaceans and according to the parasitic localization of the species above men-tionned. An hypothesis concerning the mechanism of feeding (haematophagia) is proposed. The accuracy of results is discussed.