Osmoregulation in two aquatic oligochaetes from habitats with different salinity and comparison to other annelids

Abstract

The osmoregulatory capacity of two oligochaete species, Enchytraeus albidus Henle, 1837, and Heterochaeta costata (Claparede, 1863), was investigated by direct measurements of the osmolality of the coelomic fluid. Terrestrial and marine (28%o S) populations of Enchytraeus albidus and a brackish water population (14%o S) of H. costata were used in the study. The range of salinity acclimation investigated was 0-40%o. The response to osmotic stress was measured (a) after a long-term maintenance (> 14 days) in various salinities (E. albidus only), and (b) after a hyperosmotic shock as a short-term time-course sequence. The rate of water loss following a hyperosmotic shock was measured for E. albidus. Long-term acclimation. E. albidus maintained a hyperosmotic coelomic fluid over all salinities tested. In low salinities the osmolality of the coelomic fluid of the marine population was significantly higher than that of the terrestrial population. Possible genetic discrepancies or long-term acclimation may account for this difference. The coelomic fluid of H. costata was hyperosmotic at 15%o S and isoosmotic at 30%o S. Short-term acclimation (hyperosmotic shock). Both species investigated, kept at 15%o S and then exposed to a salinity of 30%o, showed fast responses: within the first two hours the internal concentrations were adjusted to the new external condition with only small subsequent changes. Regulation of the body-water content after an exposure to a hyperosmotic shock was much slower: individuals of terrestrial E. albidus, acclimated for two weeks to either 0%o or 15%o S, had the same water content; hence, they showed a 100% regulation. However, after exposure to 30%oo S, a 100% regulation was still not attained 4 days after the hyperosmotic shock. Enchytraeus albidus is capable of actively reducing water loss following the hyperosmotic shock: the observed loss of water was only 40% of that expected for a passive osmotic flow. The observed reactions are compared with those in other annelids. It seems that an active transport of ions combined with a changeable permeability of the body wall play a major role in the regulation of body fluids.

Influence of salinity on the bioaccumulation and photoinduced toxicity of fluoranthene to an estuarine shrimp and oligochaete

“…This mechanism has been previously demonstrated in euryhaline polychaete worms belonging to the genus Nereis [34]. Euryhaline oligocheates also may have the ability to alter the permeability of their integument; this is apparently under neurosecretory control [35]. Permeability changes to the integument could increase the tolerance to PAH phototoxicity by reducing the exposure of more sensitive underlying tissues to UV radiation.…”

Responses to salinity in the littoral earthworm genus Pontodrilus

“…Understanding the fundamental knowledge of osmotic strategies in gaining salinity tolerance should provide insights into the evolutionary processes of physiological adaptation to saline waters and habitat selection strategies. Several studies have been reported on osmoregulation in earthworms 28 , 31 , 32 . Since, osmoregulation is very important in estuarine intertidal species, we investigated how the coelomic fluid osmolality of these two Pontodrilus increases with increasing medium salinity to evaluate how they the species handle salinity fluctuations.…”

Environmental impact of heated mining waters on clitellate (Annelida: Clitellata) assemblages

“…Some species, such as Propappus volki, show a strong negative correlation with water hardness, which is often tightly associated with conductivity (Dumnicka & Pasternak 1978), and we observed that this species was completely eliminated below the mining water tributary in our study (Table 2). Osmoregulatory capacity differs among oligochaete species (Generlich & Giere 1996), and Propappus volki is probably highly sensitive to osmotic stress. Second, the effect of increased water temperature was remarkable.…”