Copper Homeostasis and Toxicity in the elasmobranch Raja erinacea and the Teleost Myoxocephalus octodecemspinosus During Exposure to Elevated Water-Borne Copper

Copper exposure caused an initial transient reduction in skate plasma total ammonia (T amm), but eventually led to elevated plasma T . Despite the marked branchial copper accumulation in the skate, there was no reduction in amm gill NayK-ATPase activity. Similarly, NayK-ATPase activity in skate rectal gland and intestine, as well as in sculpin gill and intestine were not affected by copper exposure.

Plasma sodium, magnesium and chloride were not affected by copper exposure in either the skate or the sculpin. We set out to compare copper uptake and distribution in an elasmobranch, the clear nosed skate (Raja erinacea) and a teleost, the sculpin (Myoxoce- phalus octodecemspinosus). Suspecting osmoregulatory disturbance as the main toxic mechanism of copper to both species various osmoregulatory endpoints were considered.

In addition, plasma ammonia (Tamm ) was measured, because one of the most consistent effects of copper exposure in freshwater fish is elevated plasma ammonia (Lauren and McDonald, 1985; Wilson and Taylor,1993b; Beaumont et al., 1995; De boeck et al., 1995; Wang et al., 1998) due to a combined increased production and possibly impaired branchial clearance (Grosell et al., 2002).