HEMOLYMPH CONSTITUENT LEVELS AND AMMONIA EFFLUX RATES OF NEPHROPS-NORVEGICUS DURING EMERSION

Nephrops norvegicus (L.) were subjected to 8 h of emersion, either bet ween layers of seawater-soaked hessian with periodical (20 min) flushe s of seawater (high humidity, HH) or to unprotected emersion (low humi dity, LH). Blood ammonia levels rose during emersion in both groups bu t reached higher levels under LH conditions. Ammonia efflux rates afte r re-immersion were higher than those of control prawns, and amounts o f ammonia excreted at such times were considerably higher than those c alculated to have accumulated in the blood during emersion. Possible e xplanations for such differences are discussed. C-aO2 and C-vO2 decrea sed rapidly to ca. 10% normoxia values within 2 h of HH and LH emersio n and remained low throughout the remaining emersion time. Emersion-in duced tissue hypoxia increased blood concentrations of glucose and lac tate. Lactate accumulation was higher during LH emersion, compared wit h HH emersion. Blood pH dropped ca. 0.40 units but increased again aft er 2 h of re-immersion. Acidosis was probably related more to respirat ory difficulties (CO2 accumulation) than to lactate accumulation, as b lood lactate values remained high after 2 h of re-immersion. The abili ty of N. norvegicus to cope with emersion appears to be little influen ced by high humidity conditions.