Some aspects of salinity and temperature stress on Neanthes arenaceodentata Moore.
Organismic functions of Neanthes arenaceodentata Moore were studied in response to thermosaline stresses. Capacities for chloride ion concentration, osmoconcentration and body volume regulation were first considered. Chloride ion and osmoconcentrations of the coelomic fluid in relation to the environment were examined at room temperature. The chloride concentration of the coelomic fluid varied directly with that of the environment and was maintained at a hypo-chloride concentration. The osmoconcentration of coelomic fluid followed a conformity response, but was slightly and significantly hyperosmotic.Body volume regulation was studied under factorial conditions and the ratio of body water to wet weight was found to vary between 0.8 and 0.9 suggesting that the environment influenced its capacity for body volume regulation. Salinity and temperature affected the steady state levels of oxygen consumption of N arenaceodentata. Size exhibited an endogenous effect and the positive size coefficient (b = 0.51) was found insensitive to treatments. Thermal sensitivity occurred at optimal salinity, but at the lower salinities, other factors were affecting repiratory rates. No difference of oxygen consumption was attributable to sex. Ingestion and egestion were affected by thermosaline alterations. Ingestion increased with temperature at 32 ppt, but at 22 ppt, an optimal rate was seen at 20 C. Egestion at 32 ppt showed an optimal rate at 20 C, but at 22 ppt, egestion increased with increasing temperature. Feeding and egestion ceased at 18 ppt. Assimilation efficiencies varied between 60 and 90%. The growth rates of N. arenaceodentata were affected by salinity. At lower salinities, increasing temperatures were causing weight loss. Such weight losses were attributed to maintenance metabolism and loss of energy input from feeding. Weight gains occured above 20 C and 22 ppt. Optimal growth rates were observed at 20 C. Net growth efficiencies ranged between 5 and 45% and increased with increasing temperature at optimal salinity, but decreased with increasing temperatures at 22 ppt. Ammonia excretion by N. arenaceodentata increased as temperature increased at 32 ppt, but greater levels of excretion are observed as salinity decreased. Assessment of stress by O:N ratios indicated stress at all treatment conditions, but this was attributed to increasing rates of ammonia excretion. Mucus secretion was very low, but it is significant metabolic product. Mucus secretion rates increased as salinity decreased, but under extreme salinity stress, cessation of mucus production occured below 22 ppt. This study has demostrated physiological effects due to environmental alterations for N. arenaceodentata. These thermosaline alterations were shown to affect the accumulation and utilization of energy by N. arenaceodentata.