Tolerance of the barnacle Balanus amphitrite amphitrite to salinity and temperature stress: effects of previous experience

We conducted 4 experiments to study the effects of salinity and temperature on the barnacle Balanus amphitrite amphitrite Darwin, with particular focu s on the effects of stress experienced in one life-stage on the performance of the next life-stage. At 15 degrees C, typical winter water temperature in Hong Kong, larvae exhibited low survivorship, adults molted infrequently , and only a low percentage of individuals had developing ovaries and embry os. However, at 30 degrees C, typical summertime temperature in Hong Kong, larvae developed rapidly, survivorship was high, adults molted frequently, and a high percentage of individuals had developing ovaries and embryos. Th ese results suggest that low winter temperature may be a limiting factor re sponsible for cessation of recruitment, whereas high summer temperature is unlikely to be the cause for the decline in recruitment. Salinity produced significant detrimental effects on both survival and development at less th an or equal to 10 parts per thousand. In the 15 to 35 parts per thousand S range, however, none of the stages tested exhibited signs of stress. Salini ty is a limiting factor for the survival and development of B. a. amphitrit e in Hong Kong only during mid-summer when salinity in the surface water ca n drop to below 10 parts per thousand. Exposing embryos to different salini ties produced differential effects on larvae. For larvae cultured at 10 par ts per thousand S, both survivorship and time of development were independe nt of the salinity that the embryos had experienced; for larvae cultured at 15 and 35 parts per thousand S, exposing embryos to 10 parts per thousand S led to lower larval survivorship and longer larval development times. Exp osing cypris larvae to 10 parts per thousand S did not alter juvenile growt h but did result in lower survivorship. Osmotic stress experienced in one l ife-stage can be passed over to the next life-stage. In bioassays involving the use of B. a. amphitrite, results of the tested life-stage may be affec ted by stress experienced in a previous life-stage.