LARVAL DEVELOPMENT OF PAGURUS LONGICARPUS SAY REARED IN THE LABORATORY. III. BEHAVIORAL RESPONSES TO SALINITY DISCONTINUITIES

¹ Virginia Institute of Marine Science, Gloucester Point, Virginia 23062

1. Each zoeal instar of P. longicarpus was exposed to salinity discontinuities of varying magnitudes. Three distinct behavioral responses were observed: telson flips regardless of the magnitude of the discontinuity; downward swimming when the magnitude of the discontinuity was moderate; passive sinking when the magnitude of the discontinuity was extreme.

2. All zoeal instars avoided water with a salinity of ca. 20 or less, well within the range of salinity permitting complete development to the juvenile.

3. Avoidance of low salinity layers in stratified columns by Zoea I and II appeared to be a function of an absolute salinity (S20-22) when the salinity of the lower layer (S_L) was less than 25 and a function of salinity difference (S) when S_L was greater than 25 (S8 for Zoea I; S5 for Zoea II). Avoidance of bow salinity layers by Zoea III and IV appeared to be a fuction of absolute salinity (S20) regardless of S_L over the range of S_L tested.

4. Evidence is presented that the antennules and antennae may not be involved in detection of salinity discontinuities.