P5-12 Sat Jan 2 Hatching delays in extreme salinities in the intertidal copepod Tigriopus californicus Bock, AK*; Burton, RS; University of California, San Diego; University of California, San Diego firstname.lastname@example.org
Living in tidepools in the supralittoral zone, all life stages of the copepod Tigriopus californicus must contend with salinity extremes, ranging from nearly freshwater after rainfall to near salt saturation (> 100 psu) in warm dry summer months. While mechanisms and limits of survival under extreme salinity conditions have previously been characterized in this species, impacts of salinity on reproduction have not been widely assessed. Here we report that T. californicus exhibits substantially delayed hatching of fully developed egg sacs under hypersaline conditions. In T. californicus, egg sacs remain attached to females and transition from dark green to red over the course of development, providing a visual indication of the status of the embryos. The production and development of egg sacs is delayed with increasing salinity (effects seen at 60, 70, and 80 psu versus 35 psu control), and at the highest salinities (80 psu) completely developed egg sacs may delay hatching for weeks until they are moved to more moderate salinities, where they typically hatch within 24 hours. Female copepods acclimated to and fertilized in 70 psu also show a reproductive delay in that salinity, but recover when returned to seawater, suggesting a potentially limited role for acclimation. These salinities are substantially lower than the median lethal high salinity found in previous work on adult male T. californicus, emphasizing the importance of measuring effects both on survival of individuals and on their reproduction in assessing impacts on population dynamics. Such delays in hatching of fully developed embryos have not previously been shown in T. californicus, although delayed hatching in response to salinity or other stressors is known in other copepods.