PETES, L.E.*; WEBB, M.A.H.; MENGE, B.A.; Oregon State Univ.; Bozeman Fish Technology Center; Oregon State Univ.: Differential accumulation of carotenoids in mussel gonadal tissue: a potential response to oxidative stress

Field identification of mussel sex based on gonadal pigmentation is a common practice in marine ecology, based on the theory that males have white gonads, whereas females have orange gonads due to carotenoid pigments. However, previous surveys in Oregon revealed that both females and males can exhibit a gradient of gonadal pigmentation from white to orange. To further investigate this phenomenon, monthly field surveys of Mytilus californianus pigmentation were conducted from May � September 2004 at four intertidal sites on the Oregon coast. Mussels from the high and low zones were dissected and visually sexed according to reproductive cell shapes at each site. Individuals were also visually classified based on gonad coloration into �orange,� �peach,� �white,� or �non-reproductive� categories in the field. A subsample of gonadal tissues was processed for histological analyses to confirm sex of mussels and to assess stage of maturity. At all sites and during all months, females from both the high and low zones had orange gonads; however, males in the high zone also had orange gonads, while males in the low zone had white or peach gonads. Orange pigmentation was highest for individuals in June immediately prior to spawning. Spectrophotometric analysis revealed that orange pigmentation was a result of high carotenoid content in gonadal tissue. Since carotenoids are used to protect tissue from oxidative stress, it is possible that mussels in the high zone accumulate carotenoids in order to protect their gametes from oxidative damage. Future investigations will measure the concentration of carotenoids in tissue using HPLC to quantify differences in gonadal pigmentation between the high and low zones.