Poster Presentation The International Congress of Neuroendocrinology 2014

The effects of reproductive state and egg-laying decisions on bluebanded goby (Lythrypnus dalli) hormones and behavior (#298)

Tessa K Solomon-Lane 1 , Megan M Williams 2 , Ali Martinelli 3 , Alma Thomas 2 , Polina Shvidkaya 4 , Lock Rogers 2 , Matthew S Grober 4
  1. Neuroscience Institute, Georgia State University, Atlanta, GA, USA
  2. Department of Biology, Agnes Scott College, Decatur, GA, USA
  3. Colombia University, New York, NY, USA
  4. Department of Biology, Georgia State University, Atlanta, GA, USA

Reproductive decisions are complex and influenced by factors including reproductive state, social status, behavior, and hormones.  Bluebanded gobies (Lythrypnus dalli) form linear hierarchies of one dominant male and multiple subordinate females, and reproductive success is associated with patterns of agonistic interaction within the hierarchy.  In social species, behavior and reproduction can be reciprocally related; therefore, to test the direction of effect in L. dalli social groups, we primed females to make different reproductive decisions by grouping females in specific reproductive states: the highest (alpha) and middle-ranking females (beta) were either very gravid or not gravid, and the lowest-ranking female was never gravid.  Within 48 hours, eggs were laid in 41% of groups.  73% of the layers were alphas, indicating an advantage for social dominance.  To test whether reproductive state and/or egg-laying decisions drive differences in agonistic behavior, we compared behavior among treatment groups and between social groups with and without eggs.  Neither female gravidity nor egg laying led to differences in approaches, displacements, or agonistic efficiency, behavioral measures associated with L. dalli reproduction.  This suggests that behavioral variation causes differences in reproductive success.  Interestingly, beta gravidity had a subtle but significant effect on beta female and male centrality, a social network characteristic, while alpha gravidity had no network effects.  We also measured steroid hormones, which can be associated with both behavior and reproduction.  Alpha and beta females in social groups with eggs had significantly lower systemic cortisol than females from groups in which no eggs were laid.  Specifically, females that laid eggs had lower cortisol than gravid females that did not lay during the course of this experiment.  Neither gravidity nor egg laying were associated with differences in 11-ketotestosterone or estradiol.  Together, these data provide important insights into the causes and consequences of reproductive decisions in a highly social species.