ROLE OF SIZE IN MATE FORMATION OF

AMPHIPRION OCELLARIS UNDER CULTURE

 

By

 

Danny C. Chen

 

A paper submitted in partial fulfillment of the requirements of the Honors Program Department of Biology and Marine Biology.

 

 

                                                                        Approved By:

 

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                                                                            Ileana Clavijo, PhD

                                                                            Faculty Supervisor

Examining Committee:                                             

 

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                                                                                    __________________________ 

                                                                                    Department Chair

 

 

 

 

 

 

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Honors Council Representative

 

 

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Director of the Honors Scholars Program

 

 

 

 

University of North Carolina at Wilmington

 

Wilmington, North Carolina

 

December 2006

Abstract

 

            Individuals of the false clown anemonefish (Amphiprion ocellaris) were placed into groups of different size.  The objectives of this experiment were to examine the effects of size on mate formation in social groups held in aquaria and to examine how growth rates were regulated to maintain the variation in size.  Sex is determined by size and dominance in Amphiprion ocellaris.  The largest individual of a group becomes the rank 1 female.  The second largest is a functional male in rank 2.  All others are subordinate males in competition for the functional male position.  Five tanks were set up each containing five individuals of different sizes.  It was expected that once the top two fish in each tank established a bond, subordinates would compete for the male position if the top male was removed.  However, low density and group behavioral instability drove the dominant pairs in three of the five tanks to act aggressively toward the subordinates.  Over time, most subordinates were eliminated.  Fish left in each tank were measured and growth rates were calculated.  The most dominant fish (females) in social groups persisted and had the greatest mean growth rates of 0.898, 1.091, 0.941, 0.941, and 1.011mm/10-d respectively.  The original males that bonded with the females also persisted and generally had the second greatest mean growth rates of 0.500, 0.984, and 0.672mm/10-d for three social groups.  In conclusion, size is important in mate formation.  Dominant individuals became dominant by having a large size advantage; to remain as dominant fish, growth rates of subordinates were regulated indirectly by dominant fish so that they were unable to acquire higher ranks.