This fish species exhibits protogyny (females are capable of becoming males). Females, IP males, and TP males, however, are capable of reproducing. The density of TP males in the spawning sites is associated with the size of the reef. On small reefs (under 600 sq. m) with fewer than 200 bluehead wrasses, there are very few IP males and TP males defend territories of a small number of females. On large reefs (over 1000 sq. m) with over 400 bluehead wrasses, IP males may make up 50% of the population. Here, group-spawning is much more common particularly in downcurrent areas. In areas of high population density, TP males tend to be found primarily in upcurrent sites.
Mating System: polygynandrous (promiscuous)
Terminal phase males aggressively defend breeding sites and therefore gain exclusive access to females visiting the site. They may mate with more than 100 females per day, but the mean range is from 30 to 50.
Initial phase males exhibit no breeding site defense, are much less aggessive than TP males and often sneak-mate with a TP male/ female pair. The IP males mate in large aggregations where the operational sex-ratio can exceed 50 IP males per female.
Initial phase females have no breeding site defense, show little aggression toward other IP fish and visit spawning sites containing either single TP males or IP male aggregations.
Transitional sex changers aggressively defend their breeding sites from the first day with an increase over the next several days. They display a full repertoire of mating behavior including spawning, but do not contribute gametes until the sex change is complete, which happens within 7 to 10 days.
Breeding interval: Males breed daily, females breed every 2 to 3 days.
Key Reproductive Features: iteroparous ; year-round breeding ; sequential hermaphrodite (Protogynous ); sexual ; fertilization (External ); broadcast (group) spawning; oviparous
Bluehead wrasses provide no parental care for their offspring.
Parental Investment: no parental involvement
- Warner, R. R., S. E. Swearer. 1991. Social control of sex change in the Blueheaded Wrasse, Thalassoma bifasciatum (Pisces: Labridae). Biological Bulletin, 181: 199-204.
- Warner, R. R. 1984. Mating behavior and hermaphroditism in coral reef fishes. American Scientist, 72: 128-136.
- Ford, D., J. Miranda, J. Godwin, K. Semsar, M. Grober. 1999. Sex Change in the Bluehead Wrasse: Temporal Concordance of Changes in Brain and Behavior. Arizona State University Sixth Annual Undergraduate Research Poster Symposium. Accessed 03/22/03 at http://lsvl.la.asu.edu/ubep99/abstracts/abst62/.
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