University of Miami Rosenstiel School of Marine and Atmospheric Science
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Hamlet Information

Hamlets are marine fish specifically belonging to the Hypoplectrus genus of the Serranidae family.  They are found in the western central Atlantic throughout the Caribbean and up the coast to Florida.  At least 13 different species of Hamlet exist.  Hamlets are carnivorous and prefer to consume fish, crustaceans and other invertebrates smaller than themselves.  These are reef associated fish that can be found among rock, coral or oyster reefs.  They can also be found around soft bottoms of mud, san, or gravel and among mangroves and seagrass.  No hamlet species appears to be a concern for conservation at this time.  They are not very large fish.  Some such as the indigo hamlet grow up to 6 inches in length.  Their heads and body are deep and strongly compressed.  Their foreheads are straight and their snouts relatively short.  Despite these species being very similar genetically, their color patterns differ greatly from one another. 

Hamlets are simultaneous hermaphrodites, meaning they are both male and female at the same time.  Only about 40 out of nearly 25,000 species of fish function this way.  It’s far more common for some fish to change sexes under certain conditions rather than perform both roles at the same time.  Furthermore, hamlets spawn daily year round and will even perform both roles within a single day.  One hamlet will display as a female and release eggs for another hamlet to fertilize, then they may switch roles.  These frequent breeding cycles make observation in the wild much easier for researchers.  Hamlets most often mate within their own species, but on incredibly rare occasions members of different species have been seeing pairing up.  Some hamlets are faithful pairs to one other fish and some are not.

The evolutionary divergence of hamlets has been a topic of interest among scientists because of their close genetics but selective breeding.  The original theory was a geographical separation caused species to become divided and evolve differently from one another.  Falling sea levels are one way bodies of water become split, separating populations.  However, new evidence by ecologists, such as from UEA and Simon Fraser University Canada, suggests color variety changes are the result of ecological factors as opposed to physical barriers.  Competition for food or habitat may have influenced preferential appearances.  Aggressive mimicry has been presented as a possibility.  This suggests hamlets of a certain species developed color patterns similar to smaller herbivorous and omnivorous fish they themselves consume.  The objective would be for the hamlets to disguise themselves as a more harmless species to get closer to their prey.  The population diversity of a habit would then be a big factor as to which type of fish a hamlet would imitate.

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