Emblemariopsis carib and E. arawak are two recently described Chaenopsid blennies that were previously being labeled as the Flagfin Blenny, Emblemariopsis signifer. Emblemariopsis carib and E. arawak are sympatric species which means that they co-occur along their range which so far is known to occur from Puerto Rico to the U.S. Virgin Islands.
Blennies in the genus Emblemariopsis can be really hard to distinguish since they have juvenile, female and male coloration, and the males may be lightly or darkly colored depending on their sexual activity. Many closely related diminutive fish species can look identical when dead and preserved but their subtle differences can be seen in living specimens.
Molecular analysis of the genetic markers of these fish were crucial in determining the amount of speciation between Emblemariopsis carib and E. arawak but other tools were also used. What is particularly interesting about this publication by Benjamin Victor in the Journal of the Ocean Science Foundation is that it specifically points out the significance underwater macro photography in aiding to distinguish these two species.