Sex on the reef

By Paul Whitby 10 years agoNo Comments

We all know that fish have the odd ability to change sex, pretty much at will. The prime example of this is the common clown fish, where the dominant male changes to become a female. This is referred to as protandry while the ability to change from female to male is referred to as protogyny. It has been assumed that sex change is a one-off event and has evolved as part of the breeding strategy of the sex-changing fish. For example protogyny is common in fish where the dominant male holds a harem of females. Lose a male and another one takes its place. Conversely, protandry is more common in the “one-on-one” relationships where a larger female increases brood size.

Now, new evidence is showing that the presumption of a single sex change is incorrect and that certain species can indeed have multiple changes over their life span. The report, published in the Journal Naturwissenschaften (the Nature of Science), details the effect on the population of cleaner wrasse (Labroides dimidatus) and the rusty angelfish (Centropyge ferrugata) when all of the females are removed from a natural reef. Each of these species is born female and dominants change to male. The researchers conducting the study essentially created 14 widowed adult wrasses and six widowed adult angels (as an aside, the females were relocated to a separate reef and were not harmed in the experiment). Any females that moved into the area were also removed and relocated. As one would imagine, several things happened. Either a) The widowed male left looking for a new mate, b) a female migrated in (and was removed) or c) the widow selected a juvenile male as partner. When the latter occurred, the smaller male (who was born female) reverted back to a female and spawning resumed. This process usually occurred within 40 days of pairing. While this phenomenon had been reported for isolated fish in aquaria, this is the first time it has been reported in the natural environment and is postulated to be a survival mechanism for fish with low density population.
The article is well written and can be easily understood without a science background and provides a fascinating insight to life on a reef.

  Fish, Reef, Science

 Paul Whitby

  (19 articles)

Paul Whitby is originally from the UK, but now resides in Oklahoma USA. While in the UK, he received his Doctorate in the microbiology of fish diseases, specifically diseases of fish with high economic importance and has published several articles in this field as well as medical microbiology. Currently he is an Associate Professor at the University of Oklahoma where he specializes in the microbiology of pediatric infectious diseases. Paul is the current President of the Central Oklahoma Marine Aquarium Society (COMAS) and has had several articles published in Reefs Magazine, Reef Keeping magazine and and ReefBuilders. He has published several articles on COMAS, the development of a captive propagation program to conserve coral species, pests and parasites in marine aquaria as well as numerous reviews. In October 2007 his SPS dominated display tank was selected as Reef Keeping Magazine's Tank of the Month. Paul has presented several marine aquarium related seminars at local clubs and conferences including Oklahoma's CRASE, Reef Fest, ReefStock, NERAC, IMAC west and others. In association with his good friend Ed Brookshire, Paul owns He has been keeping saltwater aquariums for over 22 years and has owned a variety of tanks ranging from under 30 to in excess of 600 gallons. His current system, including filtration, is over 1,000 gallons.

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