S is for Sequential, Serial bidirectional, and Simultaneous Hermaphroditism

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As a part of the A-Z Photographic Glossary of Biological Terms challenge, today in fact we have three terms! S for Sequential hermaphroditism, S for Serial bidirectional hermaphroditism, and S for Simultaneous hermaphroditism as illustrated by the Creole Wrasse (Clepticus parrae) and the Indigo Hamlet (Hipoplectrus puella), from Bonaire in the Dutch Caribbean.

In biology, a hermaphrodite is an organism that has reproductive organs normally associated with both male and female sexes. Many taxonomic groups of animals (mostly invertebrates) do not have separate sexes. In these groups, hermaphroditism is a normal condition, enabling a form of sexual reproduction in which both partners can act as the “female” or “male”.

Such is the case with reef fishes in the Caribbean. The most common form is the “sequential hermaphrodite” when a fish is born one gender then changes to another- this could be what is termed “protandry” (proto -first, androus -male) where the fish is born as a male and then changes sex to a female, such as the Snook (Centropomus undecimalis); or as “protogyny” (proto -first, gyno -female) where the fish is born as a female and then changes sex to a male, such as wrasses, parrotfish, and groupers. Protogynous sequential hermaphroditism is the most common form and occurs in about 70% of all reef fish- and of course an important consideration here is that when fishing is allowed to harvest increasingly smaller fish (ie. mostly females) this practice will seriously adversely affect population reproduction and recovery.

With this Creole Wrasse (Clepticus parrae) pictured above, the initial phase is made up exclusively of females who change into terminal males when they reach a length of about 6 inches; this individual has just started to change from the all blue female, and the increasing yellow color will soon be joined by lavender, orange and magenta when it is finally male.

There are some fish that possess both male and female organs and engage in “serial bi-directional” sex change, where a species is capable of switching back and forth between male and female depending on the situation, as is the case with many species of goby.

Then there is another form called “simultaneous hermaphroditism” as exemplified by the Indigo Hamlet pictured below. All the hamlets are unique in that they too possess both male and female organs simultaneously but when one discovers a mate it can choose which role to play; in most cases pairs take turns between which one acts as the male and which acts as the female through multiple matings!

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