Form and Function

The form of the Napoleon Wrasse is pretty typical of the average oceanic fish image ingrained in our heads, but it has some interesting quirks. In general, the Labridae family is formed primarily for propulsion, or “labriform locomotion” (Encyclopedia of Earth 2012). Typically, the Napoleon Wrasse only treads with their pectoral fins in the open water, only using the caudal fin, or tail, when a fast burst is required, according to the Encyclopedia of Earth (2012). The morphology of the Labridae family has been evolved for the most efficient movement through water.

This species in particular is the largest member of the Labridae family, for a glimpse of other types of wrasses view EOE's website (Encyclopedia of Earth 2012). The largest recorded length of a NapoleonHumphead Wrasse and Bumphead Wrasse or Humphead Wrasse is 6 feet according to NOAA, although females rarely surpass 36 inches (Bester 2013). Humphead are more commonly found around 24 inches at 5-7 years old, even though they can miraculously live to at least 30 years of age (Bester 2013). Their immense size causes a decrease in natural predators, but longevity still seems hard to achieve due to the increasing destructive fishing techniques, live reef food fish trade, and many other factors according to the NOAA (2009). An interesting study was done showing that, especially in males, rapid growth rates are linked to relatively high mortality rates in larger reef species (Ackerman et al. 2006). This correlates with wrasse as they have a slow growth rate and increased longevity (Bester 2013).

Pertaining to the common name, Humphead Wrasse, these fish develop a large hump on the back of their neck as they get larger. In the “supermales” mentioned in the reproduction page, they show a more prominent hump then most, according to Bester from Ichthyology at the Florida Museum of Natural History (2013). It is possible that this is due to sexual selection since it occurs more so in the largest, most dominant individuals. In addition to the larger hump, in chief males there is also a more vibrant coloration in the patterns of the face (Bester 2013). This could reveal sexual selection trait or a developed characteristic with size.

More specifically, Napoleon Wrasse have a perfectly evolved type of jaw for their prey, sea stars and brittle stars, shrimp, clams, snails, crabs, and fish, this wrasse also consumes toxic animals such as sea urchins and the crown-of-thorns sea star, along with many others (Shedd Aquarium 2006). Their jaw comes equipped with thickly padded lips to absorb the spines of the wrasses' more difficult prey like the sea urchins and crown-of-thorns star, comparable to the parrotfish (Shedd Aquarium 2006). Along with their lip adaptations, Napoleon Wrasse also have pharyngeal teeth, comparable to molars that are teeth set deep in their throat which helps crush hard organisms (Shedd Aquarium 2006). Apparently, divers have reported even hearing the crunching and observing the particles from the destruction of these hard shells near Napoleon Wrasse (Bester 2013).

To prevent prey from escaping, the wrasse can even expand their jaws ahead of their nose so they can pull prey out of various crevices, caves, and holes in the reef, according to the Shedd Aquarium (2006). If that wasn’t incredible enough, there are more behavioral adaptations in response to mouth form! The Napoleon Wrasse can also bite off coral coverings concealing their prey and even blow jets of water at the sand to expose any organisms within (Shedd Aquarium 2006). I wouldn’t want to be the prey of this predatory fish because the Napoleon Wrasse is impressively formed in reaction to its needs from evolution over time.

Click here to see a video representation from Carl Chapman of the Napoleon Wrasse form and function in their natural environment. Note the morphology and what adaptations it has evolved.

Continue to Reproduction to understand the lifecyle of these amazing fish!

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