Saturday, October 26, 2013

Fiji 2013 | Cleaning, Sex Change and Being "Wickedly Flattered." A Wrasse With A Very Full Life!

For the past several years, the New England Aquarium has participated in a joint expedition to Fiji, along with the Monterey Bay Aquarium and other conservation-minded groups and individuals. The last expedition took place in Spring 2012Today's post about cleaning stations and comes from the Aquarium's curator of fishes Steve Bailey.

In this last post post, you were promised some additional story telling regarding Joint Aquarium Fiji Expedition divers getting up close and sometimes serviced by other cleaner animals. This post focuses on one of our other favorites—the bluestreak cleaner wrasse (Labroides dimidiatus).

A Fiji morph bluestreak cleaner wrasses (Labroides dimidiatus) servicing a coral trout (Cephalopholis miniatus), dive site: Mt. Mutiny, Bligh Water (Photo: Keith Ellenbogen)

Two Fiji morph bluestreak cleaner wrasses (Labroides dimidiatus) inspecting the gills of the
bignose unicornfish (Naso vlamingii),  dive site: Archway, Namena Marine Reserve (Photo: Keith Ellenbogen)
This is a handsome wrasse, and in Fiji it often has a vibrant yellow patch on its posterior flanks, where most elsewhere in the bluestreak wrasse’s range it lacks that eye catching lemon color (Fiji endemism and regional color morphs is a whole ‘nother tale to tell in a later post!). The species is pure fish nerd eye candy while holding down that admirable job as a cleaner fish, but it has more, yes, more, to further fascinate.

Normal color phase of Labroides dimidiatus (Photo: K. Ellenbogen)

Fiji yellow color phase of L. dimidiatus (Photo: via Ryan Photographic)

Let’s talk intriguing approach to sex determination: L. dimidiatus, as do many wrasses, have all specimens born as female, with the most dominant individual transforming into the male at the appropriate time. And when that male dies or disappears, then the next female in the hierarchy will ‘ascend to maleness;’ sequential hermaphroditism is the term ichthyologists use to describe this strategy. How slick is that?! Talk about males being in touch with their inner estrogen!

And just because the natural world isn't ever finished working on a theme, the bluestreak has yet another bizarre aspect to its existence—that of imitation not being the most sincere form of flattery. Here's the scoop: A blenny named the false cleanerfish (Aspidontus taeniatus) has so closely adopted (evolved to look like) the distinctive appearance of the wrasse that it is able to pass itself off to a larger fish needing ministration as the genuine article.

The false cleanerfish (Aspidontus taeniatus) | Photo: John Randall, Bishop Museum

Compare the profile of the false cleanerfish to the bluestreak cleaner wrasse in its normal color phase

Once close enough to the host, impressive teeth are used to sever flesh from fins or elsewhere for a meal. The victim is so pained (and outraged?) that it vigorously chases the stealthy blenny back to its wormhole that often acts as a refuge from which to ply its 'despicable' trade! To see the drama unfold underwater is the sort of thing that usually has me talking to myself, which incidentally sounds quite odd with a regulator in my mouth.

False cleanerfish in an abandoned wormhole site. Dive site: Archway, North Save-a-Tack, Fiji
(Photo: K. Ellenbogen)

Check out the teeth in this blenny's mouth! The false cleaner fish has some impressive cutting blades.
Dive site: Archway, North Save-a-Tack, Fiji, Photo: K. Ellenbogen

Bluestreak cleaners do indeed investigate divers when they're passing by the wrasse's station. I've often had one check out my black and gray scuba fins, but never seeming to be fooled for long into thinking that I'm sporting any parasites. No kidding! (I mean the part about me not having external parasites.) I haven't been able to coax them into my mouth though; I won't brush my teeth next time. Hmm, already making the tast list for our next Fiji expedition.

Here's what I'm talking about. Video via YouTube.

Be sure to check out the Pacific Reef Community exhibit in the Tropical Gallery to see the bluestreak cleaner hard at work. Look for the fish's cleaning station down at the East end (left side) of the tank.


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