STEM Logo

Dive Dry with Dr. Bill

#596: The Butter Hamlet's "Slippery" Sex

My paternal grandparents were born in a tiny little hamlet in Germany with a big name, HuddesdorfbeimStolzenauuberWeser. When I visited my grandfather's birthplace in 1968, I think the town had about 300 residents (mostly Bushings and Hilgendorfs, my grandmother's family). Our line of Bushings had owned the home there since the late 1500s or early 1600s and most of our family history was carved into the wooden fachwerk of the home's exterior. Of course they had to keep expanding the house to cover the more recent family history (you, know... the 1700s on)! Oops, I think I'm digressing even before I begin. I was supposed to be writing about hamlets, but not the tiny villages most associate with that word. I guess the synapses in my aging brain just made the wrong connections... again!

I think I've got the cerebral wiring functioning properly now after another cup of caffeine. The hamlets I wanted to write about today are of the fishy kind. These generally small fish are usually about 4-6" in length although one species may reach a whopping foot in length. They come in a fairly wide variety of colors and patterns. A few scientists believe they may all belong to a single species, but most accept that there are several of them. Back when I was working on board a Lindblad Expeditions/National Geographics eco-cruise ship in Belize and Honduras during the winter of 2005, I filmed a rather unique color variant. My dive buddy was Vicky Showler, the first female instructor certified in Belize. She told me it appeared to be a hybrid between the indigo hamlet and another species. The existence of hybrids indicates that the "lines" between these species are not enough to prevent them from interbreeding. Hopefully we won't have that problem when my friends from the planet Xantusia show up.

Last month while down at Bruce Bowker's Carib Inn on Bonaire, I did most of my night dives over the house reef (Calabas). On almost every night dive I encountered at least one pair of highly amorous fish performing their mating ritual without regard to the camera. Hopefully they didn't think my filming their mating ritual would make them "celebrities" of the (ugh) Kardashian kind. At least they'll be featured in an upcoming documentary about Bonaire... and in this column. These fish were butter hamlets (Hypopectrus unicolor), one of the least colorful of the group with yellowish bodies fading to white on the belly, yellowish fins and a dark spot on the base of the tail. Looked more like margarine to me. Although not colorful in the visual sense, their behavior certainly was!

These hamlets would rest paired up close to the reef, often in proximity to a stony coral head or rod gorgonian (soft coral). Then they would rise up into the water column and wrap their bodies around one another. After a few wild contortions, they would separate and settle back down to the reef. Their light coloration made them particularly vulnerable to predators out for a late night snack, so this retreat was probably a pretty wise move on their part! I did see a tarpon or two chase what appeared to be butter hamlets near the bottom. One must be careful when mating to attract only one's potential mate and not draw the attention of one's potential muncher. I've heard it just ain't no fun becoming the "munchee..." even after one's ecstasy is achieved. Just ask the male praying mantis... his mate is also his muncher.

Now you might think from my initial description that this constituted a standard mating event as one might expect to see when Noah released all the critters from his Ark to repopulate the planet. Actually, I'm not sure what the Bible would make of these fish. After all, they are simultaneous hermaphrodites that have both sex organs functioning in their body at the same time! That's right, they are each boy-girl (as opposed to Boy George). The spawning ritual I observed is actually more complex than I described. The two fish involved actually take turns playing the male and female roles. The first one releases "his" milt while the second one releases "her" eggs, then they reverse roles and "he" releases "his" eggs while "she" releases "her" sperm. Talk about confused gender identities!

I spent some time researching their reproduction in DeLoach and Humann's Reef Fish Behavior book. The authors state that about an hour before sunset the fish begin acting "giddy" and leave their territories in search of a mate for the evening. If in their search they encounter another pair already courting, they may try to establish a menage a trois (a six?) but are usually driven off. The authors refer to "regular mates" but I'm not sure this implies full monogamy. Then again, it is already a "foursome" of sorts even if they are just two paired up! For about an hour they engage in courtship behavior, chasing each other around. Then one assumes the role of the lady and acts as the aggressor (so liberated!). "She" assumes a head up attitude in the water column, flares her fins and snaps her head back-and-forth. How enticing! The "male" apparently acts a bit shy at first until the female darts over and the two "embrace" tightly and begin the beguine.

The pairing lasts only a few seconds and the two separate. Now it's the "girl's" turn to be the shy "male" and the "boy's" turn to be the aggressive female. During the actual spawning, the functioning "male's" head is pointed down, its mouth is open and the fins are spread out. Now since this is all a bit confusing compared to the kind of reproduction we mammals engage in, it is often referring to as egg swapping by marine biologists. Of course the swapping also involves the other gamete as well, but I guess the phrase egg swapping is just a bit less lubricious and more politically correct!

Despite the controversy over whether the different color morphs of hamlets all constitute different species, and the presence of several different hybrids within natural populations; all the butter hamlets I saw paired up with similar colored fish. There were barred hamlets in the same area, but I never saw the slightest interest or interaction between them and a butter hamlet. The fact that hybrids do occur though is one argument against considering the different color variants as entirely separate species. Back when the species definition rested on the ability to reproduce and create viable offspring, things were much easier for us biologists. Each night I dove the house reef at the Carib Inn, I encountered these hopped-up hamlets getting amorous with one another. I had to admit to a bit of jealousy since, as usual, I was traveling solo. Gotta do something about that. Sigh.

© 2014 Dr. Bill Bushing. Watch the "Dive Dry with Dr. Bill" underwater videos on Catalina Cable TV channel 29, 10:00 AM weekdays and on Charter Communications Cable channel 33 at 7:30 PM on Tuesdays in the Riverside/Norco area. You can also watch these episodes in iPod format on YouTube through my channel there (drbillbushing). Please help me climb out of self-imposed poverty... buy my DVD's (see this link). Yes, take Dr. Bill home with you... we'll both be glad you did!

To return to the list of ALL of Dr. Bill's "Dive Dry" newspaper columns, click here.


Close-up of butter hamlet; two "he-she" butter hamlets doing "the wild thing" and a jealous barred hamlet looking on

This document maintained by Dr. Bill Bushing.
Material and images © 2014 Star Thrower Educational Multimedia