A lot of people don't know this about me, but in addition to my computational work I maintain a field research program studying various and sundry aspects of the evolution, ecology, and behavior of coral reef fishes.  As part of this work, I have been doing several weeks’ worth of diving in the southern Caribbean each year for the past six years, mostly in Curaçao.  During this time, I and my fellow researchers have been witness to an amazing and terrible biological invasion: the lionfish.

Lionfish are Scorpaeniforms, and are arguably the prettiest of the bunch.  They have long, beautiful, flowing fins with sharply contrasting patterns of brownish-red and white, and they get to be up to around 18” long.  Those beautiful fins conceal extremely sharp spines that can inject any fish (or person) that is unlucky enough to touch them with a venom that, while not as life-threatening as the venom of many scorpaeniforms, is nonetheless said to be exceedingly painful.  They seem quite keenly aware of their general badassery, too; rather than retreating when a diver approaches, they will spread their fins wide and shimmer their spines in what may be the world’s most intimidating display of jazz hands.

Lionfish are native to the tropical Indo-Pacific, which is thousands of miles away and on the other side of some fairly substantial land masses, so how did this happen?  Although it’s not known exactly when lionfish were first introduced to Caribbean waters, it seems to generally be agreed that it happened no more than two decades ago and was most likely at least partly due to irresponsible aquarists releasing captive fish they no longer wanted.  It’s likely that the original intent was not malicious, but the result has been devastating.  The lionfish is not just any old fish.  It’s a highly efficient and prolific predator, and looks and hunts like nothing else in the Caribbean.  The native fish just don’t seem to have much defense against it, and as a result the lionfish are having a field day.  They’ve spread southward from Florida through the Caribbean, and are now almost everywhere.

When we first dove in Curaçao in 2005, no lionfish had yet been seen there.  The first one we ever saw on a dive was two years ago, and they were something we would see maybe once every three or four dives.  On our trip this past September, however, we saw them on nearly every single dive.  Not just one or two, either – dozens of them!  These guys are under almost every overhang or boulder, just hanging there and eating anything they can get into their mouths.  And that’s one of the most amazing things about lionfish – they are just relentless eating machines.  As someone who spends a lot of time underwater (as much as I can, really), I can attest to the fact that predation in the reef environment is something that you don’t really see that often.  It happens, of course, but you really have to be in the right place at the right time to see it.  With the lionfish, though, we saw them eating native fish all the time.  I’ve been diving for my research for seven years now, but if I were to sit down and count up the number of successful reef fish predation events I’ve seen in the wild, well over half of them would be from the thirty or so dives we did in Curaçao this last September.

Unfortunately, even NOAA officials say there’s not much chance that we’ll ever completely eliminate the lionfish from the Caribbean.  People are trying really hard to respond, however.  In Bonaire, officials lifted a 40-year ban on spearfishing specifically for lionfish.  In the Florida Keys, the REEF foundation has started running “lionfish derbies”, offering substantial cash prizes for people bringing in the most, the largest, or even the smallest lionfish.  And across the Caribbean and elsewhere, there has been a push to get the lionfish recognized as a tasty dinner option.  It’s one thing to find a fish you can eat guilt-free in this day and age when so many species are in trouble.  It’s another thing entirely to find a delicious species that you can actually eat with a nice, satisfying sense of spite.

Pictures from Wikipedia, jason.nocks.com, and ipmsouth.com

So the holidays took their toll on us modelers, but we're back in full form and ready to write again.  As a reminder, this slimy segment to the blog is dedicated to our friends under the water.

For this segment, a day late I know, I want to revisit Eels for a cool life history story as well as a prime example of how a life history can potentially throw off how we determine distributions and go about modeling them.  

First, a wiki reference for a description of the American Eel: "The American eel, Anguilla rostrata, is a catadromous fish found on the eastern coast of North America. It has a snake-like body with a small sharp pointed head. It is brown on top and a tan-yellow color on the bottom. It has sharp pointed teeth but no pelvic fins. It is very similar to the European eel, but the two species differ in number of chromosomes and vertebrae."  Here's a pic:

So even thought this critter has been researched to hell, with almost 10,000 publications and studied by Aristotle and Freud, we still know little about it.  And this is due to its crazy life!  The thing is, scientists and anglers never caught baby eels. Not until about 1900 did it come together.

You see, eels spend almost their entire life in freshwater. So it was a big surprise when scientists were raising these tiny transparent 2-inch worm-like things in captivity when they turned into juvenile eels.  At the time, these "glass eels" were considered their own species, Leptocephalus brevirostris.  To this day the larvae are called leptocephalus (should that be italicized when its a Latin common name??).   

So whats the story!  Quote from the interweb: "The eel lives in fresh water and only leaves this habitat to enter the Atlantic ocean for spawning.  The female can lay up to 4 million buoyant eggs, but dies after egg-laying. It takes 9 to 10 weeks for the eggs to hatch. After hatching, young eels move toward North America and enter freshwater systems to mature."

So that states it mildly.  These fish swim from sometimes hundreds of miles inland, to the middle of the Atlantic ocean, the Sargasso sea, breed and then die (much like Salmon but the opposite, sort of). The larvae hatch, then being 2-3 inches, swim back to land and up streams, growing into juveniles by the time they reach adulthood.   

There's much more to this eel story, they're economically important and threatened from dams and overfishing, but the main reason for this post is to bring up the point of the importance of life history when understanding distributions.  Just because habitat might be marginal to one life stage, doesn't mean another stage doesn't completely rely on it for various reasons. My research right now is being complicated with decisions on ecologically relevant thresholds, so the perspective of habitat utilization among and between life stages is important.

Ben Labay is a "fish-geek" and research associate for the Texas Natural History Collections at UT Austin

See his fish art at: www.inkedanimal.com

This is a combination Fish Friday and Parasaturday post. Basically, I was looking up recent news of parasites and this little gem popped up in the San Marcos Mercury:
http://smmercury.com/53183/invasive-snail-parasite-threaten-central-texas-fish-stocks/ 

An invasive snail species, Melanoides tuberculatus, from Asia is invading central Texas waterways. The species was originally adapted to warmer temperature water (above 64 degrees Fahrenheit) which had constrained its ability to spread from warm springs at the head of the Comal River to other cooler surface waters. Alas, as evolution would have it, or fortunately from the snail's point of view, the snail began to adapt to its new climate.

"In 2009, Huffman began finding snails thriving in the much colder waters of the Guadalupe River, and by 2011 they’d moved upstream as far as Gruene Crossing and downstream through Lake Dunlap and as far as one mile into Lake McQueeny. In January 2012, Huffman found hundreds of snails seemingly thriving near Dunlap Dam in water that had been between 11-13°C (51-55°F) for weeks—temperatures that should’ve killed the snails within two or three days."

I find this next part the most interesting though:
 "Because of the continuous, wild temperature swings at the confluence of the Comal and Guadalupe rivers in New Braunfels, Huffman predicted as far back as 2000 that if the snail were to ever make an evolutionary adaptation to colder temperatures, that’s where it would happen—and that prediction now seems to have been borne out." 

I also wonder how much the mild winter, hotter temperatures and drought has contributed to the invasive expansion of this snail. Shallower streams caused by drought would most likely be warmer as well, right? Huffman goes on to say that there aren't as many mature fish appearing in the Comal anymore, he attributes this to the trematode parasite carried by the snail which he doesn't name but I'm assuming is Centrocestus formosanus based on another paper he published, "Egg predation and parasite prevalence in the invasive freshwater snail, Melanoides tuberculata (Müller, 1774) in a west Texas spring system":
http://www.aquaticinvasions.net/2011/ACCEPTED/AI_2011_accepted_Ladd_Rogowski_correctedproof.pdf

The parasite actually damages the host's fitness in the following way:"Because the flatworm encysts on the gills of fish, it interferes with the fish’s ability to oxygenate the blood. With enough parasites, the effect would be like a person trying to run a race during an asthma attack. For fish, such infections would make them slow and sluggish, easy picking for predators long before the parasites killed them outright." 

The parasite has been found in west Texas springs but I don't see any evidence that is in central Texas from this paper or news article. Readers, is this parasite in our region? 

Does anyone want to build an SDM for this invasive species and its parasite, wink, wink, nudge, nudge? It could be fun!

Author

Stavana Strutz is a doctoral candidate studying disease ecology in the Parmesan lab at UT Austin.

Welcome to Fish Fridays, our weekly value added segment about all things fishy. Today I wanted to highlight Moray eels and a really cool morphological adaptation that this critter has. It has to do with their jaws!

Vertebrate jaws are of course a product of evolution, and all vertebrates, even humans, have at some point in development serially repeated array of pharyngeal arches. We retain only the most anterior arch to form our jaw.  Fish have this jaw as well, but they retain the other arches in their hardened form as structures that support the gills, sometimes supporting additional teeth as well.  But imagine if the most anterior arch wasn't the only that developed into a fully functioning jaw? Then you would have a series of jaws! This is only the beginning of why eels jaws are unique. 

Sometime around 2008, Rita Mehta from UC Davis found that eels feed like no other fish.  Like many fish species, they have structures inside their throat called pharyngeal teeth that aid in processing food, but Moray's pharyngeal teeth have evolved to such an extent that they function as a second set of jaws, with the ability to extend forward in the mouth and grab food caught by the primary jaws. This of course is reminiscent of the creature created by Giger that was used in the movie Aliens, and thus the Moray eel has gotten even more attention as an ominous predator.  

Apparently the closest thing to this elaborate set of jaws exists in some snakes.  See the video below with the UC Davis researcher who discovered this.

Ben Labay is a "fish-geek" and research associate for the Texas Natural History Collections at UT Austin

See his fish art at: www.inkedanimal.com

Many of our group are self-described fish geeks and use this taxa group in our modeling research. So we've decided to force our love of fishes onto the readers of this blog with a weekly value-added segment known as Fish Fridays!  Fish are a fantastically interesting and large group that include many classes of organisms, and it was pointed out to me by Dan just last week that for fishes to be a monophyletic group, humans would be fishes as well! So we should have plenty to talk about. This segment is intended to provide brief and fun natural history stories about all things fishy, and so it might not always deal with species in space themes.

For this first Fish Friday, I've decided to geek-out on a relationship between freshwater fish and mussels that I've been thinking about a lot lately. It's a bit of a focus on mussels instead of fish, but it's just such a cool relationship and story of fish mimicry that I couldn't resist. 

As we study freshwater fishes, we have to constantly adapt research approaches to incorporate the distributional constraints that a river network places on these organisms, and with this in mind, we might as well be working with freshwater mussels as their ecology and distributions are fundamentally tied to fishes. This stems from the reproductive ecology of freshwater mussels.

In freshwater, female mussels produce eggs that develop into a larval stage called a glochidium, which temporarily parasitize fish, attaching themselves to the fish's fins or gills. In some species, release occurs when a fish attempts to attack the mussel's minnow or other mantle flaps shaped like prey; an cool example of mimicry. 

Mussel larva, glochidia, are generally known to be species-specific and will attach to any fish gill, but only live if they find the correct fish host. Though from what I gather there is still a ton not known about specific mussel-host relationships.  The glochidia, once attached to the correct host's gills, will live there for a number of weeks before breaking free and dropping to begin an independent and sessil life. This reproductive ecology of mussels tie them directly to the distribution patterns of their host fish, and thus research in distribution of fishes lends well to studying mussels.  I leave you with a video that explains this all using largemouth bass and the genus of Lampsilis mussels.  I think the one featured in the video is a pocketbook mussel, thought I'm not sure.

Ben Labay is a "fish-geek" and research associate for the Texas Natural History Collections at UT Austin

See his fish art at: www.inkedanimal.com