The freeloading lifestyle of fresh water mussels

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Conglutinates of the Ouachita kidneyshell – Chris Barnhart

I study oystery things. In my little myopic scientific snowglobe, I know a few things about shellfish, and I know a few more things about oysters. Then I know the most things about oyster filtration. So there’s still plenty of room for surprise.

This very thing happened this year during a local American Fisheries Society (AFS) meeting where I heard a talk about freshwater mussels. Probably because I always seem to be mucking about in briny water rather than its fresher counterpart, I was rather taken aback learning that many of these species have parasitic larval stages.

After females collect sperm that males eject externally, they fertilize their eggs and stow them in their gills where they develop into a minuscule larval stage called glochidia. These juvenile mussels cannot fully develop however until they somehow reach a host fish. They will encyst themselves into the host’s tissue where they will stay until more fully formed, at which point they will drop off and settle on the river floor. The host fish has graciously and perhaps unknowingly provided the small creature with protection and dispersal.

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The strangest detail of this whole process seems to be the intricate tactics mussels have developed to get their little parasitic spawn into hosts. Some species concentrate their glochidia into structures called conglutinates that they then release into the water. Many resemble prey items attractive to fish like in the video  and picture below:

Others, like mamas in the Lampsilis family keep their little ones closer to them while dangling parts of their mantle tissue to the same affect at the conglutinates described above.

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Lampsilis’ display attracts host fish – Paul L. Freeman, Nature Conservancy

For most species of freshwater mussel, the choice of host fish seems to be relatively specific. In some cases, the species of host has yet to be discovered, which provides fertile ground for research into the topic such as the work that Florida Wildlife Commission’s Blackwater Research and Development Center in Holt, Florida has done.

As with other symbiotic relationships within nature, freshwater mussels are incredibly dependent on the health of their host and the system around them. This has further increased the need for continued research and conservation, and in some instances agencies and institutions have fostered cultivation and propagation efforts.

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Speck of Science 8/17/16 – The Greenland Shark abides

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Source: Ocean Treasures Memorial Library

Several news outlets this week have justifiably made a big deal about the Greenland Shark. Recent research suggests these lumbering giants are now the record holder for the longest lived vertebrates we are aware of. This knocks the Bowhead whale from first place, whose age-determination story is fascinating in its own right, bolstered by the presence of an antique eskimo harpoon point.

Often sharks have been aged through examining growth bands present in vertebrae, however Greenland sharks have softer vertebrae that make this challenging. Additionally, due to challenges in reading these rings as sharks age, as well as possible disconnects between growth rate and age, radiocarbon dating has been joining the toolbox for determining fish longevity.  This study used the method with the sharks’ eye lenses.

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These sharks may take up to 150 years to reach sexual maturity, making their population vulnerable if too many individuals are culled before reproducing. They are also bizarrely prone to parasitism by a strangely-elongate copepod (most look more shrimp or lobster-like) that attaches to their eyeball and ultimately causes a march towards blindness. Only 1% of the 1500 sharks in a study concerning infection rates were parasite-free. 85% are afflicted in both eyes. However, due to their reliance on a keen sense of smell, rather than sight, for hunting, it has been suggested that the sharks may actually benefit from the copepod acting as small visible lures that interest nearby prey. However, Dr. George Benz of Middle Tennessee State University with expertise in shark and ray parasites, doubts this theory, instead favoring the idea that Greenland sharks may instead be ambush hunters, taking their targets instead through the element of surprise.

Speck of Science 8/15/16 – Nat Geo Writes About Pooping Comb Jellies

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Still from Ryan M. Bolton 2016 video: https://www.youtube.com/watch?v=weeFO6kLu5o

Lest you think National Geographic is losing their edge, the reason why ctenophores (the phylum to which comb jellies belong) defecating is a big deal is because it was thought this group of creatures had a single opening for both feeding and excreting. University of Miami researcher William Brown debuted videos at the March 2016 Ctenopolooza gathering at the Whitney Lab in St. Augustine (where I’ve done much of my own dissertation field and lab work) that prove otherwise. One of the peculiar videos is featured partway through Nat Geo’s article here. Science writes about the find as well.

One of the most interesting aspects of this find is questions regarding the evolutionary history of gut development. It was thought to be a pretty straight forward pathway from one opening to two. However, because comb jellies evolved before other organisms that still have a single opening, such as sponges, things are looking slightly more interesting. Perhaps ctenophores branched off, and smartly evolved a more complex gut tract independent of these organisms. Or, perhaps some of these single-orificed organisms started with two but lost one over time – similar to the story of some marine mammals that long ago left the sea to become land-dwellers, only to ultimately return again.

 

 

The Science PhD Experience: My Life is a Series of Home Improvement Stores

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Source: Wikimedia Commons

Never when I signed up for this whole PhD “thing”, did I think that further down along the line I would wander down the aisles of countless formless and faceless Home Depots and Lowes, familiarizing myself with PVC epoxies, pipe cutters, types of quick-pour concrete, and erratically color-coded lengths of rebar. While I am in the very last throes of the natural science component of my dissertation, for stretches within the last year, nary a week would pass without at least one, if not several, trips searching for the miscellanea one needs to make a bare-bones scientific project happen.

My method for estimating oyster filtration rates required the use of sediment traps (see my post about it here) constructed out of buckets and netting. However, the studies that used them prior and upon which I based my design, had employed them in very different settings. My traps had to withstand dynamic ocean conditions, tidal cycles, and the interest of the errant passerby. So thus began the nail-biting process of iterative design. What type of buckets to use to avoid re-suspending sediment? What kind of netting across the mouth? How to affix them to reef? How to weight them so they wouldn’t float away during the first high tide?

Practice run after practice run unfolded as I tried various proto-types. Scuba weights affixed to the mouth of buckets using hose clamps. Testing ways to keep everything in one place using ground anchors, thin lengths of PVC, rebar. Phone calls from nearby good Samaritans who had retrieved my runaway equipment (a PSA if there ever was one for labeling your gear!). A slick (if not utterly lo-fi) double-nested bucket design weighted down with rounds of concrete emerged out the mixture of mishaps and successes.  I then did it all again and tapped into the same recurrent type of process when creating a seawater flow-through system for oyster filtration lab trials.

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All the while, I was running to every hardware store in town, looking for materials of the right shape, weight, and construction for whatever small application I had in mind. Many questions directed towards employees started with “This is going to sound strange, but…”. Eyebrows were raised when I bought 30 of something generally purchased in increments of one or two – “…Doing a lot of yard work this weekend?”  I recall poorly relaying the idea of my experimental sediment traps meant to measure the amount of oyster biodeposits produced during my experiment, and the amusing follow-up question: “Are you trying to keep the oysters from getting away?”

Many questions directed towards employees started with “This is going to sound strange, but…”.

Additionally I had the help of a marine lab machine shop to drill, cut, and sand. I learned how to estimate which equipment I needed for which job. I also had the opportunity to watch those inclined towards clever design and ask plenty of questions. Is there enough water pressure to do that? How do I get the flow to be more laminar? How do I keep this from leaking?

It’s a cultivated skill set, one which rewards those who tinkered with lego and kinex as a kid. Rarely are we told as marine biologists, fisheries scientists, or field ecologists, that we will draw so heavily upon what amounts to being back-of-the-envelope engineers.It’s also a continued argument for the inclusion of the “T” (technology) and the “E” (engineering) part of STEM training that is often desired on the job, but may make scant appearance in a scientist’s formal education.

Most of us instead gain experience through more informal avenues, as the best teacher is often necessity. Also there is no better practice than to constantly build, err, and deconstruct, all while slowly incorporating new fixes and experiencing the fog of confusion out of which comes little sparks of revelation. The act of literally building our science from the ground up is one of ultimate creativity, funneling in threads of right-brain function, and helping us shape solutions in response to whatever demands our research may make of us.

Note: This content has been cross-posted on the blog “From Reef to Rivers: Florida’s Fisheries Science Blog

Speck of Science – 4/19/16 – March of the Crabs

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Source: Animal Planet

Mass migrations fascinate me – massive swarms of creatures on robotic treks to satisfy deep-seated needs for resources – nature’s automatons reaching for food, for mates, for brighter skies. One of the earliest that captured my attention is expressed in this Animal Planet video documenting the movement of red crabs on Christmas Island:

http://www.animalplanet.com/tv-shows/wild-kingdom/videos/christmas-island-red-crabs/

(Note at 1:40, crustaceans seem to be playing “frogger” while obliviously scuttling across roads and railroad tracks. Not the unexpected result of the clash between crab and human.)

A gif of the oceanic equivalent has made a recent appearance online, showing an endless carpet of sandy colored scuttlers (they were in fact red,  or “tuna,” crabs who appeared that way as they stirred up a the sediment on the sea floor). However, this article sheds more light on the unusual event captured by a manned submersible exploring Hannibal Bank off of Panama (fitting name for the location of a slightly unnerving and intriguing event to occur? ). The following video comes from Woods Hole Oceanographic Institut and features scientist Jesús Pineda explaining the details around recording the migration:

 

 

Speck of Science – 4/6/2016 – Gimme Back My Buoy

I have been through a blogging dry spell lately, but nothing like starting out again with the amusing news of 2 men essentially holding a USGS (United States Geological Survey) scientific buoy hostage.

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A Map of the Monterey Bay Aquarium Research Institute’s Coordinated Canyon Experiment. The buoy was associated with this particular project. Source: MBARI

The buoy, which was deployed to gather data related to El Niño events, drifted off its mooring during a recent storm. Two fishermen chanced upon it, recovered it, and are now demanding $13,000 in exchange for its return. Their lawyer, a seemingly rather colorful character and self-described “old trial dog”, initially set the price a bit higher based on the following mathematics: ” On good days fishing they gross $2,700. Taking the big and gouging thing onto the boat and having it there kept the boat out of action for nine days for a multiply of $24,300. Twenty percent of value would be $80,000. We offer to SELL (you can use any other word you like in an agreement) it to you for $45,000.” One has to wonder why they took it upon themselves to keep the “big and gouging thing” on their boat for nine days in the first place.

The article notes from several sources that salvage laws likely do not apply here, especially as the buoy was never properly abandoned. However, the loss of and tampering with of expensive research equipment has always been a known and pervasive issue in oceanic research.  I for one will be interested to follow the outcome of this eyebrow-raising case.

Depth of Field #2: The Sea Hare Emerges

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Photo Credit: Carrie Schuman

The sun is starting to set on expanses of mirror-reflective tide pools speckling the beach of the Tawharanui Marine Reserve in New Zealand. I’ve been walking along staring into them at random in my search for anything novel when I chance across what is at best guess an example of Aplysia dactylomelathe variable sea or spotted hare.

In a surprising contrast to the small chitins, tunicates, and other finds, the sea hare was relatively large, measuring somewhere in the range of 5 to 6 inches in length. As seen in this additional photo, a smattering of spots can be seen along its body:

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Photo Credit: Carrie Schuman

According to this source, sea hares are hermaphroditic though they do not practice self-fertilization. They may often form reproductive “chains”.

As suggested by one of their common names, they may be highly variable in appearance with their coloration primarily determined by the type of algae they feed on.

They release a purple dye as a mechanism to surprise and confuse predators. This particular characteristic was one I had once experienced first hand when handling my first sea hare in the mangroves of Key West. It certainly has a startling quality to it.

Variable sea hares tend to be more solitary, and nocturnal in nature. So perhaps no small amount of dumb luck governed this thrilling little chance encounter.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Aplysia dactylomela