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Living fossils of the mesophotic

July 7 2018

We're on a mission to study feather stars over the depth gradient from shallow to mesophotic depths. We focus on the intimate relationships between them, their infestors and predators.

July 7 2018


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Mission Underway

Introducing (w)undergrad Mikalyn: organizational and visual mastermind with priceless underwater facial expressions

We’ve told you a little about the animals we’re studying, our experiments and research sites, now we reveal the team making all of this possible. First up is one of our undergraduate research assistants, Mikalyn! Exaggerated facial expressions are key to storytelling in synchronized swimming, a skill that translates well in SCUBA diving. One glance at synchronized swimmer Mikalyn’s face reveals all about the status of her squat lobster/shrimp-host experiments. Mikalyn is delving into the world of community relationships by looking at infestor fidelity, to keep track of who is where in her cages she must carefully memorize the distinguishing features of each individual she works with. Outstanding organizational skills and visual memory allow her to seamlessly plow through a large number of replicates (she already has 120) in just a few weeks!

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Our complicated love-hate relationship with Unity Point

WHACK! That’s the sound of Unity Point hitting us straight in the face. This dive site -known for its fast flowing currents and thousands of feather stars- offers a perfect all you can eat buffet for our gluttonous feather stars. While our superstars love this, we don’t. Research here is a test of our patience and dive skills (maybe also a great workout?). Imagine swimming a 50 m pool length (essentially our transect) against a ripping current. That’s only half the battle because back on land we have to analyze the transects to see who and how many are present there (otherwise known, in ecology, as community distribution and abundance), so a 15 minute analysis (e.g. Dauin, another dive site) can quickly turn into an impossible task, taking hours (up to 4 hrs!!) to finish as feather stars are found by the thousands! We now feel fully prepared to take on our opponent. Til we meet again, Unity Point.

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Angela, this is fascinating!! Great work and a real pleasure to follow. I wish we could find a way to share this with students in Quebec. Thinking about that.

Thank you Donna! We could have a little video conference/tutorial with your students at some point. That would be fun! Thank you for reading and following :)

Feather star = big ball of Velcro!

The name “feather star” gives the illusion of something soft and fluffy, but in reality they are big balls of Velcro! In fact, their pinnules (branches off the main arm) mimic the shape of a Velcro bristle. A necessary part of their morphology that they use for capturing small particles in the water. Their Velcro like properties has also earned our superstars a bad reputation among divers. An accidental encounter with a feather star results in forever picking pinnules and arms off of your wetsuit/hair. Does this property inhibit our research? Yes, it does. Remember how we meticulously amputated a fixed number of arms off feather stars in our regeneration experiments to then calculate arm growth? This is thought to be affected by number of arms re-growing simultaneously, so arm hemorrhaging could skew our results. Not to worry, we’ve finally defeated this ball of Velcro, now used to our advantage to transport (up to 10!) specimens to their temporary homes.

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Anyone know how to “Wrasse proof” a cage? Because I need it.

We all know life is multifaceted and complex, it turns out infestors and their feather star hosts aren’t immune to this. Recently, shrimp and squat lobsters have been mysteriously disappearing from our cages. Nothing to worry it’s just a few individuals, it’s not detrimental to our experiment. But still we’re scientist (detectives?) so we feel compelled to solve this case. This week we had a momentary stroke of genius while thinking of our results and concurrently watching fish darting in and out of our cage. Our latest results tell us infestors show high fidelity to their host - they never leave their feather star, when moved they return quickly. After a brief literary investigation, we find out one fish in particular, a floral wrasse, happens to feed on small crustaceans (like our shrimp and squat lobsters)! Mystery has been solved but the problem persists and the wrasse continue to dine at our catered buffet.

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Preparation Stage

This week we have been setting up our infester experiments. We installed a large cage on the seafloor that has been subdivided into eight compartments. Here we house pairs of feather stars that are infested and uninfested with squat lobsters and shrimps. We trick the lobsters/shrimps by transplanting them to different hosts – some are very similar to their initial home, while others are vastly different. We track their movements to record host, colour, species fidelity. Stocking the cages with infested feather stars has not been an easy feat because feather star squat lobsters and shrimps are masters in disguise. Their specific colour patterns precisely match that of their host, allowing them to blend seamlessly into their feather star (or what we call a micro-habitat). Here are a few photos of the specimens collected this week. Can you spot the infestor? Any luck? We’ve zoomed in on the infestor, but still they are hard to see because these little guys are often less than one centimeter in length and well hidden with patterns and colours mimicking their host. Our first experiment testing individual host fidelity is due to begin soon! We'll keep you posted on the riveting activities of feather stars and their infestors, as well as the other experiments and observations that are due to begin in the next few weeks.

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Another aspect of our work consists of monitoring arm regeneration in our eight superstars. Here, we meticulously amputated four or more arms off 100 individuals, mimicking an injury caused by a fish, sea urchin, or other predator. Our animals feel none of this pain (we promise!), in part because they can’t feel pain (feather stars have no central nervous system like we do), but also because autotomy (self-amputation and regeneration - a magical power I wish I had!) is a natural process used by feather stars to escape fatal injuries. By sacrificing a few arms, the individual can swim away relatively uninjured from a hungry predator. This part of the experiment requires a lot of time and patience. We sit and wait for the arms to grow back (regenerate) less than a millimeter per day. We’re interested in any possible variation in growth between the eight species, and test what factors, like nutrient availability, temperature, depth and type of feather star (species), could be responsible for this dissimilarity in growth rates. Here's a picture of some regeneration in one of our feather star, at last! And the temporary home of our amputees.

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Our research much resembles a game of ‘Where's Waldo?’, in which we try to spot well camouflaged infestors, like shrimps, lobsters, snails, etc., that live among feather stars. By experimenting on these host-infestor relationships we can better examine the morphological and behavioural plasticity of infestors. For instance, we are testing host-specificity of small squat lobsters and shrimps that have uniquely adapted to living within the feather star’s arms and cirri (the fingers feather stars use to cling to their perch). In the images below we show two examples of such infestors: a shrimp (white), squat lobster (orange), and fish (brown and white) hiding in their feather stars. If you look closely, this fish has no fins - it has 100% adapted to living/slithering around on it's feather star host! Concurrently, we are documenting infestor and feather star species distribution over the depth gradient (from shallow to mesophotic coral reefs) to capture community patterns, resemblance across the bathymetric gradient, but also to try to understand factors that correlate with arm injuries in feather stars - one of which might be these inhabitants (shrimp, lobsters, etc.). Basically, we want to know who lives where, and, if absent from a locality, why? Here's a picture of Charlotte carefully examining the underside of feather star Capillaster multiradiatus during one of our surveys.

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Hello mesophotic lovers! We are back in the Philippines and continuing our research on the spectacular feather stars (or technically known as ‘crinoids’) that live here. This year we’re looking into multiple aspects of the native crinoid species’ ecology from shallow to mesophotic (30-150 m) depths. With three new research assistants from the University of British Columbia (Charlotte Matthews, Mikalyn Trinca Colonel, Rob Hechler) our team (led by Tadhg O Corcora and Angela Stevenson) is hoping to document observations from multiple depths and different sites along the East coast of Negros Oriental, Philippines, as well as conduct in situ (in water) experiments. The diversity and abundance of feather stars here, in the Philippines, is simply outstanding! Because we are interested in contrasts between species, our projects only focus on the eight most morphologically different species. Here are our superstars for this year's expedition, which you’ll see plenty of over the next few months!

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Expedition Background

We're on a mission to reveal host-infestor relationships over the depth gradient, from shallow to mesophotic depths.


We're entering a truly exciting time for mesophotic exploration. Happy to be following along here!

Thanks David!