Living Fossils of the MesophoticLatest update November 2, 2018 Started on July 7, 2018
We're on a mission to unveil the secret world of feather stars, from shallow to mesophotic depths, micro-world to voracious predators that feast on them. Enjoy the adventure!
They hear us before we see them
Hawkfish, filefish, wrasses, even cuttlefish…you name it, we’ve seen them all munching on our superstars! But these are rare sightings. Despite having seen more than 33,000 injured feather stars (out of 38,000 total individuals surveyed!), we’ve only caught a handful of fish predators in action. Why don’t we see more of them attacking feather stars during surveys? Because they hear us before we see them.
Open circuit SCUBA
The technology, called ‘open circuit Self Contained Underwater Breathing Apparatus (SCUBA)’, most divers (including us) use to breathe under water is loud. In this system, our divers suck air out of their SCUBA tanks and expel bubbles into surrounding waters (hence the name ‘open circuit’). Creating enough noise to temporarily interrupt fish during their dining activities. So, spying on fish using this gear is out of the question…unless you spend 100’s of hours watching feather stars at the bottom of the ocean like we’ve been lucky to do throughout this expedition.
There’s a solution: closed circuit SCUBA (a ‘rebreather’). This fancy diving equipment is silent, allowing researchers to undertake covert operations to snoop on fish while they feast – our next ambitious purchase perhaps! For now these chance observations into the secret world of fishes have revealed a huge wealth of information on this little-known topic (of feather star predators). We feel very fortunate to have caught a glimpse of the games fish play with feather stars!
‘Island hopping’ on underwater scooters
Venturing to deep and previously unexplored parts of the ocean is exhilarating (a joy only possible through tec diving), but sometimes we find nothing but sand. Meaning, our tec team would have spent countless hours preparing gases, planning decompression stops, all safety related logistics, etc…to drop to a deserted plain of sand, devoid of feather stars (and anything at all, really).
Forget about swimming, we ‘scoot’
Luckily, Marine Conservation Philippines have DPVs (short for ‘diver propulsion vehicle’) at the ready to save our tec team from a lot of heartache when they drop on a sand field. These underwater scooters instantaneously turn our tec team into Jacques Villeneuve (FYI one of the fastest Formula One driver, and il est un Québécois like our team leader Angela), allowing them to speed past gut-wrenching deserts to the closest deep reef without losing precious time or expending much energy at all.
Fantastic discoveries await
The team always keep their eyes peeled for shadows that we hope will turn into a mesmerizing coral reef, and such vigilance during our explorations can really pay off! On a recent dive the team was thrilled to discover a new deep reef in one of our dive sites. Exploring between 50 and 60 metres for feather stars, out of the darkness formations began to appear, and then a full blown wonderfully diverse and colourful reef, starting at 50 metres and continuing deeper than we could see. Giant pink fan corals and schools of fish distracted us (only briefly) from our superstars.
Occasionally the tec team find themselves 'island hopping', moving from one large coral bomb, assessing all feather stars (and their guests) in the immediate area, then scooting in search of the next suitable ‘island’ to survey. Who knew the sight of multiple looming shadows could bring such excitement!
Let’s pause for storms and puppies
Sometimes we’re forced to halt our research temporarily while the elements work out their frustrations. For weeks the weather wo/men threatened us with 100% chance of a typhoon - the biggest one to hit the country this year. They were right. On September 13th black clouds rolled in bringing torrential rain (typical of tropical storms) with them that pelted down on all of the Philippines until the following week. Forbidden by the coast guard from entering the raging sea (our office!), we sheltered in our hut while the typhoon caused havoc in the Philippines, on our island and dive sites. Meanwhile, found just in time, the day before the storm, we found a four-week-old puppy abandoned in a tree near one of our dive sites. We watched the storm subside while Adoba (our new-found puppy and team member!) got stronger. Now we’re patching up broken cages, tossed around at shallower depths (deeper ones were undamaged), relocating escapees, and embracing every minute of puppy Adoba. What a time to be alive!
The arms we amputated 80 days ago are showing some fine growth. Most of our superstars have regrown 5 cm (about 1/3 of their full length), but not Stephanometra - it’s the Michael Phelps of arm regeneration! Having grown twice as fast as all the others, averaging just over 1 mm per day, Stephanometra has almost fully restored its original arm length in just a short time span. While this superstar comes in first, Phanogenia, falls way behind - growing slowly, at 0.35 mm per day.
Slow and steady wins the race?
Not in this case. These differences in arm regeneration rates reflect alternative adaptations to surviving predatory attacks (aka. they departed from their common prototype and both survived). Phanogenia, who has 50-70 arms, can’t swim away from hungry fish like Stephanometra can. With that many arms, Phanogenia, we think, can afford to lose some arms to hungry fish, and regrow those missing arms slowly with their feeding efficiency being relatively unaffected. Because the other 50+ arms can continue feeding, there’s really no pressure to regenerate quickly. But for Stephanometra losing one arm is a big deal (it only has 20-30 after all), so we think it regenerates faster to compensate for this.
Mystery solved, arm number dictates regeneration rates?
No. Results aren’t that straight forward, not all of our superstars fall neatly into the Stephanometra-Phanogenia arm number/regeneration spectrum we outline above. For now, we’re getting some sense of the variation that exists among our superstars, but we’ll need to spend a bit more time understanding why some grow faster or slower irrelevant of arm number. Anomalies like these drive science (and society) forward!
Squat lobster: fussy eater or loyal costumer?
A puzzling trend emerges from our infestor experiments: squat lobsters show individual fidelity to their host. That’s right, 20 out of the 20 we transplanted always went back to the exact same individual we originally found them on, even when we provide them with another host of the same colour and type (of species). Odd, right?
It’s palate, not camouflage
At first we thought camouflage might have something to do with it, but then why are they so eager to leave a mirror image of their original host? We think it all boils down to their ferocious appetite for fine food, in combination with a feisty attitude, which have them defending their catnip (aka feather star feces) and returning to it no matter what.
Where to find the best catnip, for squat lobsters
Why would this particular feather star’s feces be better than another’s near identical ones? We’re not sure. But we like to think of it this way: imagine your favourite pizza from a specific pizzeria. Yes, other places may offer a nice pizza, but none are as delicious as your favourite which is why you remain loyal (and keep returning) to your original restaurant. Squat lobsters would agree with you, no feces are as good as their hosts' feces? And they aren’t keen on sharing it!
The ultimate jigsaw puzzle
The team surveyed 30 individuals of each of our superstars (8 x 30!), over six depth gradients (0-60 m depth)…AND repeated this three times (at three sites)! Why fuss around replicating surveys in different locations? Because site differences paint a fascinating story about our (human) relationship with reef inhabitants, like feather stars and those that chomp on (and injure) their arms.
We took a peak at those living in sites with healthy and unhealthy shallow coral reefs, comparing what we found at neighbouring mesophotic depths. We found fewer injuries at deeper depths than in healthy shallow reefs, but these numbers went up in deeper individuals bordered by stressed shallow reefs. Why? Maybe high levels of fishing activity, tourism, and other physical stress on unhealthy reefs, like the one in our expedition, leave fish predators (of feather stars) no choice but to seek shelter in deeper parts of the reef (in the mesophotic realm) where they feed on our superstars (and/or their infestors), leaving a trace for us to measure - so we think. This is only a small fraction of a complex jigsaw puzzle, eventually allowing us to fit these tessellating pieces together into a decipherable portrait!
Tiny food factory
Remember that big ball of Velcro (aka our superstars’ extra sticky arms) from an earlier blog post: nuisance to divers, but a necessary part of the feather star body morphology used to fulfill their gluttonous appetite for food. It is this voracious feeding habit that has our superstars playing a key role wherever they live. By just feeding, feather stars exchange energy between pelagic (water column) and benthic (seafloor) communities (a process called bentho-pelagic coupling). Meaning, they capture small food particles, often carried by strong currents, that brush past their arms and eventually make these particles available to the benthic community (like crabs, lobsters, and other small animals living on the seafloor – called ‘benthos’) via nutritious fecal pellets (like a tiny food factory!). The benthic community profit from feather star gluttony - small particles (too small for benthos to capture themselves) are simply repackaged into larger clumps on which benthos can feed on. As we’ve seen, some (like infestors) have abandoned hunting for food and cleverly (permanently) perched themselves on their feather star host for an all you can eat fecal buffet!
There’s life at depth, a lot of it too!
Our tec team have filmed over 20,000 feather stars in video transects spanning coral reefs in the upper mesophotic zone (between 30-70 m), called ‘mesophotic coral ecosystems’ (or MCE). From these videos we can identify our eight superstars and see how many other feather stars live there. To our surprise, comparisons with transects from shallow reefs (surface to 30 m depth) reveal similarities: feather star communities are equally diverse, but more of them are found in shallow reefs. However, while we do see overlap, some species are rare in the shallows and others are completely unique to MCEs!
You might wonder (because we did too): how can a world so rich exist in this deep and dark place? Changing light penetration is key to orchestrating the shift in communities we see from shallow to deep. Whereas shallow reefs receive total light penetration, light struggles to access the mesophotic zone (found at 30-150 m depth; ‘meso’ means middle, ‘photic’ refers to light), and none reachs past this zone to the deep sea (deeper than 150 m; called ‘aphotic’, ‘a’ = no, ‘photic’ = light). Because of this, light dependent coral, algae, other organisms can still be found in MCEs, but not deeper. Note, however, there is life in the deep sea too (even coral reefs spanning several kilometers, like in shallow and mesophotic zones!).
Life after fieldwork: where the real magic begins!
Life doesn’t stop after completion of fieldwork, this is where the real magic behind science begins! After two months of diving to the seafloor, spying on our superstars and their inhabitants, we have gathered a tremendous amount of data. Now we take ‘dry days’ (sit at our computer rather than the bottom of the ocean) to create graphs that highlight patterns hidden behind the vast sea of numbers we’ve generated.
So, what do these graphs tell us? How intimate is the relationship between feather stars and their micro-world? If you recall, we played a little game of Magic Cup, shuffling shrimp and lobsters from one feather star species to the next, some had different colours, others had the exact same - we wanted to see if they would go back to their original host. The graphs unveil a remarkably close relationship between squat lobsters and feather stars, and one that isn’t so clear for shrimp. They tell us squat lobsters are picky when it comes to selecting a forever home, with the majority returning back to their exact host after a matter of hours (we call this ‘individual fidelity’). Shrimp on the other hand show ‘species and colour fidelity’ (not individual fidelity), only reshuffling themselves if the exact colour of their new home doesn’t match theirs. It seems feather stars might in fact be a perfectly engineered home after all, providing inhabitants with everything they desire in a safe haven.
Voodoo gases that keep us sane at depth
Things get a little bit tricky in terms of gas once you start breathing it deep. For these dives our tec team need to consider not only narcosis (principally from nitrogen, which blurs the mind, much like on a good night out with friends and several bottles of wine), but also the fact that 21% Oxygen (i.e. air) becomes toxic deeper than 57m. As a general rule, dives beyond 50m require ‘trimix’ – a gas mix of Helium, Oxygen, Nitrogen. Adding Helium to the mix allows our tec team to reduce the amount of Nitrogen in the gases they breath at depth. They also carefully blend these gases to reduce oxygen content thereby lowering the dangers of Oxygen toxicity. This week's dive to 65m at Unity Point, for example, was on a blend of 18% Oxygen, 30% Helium and 52% Nitrogen. As previously discussed these dives require long decompression: 26 minutes at 65 requires more than an hour ascent switching from the gas they breathe at depth (trimix, also known as ‘back gas’) to first 50% and then 100% oxygen.
We get creative with gas blending
As we use a partial pressure blending system it can be hard to get the final few liters out of large tanks of our precious (expensive) Helium stores, but a craftily put together system using pipes, plastic bags, duct tape and a faucet allow the tec team to get Helium directly into the compressor, and blended back gas. This success was greeted with unbridled happiness that this plan (referred to as ‘trash bagging’) actually worked!
Feather star fingerprints
Keeping track of hundreds of near identical individuals seems like a cruel mind game, but fear not, some of our superstars have ‘fingerprints’ just like you and I! If you were to flip over a feather star and look at its centrodorsal (the middle part of its body where all arms radiate from) you would notice darker patches - a pattern reminiscent of an inkblot. At a glance they seem very similar from one specimen to the next, but stare at them long enough and distinct patterns form that help us differentiate one individual from another. We rely on photographs of their centrodorsals, which we match to its identical twin from the day before, to relocate the individual and then note findings specific to it. As our experiments go on we find ourselves becoming masters at this memory game. Here are some examples of the fingerprints we work with. Are you able to find the matching pairs?
Not so sessile after all - they crawl and swim!
We’ve talked previously about our swift moving escape artists (infestors), but what about our superstars? Most assume feather stars are sessile creatures, they look like a plant after all and, if undisturbed, they live on the same perch (a rock, piece of coral, anything they can grasp) for most of their lives – which is great for relocating individuals for our research! BUT they do have the potential to crawl or swim away from a predator (and our experiments). They do this surprisingly quick too! How does their physiology enable them to move so freely? Feather stars have ‘mutable connective tissue’, a ligament that they actively control, allowing them to coordinate complex movements, on multiple arms, at the same time. For example, feather stars stiffen this tissue to remain in their feeding posture against a strong current, and relax it to autotomize arms when nibbled on by a fish or other predators. These ligaments are also responsible for their highly coordinated swimming strokes: first, a short burst of alternating arms moving up and down, then the arms gather to form a parachute for the slow fall to their new perch. Here's a video of their mesmerizing dance caught on camera (by Caters Clips)!
Our bittersweet love affair with Mesophotic reefs
One key reality in SCUBA diving is the deeper you go, the shorter you stay! Unless you’re technical (‘tec’) diving. Staying within prescribed ‘no decompression limits’ (meaning that at any point of the dive it is relatively safe to surface) severely shortens your time at depth, and in our case, make it impossible to survey sites much deeper than 30 m. Thanks to tec diving, Tadhg and Angela (our ‘tec team’) can plummet safely and for long periods of time to our deep sites (30-70 m). But this comes at a cost: unlike recreational diving, the tec team does not have direct access to the surface without risk of decompression sickness (remember those tiny bubbles that cause big problems?).
Copious gas needs
Breathing under water is our (every marine scientists’) dream superpower! Until that comes true we must bring a SCUBA (Self-Contained Underwater Breathing Apparatus) tank full air to explore the seafloor. One tank typically suffices for a short and shallow dive, but not for a tec dive. The longer and deeper our tec team ventures into the deep, the more gas they need to carry to ascend slowly, stopping (‘decompressing’) and waiting several times on their way to the surface. By doing this, they eliminate gases that have quickly accumulated in their tissues, which then leave their body gradually rather than like a well shaken Champaign bottle ready to pop! To decompress, the tec team bring up to four tanks filled with various mixtures of gas (note: Oxygen becomes toxic at depth - another layer of complexity to diving that deep). In short, gas needs is where our bittersweet love affair with mesophotic reefs began!
Master blender/underwater clown – meet Tadhg (‘Irish man’)!
Known around MCP for his witty jokes and outgoing personality, it’s safe to say that this ‘Irish Man’ is a fan favourite. It’s not all fun and games though, he’s often found working hard behind the scenes, blending gases (requiring several hours of cautious work) so he and Angela can venture to deeper parts of our dive sites to survey feather stars who live there. This realm, known as ‘mesophotic’ depths (deeper than 30 m, shallower than 150 m), is severely under explored because of the challenges involved in accessing them. For example, to dive to 60 m (dubbed ‘upper mesophotic’) Tadhg uses some serious problem solving and mathematical skills to calculate the exact volume and ratio of Helium, Oxygen, and Nitrogen we need to breathe at depth and during our ascent to keep us at the bottom for long enough to finish our surveys and surface safely without any gas or decompression issues (aka build-up of small bubbles in our tissues that could cause big problems at the surface).
Perfectly engineered (feather star) metropolis
Our team’s eagle-eyed vision (we wish!) can spot the tiniest of squat lobsters (generally less than 5 mm long), ghostly shrimp (some are translucent), burrowing fish, and near invisible worms… all of whom mirror the colour and patterns of their home so perfectly that they are often only detectable when/if they squirm away when awakened by us. That’s why we’re often seen tickling our superstars underwater!
If you recall, we chose our eight superstars because of their vastly different morphologies. In theory, these dissimilarities help increase habitat complexity in a coral reef system (aka. provide a wider array of homes for potential inhabitants, like infestors, to choose from). By surveying the feather star metropolis we can see how good they are at contributing to complexity. Our surveys tell us they’re masters at it! For example, one individual can house as many as ten inhabitants from many different forms of life (snails, flatworms, and sea slugs to brittle stars, sea cucumbers, and lobsters). There’s no telling what you’ll see beneath this perfectly engineered metropolis!
Hard worker (not just because her favourite dive site is Unity Point) - Introducing Charlotte Matthews
Committed to exploring the micro-world of feather stars, Charlotte spends hours under water staring at their undersides! She (and the team) have surveyed nearly 3000 feather stars over five vastly different dive sites, inspecting every part of their body for a combination of injuries (regenerating and missing arms) and infestors to see if the two are related. Her treasure hunt (of infestors) doesn’t stop there, every day she fights ripping currents in Unity Point, surge and waves in Malatapay (her two favourite sites!) just to have a peek at this feather star metropolis. As you can imagine this work requires a lot of intimate contact with her specimens so Charlotte can often be seen carrying out her safety stop with remnants of feather star arms clinging on to her. She has even been known to sport the tip of a feather star arm as a fashion accessory for her hair.
An ocean-worthy cage
Building an ocean-worthy cage is not that easy, even Google has no answer on how to do this.
When Google fails, we get creative and improvise. In just a few hours Raffy and Ceasar build the carcass (a 1m x 1m x 0.5m frame) out of thin pieces of bamboo and for two days we tie slats of bamboo (acting as prison bars) to this carcass. Admiring our blistered fingers (sure sign of hard work?) we realize “mesh is best”. It’s much less tedious to sew mesh to the frame than each individual piece of bamboo, and water can circulate through it to feed tiny food particles to our superstars living inside the cage while also keeping escape artists (like our squat lobsters and shrimp) locked in.
The ultimate test to our newfound fitness is lugging the awkwardly large and heavy cages through 150 m of choppy surface water and securing them to the seafloor. After two months of experiments, strong currents, animals growing on/eroding them, and scientists tugging at them daily, the cages have survived and become one with the ocean (they look and smell like one!).
Presenting Rob Hechler: Canadian undergraduate student, lover of cuttlefish…and wearer of Tuque’s in the scorching Philippine weather!
With a knack and enthusiasm for all things digital, we knew Rob would love working with the expedition’s copious amounts of video transects. He and the team are collecting 100s of shallow- (0-30 m) to deep-water (30-60 m) transects, and he’s patiently analyzing them all! Here's a picture of Rob slowly filming all of the feather stars along a 50 m underwater line transect. By following this line and filming at a fixed height above the seafloor (see the object dangling from Rob's hand and hovering a few inches off the seafloor?), he knows exactly how much area he has covered, making it easier for him to compare patterns of who is where at different depths. While no one questions his scientific abilities, some do however wonder about Rob’s decision to bring a multitude of sweaters, jackets and fleeces to a country where temperatures rarely dip below 30oC but he stands by his decision, occasionally even resorting to wearing a Tuque (Canadian term for a knitted winter hat)!
Our home away from home – meet Marine Conservation Philippines
A not-for-profit organisation entirely dedicated to conserving marine habitats in the Philippines…and kindly going out of their way to make sure our research needs are fulfilled.
SCUBA diving boot camp
It was Marine Conservation Philippines (MCP) who made sure our dive team would be “research ready” in time to collect data. By their third week at MCP, Charlotte, Mikalyn and Rob were indeed that thanks to their dedicated drill sergeant, Dan (MCP’s Lead SCUBA Diving Instructor), who put our eager students through a rigorous underwater boot camp, including swimming through hoops underwater (backwards too!), hovering (sometimes upside down) above the seafloor while composing a novel (or nearly that) for Dan - all critical skills needed to record data under water.
Technical and deep diver boot camp
Meanwhile Tadhg and Angela (project leads) underwent a special boot camp of their own – a technical and deep diver boot camp. Diving deeper than 30 m brings on extra danger, requiring complex technical gear, gas mixtures, extensive technical dive training (more about this later on in the blog!), and once certified, practice. Soren (MCP Founder, Technical Dive Instructor extraordinaire, also dubbed Michael Phelps at times) is our saviour/mentor in this aspect. He has taught us everything we know and provided the shiny toys needed to successfully complete all surveys in the upper mesophotic zone (30 – 60m depths) and when one of us temporarily falls ill, mesophotic surveys continue, thanks to MCP technical divers who step in to help (thanks Ashley!).
Cages and their secret ingredient
Finally, we reveal the secret ingredient to our cages: the careful handicraft of Raffy and Ceasar, MCP's multitalented Dive Technician and Handyman. Our crinoids would be lost without them (literally).
MCP staff are not only there to provide technical support, but also, for 4-6 months of the year they are our family and home away from home. Learn more about MCP here: www.marineconservationphilippines.org
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!
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.
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.
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.
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.
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.
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.
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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