Sensory organ discovered in sponges helps them respond to their environment despite having no nervous system

by Amanda Kahn

Sponges are animals, but they do not have the features we’re used to seeing when we think of animals: no gut, no head or tail, no nerves, and no stomachs or other organs.  And yet despite not having a nervous system, sponges are able to respond to their environment by changing the canal sizes in their filter-feeding system, in an action called the “inflation-contraction response.”  It’s basically akin to what we do when we sneeze.  This was observed in the mid-1900’s, but scientists have only been able to speculate what could be helping the sponges sense and coordinate various cells in their body when there are no nerves or sensory organs observed.  Danielle Ludeman, one of the authors here at the Madreporite, has just published an article describing the sensory organ that she and her coauthors, Nathan Farrar, Ana Riesgo, Jordi Paps, and Sally Leys, discovered in many different species of sponges: primary cilia used to detect changes in water flow.  Check out the time-lapse video below to see how responsive sponges are to irritants (in this case sediments) in the water.

Danielle tested if those cilia are used to detect changes in water flow by using drugs that target and knock out the cilia.  When the cilia were knocked out or knocked down, the “sneeze” response couldn’t be initiated.  If cilia were permitted to grow back following treatment, the “sneeze” response could be initiated.  In our kidneys, primary cilia are used to detect water flow.  The structure of the paired cilia Danielle found aligns well with those of primary cilia in other animals, further supporting that these are sensory cilia that allow the sponges to detect their environment.

The cilia line the osculum, the chimney-like opening of the sponge.  If that osculum is removed, the sponge also is not able to initiate a sneeze response.  This led Danielle and co-authors to determine that the osculum can be thought of as a sensory organ, and not just a giant chimney.

Figure 4 from Ludeman et al. 2014

The “sneeze” response is shown by an increase in canal diameter followed by a rapid decrease (the black lines in the graphs). Various drugs that affect the cilia also affected that inflation/contraction. Source: Ludeman et al. (2014).

Why does this matter to us, and how does it apply to evolutionary theory?  Sponges are one of the earliest branches off of the animal tree of life (the Metazoa).  While they are animals, their distant relation to us and to all other animals (collectively called the Eumetazoa) means they diverged from whatever last common ancestor the Metazoa shared and evolved into something quite different and independent of what other animals have evolved into.  This isn’t unique–every animal phylum is very different from every other.  What is unique is their placement at the base of our collective “family tree.”  If a sponge shares a feature that we also have, it’s likely that the proto-animal–the last common ancestor that all animals shared–had that feature as well.  It brings us a little bit closer toward understanding how we evolved from single-celled organisms to the multicellular, fantastically complex and coordinated animals we are today.

Still think sponges are boring?
(Hint: they are, but only in one way that word is defined!).

Citation:

Ludeman, D.A., N. Farrar, A. Riesgo, J. Paps, and S.P. Leys (2014).  Evolutionary origins of sensation in metazoans: evidence for a new sensory organ in sponges.  BMC Evolutionary Biology, 14(3).  doi:10.1186/1471-2148-14-3.

To learn more about sponges and research on the origin of animal body plans, check out the Leys lab website.

That time I rode in a submarine – Sea of Glass Pt 3

By Danielle Ludeman
Reblogged from CPAWS-BC

As we disappeared into the depths of Howe Sound, I peered through the three-inch dome in front of me trying to catch the first glimpse of the sponge reefs below, and my excitement started to grow.  But my excitement was not just about getting to see the sponges up close, or about being deeper in the ocean than I have ever been before – although these were both pretty exciting. As we descended into the depths, I realized the opportunity the submarine dive provided to highlight the need to protect the sponge reefs.

When I was first invited to be a passenger in the submarine I was so excited– I was going to be face-to-face with the beautiful glass sponges! (Anyone who knows me will be able to tell you how much I love sponges). And then of course came slight fear – I was going to be face-to-face with the beautiful glass sponges 250 feet (76.2 m) below the surface of the ocean in a submarine! Almost twice the maximum depth for certified, recreational divers.

As we continued our descent down into Howe Sound, I began to make out creamy, white shapes in the water below. I turned to the Hon. Andrew Wilkinson, a Minister in the provincial government, and Jeff Heaton, the pilot of Aquarius, to tell them excitably that there were sponges below! We had descended right down to the sponge reef, and there were the beautiful glass sponges only a few feet from me.

As a graduate student studying sponges I have been involved in research cruises to study the glass sponge reefs. Because the sponge reefs are found so deep in the Strait of Georgia, conventional sampling methods cannot be used.  Instead, we use a remotely operated vehicle called ROPOS (picture a very large, square, yellow robot) to sample and survey the reefs, sending live video footage of the reefs up to the research vessel on the surface. I watched this live footage of the glass sponge reefs for hours on a tv screen.  Now, I have had the amazing opportunity to experience the sponge reefs with my own eyes.

The glass sponge reefs have given me a sense of awe and wonder ever since I first began my undergraduate studies in Dr. Sally Leys’ lab at the University of Alberta.  These glass sponges form massive reefs that serve as crucial habitat for fish, crabs, shrimp and many other critters.  The sponges also filter massive amounts of water, removing bacteria and excreting ammonium, a source of nitrogen that can then be used by other animals around the reef.

But sponges are not like any other animal. A sponge is an animal without a digestive system or a nervous system, yet it will respond quickly to something in the water such as sediment, causing it to stop filtering. You wouldn’t know it from looking at the sponge reefs, but sponges are almost constantly pumping water through their bodies.  One of the sponge reefs has been estimated to filter over 80,000 L of water every second! And here we have these massive reefs formed from this weird and amazing animal, right on Vancouver’s doorstep.

How have these reefs covered hundreds of square kilometers off the coast of British Columbia and we only just discovered them 25 years ago? How do so few people in Vancouver, in Canada, know that these reefs exist? And how have we, as Canadians, not protected such a beautiful and important habitat?

Protecting the sponge reefs requires public awareness, which is where the submarine dives come in. Until now, most people in Vancouver had never even heard of the sponge reefs.  I am very hopeful that the submarine dives will create the public demand for their protection.

Shortly after the submarine dive event I headed down to Fremantle, Australia to attend the World Sponge Conference (yes it exists).  While I was there I was talking to an old friend about my research. Their response was “Oh! I heard about sponges recently.  It was about some sponge reefs that are only found in Canada.  Is that what you study?” And so the ripples spread.

Photo of the week: Recycled habitat

Hermit crabs aren't the only animals to inhabit old shells once they are abandoned!  How many different species of invertebrates can you see living in this one old clam shell?  Photo: D Ludeman

Hermit crabs aren’t the only animals to inhabit old shells once they are abandoned! How many different species of invertebrates can you see living in this one old clam shell? Photo: D Ludeman

Do you have any photos of Bamfield, old or new, that you want to post on the blog? Email us at bmscblog@gmail.com

Cool Papers 3: Citizen Scientists to the rescue!

By Danielle Ludeman

Let’s face it – the world we are leaving for our children is not going to be the same one we grew up in.  But although biodiversity is being lost in our ecosystems at an accelerating rate, around the world there are countless tales of people doing their part in trying to preserve, conserve, and manage our natural resources.  Before we can protect biodiversity in ecosystems we need to know what there is to protect, and an important challenge for ecologists is to determine geographical patterns in biodiversity, which requires extensive data collection. More and more we are relying on ‘citizen’ scientists to help in this key step, and hundreds of thousands of volunteers each year take part in a variety of surveys, bioblitzes, and monitoring programs.  But how reliable can the data be?

In a paper that came out last week in “Methods in Ecology and Evolution”, researchers Dr. Ben Holt and colleagues have shown that Citizen Science can be just as effective in recording marine biodiversity as traditional scientific surveys. The study compared two methods of acquiring biodiversity data: a belt transect typical in peer-reviewed scientific articles, and the ‘roving diver technique’ used by the REEF (Reef Environmental Education Foundation) program.  Volunteers, no matter how enthusiastic they are, typically don’t have the training to use traditional scientific protocols, therefore most Citizen Science programs use alternate methods and techniques that may affect the outcome of the biodiversity survey.  This study therefore set out to try to determine how much the two methods differed when assessing the biodiversity in the Turks and Caicos Islands. They found that the two methods were consistent in their diversity estimates, with REEF’s rover method actually finding significantly more species than the belt method.  This rover method was not always the best method to use, as belt transects were more suitable for species richness estimates. However, the vast quantity of data that can be collected using REEF’s rover method and the consistency to diversity estimates of more traditional methods suggests that Citizen Science programs such as REEF can be invaluable for large-scale biodiversity surveys.

Divers performing a belt transect survey as part of a Citizen Science program called ReefCheck in Honduras.  Credit: D Ludeman

Divers performing a belt transect survey as part of a Citizen Science program called ReefCheck in Honduras. Credit: D Ludeman

Citizen Science is happening all around us. The REEF program has collected over six million sightings across 10 000 locations.  Audubon’s Christmas Bird Count has finished its 113th year, with tens of thousands of participants collecting data from over 2000 circles.  Government programs such as British Columbia’s ‘Report-a-Weed’ helps in early detection and rapid response to invasive species.  And programs such as the Canadian Wildlife Federation’s Bioblitz gets families from across Canada learning the plants and animals found in their own backyard.

So how about lets all get there and do our part!  Here is a (brief) list of just some of the Citizen Science programs that are happening out there.  Feel free to add more in the comments section, or send us a message at bmscblog@gmail.com to get us to add yours!

REEF (Reef Environmental Education Foundation)
ReefCheck
Audubon’s Christmas Bird Count
BioBlitz
Report-a-Weed
British Columbia Breeding Bird Atlas
Whistler Biodiversity project
E-flora BC
Alberta Mycological Society
Alberta Plantwatch
NatureWatch
ebird
Project Noah
ISpot
Monarch Larva Monitoring Project

The Octopus of Saanich

By Jackson Chu and Danielle Ludeman

As part of the Oceans Network Canada observatory, the Victoria Experimental Network Under the Sea (VENUS) provides real-time measurements, images, and sound to researchers and observers on-shore.

Anyone, from scientists to the general public, can access the network’s data and monitor environmental changes as they happen (see here for a previous post on accessing and graphing VENUS using R). The VENUS instrumentation is found in the coastal waters of the Salish Sea and is the sister network to the offshore NEPTUNE Canada regional cabled ocean network

Video and data provided by Jackson Chu

Captured in this time-lapse video from Saanich Inlet is a juvenile, ~10 cm long, Pacific Red Octopus (Octopus rubescens), which had temporarily moved underneath the VENUS Camera Array for a month. When the oxygen levels drop to near zero, it decides to pack up and move somewhere more hospitable. You would to if you had a dozen squatters (Munida quadrispina) hanging around your neighborhood all day!
Note: You can see the white ball sponges (Suberites sp.) contracting in the video – the first time this behavior has been captured in situ on the bottom of the ocean. You can check out another time lapse of a contracting sponge done in the lab, Tethya wilhelma, and one of a freshwater sponge Ephydatia muelleri.

Metadata:
Location: Saanich Inlet, 96 m depth
Camera: Olympus C8080WZ
Exposure Settings: 7mm @ F5.6, 1/30s, ISO100, with offcamera strobe in custom housing
Time start: Sept. 14, 2012 @ 07:47:42 UTC
Time end: Oct. 09, 2012 @ 14:47:28 UTC
Total # of images: 1691 8MP still images (3264p x 2448p) taken in doublets (10 s interval) every 30 mins
Workflow:
Images were batched processed to 1440p x 1080p dimensions (Adobe Photoshop) and made into a 15 frames per second (fps) time lapse movie (Avidemux). The time lapse video was then stabilized and re-rendered (Adobe After Effects) because the images did not perfectly overlay on top of one another which resulted in shakey raw footage. Oxygen data profile for the time sequence was downloaded from the VENUS website, processed (Matlab), and plotted (Adobe Illustrator, Adobe Photoshop). The Oxygen profile was then overlaid onto the time lapse video (Adobe After Effects), and an animated time marker was added using keyframes before finalizing the video by pillarboxing into a 1080p HD-video with audio accompaniment (Adobe Premiere Pro).

A spongy habitat

By Danielle Ludeman

The world is full of organisms, living on organisms, that are living on other organisms.  You just have to take a moment to think about the complexity of life that can occur to start to appreciate all of the life around us.  Take a tree in your front yard – at first glance you may just see a tree, but when you start to look closer you notice the bird nest that will be home to baby chicks in the spring, and the squirrel that runs up and down the branches.  Then you notice all the different types of moss, lichen, and mushrooms that are growing on the tree.  And upon closer inspection you realize that this creates even more space for a variety of spiders and insects to thrive.  And we can keep going on and on to include all of the life that we need a microscope to see. And this is just on a single tree!

This summer, while doing some field studies at Bamfield, I began to appreciate all of the life that can be found on a single sponge.  Now it is well known that sponges can be very important habitat for many organisms, with some species being obligate commensals of sponges, meaning they can ONLY live on a sponge to survive.  But when I started to look closer at some of the sponges in my studies, I began to realize just how many other organisms call a sponge its home!  One species of sponge in particular – Suberites sp.  that I collected off of Brady’s beach – seemed to have a surprise guest visiting every time I looked at it!  I managed to photograph a few of these, and thought I would share these with you in the slideshow below!

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Exploring the deep sea

The Madreporite’s Amanda Kahn is currently exploring the deep sea off the coast of California on MBARI’s “Climate and Deep-Sea Communities Pulse 80 Expedition”.  Check out the cruise’s logbook for some of her exciting stories and amazing photographs of the expedition so far!

Amanda Kahn, onboard MBARI’s Pulse 60 Expedition, is watching intently as the ROV pilot carefully places a dye chamber over a plate sponge. Photo credit: MBARI

Cool Papers! Part 2: Hermit crabs with a not-so ‘hermit’ lifestyle

By Danielle Ludeman

‘Hermit’ crabs seemingly implies that they are just that – hermits – living alone in their own (second-hand) shell, apart from society (i.e. their kin).  But are they as alone as their name implies?

According to a new study by Mark Laidre, terrestrial hermit crabs are forced to socialize if they want to find a new shell to move into! Carrying around giant shells on land would be heavy, and so terrestrial hermits, unlike marine hermit crabs, modify their gastropod shells by eroding the interior and creating a larger and more lightweight home. This also takes time, and so hermits will move into previously modified shells, if they are available, when it is time to move into a larger one.  To look at the consequences of this modification, Mark Laidre placed hermits in either 1) new unmodified shells or 2) previously remodeled shells of the same diameter, and found that only the hermits in the shells passed down from other hermits survived! The hermits in the unmodified shells could not fit into the small amount of space available, and thus they did not have full protection against ant attacks. There are virtually no unoccupied remodeled shells in the population, so when it comes time to moving on up into a bigger shell the hermits benefit from being around others if they want any hope in finding a previously remodeled shell!

Laidre calls this remodeling of the shell ‘niche construction’ (the process in which an organism changes its environment).  According to the fossil record, this ‘niche construction’ has been taking place in terrestrial hermit crabs for millions of years! Laidre argues that that is ample amounts of time for such a trait to start to drive social behavior, so that these remodeled shells become a form of ‘ecological inheritance’, where modification of the environment is reused by many successive generations.  Unlike genetic inheritance, ecological inheritance can be passed on to individuals that are unrelated.  These remodeled shells, therefore,may be a driving force for social dependence, even among unrelated individuals.

As it turns out, the need to find a new shell when a hermit crab grows drives another form of social behavior as well!  When a new shell becomes available in the environment, many hermit crabs gather round forming something called a ‘vacancy chain’. The hermit crabs will essentially line up from biggest to smallest (albeit in a not-quite so elegant fashion), taking the next biggest shell as it becomes vacant!

Waves, Caves & Humpbacks

By Danielle Ludeman

Living in Bamfield definitely has its perks, one of which is being located in the spectacular Barkley Sound. With hundreds of islands separated by deep water channels, Barkley Sound hosts abundant marine and wildlife along its diverse coastlines, which not only makes it an ideal location for doing research, it also makes for an amazing place to explore during days off! The multitude of islands that occur in Barkley Sound, such as the Broken Group Islands and the Deer Group, have become famous among kayakers and divers alike, and a couple of weeks ago I had the opportunity to see why when I did an overnight kayaking trip to the Ross islets in the Deer Group.

Visiting the seals at Wizard island. Photo credit: D Ludeman

Leaving early in the morning from the Bamfield Marine Sciences Centre to avoid the afternoon westerly winds, we packed the graduate kayak hatches full of camping gear, food, and drinking water and headed out across the Trevor Channel.  With a brief stop at Wizard island to visit some seal friends, we made it to the Ross islets within an hour and a half and set up camp at one of the two camp sites.  Lucky for us, even though it was one of the busiest kayaking times of the year, we arrived just as another group was leaving and so snagged one of the two camping spots on the islet!

Kayaking around Fleming Island in Barkley Sound. Photo credit: D Ludeman

One of the many bald eagles spotted on Fleming Island. Photo credit: D Ludeman

We then had the rest of the day to explore, and taking some advice from the departing kayakers we decided to paddle around Fleming, a large island beside the Ross islets.  Just as we were leaving (enjoying the much lighter kayaks to paddle in!) the clouds broke and it turned into an amazingly sunny day – even though the previous week in July had felt like Fogust!  The calm waters along the Trevor Channel side of Fleming made for some peaceful paddling, and we could even see some sea life through the glass-like waters!  On land, the long sandy beaches were stunning, and it wasn’t hard to spot the many bald eagles on the wind-swept trees!

As we rounded the corner at Tzartus island, we glimpsed this amazing sea cave and just had to go have a look.  Although it was tempting, we decided against paddling through it – probably a good thing too as when we were chatting to our fellow Ross islet campers later that evening, one of them had a story of going for a little impromptu swim right in the middle of the same cave!  Instead, we found a nice little beach to have lunch at, and enjoyed the amazing view that Barkley Sound has to offer.

Sea caves are abundant in Barkley Sound, such as this one on the southwest corner of Tzartus island. Photo credit: D Ludeman

After lunch, we left the calm waters of Trevor Channel behind and took off to paddle the side of Fleming along the Imperial Eagle Channel. The waves, although a little challenging, were exhilarating!  And well worth what we were about to see.  As soon as we turned the corner at the North side of Fleming we heard the explosive snort of a humpback whale and looked just in time before it dove back underwater.  We sat there motionless (or as motionless as we could in the waves) waiting for it to grace us with its presence again, and feeling the rush of being so near such a magnificent creature.  After a few more breaths the whale moved on, and so did we to battle the waves and observe the many more sea caves along Fleming.

The many colors of Pisaster. Photo credit: D Ludeman.

Late afternoon we arrived back at the Ross islets, just in time for the low tide! We gave our arms a much needed break and took off exploring the small island on foot, checking out the many tide pools and awesome creatures that they house! From the colorful starfish Pisaster, to the massive californian mussels Mytilus, and the medieval- looking gooseneck barnacle Pollicipes, there was plenty to seek and discover.  And after cooking some dinner on the beach, we sat down and relaxed, watching the tide come up on the rocks, and the sun set behind the Broken Group Islands.

Sunset at Ross islets. Photo credit: D Ludeman