Developmental Biology in the Ocean 2018May 25 2018
This three-week course at Hopkins Marine Station focuses on the embryology and larval development of a broad range of marine invertebrate phyla. The goal of the course is to give students an appreciation of the range of developmental strategies and larval forms in the ocean and why this is critical for constructing hypotheses of animal evolution.
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And that's how it ends - the class wraps up. The past three weeks have taught us to never trust our presumptions about how life functions and continues its journey on planet earth. Kudos to Chris and Paul for creating this magical world of marine biology!
Did you know that sand dollars (Dendraster excentricus) and purple sea urchins (Strongylocentrotus purpuratus) can interbreed? These two species are separated by ~250 million years of evolution, but they can still produce viable offspring...amazing! Here's a picture of a sand dollar, sea urchin, and the sand dollar-sea urchin hybrid. All are 7 days old.
We presented our final projects today...studying this hybrid species was part of my project. I had such a wonderful experience these past 2.5 weeks, and I will definitely think about how to incorporate marine invertebrates in my research moving forward. Thanks to Professor Chris Lowe and Teaching Assistant Paul Bump for all their hard work putting the course together. I think it's fair to speak for everyone in the course when I say we had a wonderful and eye-opening experience at Hopkins Marine Station!
After lots of trial and error, we finally have a working tube tank! The double tube design allows for gentler water flow and a thermal gradient in order to maintain more delicate organisms, like the ctenophore larva we saw at the Monterey Bay Aquarium.
Did you know some echinoderm larvae (sea urchins, sea star, etc.) can clone themselves? Larva can split themselves in half, or a little part can bud off and develop into a new larva (see the arrow in the image from Eaves and Palmer, 2003). This might be an adaptive response to different stresses in the ocean environment. We are trying to induce larval cloning with fish mucus in some species where it hasn't been observed before. The larvae are in the 24 well plates and we are looking for clones!
-Devon and Veronica
Witnessed an amazing lecture by Dominique Bergmann followed on the diversity of developmental strategies adopted by plants followed by direct observations of kelp buds.
Today I got to hang out with these photogenic little guys. Doryteuthis opalescens, also known as the common market squid, is one of the most common cephalopods along the California coast. As juveniles, they are objectively adorable and I love them.
We close up our developmental exploration across phylum with mollusks. We attempted to spawn snail by gluing them to clay and flipping them upside down in the sun to stress them out. Then, we attempted scallop by injecting with serotonin. Never imagined it will require several of us, pipette tips, metal bars to keep the scallop shell open. We also have octopus that we tried to feed, and also observed baby squids hatched out of its shell.
It was an exciting visit to the Monterey Bay Aquarium which involved a peek into the engineering that goes into completing a life cycle of an organism in a lab. The images show a ctenophore, a developing tunicate larva, a gastrulating sea cucumber larvae and a polyp stage of an unidentified ctenophore.
Marine embryology is so awe-inspiring! Here’s a beautifully transparent acorn worm (Schizocardium californicum) larva (left) - being transparent not only makes these larvae beautiful to look at, but also makes it easy to study their developing internal structures. Contrast this with an early brittle star larva, which is a brilliant orange (right) - their color is exquisite, but makes it less convenient to study their development.
Here are some pictures from our behind-the-scenes tour of the Monterey Bay Aquarium’s ctenophores (comb jellies) - see Devon’s previous post. Each of these unique tanks contains different species of jellies (top).
They also generously donated some Hormiphora californensis larvae, and we had the opportunity to explore their development today. Devon already wrote about their intriguing balancing mechanism…my favorite developmental stage so far is the tiny animal swimming around about ready to hatch (bottom)!
Today we went on a backstage tour at the Monterey Bay Aquarium to learn about Cnidarian and Ctenophore care and husbandry! The four spots on the developing Ctenophore embryo form the statocyst, a sense organ that allows the animal to maintain an upright position. This animal was fertilized yesterday and developed rapidly. The adult Ctenophore is on exhibit at the aquarium. Its bright colors come from quickly moving parts called ctenes, which refract light.
Live imaging of the larval form of Schizocardium californicum in its new home: a small agarose well.
Today, we geared up and went hunting tunicates. We were able to find two species in Hopkins Marine Station tide pools. Back at the base we dissected Boltenia villosa and Clavelina lepadiformis (aka Light bulb) to collect tunicate eggs, sperm and larvae. We were surprised to see a juvenile crab living inside a Boltenia. We also found a sponge species in the tidepool, whose spicules are shown in the picture. The video shows multiple developing sea urchin larvae that are on a spinning frenzy alongside a 40 micron nylon mesh to get an idea of their size.
Today we tried to get brittle stars to spawn by stressing them out. When exposed to sun, higher temperatures, and repeatedly getting flipped over by students some of these ophiuroids released their eggs and sperm.
Late stage Bat Star (Patiria Miniata) larvae, along with an early stage gastrulating one. The video shows the intricately patterned cilia all over the body of the larvae useful for locomotion and gathering food. We also tried spawning brittle stars by stressing them in sunlight.
So far, we’ve spawned and fertilized sand dollars, bat stars, warty sea cucumbers, purple sea urchins, and brittle stars. Look at how full our water table is! Each glass bowl contains developing animals…can’t wait to watch them grow!
We spawned bat stars (Patiria miniata) yesterday. Here’s a picture of one of the full-grown bat stars we spawned and a video (real time) of a bat star about ready to hatch from its egg ~1 day post fertilization! Check out those beating cilia!
We spawned warty sea cucumbers (Parastichopus parvimensis). There are 8 and 16 cell embryos, but also many irregular embryos resulting from polyspermy. This occurs when more than one sperm fertilizes an egg and causes irregular cell divisions and cell sizes.
Can you believe that the little organism on left, zoomed in on a microscope, becomes the one on the right? They look nothing alike! This is because the acorn worm (Schizocardium californicum) first develops as a larva that then goes through an abrupt and dramatic change of body structure later in development, called metamorphosis.
Our embryology adventure begins with a dive into echinoderms. Shout out to Chris and Paul for their awesome dive, we got to spawn sea star, sea cucumber, sea urchin and sand dollar to track down their different developmental stages. Here's a peak into how sea cucumbers spawn: they raise up their front end and sway from side to side to ensure maximum fertilization.
Went tidepooling at Carmel Point to check out the rich intertidal ecosystem - there was such a huge diversity of organisms! We saw mussels, barnacles, urchins, starfish, and many others.
The rest of the day was spent sifting through the plankton toes. We were able to identify copepods, ctenophores, tunicate larvae, tons of algae and even a juvenile squid. In the evening we visited the Pacific Grove Natural History Museum and began trying our hands on scientific illustration.
Diversity of life form in a drop of water never ceases to amaze us. In addition to copepods, shrimps, and various types of ciliates, capturing ctenophores and baby squid was highlight of the day. After an inspiring trip to Natural History Museum where we see some of the finest scientific illustration work, we also spend some time sketching our favorite organisms under the scope.
Today the camp started their adventure with a plankton toe. We conducted horizontal and vertical toes at multiple spots where the ocean depth was about 150 feet. The ride was calm but bumpy enough for some of us to puke out our breakfasts.
Got a chance to look at the surface of this little sand dollar under the scope last week. The little spines that cover the surface of the exoskeleton are covered in small cilia that are thought to help with feeding and locomotion.
A beautiful start to the course with a bright day and KCl induced dendraster (sand dollar) spawning and later fertilization.
One more collecting trip before the start of the course, this time the conditions were much more surge-y and soupy but we still ended up finding a bunch of cool critters for the class. We struggled for a while to find the sand dollar Dendraster excentricus but eventually realized that they had moved from the sand flat that we've typically found them of to some more small shell and rock habitat.
Along with capturing a few photos of Chris and I emerging with our collections, our wonderful dive officer Freya got some pictures from other vertebrates that joined us on our dive.
Unlike traditional model systems, working with marine invertebrates requires going out and finding them! Chris (my PhD advisor) and I went diving down at the Monterey Breakwater in search of different animals for our class. In particular we focused our collecting efforts on three different echinoderm species, the sand dollar Dentraster excentricus, the sea star Patiria miniata, and the sea cucumber Parastichopus parvimensis which we can spawn routinely in the lab. Along with both being in the echinoderm "spiny-skin" phyla these animals are also interesting from a developmental biology perspective as larva are bilaterally symmetric but become radially symmetric as adults.
Developmental biology has benefitted enormously from the era of model species, however these species only represent a fraction of the diversity of developmental strategies. Typically most model species are direct-developers which form an adult body plan from the egg, with larval stages being modest departures from the adults they give rise to. This contrasts with marine invertebrates where a distinctive larval body plan often precedes the adult body plan. These larvae often spend months in the plankton before metamorphosis into the adult. All the phyla originated in the ocean and an exploration of their developmental biology and life history variation offers up a unique opportunity to investigate how evolution has solved basic biological problems in separate animal lineages.