CreatureCast – Pattern Shifting Snails

posted by Sophia Tintori / on December 29th, 2009 / in molluscs, Podcast (Student Contribution), Science & Art

This is the fourth of four contributions from undergraduates in Casey Dunn’s Bio0041 Invertebrate Zoology class. This episode is inspired by the fascinating behavior of the flamingo tongue snail, Cyphoma gibbosum, which is described in further detail in Casey Dunn’s earlier post.

Video, music, and narration by Chris Vamos. This podcast is licensed under a Creative Commons Attribution-Noncommercial-No Deriviatives 3.0 United States License.

CreatureCast – Comb Jellies

posted by Sophia Tintori / on December 21st, 2009 / in Comb Jellies, Podcast (Student Contribution)

This is the third of four contributions from undergraduates in Casey Dunn’s Bio0041 Invertebrate Zoology class. In this episode, Daniella Prince describes the many wonders of comb jellies.

Video by Daniella Prince, with music by Ben Esposito. This podcast is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 United States License.

Stack of plates in action

posted by Sophia Tintori / on December 17th, 2009 / in Development, Jellies, lab, lifecycles

Look what we caught happening in our refrigerator.

While doing a fridge clean-out in the Dunn Lab, graduate student Rebecca Helm took a look at a forgotten bowl of Chrysaora colorata polyps from our friends Chad Widmer and Wyatt Patry at the Monterey Bay Aquarium. These creatures were left over from an RNA extraction we had done earlier for the Cnidarian Tree of Life Project, and were hidden in the back of the fridge, despite the labs strict ‘no pets’ rule.

Upon inspection, Rebecca noticed that the polyps were strobilating! This is a spectacular type of asexual reproduction, which is explained in more depth in Perrin Ireland’s post on the scyphozoan life cycle.

In this video, a polyp has pinched off into a stack of plate-like discs, called ephyrae. When they pop off of the end of the polyp, they each become a free swimming individual, and a direct clone of the parent polyp. Each ephyra will mature into adult bell-shaped jellyfish. Even before they break away from the poly, they are strongly pulsating as they flex their newly developed swimming muscles before birth.

Video by R. Helm and S. Siebert.

CreatureCast – Marine Worms

posted by Sophia Tintori / on December 16th, 2009 / in Annelids, Podcast (Student Contribution)

This installment of CreatureCast is the second of several contributions that were done as final projects by undergraduate students in Casey Dunn’s Invertebrate Zoology class at Brown University. In episode 4, sophomore Noah Rose delves into the bottom half of the circle of life, where dead things decompose and elements that can then be incorporated into other living organisms are liberated. Noah discusses how the many-legged worms we tend to think of as fish bait impact this process.

This podcast is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 United States License. The video and sound work was done by Noah Rose, with music by Noah Rose.

Making babies like a stack of plates

posted by Perrin Ireland / on December 10th, 2009 / in Jellies, lifecycles

aurelia500

Our own lifecycles are pretty simple. Making babies requires sex. Sex creates offspring with new unique combinations of genes. Many organisms are also capable of asexual reproduction, which doesn’t involve sex (as the name implies) and involves only one parent. In most types of asexual reproduction, genes aren’t reshuffled and the offspring are genetic clones of their parent.

Unlike ourselves, many species have lifecycles that combine both  sexual and asexual reproduction. Take the moon jelly, for example. Moon jellies, also known as Aurelia aurita, are perhaps the quintessential jellyfish, with a typical umbrella-like medusa that travels on ocean currents. There is more to their lifecyle, though, than this swimming organism. The swimming medusa does use sex to make babies—but the babies don’t grow directly into swimming medusae. Medusae release their eggs and sperm into the water and these combine to form a zygote (the fertilized egg). The zygote then develops into a planula larva. The planula eventually sinks to the ocean floor and develops into a polyp, an organism that looks nothing like a medusa. Polyps are attached to the ocean floor, usually on a rock or other hard surface, and stay in one place their whole life. They have a mouth surounded by tentacles, just like the more familiar polyps of sea anemones and Hydra. These polyps, however, are incapable of having sex—they cannot make eggs and sperm. Instead, they reproduce asexually. They can asexually produce other polyps, but they can also asexually produce miniature medusae called ephyra. These are pinched off from the polyp’s mouth as if they were a stack of plates, with the most mature medusa on top. The ephyra then swim away, grow into mature medusae, and complete the lifecycle.

CreatureCast – Comb Jelly Movement

posted by Sophia Tintori / on December 6th, 2009 / in Comb Jellies, locomotion, Podcast (Student Contribution)

This installment of CreatureCast is the first of several contributions that were done as final projects by undergraduate students in Casey Dunn‘s Bio0410 Invertebrate Zoology class at Brown University. In episode 3 sophomore Lee Stevens discusses how comb jellies move the same way that many single-celled organisms do, which is remarkable given how much bigger comb jellies are.

This podcast is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 United States License. Narrated and animated by Lee Stevens, with music by Tracky Birthday (this song, and also this one).

Pelagic plastic

posted by Erwin Keustermans / on November 30th, 2009 / in Science & Art

We have managed to create a huge memorial to human waste at a location that is remote from everyday human activity. In 2008 the predicted existence of a floating mass of pelagic plastic, a giant Garbage Patch, was confirmed in the stable waters of the North Atlantic gyre where plastic debris is accumulating over an area estimated to be twice the size of Texas.

Anna Hepler is a sculptor based in Portland, Maine. The subject of Hepler’s work is often the way a multitude of interlocked entities form a shape or a flock, spreading through space. On learning about the Garbage Patch, she incorporated it in a project for one of her first large scale installations. In January 2009 she spent a week together with eight assistants sowing together discarded plastic from a Portland recycling center. Once stitched together, the plastic nets formed a giant boat hull hanging from the walls and ceiling of the Center of Maine Contemporary Art in Rockport.

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An extended article about the project can be found here. Also, Hepler will be recreating this piece in the Portland Museum of Art in 2010 under the title ‘The Great Haul’.

Thou shalt covet thy neighbor’s cnidocytes

posted by Christopher Laumer / on November 30th, 2009 / in lifecycles

Microstomum lineare 20x 3

Hydra viridis

Microstotum caudatum

A small clarification, dear reader: in a recent post about the fantastic stinging cells of the Cnidaria (jellyfish and their relatives), it was stated that only cnidarians possess these cnidocytes. It is surely true that only cnidarians can make these barb cells. However, the animal kingdom has found these diverse structures useful enough that thievery of a sort has evolved, in lineages as distinct as comb jellies and sea slugs.

Consider the case of Microstomum lineare, a common resident of organic slimes in slow segments of flowing waters worldwide. These tiny flatworms spend most of the year eating detritus and dividing asexually into new clones. When in need of defense, however, the worms seek out and consume bits of the freshwater cnidarian Hydra, a favorite study organism of biologists.  The parts of Hydra that are consumed are digested by enzymes in the gut which leave intact only the stinging part of the cnidocyte. Cells of the gut then enclose these stinging cysts, pass them off to cells of the connective tissue, and ultimately, to the skin, where they are used as a means of defense and prey capture, much as the Hydras themselves use them. Remarkably, Microstomum has found a way to prevent these otherwise hypersensitive cysts from firing until the very end stage of this process of manipulation. The cysts persist in the skin until used, and can be passed onto clonal offspring, grand-offspring, and beyond. Even clonal lines that have not been exposed to Hydra for tens of generations will exhibit this behavior, but a Microstomum with a full stock of cnidocytes will ignore Hydra completely.

Photographs of Microstomum lineare (top: whole animal, dorsal view; bottom: head, ventral view, showing stolen cnidocytes), and the tentacles of Hydra viridis, a favorite source of cnidocytes, were taken by Christopher Laumer.

The art of knotting

posted by Stefan Siebert / on November 27th, 2009 / in Chordates

Hagfish have a skull, but no spine. They diverged from vertebrates prior to the origin of many other structures that are widespread within the group, including jaws. Hagfish are extremely important for understanding the origins of these key structures, but they are also famous for an unusual behavior—tying themselves in knots.

Hagfish have an eel-like body. They lead a bottom dwelling life and have a great sense of smell, but lack well developed eyes. When stressed, hagfish release a secretion that contains special filaments from glands along the body. When it contacts water, this secretion forms a massive slime and makes the hagfish an unpleasant bite for potential predators. To sneak out from this slimy shelter, the Atlantic hagfish, Myxine glutinosa, makes knots, which wring off the layer of slime. The knot, traveling along the body column, can provide a surface for the hagfish to push off. This enables the animal to pull its body out of the hole it makes in it’s prey’s flesh, or escape the grasp of a scientist.

Hagfishsat

Pictured above are the heads of two Atlantic hagfish, whose bodies are burried in soft sediments. They were caught in the Gullmarfjord on the Swedish Westcoast.

Photo and video by Stefan Siebert. Video edited by Sophia Tintori. “I’m learning a song for Christmas” from Jack Pleasants.

Star colonies of sea squirts

posted by Perrin Ireland / on November 17th, 2009 / in Chordates, lifecycles

Botryllus_s

Botryllus schlosseri is a colonial tunicate (or sea squirt), so named because it lives in colonies that are communally covered by a leathery tunic. Its larvae bear a striking resemblance to vertebrates, and are even called tadpoles. The resemblance is not superficial or coincidental, tunicates and their kin are the closest living relatives of vertebrates. Each tadpole attaches itself to a rock, pier, or other hard surface in the sea, and metamorphoses into a sack-like adult that will spend the rest of its life stuck in that one spot.

Tadpoles are produced sexually–they arise from an egg that is fertilized by a sperm. Like many other animals, though, Botryllus also reproduces asexually by budding off clones of itself. Each adult (also called a zooid) produces a bud, and this bud in turn begins producing another bud even before its own heart begins to beat. These clones remain attached to each other in a star shaped group with common central opening, called a siphon, and continue to share resources through their connected circulatory systems. Once the colony is large and robust enough, usually with 5 to 10 members, each adult forms a pair of ovaries and testes, and the next generation of tadpole larvae can be produced.

This is the first in a series of illustrated lifecycles I’ll be posting to CreatureCast.