I'm going to try something new - here's a thread of the talk I gave at #WSN2019 with @Matt_Leray. The talk was about the diet of the giant plumose anemone 𝘔𝘦𝘵𝘳𝘪𝘥𝘪𝘶𝘮 𝘧𝘢𝘳𝘤𝘪𝘮𝘦𝘯 and how it compared to the plankton community. Please ask questions!

PC: T. Dwyer.

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You may be asking: "Why should I care about the diet of anemones?" Well, for one, it's eating some of the things you may like to eat: fishes, clams, and crabs to name a few. They can dominate a system and have been shown to beat out most other things attached to the bottom.

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The bottom of the ocean, especially in the shallows, is dominated by predators consuming the prey floating by (plankton) and can have major impacts on the plankton. Several studies found that this community can completely deplete the nearby floating microalgae.

PC: T. Dwyer

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That's not to say that plankton can't defend themselves. They can be toxic, have standing defenses, or avoid predators. This thread is all about prey selectivity: the consumption of prey in a ratio different from available prey.

PC: P. Bryant - http://nathistoc.bio.uci.edu/crustacea/Larvae/Larva1.htm

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Why do these types of study matter? They help us understand the effects of predators on their ecosystem, how prey are captured, and how predators partition the available prey. Unfortunately, quantifying the diet of animals that eat plankton is difficult.

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Plankton are frequently microscopic and soft-bodied plankton are digested quicker than hard-bodied ones (think v). This makes it difficult to identify plankton beyond the most broad of groups using traditional diet analyses.

PC: B. Vellutini

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For those that aren't aware of how one would traditionally examine gut contents, here's the recipe for working with anemones: Collect an anemone, ice it, cut it in half , scrape out the contents, rinse with LOTS of alcohol (for the mucus and preservation), ID everything.

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In this dish of gut contents, you can see an amphipod (relative of +) circled. There's a whole lot of anemone tissue also. With new molecular techniques like DNA metabarcoding, we can analyze diets a lot faster, more cheaply, and with less need for taxonomic expertise.

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To metabarcode a sample, all you need to do is collect a community sample, grind it all up, extract the DNA, send that DNA off to a sequencing center, and then match those sequences to previously collected sequences to identify what's in the gut contents.

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We used metabarcoding to compare anemone diets to the available plankton. Plankton was collected with two mesh sizes: 80 um (nearly everything) and 330 um (big things). We wanted to know, 𝘄𝗵𝗶𝗰𝗵 𝗼𝗳 𝘁𝗵𝗲𝘀𝗲 𝘄𝗮𝘀 𝗺𝗼𝗿𝗲 𝗹𝗶𝗸𝗲 𝘁𝗵𝗲 𝗮𝗻𝗲𝗺𝗼𝗻𝗲'𝘀 𝗱𝗶𝗲𝘁.

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This work was all done at Friday Harbor Labs ( @MarineBiol_FHL ) as part of my PhD work. FHL is located on the San Juan Islands in the Salish Sea in Washington and is a wonderful place to learn about the field of invertebrate zoology, amongst other fields.

PC: J. Mabel

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We had two questions for this project: 𝗗𝗼𝗲𝘀 𝘁𝗵𝗲 𝗴𝗶𝗮𝗻𝘁 𝗽𝗹𝘂𝗺𝗼𝘀𝗲 𝗮𝗻𝗲𝗺𝗼𝗻𝗲 𝗵𝗮𝘃𝗲 𝗮 𝘀𝗲𝗹𝗲𝗰𝘁𝗶𝘃𝗲 𝗱𝗶𝗲𝘁 𝗮𝗻𝗱 𝗵𝗼𝘄 𝗱𝗼𝗲𝘀 𝗺𝗲𝘁𝗮𝗯𝗮𝗿𝗰𝗼𝗱𝗶𝗻𝗴 𝗰𝗼𝗺𝗽𝗮𝗿𝗲 𝘁𝗼 𝘁𝗿𝗮𝗱𝗶𝘁𝗶𝗼𝗻𝗮𝗹 𝗴𝘂𝘁 𝗰𝗼𝗻𝘁𝗲𝗻𝘁 𝗮𝗻𝗮𝗹𝘆𝘀𝗶𝘀?

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Now for some results. You can see that there is 𝗮 𝘀𝘁𝗿𝗼𝗻𝗴 𝘀𝗶𝗺𝗶𝗹𝗮𝗿𝗶𝘁𝘆 𝗶𝗻 𝘁𝗵𝗲 𝗰𝗼𝗺𝗽𝗼𝘀𝗶𝘁𝗶𝗼𝗻 𝗯𝗲𝘁𝘄𝗲𝗲𝗻 𝘁𝗵𝗲 𝗮𝗻𝗲𝗺𝗼𝗻𝗲 𝗴𝘂𝘁𝘀 𝗮𝗻𝗱 𝘁𝗵𝗲 𝟴𝟬 𝘂𝗺 𝗳𝗶𝗹𝘁𝗲𝗿𝗲𝗱 𝗽𝗹𝗮𝗻𝗸𝘁𝗼𝗻 and less between the 330 and gut contents.

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If we break up the Arthropoda group and look at subgroups, the differences between the plankton and the anemones becomes more apparent. Blue bars: anemone diets; red bars: plankton. There are some large differences you can see here (including 9% of the diet being insects)!

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The DNA for these insects matches the yellow meadow ant which, at the time of this work, was releasing winged queens and drones, some of which likely ended up in the water. This is an interesting link between the terrestrial and marine environment!

PC: Getty

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Here's an nMDS plot. While the nem gut contents (GC) overlap the 80 um plankton samples (indicates similarity), the GC are more dispersed - 𝗻𝗲𝗺𝘀 𝗰𝗮𝘁𝗰𝗵 𝗽𝗿𝗲𝘆 𝗼𝘃𝗲𝗿 𝗵𝗿𝘀 𝘄𝗵𝗶𝗹𝗲 𝗽𝗹𝗮𝗻𝗸𝘁𝗼𝗻 𝘀𝗮𝗺𝗽𝗹𝗲𝘀 𝗮𝗿𝗲 𝗮 𝘀𝗻𝗮𝗽𝘀𝗵𝗼𝘁 𝗶𝗻 𝘁𝗶𝗺𝗲.

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When compared to either plankton sampling, there were many species that were significantly less abundant in the gut contents (pref. avoidance or can't be captured), but no significantly more abundant (no. pref. consumption).

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What this means is 𝘁𝗵𝗲𝗿𝗲 𝗶𝘀 𝗽𝗿𝗲𝘆 𝘀𝗲𝗹𝗲𝗰𝘁𝗶𝘃𝗶𝘁𝘆 𝗶𝗻 𝘁𝗵𝗲 𝗴𝗶𝗮𝗻𝘁 𝗽𝗹𝘂𝗺𝗼𝘀𝗲 𝗮𝗻𝗲𝗺𝗼𝗻𝗲; they seem to consume all prey that they can capture, missing species that are too small (like rotifers) and good swimmers (like copepods).

PC: Kils

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Now let's compare traditional techniques to metabarcoding. Columns are different studies and shaded boxes indicate that that group was present. There's a much higher diversity of groups found using the metabarcoding approach (26 v 7 groups).

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TL;DR:

1. There was prey selectivity
2. Diet was similar to the 80 um plankton samples
3. Surprising amount of terrestrial input () in the diet
4. Metabarcoding was an excellent approach for examining the diversity of prey in a plankton predator

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This work was done with funding from @AMNH, @UWBiology, and @MarineBiol_FHL. We had lots of lab and field help from @chiton_chitoff, @thefishbotherer, and C. Alexandra.

Thanks to @WSN_Secretariat for the conference and thank you for taking a read!