Posts Tagged: bryopsis

When Did I Earn Some Good Karma?

On December 5, 2021 by Dave With 0 Comments - Box of Slugs, General Slug Things

The colony had no business succeeding, or even surviving this fall, but somehow things have gone quite well.

As I posted a few months ago, Michael Middlebrooks was nice enough to send some freshly collected Bryopsis plumosa from Florida.  After cleaning, it settled in and started to grow.

It had been over a year since the colony had been running, so I was out of the habit of performing routine chores, then classes started to ramp up, and it was difficult to keep up with maintenance.  Flow from the CO2 cylinder stopped periodically, dosing with nutrients started too high, then dosers would run out, and I fell behind on water changes.  As a result of neglect and nutrient imbalances, Ulva (sea lettuce, a non-desirable species) was absolutely thriving, but Bryopsis was struggling.

In late September I considered posting a sad entry about all the preparation resulting in yet another failure.

I was mentoring students in Slug Club (officially “Invertebrate Behavioral Physiology Research Seminar”), so there was no choice but to persevere.  We would be performing experiments starting in late October, so it was time to order some new Elysia from KP Aquatics, and hope for the best.

I ordered 10 slugs, plus a generous collection of algae (from KP and Gulf Coast Ecosystems) to support the parents.  The slugs arrived, looking pretty good (one was yellow and ultimately did not make it, but they had sent extras), and I split them between a tank in the lab and the Box of Slugs at home.  All of the new algae were planted at home to avoid contaminating the lab cultures with any more undesirable species of plants, predators, or pathogens.

Two of the new cohort of E. clarki from KP Aquatics. The slug on the left is very yellow, and is probably not going to survive, but they sent plenty to start the next generation of slugs. 10/16/21

Elysia are durable creatures, and most settled in quickly.

Elysia clarki from KP aquatics. Good size and color. Note the blue edges to the parapodia. 10/16/21

One of the slugs at home laid eggs almost immediately.  I collected them and set them up in a dish in the lab, thinking that there was a slight chance I would have enough B. plumosa to rear them.

Eggs laid by newly arrived E. clarki. These were collected and reared, resulting in the larvae and small slugs described below. 10/16/21

Meantime, the semester did not lighten up, but I had developed a routine that kept the algae tanks cleaner and kept conditions relatively constant.  There seemed to be some Bryopsis in the algae tanks, but they still seemed to be dominated by Ulva and Derbesia (a finer hair alga that Elysia do not seem to like).

One component that I added to the routine was cleaning out one of the algae tanks each week.  The algae are supposed to be growing on tiles, so I am pulling out one of the tanks, rinsing the debris off the tiles with clean saltwater, and thoroughly scraping and scrubbing the tank.  Bryopsis thrives in clean water with strong circulation, so keeping the tanks clean and the circulation vigorous should favor growth of Bryopsis over that of less desirable algae such as Ulva or Derbesia.

The eggs hatched right on schedule, but the veligers were not swimming particularly vigorously, and I expected the juveniles would probably succumb to bacterial or protozoan pathogens.  At this stage, they need to have food algae to settle on and start eating, and I would normally pre-treat the algae with ivermectin to kill off potential predators, and rifampicin to reduce pathogens.  The survival of the larvae was not a high priority, so I simply grabbed a glob of mixed algae from one of the algae tanks, rinsed adherent cyanobacteria and dinoflagellates off of it, and tossed it into the dish with the eggs.  I fully expected failure and kept a later batch of eggs in reserve.

Slugs at varying points of development, moving among the mixed algae. All have fed and contain chloroplasts in their guts, but the larger slugs show the beginnings of structures such as rhinophores and parapodia, while the smallest are much simpler. 11/15/21

Imagine my surprise when I looked at the dish several days later and saw juveniles with chloroplasts in their diverticula.  They had settled and started feeding!  There were many more that were crawling around, looking healthy, but had not yet eaten.

Juvenile Elysia, about a week after settling. Bumps in the nose show where the rhinophores will develop, and swellings are forming along the back where parapodia will appear. Note the smattering of sparkles, especially between the eyes. 11/15/21

Within days, I had hundreds of baby slugs that seemed to be healthy and feeding.

One thing that puzzles me is that they are very “sparkly.”  In addition to the deep green of the chloroplasts in their bodies, they have a collection of iridescent little beady things, especially in their heads.  I have seen such things in the parapodia of adults in the past, but do not remember the juveniles looking like this.  Whether they are derived from diet or the slugs’ own metabolism is not clear, but they do not seem to be causing harm.

Two young Elysia clarki. Very small (1-2 mm), but already showing rhinophores and parapodia. Note the iridescent spots, especially around the head. 12/2/21

In the ensuing weeks, the baby slugs have gone through the usual routine of being moved into baking dishes, and then into their own 3-gallon tank where they will continue to grow.  Despite being neglected, including being left for a week while I traveled to the west coast, there are still hundreds of them.

Baby Elysia, indicated by arrows, feeding on a mix of Bryopsis (thicker fibers) and Derbesia (finer filaments). The field is 2-3 cm across, taking up only a very small part of a larger tank, so the total population is in the hundreds. 12/4/21
Bryopsis plumosa starting to thrive and take over the tiles on the bottom of an algae culture tank. Red objects are mostly cyanobacteria (“blue-green algae”) growing on the filamentous algae. 12/4/21

Fortunately, the number of labs interested in Elysia biology continues to grow, albeit slowly, so I will send most of them away in a few weeks.

Juvenile slug, now just visible with the naked eye, with clearly formed rhinophores (right end), parapodia, and green dots indicating chloroplasts. 12/3/21

There may be some lessons here:

My theory about algae growth seems to be supported, and the Bryopsis is taking over the tiles.  There is still plenty of the other two species of algae, plus more cyanobacteria and dinoflagellates than I would like, but I think the algae cultures are moving in the right direction.

Also, tearing down the system, scrubbing and bleaching as much as possible appear to have been successful.  Although Ulva and Derbesia are competing with the Bryopsis, and are not terribly desirable, Valonia (bubble algae), and Cladophora (Brillo® algae) were completely taking over the system.

I believe there may have been some simple, dumb luck involved as well.

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Clean Start Fall 2021

On August 18, 2021 by Dave With 0 Comments - Box of Slugs

I do not need to provide anyone with examples of how awful the Covid-19 pandemic has been.  There have been a few bright spots, though, such as all the time we have been able to spend at home with our dogs.

One negative thing that had a slightly positive aspect was having to put the slug system on hold.   I took the remaining slugs home, hoping that they would be the parents of the next generation.  They did remarkably well for about a year living on the Bryopsis pennata that was growing in the reef and seagrass tanks.

Last slug from the last brood raised in the USG system. They came home last spring, and held out for over a year. 3/13/21

Over the course of the summer, the last one has faded and shrunk as she reached old age and lost the ability to eat algae and to maintain her chloroplasts.

After about 16 months, the last of the Elysia that grew up in the system is just about gone. As they fade away and use their tissues for energy, they get increasingly small and yellow. This one is about the size of a pea. 8/11/21.

After at least five generations, it is sad to say goodbye to the last of the progeny.  Nonetheless, the lack of slugs meant that I could clean the USG system thoroughly.

During the years that I have been trying to culture Bryopsis, I have managed to introduce at least half a dozen invasive and undesirable species of algae, some of which were outcompeting the desired species.  Valonia (bubble algae) and a coarse red alga were thriving under the same conditions as Bryopsis.  Also, Bryopsis plumosa, the finer species that is a favorite of the hatchlings, was being overrun by B. pennata, which the babies will not eat.  I had been trying to push the balance toward Bryopsis by manually removing the other species, or introducing grazers that prefer the nuisance species, but I was not winning.  It was a wet mess.

Enter the pandemic.  The system was unoccupied, allowing for a fresh start.  Even if I will not be able to keep the system as an absolute monoculture, it would be worth getting rid of as many pests as possible, and maybe eliminate some of the bristleworms and flatworms that prey on the babies in the process.

Step one was to dismantle the system, scrub out the tanks, and clean as much of the plumbing as possible.  Drainpipes, pumps, powerheads etc. were soaked in warm bleach solution, then scrubbed and left to dry.

Trying to eliminate at least some of the unwanted algae species by bleaching plumbing and equipment. 3/2/21

Once everything was clean and dry, it was reassembled, and left dry for a few months.  Then it was filled with fresh water to flush out remaining debris and organisms, and to check for leaks.

Tanks back in place after scrubbing (center shelves). The tanks to the left contain crayfish for the neurobiology lab.  3/9/21

With the tanks in place and plumbing reassembled, I let it run for a couple of months to see what grew.  The good news was that almost none of the species of pest algae has made a reappearance.  There was little Ulva and some diatoms, but none of the worst characters had come back.  It was time for new algae.

Elysia system filled with saltwater and circulating. There is a small amount of residual algae, but most species seem to have been eradicated. 3/25/21

This time around, my goal was as pure a culture of B. plumosa as possible.  Hatchlings eat it, adults eat it, everybody eats it, so there is no need for other species.  I contacted Michael Middlebrooks at the University of Tampa to find out if he would be able to send me a small amount as a starter.

At last, we found a time that he could send the algae and I would be here to receive it.  It arrived last week, having survived near-record heat here in MD, and looked great.

Bryopsis freshly arrived from Florida. Ready for the first treatments to reduce predators, parasites and pathogens. Hopefully, I can get rid of some of the non-Bryopsis algae as well. 8/11/21

Under the microscope, you can see dark filaments full of green cytoplasm, indicating good health and growth potential.

Bryopsis plumosa, close up. Many of the filaments appear uniformly green, which is a good sign that much of the algae arrived healthy. 8/11/21

The wild intertidal zone is a complex environment, so there were other algae in the mix.  There are a few species of red algae that grow closely with B. plumosa, often intertwined at the site of attachment to the rock.

Red macroalgae mixed in with Bryopsis. The green “fingers” to the left are part of a healthy growth of Bryopsis plumosa. Unfortunately, the red stuff likes to grow in and among it. 8/11/21

I removed as much of the non-Bryopsis algae as possible, and will try to be vigilant about removing whatever crops up as the new algae take hold in the tanks.

Meantime, the algae are settling in and growing.  It is remarkable how quickly Bryopsis will find a place to anchor itself and start growing.

Filaments of Bryopsis plumosa extending from a clump that arrived on 8/12/21. Photo 8/17/21

 

Healthy Bryopsis plumosa growing on a powerhead. 8/17/21

Some algae are making small adherent spots on the tiles that I added as a substrate, along with the glass and silicone sealant.  At this point, it is impossible to know whether it is a species I want or a pest, but let’s keep our fingers crossed.

Dots and threads of small unidentified algae stuck to ceramic tiles. 8/17/21

If all goes well, it will be time to add some slugs in a month or so.

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