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.

Elysia are durable creatures, and most settled in quickly.

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.

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.

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.

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.

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.

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.

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.