More Pikeblennies
They were less shy today.
Male Pikeblenny 8/21/15
Female Pikeblenny 8/21/15
Their eyes are quite entrancing. It must be nice look straight ahead when hunting amphipods.
Male looking straight at you.
Gearing Back Up
Between teaching on the other campus and taking a little vacation, I have been letting the colonies coast for a few months. The second generation of E. clarki have not been growing particularly quickly, so I have not seen eggs in quite some time.
It is time to get more serious for the fall. I got some new Bryopsis from Justin to refresh the stuff that has been growing in the tank for months. The good news for him, but not so much for me, is that he is finally defeating Bryopsis in his >500 gallon system, and it has dwindled to very little. Unfortunately, that means I will not have a backup supply if the current crop starts to die off.
More importantly, the newest infusion of broodstock arrived from KP Aquatics yesterday. I ordered 3 new E. clarki for the office and 3 E. crispata for home, plus about 20 Penicillus to try to stay ahead of their appetites.
The clarki have settled in, and are looking happy.
New E. clarki 8/20/15
E. clarki enjoying a meal 8/20/15
As always, the good folks at KP threw in a few extras, including this presumed E. papillosa. By the time I arrived this morning, she had already laid eggs.
Presumed E. papillosa and eggs, 8/20/15
In the ongoing effort to reduce the amphipod population, I am trying a pair of pikeblennies in the growout tank. The idea was that they would make a dent in the amphipods, then I would move them to Box of Slugs 2, at home, to be able to enjoy them more. Given their shyness and speed, I am now a bit dubious that I will ever be able to catch them. One is considerably larger and more colorful, and they have not tried to kill one another yet, so I am thinking they may be a male-female pair. They are so interesting to watch, like tiny snakes hunting in the undergrowth, that I am very much enamored with them. With a little time, I hope they settle down and let themselves be photographed in more flattering poses.
Larger pikeblenny, possibly a male. Peeking warily from a pile of algae. 8/20/15
Smaller, drabber, possibly female pikeblenny. Bolder and more aggressive humter. 8/20/15
When possible, I will post photos of the pretty new E. crispata.
Site Reorganization
In an effort to make navigation a bit more sensible, I have started making a few changes. There is now a top-level page devoted to slug husbandry, Slugkeeping, which contains information (from this Web site and others) regarding how to keep and breed Elysia, as well as sources of slugs, food plants, and hardware. The new Slug Science page collects the links to the labs and scientific papers that make up the world of Elysia research. There is also a link to the occasional Solar Slug Journal Clubs that examine current papers in more detail.
Keep an eye out for more updates in the near future. Also, please let me know about links that may have been broken in the process of rearrangement.
In the meantime, here is a photo of a presumed E. papillosa that rode in on the recent batch of plants from KP Aquatics.
Elysia papillosa, June 2015
Dosing Pump is Here
Although the slug system does not require much in the way of chemical supplementation, the plants do require a little input beyond the weekly replacement of about 25% of the artificial seawater in the system. Because there are no fish or other creatures generating nitrogenous waste for the plants, I am adding small amounts of potassium nitrate (KNO3). Plants also require phosphate as a major nutrient, but they consume it in much smaller quantities, and the presence of some cyanobacteria (blue-green algae) implies that there is at least a small amount. I am also monitoring calcium (Ca2+), which is used by some (e.g., Penicillus and Halimeda) but not all (e.g., Bryopsis) of the food plants. Possibly most important is bicarbonate (HCO3–), which acts as both a buffer for the system’s pH and as a carbon source for the growth of the macroalgae. For the moment, the goal is to maintain ~5 ppm NO3–, ~400 ppm Ca2+, and ~3.2 mEq/L HCO3–.
Up to now, I have been adding supplements as needed to maintain parameters, and it has been fine. However, being away from the office due to other obligations or short vacations can cause parameters to fluctuate. This can lead to slowing of the growth of food plants, enhanced growth of pest algae (defined as species the slugs won’t eat), or both. Plus, it might be nice to take an extended vacation.
In an effort to stabilize parameters, I have added a Bubble Magus BM-T11 three-channel dosing pump. It can add NO3–, Ca2+ and HCO3– independently, in whatever volumes and intervals I choose. As part of the kit, I also got a set of reservoirs, a small fitting to mount the tubing on the sump, and a set of three reservoirs to hold solutions. Always fun to open the box and set things up.
Pump and Accessories from Marine Depot, 7/20/15
Then it was time to assemble things, fill up the reservoir, and see how things go. The pump was remarkably easy to program, but each of the the reservoirs had a poorly sealed connection on one of the critical fittings. All it took was a little cleaning and silicone sealer, and we were good to go.
Dosing system, in place and working. 7/21/15
Now it’s time to put the feet on the desk, chomp a cigar, and let the pump do all the work. Now that the pump is adding supplements at a known and constant rate, it should be straightforward to adjust the doses up or down to optimize plant growth and slug health.
New Slugs!
One of the members of the Washington DC Area Marine Aquarist Society (WAMAS) recently posted on the club forum that he had an outbreak of small slugs. When I looked at the photos, I was pleased and amazed to see that his slugs looked like small Elysia. Amazed because his was a traditional coral reef tank, which, given the hazardous pumps and lack of appropriate food, are not conducive to survival, much less propagation of Elysia. Nonetheless, there they were.
Ryan, the slugs’ accidental owner was happy to meet up and hand off a few. It took a few weeks to find the right time, but he gave me a baggie of six little slugs yesterday. Meantime, most of the little guys had done what Elysia usually do in reef tanks, and had climbed or been blown into the filtration system to their doom.
Even a quick, unmagnified look at the slugs suggested that they were not the usual suspects (clarki, crispata, papillosa…). Once under the microscope, they were clearly unlike the other species that I have either purchased or been lucky enough to obtain as hitchhikers on live plants. They are quite small – about 7 mm – have reduced parapodia, stubby, tubular rhinophores, little white bumps, and squarish hearts.
Two unidentified Elysia. Total magnification 70X. 6/28/15
Unidentified Elysia. Ruler shows how tiny the slug is. 6/28/15.
Small unknown Elysia. Each mark represents 1 mm. 6/28/15
They are now in the growout tank of the hatchery system, where I hope they will find a species of algae to their liking. Of the species that fit the rough description on the Sea Slug Forum, Elysia serca, and Elysia flava, two western Atlantic species, or E. obtusa, from the Pacific seem, to be the closest fits. However, none of them seems perfect. The mystery species lacks the characteristic trio of white spots on the heart and parapodia of E. serca, as shown in the photo below, but the small body size, large head, and small rhinophores look like a fairly close match. E. flava and E. obtusa appear much more translucent in photographs, but the pattern of white specs strongly resembles E. obtusa. If they settle in and produce progeny, there should be some opportunities for proper analysis.
Elysia serca from the Sea Slug Forum
Elysia obtusa from the Sea Slug Forum
E. serca, feeds on seagrasses, such as Thalassia (turtle grass) and Halophila (tape grass), which are true vascular plants rather than the macroalgae that serve as food for most of the genus. The food plants of the other two candidate species do not appear to be known. In their new home, there are at least a half dozen species of macroalgae, plus some shoal grass plants (Halodule) that rode in with them, so there is a decent chance they will find something to eat.
It would all be made a lot easier if we knew where they came from. As far as Ryan knew, no plants or macroalgae were placed into his system, so there is no obvious way for the slugs to have ridden into the tank. At this point, we don’t even know which ocean they came from.
Here’s a final look, in their new home. Will she thrive or fade? We’ll see.
Mystery slug in growout tank. 6/29/15.
Going Old School
I have been using a variety of different lighting systems in the hatchery. The Broodstock tank, with the adults, larger juveniles, and plentiful food, is lit with an old Coralife 2X55 watt compact fluorescent (CF) hood, whereas the growout tank has two 20-watt Marineland “Reef Capable” LED fixtures. The macroalgae have been growing like weeds under the old Coralife fixture, whereas the Marineland fixture has not performed all that well.
I suspected that the problem was the spectrum produced by the LED lights. Although many high-end LED systems contain red and far-red LEDs, the Marineland lights had arrays of blue and white LEDS, which produced very little red light. On the other hand, “daylight” CF lamps produce light with a broader spectrum, including significant amounts of the red and blue needed by Elysia food plants.
The solution seemed obvious. It is relatively easy and cheap to assemble CF fixtures using surplus ballasts, endcaps, clips and reflectors, so why not just build one?
Step 1 was to find the right parts, a wiring diagram for the ballast (in this case a Workhorse 5), and to make sure the parts still worked. A quick and dirty assembly shows the ballast, lamps and endcaps are ready to go.
Do all the old parts work?
Next, it was time to cut an old reflector to the right length, and figure out the rough positions for everything.
Ready for soldering.
Although wire nuts would be faster, soldering and shrink-tubing the connections seemed best, given the moist, splashy location.
Soldered, ready for final assembly.
All that remained was to secure the ballast, power cord, and the clips for the lamps (bulbs) to the reflector. Bingo! A new fixture that will produce a spectrum more appropriate for aquatic plants.
New compact fluorescent light, ready for installation.
Frilly Slug Going Home
There has been a frilly sacoglossan (Cyerce?) in the growout tank, which presumably rode in with the last batch of algae. In an effort to focus on E. clarki in the hatchery, and because there is probably another one of these guys remaining in Box of Slugs 2, she is getting moved home tonight.
Frilly sacoglossan 060115
Despite the utter failure of the environmental system at USG (temperature 28 – 30 degrees C over the past few days), the hatchery has muddled along. Even got the first small batch of eggs from the second generation of E. clarki. Thought it might be useful to start providing a sense of scale of these things.
First batch of eggs from the second generation.
Slug Makes New Species Top 10 List
The Washington Post reported that a species of photosynthetic nudibranch has made the SUNY Environmental Science and Forestry list of the Top 10 New Species of 2015. The field was large, about 18,000 species in all, but Phyllodesmium acanthorhinum made the list based on what the animals tell us about the evolution of the symbiosis between the slugs and the photosynthetic algae they host.
NEW SPECIES, PHYLLODESMIUM ACANTHORHINUM. PHOTOGRAPH: ROBERT BOLLAND
Like Elysia, species of Phyllodesmium steal the ability to perform photosynthesis from their food organisms and maintain the required components in sacs extending from the gut called digestive diverticula. There are some important differences, though. Unlike Elysia, Phyllodesmium is a true nudibranch, and it feeds on corals rather than macroalgae. Another important difference arises from the different biology of the algae that Elysia eat and the corals upon which Plyllodesmium feeds. Photosynthetic corals, such as Xenia, contain symbiotic algae (dinoflagellates, actually) called zooxanthellae, which provide the corals with most of their nutritional needs. When Phyllodesmium feeds on Xenia (or other coral species, depending on the species of Phyllodesmium), it steals the zooxanthellae and stores them in the diverticula. In this way, Phyllodesmium has it a bit easier, the stolen algae are autonomous cells, and the slugs do not need to worry about maintaining isolated chloroplasts.
So how did this species end up in the top 10? A recent paper describing Phyllodesmium acanthorhinum and analyzing the interrelationships of species within the genus (E. Moore and T.Gosliner, 2014, The Veliger 51:237) provides some new insight into how the ability to maintain zooxanthellae evolved within the group. Earlier work had suggested that the branching of the diverticula, and their extension into the cerata (the frills on the back of the nudibranch) increases with the increased ability to sequester and maintain zooxanthellae. In other words, species that simply digest the zooxanthellae have minimal branching, while those that maintain large collections of active zooxanthellae have more elaborate diverticula that branch deeply into the cerata. Based on the descriptions of P. acanthorhinum and another species, P. undulatum, both of which are relatively less specialized for maintaining zooxanthellae, Moore and Gosliner provide additional support for this hypothesis. Further, they suggest that the larger body sizes achieved by more derived species, i.e., those that are better able to maintain populations of zooxanthellae, result from the additional nutrients produced by the symbionts.
Once again, slugs find a way of hijacking photosynthesis from their food. Because Elysia and Phyllodesmium are only distantly related, and their biology and that of their food are so different, the two forms of theft-based photosynthesis must have evolved independently. The similarities are striking, though. It does make one wonder if there is some aspect of the biology of sea slugs that predisposes them to separate chloroplasts or entire zooxanthellae from their food and maintain them in digestive diverticula.
Hatchery in Progress
As described a while back, all steps in the culturing process seems to be going pretty well, except for one bottleneck. The adult broodstock is (are?) happy to lay eggs, the eggs hatch consistently, and the veligers settle. However, they will not develop much farther after settling in a controlled environment. Oddly, the settled veligers will develop if left on their own in a large tank full of algae. Although I have now reared E. clarki from egg to adult, it is not really possible to plan experiments based on when slugs may or may not decide to develop in a display aquarium. A more systematic approach was needed.
The hatchery is an attempt at making the juveniles happier during and after settling. Egg masses will still develop in glass crystallization dishes, but they will be placed in the new setup just before hatching. There were a few issues that may have impeded development, and they should be addressed by the new setup.
The tank is an acrylic “half-ten” from Glasscages.com. It is essentially a half-height 10-gallon tank (10″ W X 20″ L X 6″H). I had originally planned on using a standard 10 gallon, but it became clear that it would be clumsy and result in a lot of wasted space.
Acrylic “Half-Ten” tank from Glass Cages. 5/19/15
One problem that arises with free-swimming veliger larvae is that they are positively phototactic (attracted to light). This may not be a problem in the open sea or a large aquarium, but in the small dishes I was using for hatching, it meant that they would swim to the surface and promptly get stuck in the air-water interface. This would leave little rafts of veligers on the surface. These floaty veligers were capable of settling, so it was not a complete disaster, but it could not be good for them. Some authors (e.g., Dionisio et al, 2013) go so far as suggest rearing them in the dark. My solution is to illuminate from below. Marineland makes a nice little submersible LED light that can be used to keep the veligers swimming downward. Below are views of a prototype hatching chamber (2″ PVC pipe, with 50 micron nylon mesh to retain the veligers and larvae), showing the light coming from underneath.
Light from below, with prototype hatching chamber. Front view. 5/19/15
Light from below, with prototype hatching chamber. 5/19/15
Secondly, the presence of a relatively large food plant (large enough to be certain all of the little slugs can climb on) might have altered water chemistry, either through the process of photosynthesis (raising pH, e.g.) or by releasing chemicals that inhibit the slugs’ feeding or development. Continuously recirculating ASW (artificial seawater) from the larger system through their hatching chambers should reduce or eliminate this problem. In order to keep voracious invertebrates from entering the chambers, ASW will pass through a UV sterilizer before being distributed in the hatchery.
The manifold for distributing the ASW to the chambers is made from a few PVC pipe fittings. Once the cement has cured, it will be drilled to accommodate valves to control the flow to each chamber.
Components of the manifold. 5/19/15
Manifold, assembled but not drilled. 5/19/15
Naturally, water arriving in the tank needs to leave, so I drilled it and added a bulkhead to drain to the sump.
Tank drilled and bulkhead installed for drain. 5/19/15
Once the manifold is finished, and the UV unit arrives, it will be ready to hook up and accommodate the next available brood. Stay tuned.
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