Monthly Archives: September 2015
Little Slug Eggs
A little over a month down the road, the little slugs that rode in with the last batch of macroalgae are still pumping out eggs. At some point, I will really need to figure out the actual species, rather than referring to them (probably erroneously) as E. papillosa. Always more to do than time to do it.
Here is the young lady laying eggs this morning. No scale, but she is probably about 4 cm at this point. Note that the egg mass is different from the tidy coil seen in a previous clutch, seen here.
Small Elysia species laying eggs. 9/30/15.
If past experience holds true, the eggs will hatch within about 5 days, which is a lot faster than the larger E. clarki. In order to compare the developmental sequences of the two species, I have started taking photos of the little guys’ development.
Below is a shot at about 20X, showing a couple of strands.
Eggs of small Elysia species (papillosa?), about 7 hours old. Debris from surrounding algae. 9/30/15
At higher magnification.
Eggs of small Elysia species. Photographed at 40X, black bars in background spaced at 1 mm. 9/30/15.
Given their rapid development, it will be interesting to see what they look like tomorrow. For a sense of scale, try to compare the eggs in the micrographs to the barely resolvable dots in the egg cluster as the eggs are being deposited.
One Man’s Trash…
Although they will eat a number of algal species, Elysia clarki strongly prefer Bryopsis, which is a feathery filamentous alga considered by most aquarists to be a pestilent nuisance. For the past year, I have been benefiting from the struggles of a local reefkeeper who has had a plague of the stuff in his 500 gallon system. Alas, through rigorous reduction of phosphate levels, his battle with Bryopsis seems to be coming to an end.
That sent me into a panic. Well, more like mild anxiety. Even though it has been possible to maintain my own stock of Bryopsis, it had started to run low. Hard to believe, but I am having trouble growing enough of a nuisance alga. In my defense, it is a bit of a trick to grow one form of plague without another taking over. I was starting to be concerned that the slugs would not be ready to lay eggs if they ran out of their favorite food and had to make do with other algae.
Fortunately (for me), another WAMAS member is in the midst of a battle with Bryopsis. It required a trip to Virginia, but I returned with a bucket full of soft, feathery algae. It seems finer than the variety I was getting from the previous source.
Nonetheless, the slugs are lapping the stuff up. Despite their reputation for slow movement, slugs are pretty good at moving around when they have appropriate motivation.
Elysia clarki on new batch of Bryopsis, 9/3/15
The adult above dug right in. As did the juvenile, below. Up to her rhinophores in Bryopsis.
Young E. clarki feeding on new Bryopsis, 9/3/15
Below is a shot of her cruising around, before having found the food pile.
Young E. clarki, exploring. 9/3/15
Now that they have been fattening up on algae, they have taken on a much deeper green color. Will have to post some before and after photos next.
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