Scutus sp.: Breeder Challenge #3 candidate information

[BrianPlankis]

Hey all,

Scutus sp. are another candidate for BC #3. They would appear a promising candidate as they have already bred on their own in captivity, so an effort to figure out how to breed them could lead to a large number of them quickly.

A couple of downsides though: They only come out after lights off and they are extremely hard to remove from surfaces. Live rock is virtually impossible unless they are on the edge.

Some general information on these guys and information that at least one species of them is a broadcast spawner:

http://www.seaslugforum.net/display.cfm?id=15037
Broadcast spawner link:
http://www.seaslugforum.net/display.cfm?id=11385

I have not done a literature search on these guys yet.

Brian

[luis a m]

Hi Brian,
I keep three adult Scutus (they were four,but one died)in a ten gallon bare tank with just a small piece of rock (where they came)and a flower pot.The tank is part of a larger system.They share the tank with a ringed pipefish D.dactylopophorus,a couple of mandarins S.splendidus,a CB Lysmata amboinensis and two Thor amboinensis.I know they are not slugs,but should we call them snails or limpets?
These Scutus were given to me by a friend who keeps them in a reef tank.She found that they reproduce there and many offspring were produced.
However I did never see reproduction activity or small ones in my tank.I did not know that some primitive gastropods like this one use external fertilization.
But I have recently found two, 3cm and 2cm young ones on the system´s filter matt and on the drip plate.
So I think that all the eggs-larvae-newly settled snails were consumed in my tank,and the only ones that could make it, settled in the system´s pipework until they ended in the mechanical filter.:confused:

[BrianPlankis]

Luis,

They are considered a snail within the family Fissurellidae, which includes slit and keyhole limpets, so I think it would be safe to call them a limpet. Remove the fleshy covering and their shell looks like that of a limpet, except that their shell is notched, it does not contain a slit or a hole.

You certainly have a number of animals in that tank that could potentially prey on the babies, but to be honest not a lot is known about predation on them, their reproductive biology or if they need settling cues. The breeder where I got mine from says he finds almost all the babies in the sump of his system. He has around a 200 gallon main tank and only a 35 gallon sump, so at least with your system and his it appears they like to settle in the dark.

So far I have not found any babies in my tank, nor have I witnessed them reproducing. I still see one or two of them at night, munching away, but that is all.

I still have not done a scientific search on them, so there could be some articles out there on their reproduction that I'm not aware of yet.

Many of the primitive gastropods in the hobby use broadcast spawning, with many Ceriths, Columbellids, Nerites and the DIBS Turbos being some exceptions.

Brian

[luis a m]

Last night I checked their tank at 2 AM and witnessed a massive spawning in which all my six S.unguis took part.They are four large adults of 6cm long foot and two 3cm young ones.Five were together in close contact near the surface,one partly out of the water and one was about 20cm away also close to the surface,yet spawning as well.
They began producing whitish clouds of milt and after some time they released greenish egg masses.
It was an impressive event,the whole tank was soon cloudy with this gametes discharge.:cool:

[BrianPlankis]

Last night I checked their tank at 2 AM and witnessed a massive spawning in which all my six S.unguis took part.They are four large adults of 6cm long foot and two 3cm young ones.Five were together in close contact near the surface,one partly out of the water and one was about 20cm away also close to the surface,yet spawning as well.
They began producing whitish clouds of milt and after some time they released greenish egg masses.
It was an impressive event,the whole tank was soon cloudy with this gametes discharge.:cool:

That is very good to hear! Did you happen to take any pictures of the eggs or attempt to fertilize them?

Brian

PS. Still no successful reproduction in my tank.

[luis a m]

Yes,Brian,took some samples of eggs and sperm for closer examination and pics.
And mixed some in a Petri dish to check for fertilization and early development.

[luis a m]

This is a close view of an egg during fertilization.Three sperm cells were seen inside the external capsule but don´t show well in the pic.Size of the egg is 270 mic.
http://i175.photobucket.com/albums/w133/magnasco/desoveScutus002.jpg
Only one hour later and during the following hours celular division proceeded to two,four,eight blastomers,amazing,like in a biology sketch:cool:
Very few of the "in vitro fertilized"eggs developed though:
http://i175.photobucket.com/albums/w133/magnasco/desoveScutus003.jpg

[BrianPlankis]

Luis,

So what microscope are you using for these pictures? Great shots!

Brian

[luis a m]

Two scopes;an Indian compound and a Tasco dissecting,both old cheap stuff!:)

At 12 hrs the embryo (gastrula I think) is covered with cilia which make it spin continuously in the capsule.It measures 120 x 100 mic.
http://i175.photobucket.com/albums/w133/magnasco/desoveScutusembrion12hrs3.jpg

[luis a m]

At 24hrs it is a trochofore,with long cilia tufts that make it spin over it´s axis.
http://i175.photobucket.com/albums/w133/magnasco/desoveScutusembrion24hrs3.jpg

[luis a m]

At 48 hrs,the veliger:
http://i175.photobucket.com/albums/w133/magnasco/desoveScutusembrion48hrs1.jpg
It is basically like a snail shell with the velum,two ciliated membranes used for swimming.But it is still inside the egg capsule.Size has not changed,it is developing and changing but not growing.

[BrianPlankis]

Luis,

Thanks for the great pictures! So far I have not found anything in the literature that describes their larval development, so you are doing great work!

Cheers,

Brian

[luis a m]

Thanks:o
The paper in your links about keyhole limpet development is helpful as the larval stages are very similar.
At four days my larvae look like tiny snails,complete with tentacles,eyes and foot.But they still show the cilia in the reduced velum,they are late veligers.
Still inside the egg capsule,they glide fast attached to it.I could rescue two live ones from the decompossing egg mass.
One of the eggs hatched in the process of pipetting them,the capsule was expanded and thin,so hatch was close to happen anyway:o
The veligers measure 80 mics.The one at the right is still in the egg,while the one at the left is just hatched,attached to the empty egg capsule.
http://i175.photobucket.com/albums/w133/magnasco/desoveScutus3dias003.jpg
http://i175.photobucket.com/albums/w133/magnasco/desoveScutus3dias001.jpg

[luis a m]

See that in the last previous picture,the specimen at the right-top is seen from above, while the other one shows a full profile.
The shell has the aproximate shape and proportions of the shell of a Planorbis,like the FW red ramshorn snail.They also have an operculum.
Today (day 5)the two veligers roam freely in their Petri dish.They can both slide on the substrate or swim in the water column.The body withdraws into the shell when swimming.It is whitish-transparent with some greenish yolk remnant inside the shell.
I guess the lecitotrophic phase is over and put some phyto and benthic algae in the dish.

Watching them developing has been an amazing experience.And if they survive,it will be quite a thrill to see how a tiny white round shelled snail becomes a big black limpet that looks like a slug!:D

[luis a m]

One died,and the shell remained intact,so it must be calcified.
The only survivor looks about the same at 12 days.It shows green colour inside the shell,so it must be feeding.

[BrianPlankis]

I guess the lecitotrophic phase is over and put some phyto and benthic algae in the dish.


Did you add a specific type(brand) of phyto or benthic algae? Or did you just scrap your glass or add in tiles?

Also, what volume of water do you have them in?

Brian

[luis a m]

I put a little piece of scrappings and live T-ISO and lioph.TET and NAN.
Volume of a Petri dish?Let see...30 ml!.
I tried twice to pipette it for micro examination and it outsmarted me and got lost.I´ll better leave it alone for some time.:rolleyes:
I changed water though.

[CELACANTHr]

This is very awesome!

So did only two get to the late veliger, or were the rest just trapped in the egg mass?

[luis a m]

This is very awesome!

So did only two get to the late veliger, or were the rest just trapped in the egg mass?

Right,only two,and then one died:(
But now since several days I can't find the survivor,not even the shell:confused:
But I imagine many other little veligers are growing in the adult's tank and some day they will become visible.
I recently found a small juv in another tank of the system.To get there the larva must have gone across the filter matt and the bioballs,into the sump and been caught by the return pump,pipework and return valve!:eek:

[BrianPlankis]

I briefly looked inside my tank last night and discovered I still have the Scutus sp. in my tank. I found two adults (one over 3" long!) and also a baby no more than 1/2" long (very cute). I had not seen any for over 4 months.

So I now have confirmed successful reproduction in my tank. But certainly not very prolific as they have been in the tank for at least a year now, maybe approaching two (I would have to look back on my records).

Brian

[luis a m]

I found another 3cm young Scutus on the drip plate.Must have grown in the system´s pipework and somehow negotiated the filter floss.
It holded so tight to the plate that a metal spatula hat to be used to make it let go.No way to do it if it was a rock.;)