polyclad diet- Leslie?? anyone?? :)

[flyyyguy]

Over the years I have had experiences with both clam eaters and snail eaters, but in the last couple months I have found two more polyclads yet havent added anything in well over 6 months.

I do not think that either of them are snail or clam predators, and this is why.

1. There is but one decent sized gigas in the tank. Its a BB tank and he sits alone very easy to inspect. I have montitored him day and night, blown on him in an effort to dislodge any, and even pulled him out for inspection. nothing

2. The last one I found, while somewhat small(1.5"), I did a little experiment as i wanted to see exactly how the thing would eat snails. In with him for nearly 3 weeks I put a few collonistas, a few stomatellas ranging from baby to adult, a astrea and a cerith. He didnt touich any of them and while I still have him alive, he has shrunk to half his size in this time. Im done with the experiment as I am confident he is not a snail predator. I will get rid of him and return the snails.

Being as the polyclad did shrink so rapidly it leads me to believe he is eating something, but neither my clam or snails. Being as I have found two of them recently, there is no doubt in my mind that there are more in my tank, and they are eating something. What else could be on their menu?? Or are they maybe in fact munching on my clam but he is big and healthy and just can deal with it? Both of the ones I found incidentally were 4-5 feet from where the clam resides.

 

[LeslieH]

Not that much is known about specific food preferences of polyclads. A few are well studied because they're mollusc predators that have an economic impact on fisheries & mariculture. The big color Pseudoceros & Pseudobiceros are thought to be primarily tunicate eaters. Others specialize on sponges, corals, etc., some are hunters that go after worms & small crustaceans, some are probably generalists, and some are scavengers.

Animals with a similar color pattern as your two flatworms have been observed to actively hunt down molluscs in marine aquaria. You've seen lots of those posts, I'm sure. Some swallow snails whole. Others go after Tridacna & clams & feed by extending their proboscis over the clam's flesh then they produce digestive compounds which break down the flesh, & the flatworm sucks up the semi-digested fluid. You can rule out snails because of your experiment but we can't rule out that they eat Tridacna. Maybe they do, maybe they don't. In the ocean a healthy Tridacna might be able to regenerate fast enough to compensate for predation as you suggested. Another possibility is that the commensal shrimp which live inside Tridacna in the wild will defend their host clams against predation.

Flatworms store their food reserves as fat much as we do. If they're not eating, the reserves get used up & they start to digest their own tissues. Individuals have gone as long as 6 months without eating.

 

[flyyyguy]

Thanks Leslie. Just the woman I was hoping to answer.

Being as I havent added anything for at least a year, if not 2 that could have introduced these guys, I imagine he is either feeding on molluscs, or my clam is just dealing with it. This gigas is incidentally the fastest growing clam I have ever seen. In just a year he has went from 3" to over 8" I would guess. I wonder how big he would be if he wasnt possibly being chowed on.

I was really wondering if there was something known on their potential diet that I hadnt heard of besides clams/molluscs and snails.

As always, thanks for your input

 

[pagojoe]

As I recall, someone reported this species feeding on Tridacna squamosa, and noted how well the worm's pattern matched the mantle. I think it was on Reef Central, although it might have been somewhere else. There were also several reports of this species wrapping up and killing snails, although none of the ones you "tested" were the species that were eaten. There are several species that are known to feed on cowries, although I didn't find your animal accused of that behavior, and some feed on other animals including oysters, non-tridacnid clams, and ascidians.

Here are some links you might find interesting:

http://pubs.acs.org/cen/news/84/i08/8408flatworm.html

http://www.thefreelibrary.com/Killer+flatworms+hunt+with+poison-a0145483002

http://www.youtube.com/watch?v=-f7e1tBOSKE

Cheers,



Don

 

[LeslieH]

that's assuming that flyyyguy's animals are the same as the Tridacna-predator, Don. The same color pattern can show up in unrelated species with different behaviors & feeding preferences.

I suspect that between the specialists & the generalists there's a flatworm predator for just about anything. Some might even digest organics off sediment for all we know.

 

[pagojoe]

Good point. I didn't intend to add to your post, it's just that I typed my response so slowly that you guys had all had a conversation in the background, lol. The most common Indo-Pacific polyclad looks just like that, though. They aren't as spectacular as the brightly-colored ones, but you find "brown with white/tan spots" about four or five to one over the others on the reef. I got a little education on them myself as I was reading all the Google results. I had no idea the different species fed on such a large variety of food items.

Cheers,



Don