Crangonyx as an algae eater

[dw1305]

Hi all,
I don't think I have any "Northern River Shrimp" Crangonyx - <"Live food culture - Crangonyx pseudogracilis"> left in the <"tanks with fish">, but I have a "spare tank", until it goes to @megwattscreative, with plenty present and I tried putting a Frogbit (Limnobium (Hydrocharis) laevigata) plant, with some green algae on the roots, in with them to see what happened.

This is the result:
Before

After

So I'm looking on that as a success.

Cheers Darrel

 

[Ratvan]

That's a pretty drastic change, over what time period was this?

 

[dw1305]

Hi all,

That's a pretty drastic change, over what time period was this?

I'm going to say ~72 hours, I just meant to leave it in overnight, but my wife and I both have COVID at the moment (unfortunately it is still a "thing") and I just forgot about them.

I thought of doing it because I had some Frogbit that has been <"sitting in a bowl and has algae">, and I'd moved some moss and Susswassertang (Lomariopsis lineata) into the tank and noticed that it rapidly had Crangonyx all over it. I couldn't see what they were eating (diatoms perhaps?), but they were definitely eating something.

cheers Darrel

 

[NathanB]

Wow they did a brilliant job, I remember setting up a small native invert tank with some algae covered rocks that I collected from the local stream, I also added some duckweed from my pond that was covered in a few Asellus sp. I watched as some larger "scuds" grabbed a poor little water louse and started to eat it! Never properly identified them but my guess was maybe a Gammarus species. Have you ever experienced anything like that with amphipods Darrel? Im not so experienced with them apart from that and one of our native saltwater species, but I only occasionally get a glimpse of one creeping between some smaller rocks once in a blue moon.

 

[Bradders]

my wife and I both have COVID at the moment (unfortunately it is still a "thing") and I just forgot about them.

Get well soon. (Although the forced plant focus might be of some consolation!)

 

[dw1305]

Hi all,

Asellus sp. I watched as some larger "scuds" grabbed a poor little water louse and started to eat it! Never properly identified them but my guess was maybe a Gammarus species.

I think that Hyalella azteca and Gammarus spp. are a lot more omnivorous than Asellus or Crangonyx, which are detrivores. From - <"https://invasions.si.edu/nemesis/species_summary/95082">

..In Northern Ireland, predation by other Gammarus species (G. pulex, G. duebeni, G. tigrinus, in descending order of predation rate), limited the distribution of the smaller Crangonyx pseudogracilis (MacNeil et al. 2003).

Personally <"I've not tried Hyalella">, and Gammarus ssp. don't last at tropical temperatures.

,Have you ever experienced anything like that with amphipods Darrel?

No, but I still have nightmares about potentially introducing the <"Killer Shrimp"> - Dikerogammarus spp - <"https://www.nonnativespecies.org/assets/InvasiveFWShrimpsIsopods.pdf">

Cheers Darrel

 

[dw1305]

Hi all,
I put another Frogbit plant in, much less noticeably green in the root department, but this was about 10 minutes afterwards.

Apologies for the quality of the photos.



Cheers Darrel

 

[RickyV]

@dw1305 Do you know their rate of reproduction? Brood sizes and time to reproductive age? I have a bunch of these in my tank at home that I want to use to make a culture for 3000 Liter High Tech Planted Tank I'll probably make a culture connected to the main tank flow like the blackworm cultures. But I'm wondering if they reproduce fast enough to be worth culturing.

 

[dw1305]

Hi all,

@dw1305 Do you know their rate of reproduction? Brood sizes and time to reproductive age?

Quicker than Asellus, but after that I don't really know.

Because they are used for aquaculture and as a bioassay organism (as well as being an invasive) I should be able to find some figures.

..... But I'm wondering if they reproduce fast enough to be worth culturing.

I think they do.

Cheers Darrel

 

[Gill]

Cool little things aren't they, they were a permanent resident in the filters at Coalville.

Rest up and take care, A few of the engineers lost toe nails with this covid, they just fell off.

 

[dw1305]

Hi all,

I should be able to find some figures.

These are for <"Crangonyx floridanus">, but it is morphologically and ecologically pretty much identical to <"C. pseudogracilis">:

<"Reproductive Biology and Adaptability of the Invasive Alien Freshwater Amphipod Crangonyx floridanus (Crustacea: Amphipoda, Crangonyctidae)">.

cheers Darrel

 

[Little]

I adore your dedication to science and the coupling of free and effective aquarium solutions… but… man those things look fugly.
It’s like hairless cats to avoid fluff on the sofa 🤣

 

[dw1305]

Hi all,

I adore your dedication to science and the coupling of free and effective aquarium solutions… but… man those things look fugly.
It’s like hairless cats to avoid fluff on the sofa 🤣

Get away with you, Crangonyx are quite cute, although that maybe doesn't show in the picture.

Asellus are possibly a bit more <"aesthetically challenged">.

They are both definitely hairless.

Cheers Darrel

 

[Bradders]

Striking resemblance?

 

[simon_the_plant_nerd]

@dw1305 Did you send me some of these a while ago? I have a lot of beasties from you living in my shrimp tank but I don’t think I have these. I’m tempted to change my main tank from high tech to medium tech and see if I can get more diverse life living in there. Seems to be positive and I quite like ‘ugly’ creatures.

 

[dw1305]

Hi all,

@dw1305 Did you send me some of these a while ago? I have a lot of beasties from you living in my shrimp tank but I don’t think I have these.

Yes, I'm pretty sure I sent some to you. They are hyperactive, so if you had some left you would probably know.

Cheers Darr

 

[louis_last]

Hi all,

I think that Hyalella azteca and Gammarus spp. are a lot more omnivorous than Asellus or Crangonyx, which are detrivores. From - <"https://invasions.si.edu/nemesis/species_summary/95082">

The species I assume to be hyalella azteca, although they were just sold as 'mini scuds' on ebay, are not only omnivorous and great algae eaters but aggressively predatory if they start running out of food. If there isn't food constantly available the larger ones immediately begin actively hunting down and eating any smaller than themselves. I've seen people saying it's a myth that scuds will eat neo shrimp eggs right off the female shrimp and hunt babies but whatever the kind I have are most definitely would if they were hungry and I assume they would eat all your plants first too.
I've never witnessed this kind of predatory behaviour with crangonyx and have also found them to be a good algae eater. Before I added them to my tank I was keeping them in a plastic tub and feeding them solely on hair algae from a bucket outside. I've noticed with crangonyx that they tend to avoid light more than some other scud type species so I only see them now when I assume a female has moulted and all the males start frantically swimming around trying to find her.

 

[louis_last]

@dw1305 Do you know their rate of reproduction? Brood sizes and time to reproductive age? I have a bunch of these in my tank at home that I want to use to make a culture for 3000 Liter High Tech Planted Tank I'll probably make a culture connected to the main tank flow like the blackworm cultures. But I'm wondering if they reproduce fast enough to be worth culturing.

females reach sexual maturity in 2–3 months, having a longevity that can reach up to two years, being able to produce up to eight broods during this period.........The reproduction season of Crangonyx pseudogracilis differed between locations. Additionally, its fecundity also differed, since in Ferrarias there was an average of 25.94 eggs per female, while in Coruche these values were much lower, with an average of 10.96 eggs per female.

In the laboratory, C. pseudogracilis breeds at 5 to 25C, and the egg development time decreased from 66 to 7 days over that temperature range (Sutcliffe and Carrick 1981). In an English river, breeding took place year-round and the monthly average number of eggs per female varied from 25 to 54 (Hynes 1955).

Crangonyx pseudogracilis Crustaceans-Amphipods northern river crangonyctid
Population dynamics and expansion of Crangonyx pseudogracilis, a potentially invasive amphipod
This information is from wild populations. I think you can safely assume they will mature faster and reproduce more often in optimal captive conditions.
In my experience with some direct side by side comparisons the more commonly available hyalella azteca scuds reproduce much, much more quickly though and are only very slightly larger. If you were just culturing them for food they would probably be a better option. Crangonyx being the much better option if you want tank custodians though.

 

[dw1305]

Hi all,

The species I assume to be hyalella azteca, although they were just sold as 'mini scuds' on ebay, are not only omnivorous and great algae eaters but aggressively predatory

You need to look at <"their urosomes">.

cheers Darrel