Isopod Genus/species ID?

[RedFrog211]

I’m doing a personal project where I find the Binomial Nomenclature of every organism in my reef. It’s been going well, up until now. I have these isopods, commonly referred to as “Munnid Isopods” obviously from the Munnidae family; but as for genus and species, I’m at a loss. I’ve checked the Integrated Taxonomic Info System, World Register of Marine Species, Global Biodiversity Info Facility Etc.. this is a shot in the dark— but does anyone have any ideas about Genus? I know this is an odd post, just wasn’t sure where else it would belong

 

[fishguy242]

hi,@KJ @samnaz ,any idea

 

[KJ]

I’m doing a personal project where I find the Binomial Nomenclature of every organism in my reef. It’s been going well, up until now. I have these isopods, commonly referred to as “Munnid Isopods” obviously from the Munnidae family; but as for genus and species, I’m at a loss. I’ve checked the Integrated Taxonomic Info System, World Register of Marine Species, Global Biodiversity Info Facility Etc.. this is a shot in the dark— but does anyone have any ideas about Genus? I know this is an odd post, just wasn’t sure where else it would belong

Isopod munnid.

 

[taricha]

It’s been going well, up until now. I have these isopods, commonly referred to as “Munnid Isopods”

I went down that rabbit hole on these, and came up pretty empty as well!

So let me expand a bit...
The hobby calls them "munnid isopods" because of this article by Shimek, and the adoption of that info in hitchhiker guides like lionfish lair.

Presume he's right and dig up family munnidae(wiki) and there are 6 genera included. See what you think. None of them look great to me but I have no expertise.

If you want to see if he may be wrong, then you can go waaaay the heck back from munnidae, up two levels and start at suborder Asellota, as in "Asellota isopods, Ase-whole-llota isopods" (don't ruin the joke and tell me I'm saying the name wrong in my head)
You will almost certainly be right, as there are 1/4 of all isopods in asellota.

You could wildly guess that they look super similar to the freshwater common isopod Asellus aquaticus(pic), but that whole genus and everything related to it seems only in freshwater, so we'd be wrong.


so here's my best terrible efforts:
Asellota->Janiroidea->munnidae->?6 genera?
or
Asellota->Janiroidea->Janiridae->ianiropsis genus(images)
or
it also looks like idotea genus which is in a whole 'nother branch of the isopod family.

 

[RedFrog211]

I went down that rabbit hole on these, and came up pretty empty as well!

So let me expand a bit...
The hobby calls them "munnid isopods" because of this article by Shimek, and the adoption of that info in hitchhiker guides like lionfish lair.

Presume he's right and dig up family munnidae(wiki) and there are 6 genera included. See what you think. None of them look great to me but I have no expertise.

If you want to see if he may be wrong, then you can go waaaay the heck back from munnidae, up two levels and start at suborder Asellota, as in "Asellota isopods, Ase-whole-llota isopods" (don't ruin the joke and tell me I'm saying the name wrong in my head)
You will almost certainly be right, as there are 1/4 of all isopods in asellota.

You could wildly guess that they look super similar to the freshwater common isopod Asellus aquaticus(pic), but that whole genus and everything related to it seems only in freshwater, so we'd be wrong.


so here's my best terrible efforts:
Asellota->Janiroidea->munnidae->?6 genera?
or
Asellota->Janiroidea->Janiridae->ianiropsis genus(images)
or
it also looks like idotea genus which is in a whole 'nother branch of the isopod family.

This is the exact problem I encountered, and explains the past 48 hours of my life! Hahaha, glad to know I’m not the only one. It bothered me that “munnid isopod” wasn’t mentioned in any scholarly article or research papers, and was only cited in forums. I also found Asellota to be promising- But like you said, with that being the Suborder, it encompasses a vast amount of families. That’s exactly where I was when I posed this thread Isopoda -> Asellota -> Janiroidea -> Munnidae.. but since then, I think I found it! Check out “Janira maculosa”!

 

[taricha]

This is the exact problem I encountered, and explains the past 48 hours of my life! Hahaha, glad to know I’m not the only one. It bothered me that “munnid isopod” wasn’t mentioned in any scholarly article or research papers, and was only cited in forums. I also found Asellota to be promising- But like you said, with that being the Suborder, it encompasses a vast amount of families. That’s exactly where I was when I posed this thread Isopoda -> Asellota -> Janiroidea -> Munnidae.. but since then, I think I found it! Check out “Janira maculosa”!

since on we're well on the bus to crazy town, lets go a little further shall we.

some fellow nuts here:
British Myriapod and Isopod Group
"Promoting the study of Centipedes, Millipedes and Woodlice in Britain and Ireland"
Marine Isopods of Britain and Ireland: systematic check list
(systematic checklist because ya gotta catch 'em all)
Janira maculosa:
"This species is oblong and flattened in shape, measuring up to 10 mm for males and 7 mm for females. Its most striking characteristics are its very long antennae (longer than its body) and long uropods (longer than the pleotelson), as well as the concave edges on the first four pereon segments. The male preoperculum is also a useful diagnostic. The species is a yellowish colour with red or brown mottling. "

This is the best image I can find of our reef isopods, source and other wildly great photos of this isopod are here(flickr)

for comparison, here's professionally ID janira maculosa
thumbnail (click through to Aphotomarine for full sized pic)

Note the tapering down of the width from the middle of the body to the head - not the case in our aquarium type, and if you click through for the full size you can see the slightly fluted edges they call "concave". Oh, also the species distribution seems to restrict janira maculosa to pretty far north. nothing tropical. So not the same species, but honestly species-level identification by hobbyists in something that is as diverse as isopods is totally nuts.

This page on Aphotomarine with amazing photos of most of the relevant genera does drive home the idea that we are almost certainly in the right ballpark...
https://www.aphotomarine.com/isopoda.html

Asellota (Suborder) > Janiroidea (Superfamily) > Janiridae (Family) contain two genera that look really good: Janira discussed above and ianiropsis (google images)

none of the other families pictured - including munnidae (Family) > munna (genus) - look very close at all.

 

[RedFrog211]

So at least we’re making progress. I certainly agree that Janiridae seems like the right family- I’ll update tomorrow if I find anything!

 

[taricha]

Went looking for some expertise ....

here's a reply I got (shared with permission) - very enlightening.

Thanks for the message. Interesting - and I especially liked the images of the isopod. It looks like people on the reef2reef forum honed in on maybe the right genus. Ianiropsis is a common genus in the tropics and subtropics and has many undescribed species, but it could also be Carpias, which is even more common in reef environments. Brenda Doti and I published a key on the described species a few years ago although given the probable diversity in these genera, the key is likely to be contradictory in the case of trying to key an undescribed species. If you at least want to get to genus, someone needs to get good images of an adult male. These are obvious because their first pereiopod, which is a gnathopod, is extremely different between the two genera. Also useful is an image of first pleopod, so maybe a good ventral view of the whole animal is needed. The nice images in your link are showing a female, which is can be determined by the long paired ovaries on each side of the gut, as well as the lack of an enlarged pereiopod I - and I saw no evidence of the male pleopods. Also look for really large maxillipedal palps - observed in males of some Ianiropsis species.

hope this helps!

Buz


--
George D.F. (Buz) Wilson, Ph.D.
Saugatuck Natural History Laboratory, LLC

I haven't had a chance to chase down the other genus he suggest: carpias, which is apparently even more common than the ianiropsis. Since we're talking about organisms that are virtually everywhere in the hobby, I think undescribed species aren't what we're looking at. The more widespread tropical genera should probably be considered likelier barring evidence otherwise.

 

[RedFrog211]

Awesome info! I reached out to a marine biologist @the_story_of_a_biologist on Instagram, but he’s over seas, away from his equipment and work, so he’s unable to help aside from confirming our suspicions of it being Asellota. Unfortunately I don’t have access to a microscope to get a clear image of a male, but I’ll see if I can get any pics tonight with a macro lens

 

[taricha]

Unfortunately I don’t have access to a microscope to get a clear image of a male, but I’ll see if I can

I do have a microscope that would be up to the challenge, but I think the pictures we need have already been taken and posted, just need to find them. Sounds easier than catching one of those little buggers from my tank.

By the way, there's an interesting reason for chasing down this rabbit hole at least a little bit. These isopods are virtually the only herbivore / grazers I can think of that show up disproportionately around dino outbreaks, including some toxic ones. Snails and copepods disappear, either by being killed off or avoidance. These seem indifferent to whether they eat dinos or not, and in some cases congregate in dino patches.
Now nothing, so far as I know, grows well on toxic dinos, but nature is full of examples of things that are widely toxic, but a niche species here and there tolerates the toxin just fine.

 

[ReefMind]

Revival! Was the species ever identified?

 

[taricha]

Revival! Was the species ever identified?

another year, and still no.

A later email I missed at the time from the biologist ruled out munnids and Ianiropsis.
another thing that made me remember this thread lately is that these isopods have been documented by hobbyists to be bioluminescent.
see this article... (2/3 of the way down)
https://www.reef2reef.com/ams/reefing-after-dark-part-2-bioluminescence-observations-research.511/
That doesn't help with the ID. Many copepods etc are bioluminescent. It's just interesting.

I'll follow up with the isopod specialist.

 

[taricha]

Time for another installation on this thread....
I finally saw more of these isopods in my system again so took the advice of the biologist I spoke with earlier and preserved them in ethanol. (3 individuals)

Sent these to the two authors of the paper attached in this post....

Summary of their thoughts:
They both think it looks to be a member of the genus Ianiropsis, family Janiridae. It might be Ianiropsis epilittoralis, which was common on the US west coast.
It was suggested that I use the identification key in the paper to try to nail it down, as there was some amount of guessing done just looking at my photos.
Also there's a lot of similarity to the genus Iathrippa. But those usually have a rostrum on the anterior margin of the head. I'll need to take a closer look to rule that out (and read up on what that is ) before attempting to work through an ID key for Ianiropsis.


So the TLDR is that these isopods are likely genus Ianiropsis, according to authors of the identification key for that genus.