Red Sea Mysids??

I photographed these little chaps in the Red Sea. They were always on red sponges. They are very tiny ~ 5mm long.

They look like the image on p198 of Gosliner et al "Coral reef animals of the Indo-Pacific" - which lists them as mysids. But these shrimps were very host specific only settling on this type of sponge. Plus when I found swarms of mysids swimming around the reef these didn't have these distinctive thick white antennae. I think that they are mysids, but not the same as the ones swarming around the reef.

I have 2 further questions:

What is the white oval on the backs of some individuals. Mysid's have brood pouches - but I don't think that this is it.

Plus on some sponges the shrimps seemed to have covered themselves with sediment. I wondered why this was and whether it helps ID them:

Thanks,

Alex

Hasn't anybody got a clue about these lil' guys. Or are you just ignoring me! That'll teach me for posting a chicken's egg for ID here in the past. Alex

I can't believe I still haven't got any replies. Has anyone else got a shot of them? Alex

I didn't ID them but they populate red sponges all the way up north to Eilat usually covered with cediment.

I have forwarded the question to a marine biologist I'm working with and hopefully I'll have some answers.

Well the ID is probably some type of Spionid (type of worm) Polydora sp.

Thanks for the reply Ilan.

An interesting suggestion that I had not considered. When they are covered in sediment (lowest picture) I am more convinced by your suggestion than when they are naked (top picture and crop).

Do you have a genus name I could check against?

Thanks again for your help,

Alex

Spionidae Polydora sp.

Hi Alex

it looked like a spionid, so I forwarded your photos to the curator of Polychaeta in the Natural History Musuem of Los Angeles County, Leslie Harris, and here is what she wrote (all credits to her, of course, I just post her reply to me):

Yes, it's a spionid, genus Polydorella, possibly Polydorella smurovi Tzetlin and Britayev 1985. This species was first collected from a red sponge, 25 m, in a coral bank near the Dachlak Archipelago, Red Sea. Living animals of P. smurovi have white palps (the paired appendages at the head) and orange bodies; they build thin mucous tubes on the surface of the sponge; an illustration in the original description shows dark pigment on the prostomium (the median part of the head) and lateral stripes on the first 3 setigers. The animals in the pictures differ by having very obvious lateral stripes on the whole body and the tubes appear to have attached bits of sand or debris. Without specimens to examine I can't tell if the differences are intra- or interspecific. The genus is very interesting as the life cycle includes alternation of sexual and asexual reproduction. Even more interesting, the mode of asexual reproduction is paratomy, in which the growth zone producing the new individual is in the middle of the animal rather than at the posterior end or sides.

Good references are:

Tzetlin, A.B., and Britayev, T.A. 1985. Zoologica Scripta 14: 177-181.

Radashevsky, V.I. 1996. Morphology, ecology and sexual reproduction of a new Polydorella species (Polychaeta: Spionidae) from the South China Sea. Bulletin of Marine Science 58(3): 684-693.

hope this helps !

cheers

Art

Art is back and in full force!

Thanks Art.

Cheers

James

Awesome, Art! That is fantastic. And of course many thanks to Leslie.

I'll be down the British National Oceanographic Library this am!

And I have to tip my hat to Ilan as well for getting to the spionid, first. I was really lost on this one!

Case Closed!

Alex

Hi guys !

Case closed ?

it would be too easy

Leslie wrote that this one is slightly different from Polydorella smurovi, but by pure coincidence I know very well Temir Britayev (Severtzov Lab of Ecology and Evolution RAS, Moscow), so I sent him Alex's photos, too, just to confirm if it's really their species or not

maybe Temir also has a comment on the whitish mass seen on the close-up of one of these chaps, although I guess it's either ovary or some odd internal parasite ..

cheerio

Art

Hi Alex --

I took a second look at your images. So there were 2 types of Polydorella? One with the mucus tubes with attached sediment and one without tubes? Possibly these are different species as life history and pigmentation can be diagnostic characters for spionids. Last year Johann Hinterkircher sent me pictures for id which included 2 Polydorella species. One was identical to yours, apparently free living on a red sponge & with the same prominent lateral banding, inconspicuous eyes, & white dorsal mass. The other species was brown with a middorsal white stripe, white eyes, and thin clear mucus tube on a pink sponge. P. smurovi was reported to deposit its eggs in capsules inside its tubes. Your tubeless species may be carrying its egg capsules around on its back similar to some syllid polychaetes, but this is complete conjecture on my part. The white mass just doesn't look like any polychaete-associated copepod I've ever seen. I'll be very interested in seeing Temir's opinion. As a good taxonomist I'm sure his immediate response will be just like mine "I need those worms!"

Any more polychaetes in need of id?

(And Art, thanks for the promotion, but I'm the collection manager of polychaetes here at NHMLAC, not the curator!)

Leslie

Does Jonothan Lowrey (sp?) still work there?

Cheers

James

Jonothon Lowry? In Los Angeles? Not a familiar name.... but I live in the basement among bottles of dead things & may not have known him if he was on another floor. The only Lowry currently at this museum is a woman in charge of the gift shop.

Sorry, Leslie

He is a fellow that formerly took care of live animals, I _thought_ at the museum.

Just curious, sorry to bug you (no pun intended).

Cheers

James

Live animals, huh? Their keepers belong to the Education department & don't venture down into our collection areas (also known as the worm tomb, crab crypt, mollusc mausoleum and echinoderm embalming studio) very often. And you can't bug me.... those belong on the second floor....

L :wink:

Thanks for your help with the ID, Leslie. Here are a few more pictures that might offer slightly different info.

The first one shows the Polydorella worms on a sponge next to a young hawkfish. Just to provide an idea on scale and habitat.

This image is a slightly higher res shot of a group of the worms all with the white blob on their backs (stop me if I am getting too technical!).

And finally another more detailed shot of a couple of individuals.

Alex - thanks for the new pictures - they're really great! In the close ups there's some sign of transparent mucus tubes. What's especially interesting is that none of the individual worms show any signs of asexual reproduction. In other species it's hard to find any non-reproducing individuals. I wonder how such juicy morsels can live on the sponge's surface unmolested; perhaps they rely on the sponge's toxicity for protectiion or acquire it themselves by feeding on sponge cells. thanks again, Leslie