Echiura & Hemichordata

[ptychoptera]

Collected last night in shallow wave-washed area of basalt rock here in the aloha state. The substrate were they were collected was shallow crushed coral; not where I expected to find these guys. The Hemichordate is Ptychodera flava.

Leslie, could you perhaps aid me in identifying the echiuran. It is technically a polychaete.

NOTE: size when retracted is around 3cm, extended it was around 12cm or so.

 

[LeslieH]

If we're going just by the picture then the hemichordate might be Ptychodera flava. I emphasis "might" because there are very few reliably identified hemichordate pics around and the yellow color can be found in several species. On the other hand if you were able to match it to a detailed description you know more than I do.

Was the echiuroid proboscis bifurcate when fully extended? Then it's a bonellid but that's as far as I can go from the picture. Again, there's a real lack of reliably identified pics because identification depends on internal characteristics.

 

[ptychoptera]

<a href=showthread.php?s=&postid=11064103#post11064103 target=_blank>Originally posted</a> by LeslieH
If we're going just by the picture then the hemichordate might be Ptychodera flava. I emphasis "might" because there are very few reliably identified hemichordate pics around and the yellow color can be found in several species. On the other hand if you were able to match it to a detailed description you know more than I do.

Was the echiuroid proboscis bifurcate when fully extended? Then it's a bonellid but that's as far as I can go from the picture. Again, there's a real lack of reliably identified pics because identification depends on internal characteristics.

The hemichordate ID was based on a photo in John P. Hoovers book on Hawaii inverts. I have no idea how many largish yellow hemichordates there are in these waters, so I suppose it would be best to refer to it as possibly being Ptychodera flava.

The proboscis on the echiuran didn't appear like the pictures I've seen of bonellids. It seemed to be shaped like the leg on a pair of flared jeans. Great description, right? Any ideas?

 

[LeslieH]

Good book, isn't it? I've been told there are some mistakes but as soon as John learns about them he adds them to his on-line errata list.

There are two big problems with any kind of photo guide book - especially UW ones. From your nickname I'm guessing you're familiar with insect books & keys which have the same problems. First, too often the photographed animals aren't collected so ids are strictly photo based. Many animals can't be reliably id'ed from photos; the smaller they are the harder it is. Second, the books only contain a limited number of species. The very best polychaete chapter I've seen in a photo guide had about 80 species (usually there's more like 10) That was for a region which has somewhere around 1000 known species which means every diver & beachgoer will fit any species they see into one of those 80 names.

Back to your animals. Apparently there's only 3 enteropneusts known from Hawaii. P. flava was described from the Marshall Islands. What's listed as Ptychodera flava in Hoover is now regarded as Ptychodera flava laysanica which was described from Laysan Island. With so few enteropneusts in the area the odds are good your critter is really P. f. laysanica.

The echiuroid? Well, it's not a bonellid. Flared leg is actually not a bad description but it doesn't help much. To figure it out I'd have to 1) do a dissection and 2) know what I was doing!

 

[ptychoptera]

Thanks for your help with the identifications. I was wondering if you could recommend any books/websites to broaden my polychaete knowledge.