Wednesday, December 23, 2009

Ostra-blog 9. Postasterope barnesi

It's unfortunately been too long since I've posted an 'ostra-blog', a post about my main study group, the Ostracoda. If you haven't seen these, I encourage you to read some of them. Most contain little anecdotes, personal vignettes about interesting experiences I've had with ostracods.

Try this link, if you interested.

This installment is a quick post inspired by a colleague who is trying to collect bioluminescent Vargula (subject of previous posts). He did some plankton tows out by Catalina Island, and came up with some ostracods, but these are a different family. See our exchange below, and a picture sent by his student:

The query:
Hi Todd,

I apologize for the out of focus, low magnification photo attached -- but is it likely that these ostracods are Vargula tsuji? These are not from a trap, but instead from night surface plankton tows from the dock at Wrigley. These are quite large for ostracods (up to 1.5 mm or so in length, I'd guess), fairly bright orange, and very abundant in the plankton soon after dusk.

Thanks for any simple confirmation/rejection of our tentative id. I appreciate it. Sorry again for the low quality image; I'm not at Catalina or I'd take a better one. This was sent to me by a student.

The Picture:

The reply:

No, those are not Vargula, which is in the family cypridindiae. These that you found are in the family cylindroleberididae. I think the common sp out at Catalina is Postasterope barnesi, and this looks like it could be that species. Both are myodocopids, which are larger than the somewhat more common podocopids...

I've found males of this family to be attracted to lights at night. Most myodocopids mate in the water column after sunset, and the males of some sp are attracted to lights. Probably just about all the individuals they found are males, I'd guess. The one pictured looks like a male, based on the tapered carapace (hard for someone to see who hasn't looked at a million ostracods). But an easy way to tell a male in these is that the males have a REALLY long sensory bristle. It's a "hair" (2 actually, one on each side) that emerges from the front of the carapace along with the swimming appendages. But this sensory "hair" is really long, longer than the body in many cases. I actually can't tell from this picture if there are the long sensory bristles because of the focus, but I'll bet they are there... I do see a white line across the carapace in the right spot, but I can't tell if that is part of the swimming appendage, or the sensory bristle....