In The Bay 3 July 2007 II

Another diatom this time. Striatella unipunctata in girdle view. These cells form chains with adjacent cells often attached by the corner as seen at the top if this image.



400x phase contrast image.

In the Bay 3 July 2007

Since I wrote about marine cilliates in my previous post, I thought I'd try to find some for this edition of In The Bay.

This is a group of Vorticella or Vorticella-like stalked cillates. As you watch the movie you can see the feeding current they are creating with their cillia. About 21 seconds into the movie (6 seconds from the end) the whole colony retracts. This is a defensive mechanism and occurs extremely fast.

In the Bay 24 Jun 2007

Dactyliosolen fragilissimus, a chain forming diatom, one of the most abundant species of phytoplankton in the bay.

In the bay 6 June 2007

One word: SNAILS! They were abundant last time and there are even more of them out there this week.

I know a fair amount about phytoplankton and am pretty good at identifying them. See the list of previous students here. When I came up with the idea of posting microscope images take of samples from the bay here on mixotrophy, I was ( and still am) planning on focusing on phytopankton. Of course this time of year, the zooplankton population is high and all of these little heterotrophs are busy grazing on the phytoplankton. This keeps phytoplankton cell abundance low. As a result, I am not seeing much of what I was planning on photographing. There are plenty of zooplankton to look at of course. The problem is, identifying zooplankton is much harder for me. Getting good live pictures is also a challenge because they move around.

I did get a few nice images though. Here is another larvae viewed in bright field. It is the nauplius stage of some type of crustation (I think).



This is the same view in dark field:

In the bay 30 May 2007 II

Snail larvae. The water was loaded with these. Probably the periwinkle Littorina littorea. An invasive species introduced to Canada from Europe in the 1800. It is abundant on rocky shores throughout New England. I am not sure how far south they are found.

Here are 2 pictures:


Side view of the shell. the blurring at the top right of the image is due to the movement of cilia along the edge of their feeding apparatus called a velum.

End on view:

the picture is fuzzy but you can see the extended velum and the cilia along the edge.

And a video:

In the bay 30 May 2007*

The marine diatom
Asterionellopsis glacialis

Check out some better picures here and here.









*I am still experimenting with sample collection locations and and I hope to get access to a better microscope/camera setup, but I intend to make "In the bay" a regular feature of the blog. This image was taken on an old Bausch & Lomb compound microscope at ~100x with an inexpensive 0.3 megapixel digital camera. Water was collected with a fine meshed plankton net in a shallow cove on the north end of Aquidneck Island in Narragansett Bay, RI (see the red arrow below).