Crinoids! written by Summer Student Fellow Mimi Smith

Hi all! My name is Mimi Smith and I am a WHOI undergraduate student fellow working in Kirstin’s lab this summer. For the past month or so, we have been messing around with stalked crinoids from the arctic deep sea--specifically, Bathycrinus carpenterii, and today, I will provide a brief overview of what we have come up with so far.

Crinoid anatomy. Image from Wikipedia.

A juvenile crinoid specimen on a terra cotta tile.
Collected from a long-term experiment in the Arctic deep sea.

For starters, what are crinoids and why are they important? They are a member of the phylum Echinodermata, which also includes starfish, brittle stars, sea cucumbers and sea urchins. They are found in the deep sea attached to a substrate, feeding by filtering plankton and detritus off of the seafloor. They are important because they might provide important information related to climate change, particularly in relation to ice cover and water temperature. Initially, we had wanted to age the crinoid specimens, in order to see if ice cover had anything to do with recruitment or growth.

This is where I came into the picture! I began analyzing the crinoid specimens that had been collected and photographed under a microscope, using ImageJ software. I measured the stalk lengths, and columnal lengths and widths, of approximately 150 specimens. We then compared these measurements to two “1-yr-old” species, and found that a majority of the specimens appeared to be less than a year old (1-yr-old meaning, one year since they recruited). We then decided to pivot our project and focus on characterizing larval development.

After reviewing some of the literature and combing through photos, we realized we had two distinct larval forms, cystidean and pentacrinoid. The cystidean phase is the first larval form, where the head is ball shaped and the stalk is translucent. The pentacrinoid phase follows, where finger-like appendages begin to form in the head and the stalk is more opaque. From here, we decided to continue characterizing these larval forms, as it had never been done before! So now, we will be the first people to ever characterize the larval development of stalked crinoids.

We put together some figures, showing the progression of the development process. Moving forward, we will focus on explicitly characterizing the head of both forms, and comparing the appearance to both the juvenile and adult forms.

We will also investigate the larval development of all crinoids, stalked and unstalked, to evaluate whether or not the process is a standard or not. Currently, we hypothesize that this process is pretty standard among all crinoids, and from there we can look into the implications of low plasticity and low adaptability in relation to environmental stress and/or climate change.

Overall, this project is really coming together and I could not be more excited. This research opportunity and working with Kirstin has been incredibly rewarding, and I’m looking forward to what we will produce in the end.