The only thing better than a picture of a slug is a photo of a slug projected on a giant screen and admired by a bunch of people.

The Photobiology students presenting their results at the annual Report to the Community at the San Diego Museum of Natural History. 8/9/18.  Photo Drew Talley

A few weeks ago, the Photobiology students presented at the Ocean Discovery Institute Report to the Community, held at the San Diego Museum of Natural History.  This is the opportunity for the students to tell their parents, the community, supporters, and everyone associated with Ocean Discovery, about what they did this year in Bahia.

They started with the background and general questions that drove the research: what is kleptoplasty, and how can we learn more about the mechanisms and evolutionary benefits of the phenomenon?  Because they had limited time on stage, they focused on the work we did collecting samples of slugs and algae for identifying food plants.

The punch line was satisfying.  We found that the DNA sequence of the Codium algae collected in front of the station and that from the slugs’ tissue samples came from Codium decorticatum.  I managed to get about 400 bases of sequence from the slugs and the algae, and it was about a 99% match to C. decorticatum.

Short region (54 of >400 bases) of rbcL gene sequences derived in Bahia this summer to show similarities of our data (top two lines) with Codium decorticatum sequence in NCBI database. Elysia diomedea and Codium collected in Bahia were 99% identical to C. decorticatum. Closely related C. fragile only 91% identical (differences indicated by asterisks at bottom).  Asterisk at top indicates difference between E. diomedea and Codium.

The figure above shows a short, representative stretch of DNA from the rbcL gene, from Elysia diomedea and the Codium species we extracted in Bahia (top two rows), along with sequences from two species of Codium from the National Center for Biotechnology Information (NCBI; bottom two rows).  The Codium from Bahia matched C. decorticatum almost 100%, whereas the match was only about 91% for the very similar C. fragile.

There were, however, a few differences between the kleptoplast DNA from E. diomedea and C. decorticatum (e.g., asterisks above E. diomedea sequence).  At this point, we don’t know whether this is due to variation within the species that the slugs are consuming, or the slugs are eating more than one species.  We are still waiting for results from NextGen sequencing, which should be more informative and may clear up this puzzle.

A couple of notes about the algae.  First, the Codium and slug sequences are identical to those we obtained in 2016.  At the time, however, C. decorticatum had not been entered into the database, so all we knew was that we had a new species.  The other observation is that the species of Codium we sampled (see photo of tissue here) is relatively low-growing and branchy, unlike the usual tall, sparsely branched appearance of C. decorticatum.  There were specimens that looked like that (e.g., here), and it is likely that the appearance of the alga depends on the local conditions.

Most importantly, the students did a fantastic job of presenting.  I was away visiting family, but I got multiple independent reports from people in the audience who talked about how strong and clear the students’ presentations were.

The Photobiology crew, as drawn by the ever-creative and wonderful Ric Desantiago. Pleas visit his site (Da Hood Scientist) to check out more of his observations and artwork.

I am very pleased and proud to have played a part in the students’ project this summer. Despite all of the up and downs and improvisation, it was a deeply satisfying experience.  I am always amazed how a misanthrope such as myself can have such a great time packed like a sardine into the field station with so many people.  Thanks to the students, the Ocean Discovery staff, Ric, Thiago, the visiting scientists, and everyone.  Especially, thanks again to Dr Drew Talley, mi gemelo de otra madre, for making it possible.

Dopplegeezers at BLA station, 7/5/18

I still have a few posts left regarding the results of the feeding assays and slug surveys, and hope to have them ready in a few weeks’ time.