Timing is everything: where and when to collect specimens

It’s often said that museum specimens offer us a snapshot into the past. More than simply being a record of what existed where and when, however, specimens can tell us about parts of the life histories of organisms that can’t easily be observed in the long term. As an adult human, I don’t change very much over the course of the year (holidays excluded), but many species undergo seasonal cycles that can be completely missed when collection only occurs during the “field season” (usually summer).

In the course of my work on sea anemones, I came upon a species identity crisis. A group of sea anemones from Alaska were combined with a Japanese species by certain authors, while others considered them to belong to a species found in California. They surely don’t all belong to one and the same group because the Japanese and Californian species have very different reproductive behaviors. In Japan, baby sea anemones are brooded upon the surface of the adult, and in California, the babies are brooded within the adult’s body.

Do the Alaskan sea anemones belong to the Japanese or Californian species? -or neither?

The obvious question is “Do the Alaskan sea anemones brood (and, if so, how)?” To figure this out I contacted curators and searched databases from museums around the country and borrowed each specimen from Alaska that I could find (less than 10 in total, and none of them handled by the original author of that species). The specimens all had two important things in common: None had any sign of babies, either in or on their bodies, and they were all collected in the summer. The Japanese species broods primarily in the winter so, if the Alaskan ones are also external brooders, maybe they have just not been collected during the brooding season!

Thanks to a grant from the American Museum of Natural History (AMNH), I began planning the logistics of a field trip to Alaska. The timing for this trip was critical. Too early in the year, and I risk being stuck in Anchorage due to hideous weather at my sampling localities; too late, and I get nicer weather but possibly miss the brooding season. I planned the trip for early April, hoping to hit a sweet spot between the two extremes.

Brooded babies on the surface of Epiactis japonica, from Hokkaido, Japan.

My first sampling site was Popof Island. Unfortunately the prime rocky locality (I had identified it in satellite images) for my species of interest was inaccessible due to winter conditions, and most of the rest of the island was sandy shores. It’s also the original locality for the Alaskan species, so that site was a disappointment for my immediate purposes. So far, off to a bad start.

My next sampling site was Adak Island where I had better luck. Not only did I find the species I was looking for, but they were ringed with little baby sea anemones! Before returning home to the OSU Museum of Biological Diversity, I had another equally successful collecting stop on Kodiak Island where I found more of the external brooders. These animals partially answered the question I traveled all that way to investigate: The Alaskan sea anemones were not the same species as the Californian ones (and the Californian ones would need a new name). But are the Alaskan and Japanese species the same, or do they just behave in a similar way?

Epiactis ritteri with a ring of brooded babies (beige). Adak Island, Alaska.

A long walk on a sandy beach on the way to collecting in the rocky intertidal on Adak Island.

Based on anatomical study of the specimens I had already borrowed (and previous collections I’d made of the Japanese species) I had strong reasons to consider that all three groups were different species. Seeing the animals alive in the field gave me even more features to draw from (their color patterns and their resting posture -things which are frequently lost in preserved specimens). By chance I subsequently came across another specimen of the Alaskan species from another museum. This one had been identified by the original author (several years after he published the species description) and also had very large offspring all over its body!

It turns out all the information I needed already existed in previously collected specimens. Was my trip a waste?  Absolutely not! The new collections represent a time between the non-brooding summer season and the late-stage brooding of this new (to me) specimen. It turns out that during this intermediate time, the relatively small offspring are kept within a special groove that forms by a fold in the adult’s body wall and seals the babies inside. As the babies grow, the groove opens up and they simply live on the surface of the adult. My collections are the first record of this type of sealed groove, and they include life stages from early embryos to juvenile sea anemones, and of course the brooding adults. Furthermore, I needed fresh material for DNA analysis (formalin-fixed specimens are extremely difficult to get good DNA sequences from).

The sealed brood groove (horizontal band) in Epiactis ritteri has partially broken open to reveal one of the offspring held within it (see two tentacle tips).

Since the OSU Museum of Biological Diversity doesn’t house a sea anemone collection, I returned the favor to AMNH and donated the new specimens to its collections. The specimens I collected are just as much of a static ‘snapshot’ in time and space as any other single collection event, but when you combine snapshots from different times, you can begin to make a flip-book (or a .gif, if you must) that tells a dynamic story.

About the Author: Paul Larson is a PhD candidate at the Department of Evolution, Ecology and Organismal Biology at The Ohio State University studying evolution of marine invertebrates. email: larson.309@osu.edu twitter: @mar_inv