Who's related to who and why does it matter?

Model of USNM 1100247, Macrocheira kaempferi, from Japan.

Model of USNM 1100247, Macrocheira kaempferi, from Japan.

Who is it related to? That's a question I've been asking about spider crabs for years. DNA is helping me solve that question so I can ask the next question: "Why is it important to know who it is related to?" My answer to this is that trying to study biological patterns in unrelated crabs is akin to comparing apples and oranges. If I wanted to study decorating behavior in a family of crabs where half the crabs were more closely related to crabs in other families those crabs may show wildly different behaviors that obscure the pattern that is held by the crabs that actually are related to each other. But if I can only compare crabs that we know are closely related based on DNA analyses, then I am better able to test hypotheses about those crabs. I'm already seeing patterns in geographical distribution and habitat type that have only emerged since grouping crabs based on DNA rather than the traditionally used morphological characters. Perhaps knowing who is related to who will help us understand the underlying drivers of crab diversity. As far as I'm concerned, knowing who is related to who is just the beginning. The real fun starts when we can answer that question and I'm ready to start asking all those next questions. So who is that big, beautiful Macrocheira kempferi up there related to? Well, you'll just have to wait to find out.

 

Giant Damithrax

I've seen some impressively large crabs in the museum's collections, but nothing quite like what I saw on the reef off Southwater Cay in Belize. The team were out for a late afternoon snorkel and came across 2 very large Damithrax spinosissimis. The first one was larger than any I had seen, but the second one (pictured) was even larger. I would estimate the cheliped dactyls at close to 5" long and the gape large enough to accommodate my wrist. This crab was probably the coolest animal I saw in the two weeks on the island. I had no impulse to collect either of these magnificent crabs. They belong on the reef contributing to the gene pool and to reef diversity. I do wish there way a way to know just how old crabs of this size are. 

So many worms

a few of the vouchered specimens

a few of the vouchered specimens

I'm just back from my 2 weeks in Belize. It was probably the best field work experience I've ever had. We worked hard, but we had enough time to get everything done with only a very few loose ends to tie up back home. We collected nearly 1000 individuals and have barcode-bound tissue samples from over 700 of them. The idea of the trip was to begin quantifying diversity in this Caribbean ecosystem using DNA barcodes.

We chose 3 sites (mangrove roots, back reef lagoon, and seagrass) to sample every creature larger than 5mm found in one cubic foot. I thought I was prepared for what we would find given my experience with reef diversity in Indonesia. I was not prepared at all. In Indonesia we were only interested in the decapod crustaceans, but in Belize we were interested in everything. And everything included more worms than I had ever thought of before. I'll be excited to learn how many species we collected because they are quite difficult to tell apart and that's if you can tell if you have a whole worm or just part of one. There were also masses of sipunculans that formed writhing balls when they were put into a cup together. In both of my invertebrate zoology classes I never even considered that I would see a sipunculan in the wild, let alone collect hundreds of them over the course of a few days. I'm truly in awe of the diversity of the sites we sampled. 

A ball of sipunculans 

A ball of sipunculans 

Through coral isle, over blue lagoon

Next week I travel back to Carrie Bow Cay, Belize to the Smithsonian's CCRE station. It's been 7 years since my first trip there, and needless to say I'm excited to be going back. My main duties while there will be organizing tissue sampling of a wide variety of organisms, everything from sea grasses to fish, for DNA barcode and genomic sequencing. I've had lots of conversations with lots of other scientists at the museum about how to optimize sampling of their specialty. My goals for myself on this trip are to improve the quality of specimen photo vouchers, learn new underwater collection methods, and become more familiar with crabs outside Majoidea. Another NoBones post is probably going to come out of this too. 

CarrieBow

Guest Post on NoBones

Working in a museum that is as popular as the National Museum of Natural History really makes me want to become a better science communicator. The road to becoming a better communicator needs to start somewhere, so I started with a guest post on the department of Invertebrate Zoology's blog, NoBones. Please take a look at the post about why all the crustacean frustration that comes along with studying spider crabs is worth it.