With a solid couple of days of discovery behind us, patterns already begin to emerge. It is always that way when a group of like-minded people get together on a mission, especially one for which a major purpose is to gather expertise in an intense environment of exploration. So when I say “like-minded”, I mean this in only the general sense of wanting to explore and disseminate information about biodiversity. From here on in, the joys and value-added are all in the synergy of squeezing together people with less like-minded backgrounds and different expertise. Collaboration. Different search images, different approaches. The result is always greater than the sum of the parts, and the 2011 Philippines Biodiversity Expedition has this firmly in mind as part of its design.
The natural world is like this too. Organisms with very different evolutionary backgrounds come together to encourage systems and interactions in ways we have still to try and figure out. One thing is very clear. In the sea, everything lives on everything else. Or nearly so. Some organisms use others as substrates to which to attach. Others find protection among stinging bits of the host. And so on.
A seemingly minor observation about a strange and not very well studied little sea biscuit (a flattened sea urchin closely related to the sand dollars, family Clypeasteridae) serves to illustrate not just inter-organismal collaboration, but that among scientists with very different interests in being here in Mabini.
I have had a long-time interest in sea urchins, sand dollars, and relatives such as the sea biscuits, and my earliest work was to study how these animals feed, and upon what. Turns out that things like sea biscuits really like to eat sand and the things living in it. So while I was here finding specimens of one species, Clypeaster reticulatus, I couldn’t help but notice that in the hollow space around the mouth on the underside of this little sea biscuit, there were dozens of odd little stars packed in like tiny little medieval mace heads:
This photo, taken today, shows a Clypeaster reticulatus flipped over onto the sand (by me) in order to show the tiny little stars in a depression around the mouth, which is obscured by the stars. I had never seen anything quite like this before, but it didn’t take long for me to realize that this was food of some kind (not baby urchins), being stored for consumption by the Clypeaster. Michele Weber (UCLA), who is a visiting expert on single-celled algae that live symbiotically in corals and other organisms (yet another example of synergies set up by collaboration), immediately recognized these as calcarinid foraminifera.
Whoa. What are those? Well, it turns out that sand, especially coarse sand, is full of life. One of the forms of this life is a group of tiny, often microscopic amoeba-like forms called foraminifera. They are single-celled, and live in minute houses made of limestone that they secrete around themselves, much like a snail makes a shell. In the case of these little calcarinids, the house has big spikes on it, making it look like a little star.
The “nature nugget” thing here is that calcarinids of this type are also symbiotic with tiny, single-celled plants called diatoms, which are usually the natural food of sand dollars and sea biscuits. Diatoms, being plants, make their food by photosynthesis, and therefore need access to sunlight. So the calcarinids themselves need to be close to the surface of sand, which puts them within detection range of the little sea biscuits that like to eat them. The sea biscuits carefully and deliberately select them from the rest of the less-interesting and presumably less nutritious sand grains, and pile them up in the unusual depression around the mouth. In Clypeaster reticulatus, this depression is unique among the 40 species of the genus in having almost no spines, making more room for the much spinier calcarinid foraminifera.
The calcarinid-diatom collaboration makes a whole new set of relationships possible. The collaboration among scientists such as Michele and myself on the Expedition makes it more possible to understand some of these relationships right here, on the ground.