Echinoderm anatomy made easy

The things that randomly cross my mind when I'm should be busy with work...

This one made me happy in invertebrate zoology class back in my 3 seas days.

 

The water vascular system song

The madreporite's connected to the... stone canal

The stone canal's connected to the... ring canal

The ring canal's connected to the...radial canal

The radial canal's connected to the... ampullae

The ampullae are connected to the... tube feet

And that's the way a starfish works!
Yay!

Mr. Pentaceraster and Mr. Nidorellia would like to inform everyone that the label 'starfish' is a gross misnomer and wrongly represents their true affiliations. They would like you to know that they have nothing to do with those smelly, stuck-up, vertebrae-possessing fish, and are in fact part of the phylogenetically oppressed 97% of animal life. Mr. Eucidaris, who is lurking about in the background, would like to inform Mr. Pentaceraster and Mr. Nidorellia that they are "a pair of spine-less weenies, and should go stick their complaints up their cardiac stomachs."

Smurfing up the stats

Things have been ridiculously busy, and my final year of undergrad is flying by like its pants are on fire. I've been tied up with class, starting applications to graduate school and contacting potential advisors, and research. The field and lab part of my research is gone till January break, but there is always plenty of the other half: organising data and analysing data and writing, writing, writing.

Scuba Smurf is a little sad about being out of the water this long (as am I) but he is keeping me company as I try to run statistical routines that I am unfamiliar with, on software that I am fairly new to. And because I am working through it slowly and over long periods of time, I came up with another work song...


The Variances Song
(To the tune of 当我们都在一起 aka 'The More We Get Together')

What's wrong with my variances, my variances, my variances
What's wrong with my variances, they are unequal
Transformations are futile
Rank-sum tests lack power
And so to fix the variances
I tried GLMs*


* and by GLM, I mean a generalised linear model, not a general linear model

More fun and cagery

When we did our first few dives at Baltra, I set up a single cage for my Pentaceraster starfish as a test to see if (1) the cage would hold up against the current/surge; and (2) if the cage would keep my Pentaceraster enclosed. We visited the site again on the final day of the research cruise, and I was very glad to see that the answer was yes on both counts (with n=1, but I'm okay with that...)

One week later: Inti from the Darwin Station examines my still-caged Pentaceraster.

Now that I know this kind of cage can work as an enclosure/exclosure, I'm going ahead and scaling up cage production in preparation for deployment next week. The test cage had a diameter of 0.5 m, which is a little small for a Pentceraster that can have an arm radius of ~20 cm. The new cages are 1 m in diameter, and I am constructing them from old caging material previously used to enclose sea urchins (yay for recycling old and fouled research gear). I have been working with wire cutters and cage wire and lots and lots of cable ties over the past 3 days.

Fun with cages. About 10 minutes after this picture was taken I switched to actually wearing work gloves.

I also made a few friends, and learnt that baby marine iguanas are small enough to fit through the holes of my cages.

This little guy came by and visited me several times.

Any kind of tedious and/or repetitive job needs a work song, so here is my cage building song:

I've Been Making Starfish Cages
(to the tune of "I've Been Working On the Railroad")
I've been making starfish cages
For hours every day
I've been making starfish cages
And the time just slips away
Hope my predator inclusions
Show me interaction strengths
Hope my starfish cages weather
The storms and surge and waves!

So what exactly am I doing with all this algae?

This is what I have been doing for the past week.

We've gone diving at sites in Nahant and in Rye, NH and put down 0.5m x 0.5m PVC quadrats like the one below. First, we visually identify each species of algae and record the approximate percentage of the quadrat that it takes up. Then we collect all the algae in the in the quadrat, put it in a bag and take it back to the lab. We collect about 10 bags per site.

This is a quadrat (pre-collection) from Nahant last year. I haven't yet taken my camera underwater this summer.

In the lab, we sort the algae by species and clean it - i.e. remove little critters like amphipods, isopods, little crabs, little starfish*. The result is something like in the picture - neat piles of algae on a lab tray. Then we weigh the algae by species in two ways: 'fresh weight' which is just spinning it down in a salad spinner to remove excess water and then putting it on a scale; and 'dry weight' which is putting it in an oven at about 65ºC so that it is completely dried out, and then weighing it (this destroys the algae so you can't do anything with it after).

This is all the algae from one (0.5 m x 0.5 m) quadrat from our Rye, NH collection site. I am pretty sure that if I cleaned up the algae up a bit better and arranged everything a bit more prettily, I could convince someone that it is some kind of Japanese delicacy that they should try.

This whole long process gives us estimates of two things:
1. How many species of algae are out there, and what they are
2. How much of each species is out there, in absolute terms and relative to the others. This can be measured by percentage cover of the quadrat or by weight. We are doing both to see how well the two agree (i.e. if one is an accurate proxy for the other).

These two things can then be used to tell us plenty of other things such as how diverse the algal community is, and which species we should use in lab experiments.


*This is described in one sentence, but is the longest, most tedious part of the whole process. It took us <1 hour of underwater time to collect 10 bags of algae, and a full day to clean, sort and weigh only 7 of those bags. During the process I wrote this song.

The Algae Song
(to the tune of "Daisy Bell")
Algae, Algae, give me your answers true
I've gone crazy, just from sorting you
The amphipods are too many
And Desmarestia is nasty
But soon I'll find
If Hetsiph might
Influence diversity