Forams

The case of the three species of protozoan (I forget the names) which apparently select differently sized grains of sand, etc., is almost the most wonderful fact I ever heard of. One cannot believe that they have mental power enough to do so, and how any structure or kind of viscidity can lead to this result passes all understanding.

-- Charles Darwin, letter to W.B. Carpenter, 1872, quoted at Bowserlab

Foram shells are formed from a number of different materials; sand grains, calcium, sponge spicules and other foram shells are base essentials. Certain species – Astrammina rara, for example – demonstrate a deliberate (and quite staggering, I think) process of selection. They repeatedly select opaque sediment grains of a consistent shape and size, which they proceed to glue together to form a tight sphere. They complete their elegant structure with the addition of one larger red stone. Why is this? How do they differentiate scale and colour? Is it possible that uni-cellular organisms possess intelligence? A sense of aesthetic?

-- Claire Benyon (2009)

Multitudes

The Foraminifera Sculpture Park in Guangzhou Province officially opened this month and is dedicated to large sculptures of these single-cell marine organisms. Marine geologist Bilal Haq of the National Science Foundation got the idea of a sculpture park a decade ago after seeing palm-sized models of foraminifera in the lab of marine biologist Zheng Shouyi at the Institute of Oceanology in Qingdao, China. Zheng persuaded local authorities to pursue the idea. The 114 sculptures were carved out of marble, granite, and sandstone.

-- a random sample in Science.

D'Arcy Thompson wrote of the Foraminifera:

In few other groups, perhaps only among the Radiolaria, do we seem to possess so nearly complete a picture of all the possible transitions between form and form, and of the whole branching system of the evolutionary tree: as though little or nothing of it had ever perished, and whole web of life, past and present, were as complete as ever.

He adds:

in days gone by I used to see the beach of a little Connemara bay bestrewn with millions upon millions of foraminiferal shells, simple Lagenae, less simple Nodosariae, more complex Rotiliae: all drifted by wave and gentle current from their sea-cradle to their sandy grave: all lying bleached and dead: one more delicate than another, but all (or vast multitudes of them) perfect and unbroken.

Image: Micropolitan

Dancing

New Scientist reports that 'dancing' Volvox algae can 'waltz' and 'minuet'. [1]



It's another reminder that while green, red and brown algae are often called 'plants', some of them have properties that are almost 'animal'-like. [2] Some dinoflagellates, for example, have simple eyes to hunt for food. [3]

And at a macro scale, kelp (which are brown algae) do remarkable things, as Charles Darwin saw:

The number of living creatures of all Orders, whose existence intimately depends on the kelp is wonderful.

A great volume might be written, describing the inhabitants of one of these beds of seaweed….I can only compare these great aquatic forests of the southern hemisphere, with the terrestrial ones in the inter-tropical regions. Yet if in any country a forest was destroyed, I do not believe nearly so many species of animals would perish as would from here, from the destruction of the kelp. [4]

[1] Dancing Volvox: Hydrodynamic Bound States of Swimming Algae by Knut Drescher, Kyriacos C. Leptos, Idan Tuval, Takuji Ishikawa, Timothy J. Pedley and Raymond E. Goldstein (pdf).

[2] Other 'simple' protists such as forams display remarkable properties too. Lynn Margulis is a microbiological William Blake in her vision of these creatures:

Large single-celled forams choose from brightly colored sand grains the correct ones with which to make shells. Aware of shape and color, they make choices and reproduce their kind. Awareness in some form has been naturally selected for at least 550 million years. For me, our spirituality and moral nature help perpetuate our living communities, just as similar attributes aided previous living communities whose evolution is chronicled in the fossil record.

[3] "By most definitions...the planktonic dinoflagellate, Erythropsidium, must have among the smallest of eyes, since the creature is only 50–70 μm in diameter." -- from You are what you eat by I R Shwab. Others with eyes include: Peridinium foliaceum and P. balticum. See Ultrastructure of Microalgae: nonphotosynthetic plastids.

[4] The Voyage of Beagle, Chapter 11:

Almost all the leaves, excepting those that float on the surface, are so thickly incrusted with corallines as to be of a white colour. We find exquisitely delicate structures, some inhabited by simple hydra-like polypi, others by more organised kinds, and beautiful compound Ascidiæ. On the leaves, also, various patelliform shells, Trochi, uncovered molluscs, and some bivalves are attached. Innumerable crustacea frequent every part of the plant. On shaking the great entangled roots, a pile of small fish, shells, cuttlefish, crabs of all orders, sea-eggs, starfish, beautiful Holothuriæ, Planariæ, and crawling nereidous animals of a multitude of forms, all fall out together. Often as I recurred to a branch of the kelp, I never failed to discover animals of new and curious structures.

Darwin was writing about kelp in cool southern waters. But kelp 'forests' have recently been discovered in deep tropical waters too. It's thought that these may act as refugia under some conditions of climate change.