Organisms without the organs we expect them to have
Desmond Morris described us human beings as “Naked Apes”, but as I pointed out in an earlier blog, we are not totally naked, even without clothes. However, we do lack a tail – just like the other so-called “great apes”, but not the gibbons, the baboons, macaques, etc. When something is missing we notice it at once: a snake has no legs, but still does pretty well without them; whales and dolphins also lack them, and the kiwi bird of New Zealand, even though it’s a bird, does not even have wings.
When something internally is missing like lungs, for instance, it’s harder to notice, but a whole group of lungless salamanders, especially in North America, exists: gas exchange in them occurs across the entire body surface. But unlike the Antarctic ice fishes, whose blood is colourless, all newts and salamanders possess haemoglobin as a respiratory pigment and thus have red blood.
Actually wings have been evolutionarily lost in a number of insects: there are moths in which the females are wingless and sheep farmers would know very well what I mean when I refer to the sheep louse. It’s not a louse: it’s a species of fly, just like the deer ked Lipoptena cervi, which doesn’t have any wings. Ants, well at least the worker ants, and non-reproductive castes of the termites come to mind, but surely all animals must have a head. Hmm, not so, because where on the body of a starfish or a jellyfish would you say is the head? And what about mussels, bivalves, oysters? They are animals without a head. And even without a brain! The ultimate has to be the male Praying Mantis, for it gets decapitated by the female and then copulates with her very nicely – without a head; a “brainless” act so-to-speak.
Even weirder are species that have neither mouth nor anus, or even a gut! You simply don’t need a mouth or a digestive system if you live in a suspension of nutrients and that exactly is the environment the tapeworms find themselves in. They absorb with their bodies whatever they need from the environment around them and vestimentiferan beardworms of deep sea hydrothermal vents, also lacking a gut, do the same albeit with the help of resident bacterial symbionts in the worms’ tissue.
However, one thing you may think that you learned at school that has to be true: all cells have a nucleus – or perhaps not? Human red blood cells, the so-called erythrocytes, possess no nuclei, but after a “life” of a few weeks they are constantly replenished by new ‘recruits’ from the bone marrow. At least there is a heart, well, in most animals, but not in all of them. The smallest and especially the smallest of the smallest insects do not need a heart; and according to the Russian miniaturization expert Alexey Polilov there are some in which even certain nerve cells lack nuclei. And what about the powerhouses of a cell, the mitochondria? The microorganism Giardia and pathogenic microsporidia have been celebrated as mitochondria-less, but whether they really are, has been cast in doubt since fragments of them have been reported to be present at least in Giardia. However, distinct mitochondria are certainly absent.
So, what do we learn from organisms that lack organs or organelles? We learn that they are ‘non-conformists’ and they show us that it’s possible to be successful even when not “fitting the mould”, i.e., meeting our expectations.
© Dr V.B. Meyer-Rochow and http://www.bioforthebiobuff.wordpress.com, 2020.
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