Jellyfish, being one of the biologically simplest kinds of animal that lack brain, we would think that they cannot learn. Researchers had generally assumed that learning from experience and adapting a behaviour was limited to biologically complex animals with relatively large brains, which include mice, birds and primates. According to Jan Bielecki at Kiel University in Germany, “Learning is the pinnacle of nervous system performance.” But some studies have hinted that it is possible for simple creatures also to have this ability, and this led Bielecki and his colleagues to investigate learning in jellyfish, which has shown that Caribbean box jellyfish can learn from experience, even though they lack a central brain.
It is useful to know that the box jellyfish tend to reside closer to shore and are spotted in near-shore habitats such as mangroves, coral reefs and sandy beaches. In case of mangrove, the tree grows in wet ground at the edge of the river and has some roots that are above ground. The larvae settle on mangrove roots and form polyps. Adult jellyfish live in between the roots of the trees searching for copepods to eat.
The researchers created an experimental environment that mimicked the Caribbean box jellyfish’s native mangrove-rich habitat. They painted the walls of a round tank, in which a fingernail-sized jellyfish was placed, with white and grey stripes which looked like vertical mangrove roots. The grey coloured stripes created the illusion of the so-called roots being further away than they really were, and as a result initially the jellyfish would bump into the tank walls. In an experiment carried out with twelve different jellyfish, it was found that in about seven minutes’ time each jellyfish had learnt the lesson from collision, and had started avoiding the wall by pivoting or swerving. The researchers think that instead of a traditional brain, learning happens in the jellyfish’s four visual sensory organs, called rhopalium, which are embedded throughout its body. Each rhopalium has six lenses that sense light and help in guiding the swimming jellyfish’s pulses and pivots, writes Corryn Wetzel. (New Scientist, 30 September 2023)
It appears that the jellyfish can learn from experience through visual and mechanical stimuli. It may be looked upon as associative learning in which a new response becomes associated with a particular stimulus. The response comes from the mind or intelligence working in the animal, which expresses itself as instinct. What we call learning is based on this acquired experience. There is wisdom in the instinct. H.P.B. puts it thus:
“Instinct, as a divine spark, lurks in the unconscious nerve-centre of the ascidian mollusk, and manifests itself at the first stage of action of its nervous system as what the physiologist terms the reflex action. It exists in the lowest classes of the acephalous animals as well as in those that have distinct heads; it grows and develops according to the law of the double evolution, physically and spiritually; and entering upon its conscious stage of development and progress in the cephalous species already endowed with a sensorium and symmetrically-arranged ganglia, this reflex action, whether men of science term it automatic, as in the lowest species, or instinctive, as in the more complex organisms which act under the guidance of the sensorium and the stimulus originating in distinct sensation, is still one and the same thing. It is the divine instinct in its ceaseless progress of development….This instinct may, for the sake of exact definition, be termed automatic; but it must have either within the animal which possesses it or without, something’s or some one’s intelligence to guide it.” (Isis, I, 425)
“Instinct is simply a direct perception of what is right, within its own realm. Animals have right instinct in regard to what to eat, and in regard to what is dangerous to them, for their instinct is acquired experience. Both instinct and intuition have been gained in no other way than through observation and experience,” writes Mr. Crosbie. Science seems to agree with this view. According to William Homan Thorpe: “Ideally, instinctive behavior seems not to depend on learning or practice but to emerge in full complexity without rehearsal when appropriate stimuli or circumstances are encountered. Often, such stimuli do not guide or mold the instinctive behavior but seem simply to trigger or release it. This characteristic gives instinct the appearance of driving the animal endogenously (from within); the quality of instinctive activity thus appears to depend only secondarily on exogenous (external) stimulation.”
Theosophy teaches us that everything is sentient. Life wave has passed through many transformations or re-embodiments, from simplest to most complex forms and has gathered experience in mineral, vegetable and animal kingdoms evolved under “Natural Impulse.” The impulse which evinces a progressive march towards higher life may be termed as “Divine Impulse” because it is guided by intelligences. The experience gained in various forms is not lost but becomes part of the nature of the organism which is termed as instinct. It is impressed on the very cells and atoms of various forms as knowledge and this knowledge or learning is passed on to the offspring, thereby producing better and fitter forms through which the consciousness can exhibit itself more fully. In the article, “Kosmic Mind,” H.P.B. writes: “Occultism tells us that every atom, like the monad of Leibnitz, is a little universe in itself; and that every organ and cell in the human body is endowed with a brain of its own, with memory, therefore, experience and discriminative powers. The idea of Universal Life composed of individual atomic lives is one of the oldest teachings of esoteric philosophy.” This might give us some more insight in the working of the instinct in lower r organisms.
[This article also appeared in The Theosophical Movement. For more articles published in this excellent magazine follow this link: https://www.ultindia.org/current_issues.html