Author: Ibon Cancio, UPV/EHU Associated Professor in Cell Biology; researcher in the ‘Cell Biology & Environmental Toxicology’ (CBET) research group of the Plentzia Marine Station (PiE-UPV/EHU); Spanish scientific representative in the EMBRC Committee of Nodes

The sea and its fathomless nature have always lured humans, and not only through the songs of mermaids. The sea and its biological diversity were explored by the Greek classics and especially by the infamous Aristotle (384-322 BC), who should be considered the first marine biologist. 

Aristotle is for most people a philosopher and not a scientist, but his philosophy has exerted a unique influence on almost every form of knowledge in Western culture. Aristotle was a polymath and a great observer interested in zoology and marine creatures. He distinguished about 500 species of animals, arranging them in his book 'History of Animals' in a graded scale of perfection with man at the top. 

Aristotle's History of Animals
Aristotle's 'History of Animals' (Historia de Animalibus, written in the 4th century BC)
Illustration of the octopus's hectocotyl arm
Illustration of the octopus's hectocotyl arm in a page of a 1910 translation of Aristotle's 'History of Animals'

Aristotle deeply analysed the fauna and flora of the island of Lesbos and its internal lagoon for two years before being appointed tutor of Alexander the Great. The chewing organ of one of the most prominent marine model species in biomedicine that he described, the sea urchin, was named ‘Aristotle’s lantern’ after him. 

Aristotle's Lantern
Aristotle's 'lantern' (a complex dental apparatus in sea urchins)
Sea urchin mouth
Sea urchin mouth. Photo by Ibon Cancio. 

Aristotle showed special interest in ‘ichthyology’ (ie the branch of zoology that studies fish) describing more than 100 fish species and the reproductive life history of over 40 of those species. The first descriptions of hermaphroditism (organisms without separate sexes) in fish are ‘Aristotelic’. The Serranidae fish (sea basses) are a classical example of simultaneous hermaphroditism, with functional testis and ovary coexisting in mature individuals. Other hermaphrodite fish species mature first as males or females and then change sex.  

Sea bream gonad transition
Gilthead sea-bream gonad in transition from male to female, showing oocytes and sperm-line cells.
Photo by Ibon Cancio.

Aristotle also described the reproductive behaviour of some ovoviviparous sharks (ie embryos develop in an egg but within the mother). Fascinated by reproduction in cartilaginous fish, he described the ‘mermaid’s purse’, a casing that surrounds fertilised eggs of many sharks and skates.

Mermaid´s purses of small-spotted catshark
Mermaid's purses of small-spotted catshark. 
Photo by Ibon Cancio, at EMBRC partner Station biologique de Roscoff (France). 
Mermaid´s purse with shark embryo
Mermaid's purse with shark embryo. Photo by Ibon Cancio, at Aquarium Donostia (Spain). 

Another of Aristotle's precise descriptions is that of the octopus’s reproductive ‘hectocotyle’ arm (ie the one that is specialised in storing and transferring spermatophores to the female). 

Aristotle did not get it all right though. Puzzled by the reproductive strategy of the eel, as thousands of naturalists for centuries after him, he concluded that eels come from the guts of the Earth, ‘earth worms’, in some sort of spontaneous generation. The gonad development and reproductive strategy of the eels remained a mystery and research in marine stations at the turn of the 19th century would be necessary to find a response to the way in which European eels develop and reproduce….far away from Europe in the Sargasso sea!! In any case, Aristotle, this ‘polymath’ (or ‘universal man’) of human culture, deserves to be our first featured marine biologist!

European eel at Lisbon market
The European eel at a modern fish market in Lisbon, Portugal. 
Photo by Ibon Cancio.


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