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Something really fishy: A brief look at the coelacanth, the ‘living fossil’

In one of my more previous frivolous blogs (‘The beast inside: What does your favourite animal say about you?’) I wrote that my favourite animal is the coelacanth. It’s been my favourite animal ever since I did a junior school project on it when I was nine-years old. At that age I was fascinated by dinosaurs, fossils, and paleontology. Like many boys in my class, I devoured books on dinosaurs. One of the ‘dino-books’ I read talked about a fish called the coelacanth, a prehistoric fish that lived on earth during the late-Devonian period (known as the ‘age of fishes’) dating back 360 million years. What grabbed my attention was mention that a living coelacanth had been caught in the Chalumna River off the east coast of South Africa in 1938. According to fossil records, coelacanths had died out and become extinct 65 million years ago (having lived 200 million years before dinosaurs had even come into existence). I found the idea of a real life coelacanth unbelievable. Although my passion for psychology overtook paleontology in my late teens I still love all things coelacanth. It’s probably one of the subjects I would pick if I ever appeared on the Mastermind television show. I rarely read academic papers outside of psychology but for ones on coelacanths I make exceptions. I must have watched every documentary and video clip on YouTube (and in my opinion, the 2001 Equinoxe documentary ‘The Fish That Time Forgot’ is an excellent primer on the coelacanth. You should also check out the more recent ‘Diving With Dinosaur Fish‘).

The coelacanth has often been dubbed a ‘living fossil’ (in simple terms referring to an organism that closely resembles another organism that is only known from fossil records) and the name ‘coelacanth’ derives from both Greek and modern Latin and means ‘hollow spine’ (one of the fish’s interesting anatomical features). According to Wikipedia, there are two key characteristics of something defined as a living fossil (and some scholars have added a third):

“The first two are required for recognition as a living fossil stasis but some authors include the third. They (i) are members of taxa [a group of one of more organisms] that exhibit notable longevity in the sense that they have remained recognisable in the fossil record over unusually long periods; (ii) show little morphological divergence, whether from early members of the lineage, or among extant species, and (iii) tend to have little taxonomic diversity”.

Based on such characteristics, there are dozens of ‘living fossils’ on the planet including reptiles (e.g., crocodiles, various turtles), birds (e.g., pelicans, magpie geese), many types of shark, and mammals (e.g., aardvarks, red pandas, okapis), as well as bony fish such as the coelacanths and African lungfish. Just as an aside, in 2018, I co-authored a paper (published in the journal Social Sciences, see ‘Further reading’ below) with Dr. Mike Sutton debunking the assertion that Charles Darwin coined the phrase ‘living fossil’. The Oxford English Dictionary claims Charles Darwin (1859) coined the term ‘living fossil’. Using the ‘internet date detection’ method, we highlighted that the term ‘living fossil’ first appeared in the literature at least 147 years earlier in the work of a Welsh Botanist Lhwyd (1712). He used it in Philosophical Transactions, the journal of the Royal Society of London (which was also thefirst ever peer-reviewed scientific journal).

It could be argued that the twentieth century history concerning the coelacanth was due to one man’s obsession, namely Professor James Leonard Brierley Smith (but known to all in the field as ‘J.L.B.’ Smith and who was an ichthyologist at Rhodes University). For those who don’t know, ichthyology is the branch of zoology that concern itself with the scientific study of fish. (And as another aside, when I worked in the University of Plymouth’s psychology department [1990-1995], one of my colleagues [Dr. Phil Gee] described himself – at least at the time – as an ‘ichthyopsychologist’ and published a paper in 1994 from his PhD entitled ‘Temporal discrimination learning of operant feeding in goldfish’ in the Journal of the Experimental Analysis of Behavior). Smith is credited with formally identifying the coelacanth that was caught in 1938 but the story actually began with Marjorie Courtenay-Latimer, the curator at the East London Natural History Museum, who spotted a strange looking blue-finned fish among the catch of a local fisherman (Hendrick Goosen) on December 23, 1938. She made a sketch of the 1.5-metre fish and contacted her friend Smith who instantly knew he was looking at something history-changing. It actually took nearly two months before Smith actually saw the fish in the flesh (he lived over 500 miles away and finally visited Courtenay-Latimer on February 16, 1939).

Courtenay-Latimer had tried to preserve it as best as she could but all the internal organs were disposed of (she had sent it to a taxidermist) before Smith was able to examine the specimen (the refrigeration facilities were poor in the 1930s so she had the fish skinned and mounted). The specimen was eventually named after Courtenay-Latimer and the river where it was found (genus name Latimeria chalumnae). Coelacanths were actually known to the local fishermen who called them ‘gombessa’ or ‘mame’.

Smith knew the importance of the find and spent years trying to find a second West Indian Ocean coelacanth. He distributed leaflets for thousands of miles all along the East African coast and offered a large financial reward to any fisherman who caught one. Fourteen years later, a second coelacanth turned up in the Comoro Islands (followed by over 80 other specimens up to 1975 including catches off the coasts of Tanzania, Kenya, Madagascar and Mozambique). Smith managed to persuade the South African Prime Minister (Daniel Malan) to get the military to fly him to the Comoros (islands that were actually owned by France). Smith subsequently began the first ever dissection of a coelacanth and concluded it was different in many ways from all modern fish (see bullet point on ‘Body characteristics’ below).

One of the most interesting features of coelacanths are its fins. They are almost limb-like and because of this anatomical feature, Smith (wrongly) believed that the coelacanth was evidence of the evolutionary ‘missing link’ between fish and land-walking mammals (in fact on December 30, 1952, the New York Times front-page article was headlined ‘14-Year Hunt Yields ‘Missing Link’ Fish’). Much of Smith’s post-1952 career was spent writing about and researching the coelacanth (most notably his 1956 book The Search Beneath the Sea – The Story of the Coelacanth also known as Old Fourlegs: The Story of the Coelacanth).

Remarkably, the story of the coelacanth didn’t end in the east coast of Africa. In September 1997, a different species of coelacanth was identified at a local market in Sulawesi (Indonesia) by Dr. Mark Erdmann (a coral reef ecologist) who was on honeymoon with his wife. Erdmann took photographs but someone bought the fish so was unable to carry out any research on the specimen. Erdmann subsequently returned to Indonesia and in July 1998, local fisherman caught a second Indonesian coelacanth (and was subsequently given the genus name Latimeria menadoensis). The fish was known to local Indonesian fisherman as ‘raja laut’ (king of the sea). So what else do we know about present-day coelacanths? Here’s my brief bluffer’s guide to coelacanths.

  • Maximum size and weight: Coelacanths can be as long as six feet and weigh up to 200 pounds, and females are bigger than males.
  • Life expectancy: It is estimated coelacanths can live up to 80 to 100 years based on the growth rings in the ear bones (called otoliths).
  • Body characteristics: Coelacanths have thick (almost armour-like) scales and a tiny brain (comprising 1.5% of the cranial cavity). They have hinge in their skull (i.e., an intracranial joint) that allows them to open their mouths wide to consume their prey, and instead of a spine they have an oil-filled hollow pressurized tube called a notocord. They also have very primitive hearts described as the most primitive in the vertebrate world. In their nose they have an electro-sensory system (a rostral organ comprising a jelly-filled cavity) that has been speculated to help sense its prey (similar to that found in some sharks – in fact coelacanths and sharks have almost identical blood chemistry). The East African species is blue in colour whereas the Indonesian species is brown in colour.
  • Body metabolism and diet: Coelacanths are carnivorous and also have the lowest metabolism of any fish its size. It is speculated that it is this feature that may have allowed them to survive on earth for so long. They feed on small fish and occasionally squid, eels and small sharks. The low metabolism means they don’t need much food to survive and they live in relatively low-food environments.
  • Number of species: Historically there were over 120 species of coelacanth identified by fossil records but only two extant species have been verified.
  • Movement: J.L.B. Smith speculated that coelacanths ‘walked’ on the sea bed but the four (almost limb-like) facilitate a form of locomotion that is similar to tetrapods (four-legged animals) but ‘walk’ in the water not on the sea bed (Smith described their fins as “paddles”).
  • Habitat: During the daytime they tend to be relatively stationary (inside underground caves and crevices up to 700 metres below the water’s surface although some coelacanths live in shallower depths of 90-150 metres such as those found in Sodwana Bay off the South African coast) and are nocturnal and move around (up to 8 km) during the night. The fact they live so deep underwater means they cannot live in captivity so almost everything known about coelacanths comes from dead specimens or study in-situ.
  • Reproduction and giving birth: Very little was known about how coelacanths until a pregnant coelacanth was dissected in 1975 (at the American Museum of Natural History in New York) and five fully-formed coelacanth ‘pups’ were found inside the female. The gestation period has been estimated to be around 13 to 15 months (the longest among any living fish and some papers claim a gestation period of up to three years) and they give birth to live offspring (i.e., ovoviviparous – producing offspring via eggs which are hatched within the body of their mother). Coelacanth eggs are larger than any other fish (around the size of tennis balls) and are full of nutrients to help the growing embryos. It is thought that coelacanths can give birth to between five and 25 pups. Coelacanths become sexually active at around 20 years of age. However, as far as I am aware, no-one has ever seen coelacanths mate. However, a paper published in a 2013 issue of Nature Communications carried out analysis on pregnant coelacanths and concluded that coelacanths appear to be monogamous and that offspring do not appear to mate with each other.
  • Edibility: Because of the excessive amounts of oil and wax esters within their bodies, they are slimy, ooze a mucus-type substance, coelacanths have a foul flavour (and because of the high urea content in their body they can also smell and taste of urine). In fact, people can become sick after eating coelacanth.
  • World population – It is estimated that there are approximately 350 coelacanths living on the planet and it is now classed as an endangered species which although better than extinct, could still mean they become extinct within a few generations. A genetic study of the two different extant species estimated that they had diverged 30-40 million years ago.

In my research for this article, I did come across a 1997 paper by Hans Fricke (in the Marine Ecology Progress Series) that had a whole section on the psychology of coelacanths. He noted:

“The long evolutionary existence and unchanged appearance of coelacanths since the Devonian provides spiritual insight into our own comparatively short human existence on earth. Furthermore, coelacanths are of interest not only because of their long evolutionary history but also because they remain for the public – and also for many scientists – the nearest living relatives close to our own tetrapod roots. This makes the coelacanth unique among living fossils. We appreciate the timeless existence of this ‘old cousin’ which provides a window into the past. This existence value was nicely expressed in a German youth magazine. Youngsters selected a hit list of reasons ‘Why it is worthwhile living this week’. One entry contained the statement ‘…that coelacanths still exist’.”

The paper also talked about how humans can become emotionally and strongly affected after seeing films about coelacanths. I can attest to this. I was gripped as an adult in my thirties when I first saw a coelacanth on film (and I have never lost that feeling). Their existence is quite simply life-affirming and life-enhancing.

Dr Mark Griffiths, Distinguished Professor of Behavioural Addiction, International Gaming Research Unit, Nottingham Trent University, Nottingham, UK

Further reading

Amemiya, C. T., Alföldi, J., Lee, A. P., Fan, S., Philippe, H., MacCallum, I., … & Organ, C. (2013). The African coelacanth genome provides insights into tetrapod evolution. Nature, 496(7445), 311-316.

Bates, M. (2015). The feature creature: 10 fun facts about the coelacanth. Wired, February 3. Located at: https://www.wired.com/2015/03/creature-feature-10-fun-facts-coelacanth/

Fricke, H. (1997). Living coelacanths: values, eco-ethics and human responsibility. Marine Ecology Progress Series, 161, 1-15.

Gee, P., Stephenson, D., & Wright, D.E. (1994). Temporal discrimination learning of operant feeding in goldfish (Carassius auratus). Journal of the Experimental Analysis of Behavior, 62(1), 1-13.

Holder, M.T., Erdmann, M.V., Wilcox, T.P., Caldwell, R. L., & Hillis, D.M. (1999). Two living species of coelacanths? Proceedings of the National Academy of Sciences, 96(22), 12616-12620.

Inoue J. G., Miya, M., Venkatesh, B., & Nishida, M. (2005). The mitochondrial genome of Indonesian coelacanth Latimeria menadoensis (Sarcopterygii: Coelacanthiformes) and divergence time estimation between the two coelacanths. Gene, 349, 227–235.

Johanson, Z., Long, J. A., Talent, J. A., Janvier, P., and Warren, J. W (2006). Oldest coelacanth, from the early Devonian of Australia. Biology Letters, 2(3), 443–446.

Lampert, K. P., Blassmann, K., Hissmann, K., Schauer, J., Shunula, P., El Kharousy, Z., … & Schartl, M. (2013). Single-male paternity in coelacanths. Nature communications, 4, 2488.

Lavett Smith, C., Rand, C. S., Schaeffer, B., and Atz, J. W. (1975). Latimeria, the living coelacanth, is ovoviviparous. Science 190(4219), 1105–1106.

Pouyaud, L., Wirjoatmodjo, S., Rachmatika, I., Tjakrawidjaja, A., Hadiaty, R., & Hadie, W. (1999). A new species of coelacanth. Genetic and morphologic proof. Comptes Rendus de l’Academie des Sciences. Serie III, Sciences de la Vie, 322(4), 261-267.

Smith, J.L.B. (1956). The Search Beneath the Sea – The Story of the Coelacanth. New York: Holt.

Sutton, M. & Griffiths, M.D. (2018). Using date specific searches on Google Books to disconfirm prior origination knowledge claims for particular terms, words, and names. Social Sciences, 7, 66. doi:10.3390/socsci7040066.