Living a long time

Article and images by Dr Julie O'Connor, senior conservation partnerships officer

Have you ever wondered why some organisms live extraordinarily long lives, while others, even with all the luck running their way, get just a fleeting glimpse of the planet? This has probably long occupied human thought. In 350 BC, Aristotle pondered the diversity of lifespans in nature in his treatise On Longevity and Shortness of Life.

Some species are unsurprisingly short lived. For example, in the kingdom fungi, baker’s yeast Saccharomyces cerevisiae has a maximum lifespan of 14 days. A fruit fly in optimal temperatures can live 40-50 days, although 109 days has been recorded in captivity.

But determining a lifespan can be tricky. For example, dragonflies only live for two to four months as an adult, but as a nymph they progress through 9 -15 development stages, which can last up to four years.

The 17 year (or periodic) cicada, as the name suggests lives for seventeen years, almost all of which is spent underground as a nymph. After emerging from the ground as a nymph to undergo a final moult, the adult will only live for another 4–6 weeks, giving just enough time to mate and lay eggs to start the cycle all over again. By the way, if you are interested in tracking the 17 year cicada emergences, 2021 was a cicada emergence year for parts of the eastern and central United States.

One of the world’s oldest known organisms, the Oregon honey mushroom Armillaria osyoyae (estimated to be up to 8,650 years old) also happens to be the largest known living organism on earth. DNA tests confirmed that one giant individual in Oregon’s Blue Mountains occupies an area of 965 ha.

There’s other surprisingly long-lived species too. The orange roughy Hoplostethus atlanticus has been known to live as long as 149 years. Orange roughy is slow-maturing deep water fish that is listed as Conservation Dependent under the EPBC Act and is managed under the Orange Roughy Rebuilding Strategy 2015.

Some marine sponges also have amazingly long lives. The hexactinellid sponges, also known as glass sponges, are believed to be the longest living organisms on Earth, possibly reaching an age of 15,000 years. The distantly related Epibenthic sponge Cynachyra antarctica is no spring chicken either, reaching ages possibly as high as 1,550 years.

In the plant kingdom, a specimen of the Great Basin bristlecone pine Pinus longaeva has been aged at 5,062 years old. Even its leaves are exceptionally long lived, with some individual leaves staying green for 45 years. The bristlecone pines reproduce through windblown seed dispersal and a little assistance from birds like the Clarke’s nutcracker.

Australia also has its fair share of very old trees. An individual 2,000 years old Huon pine Lagarostrobuos franklinii in Tasmania could be a stem of a common root stock, potentially putting the tree’s age at around 11,000 years. Researchers from Australian National University suggest that if we can accept a clonal life form as a tree then Tasmania’s 43,000 year old king’s holly Lomatia tasmanica, can also be considered ancient. If we stay with that line of thought, then Australia’s Wollemi pine Wollemia nobilis, which reproduces both sexually and clonally, is very old indeed. The Wollemi pine has been found in the fossil record dating back 90 million years and is thought to have covered much of Gondwana 200 million years ago, so its rediscovery in 1994 was exciting news. Wollemi pines growing in the wild numbers only in the hundreds, which makes it extremely vulnerable to extinction. However, its distribution to botanical gardens around the world and its affordable availability as a garden or indoor plant will help to ensure its continued existence.

If you would like to know more about the longevity of many other species, you might like to take a look at the AnAge curated database linked below. Much of the senescence data is based on the known lifespan of captive individuals, which is usually longer than an individual might survive in the wild. Nevertheless, be warned - the AnAge database is a fascinating rabbit hole. I’d recommend a bottomless pot of tea and a comfy chair because you will be hooked before you know it.

References:

• AnAge Database at http://genomics.senescence.info/species/
• Australian Fisheries Management Authority http://afma.gov.au
• Brack, C & Brookhouse, M. Where the old things are: Australia’s most ancient trees. The Conversation April 18 2017
• De Magalhaes, J. P., & Costa, J. (2009). A database of vertebrate longevity records and their relation to other life‐history traits. Journal of evolutionary biology, 22(8), 1770-1774
• Theischinger, G., & Hawking, J. (2006). The complete field guide to dragonflies of Australia. Csiro Publishing
• Young, A. M., Hobson, E. A., Lackey, L. B., & Wright, T. F. (2012). Survival on the ark: life‐history trends in captive parrots. Animal conservation, 15(1), 28-43.