The Citrus-Primate Connection

Around 5000 species of mammals inhabit the Earth today, and almost all make their own Vitamin C from simple sugar. Your dog doesn’t need orange juice to live a scurvy-free life.

Human ancestors, and most other primates, lost the genetic ability to perform this impressive biochemical feat around 61 million years ago [1]. How did they/we survive?

Short answer – don’t know (yet).  It’s accepted that these primate ancestors were insectivores. Insects, in general, do not contain high levels of Vitamin C [2]. But, insects do like hanging around flowers, fruits, and leaves. An insect could be noshing on some C-rich fruit (insects do require Vitamin C for development and reproduction) when the primate ate it. Or the primate could accidentally eat plant material while aiming for the insect.

What about other Vitamin C deficient mammals – Guinea pigs and bats? Guinea pigs… and fruit bats… certainly get plenty of Vitamin C in their diet. What about insect-eating bats? Well, maybe they aren’t as Vitamin C inept as we thought [3]. And, we deficients may be able to survive on less Vitamin C and/or recycle the little we do ingest [4].

 

1.  Lachapelle M.Y. and G. Drouin. 2011. Inactivation dates of the human and guinea pig vitamin C genes. Genetica 139:199–207. 
2. Kourimska L. and A. Adamkova. 2016. Nutritional and sensory quality of edible insects. NSF Journal. 4:22-26.
3. Cui J., Y.H. Pan, Y. Zhang, G. Jones, and S. Zhang. 2011. Progressive pseudogenization: vitamin C synthesis and its loss in bats. Mol Biol Evol. 28(2): 1025-31. 
4. Troadec, M. and J. Kaplan. 2018. Some vertebrates go with the GLO. Cell. 132(6)921-922.

Homegrown Squash

These heirloom varieties of squash are the literal fruits of my springtime obsession with Cucurbits (the gourd family – almost 1000 species of zucchini, pumpkin, watermelon, cucumber, etc).

This obsession grew thanks to Dr. Lori Shapiro who knows the coolest facts about squash! For instance, before domestication, wild gourds contained bitter toxins. Only megafauna like mammoths could ingest and disperse the seeds of these protected fruits (1). In the Americas, early hunter-gatherers used dried gourds as floats for fishing nets and to hold food and water. They also used fresh wild gourds for the medicinal properties of the bitter compounds (2). The wild gourd (Cucurbita pepo) was the first plant domesticated in the Americas, and the first agriculturalists likely grew them for their nutritious seeds rather than the bitter flesh. Thanks, Lori!

1. Kistler, L., L.A. Newson, T.M. Ryan, A.C. Clarke, B.D. Smith, G.H. Perry. 2015. Adaptive domestication in squashes and gourds. Proceedings of the National Academy of Sciences, 112 (49) 15107-15112.
2. Hart, J.P., R.A. Daniels, C.J. Sheviak. 2004. Do Cucurbita pepo gourds float fishnets? American Antiquity. 69(1) 141-148.

 

An Apple a Day

I grew up in the great apple-producing state of Michigan. If you haven’t been to an apple cider mill during October in the mitten state, you are missing out on one of the great joys of life.

Thousands of apple varieties grew in agricultural fields when nation’s founders declared independence. Today, 80% of that diversity is gone and with it, the genetic variation that can save apples from pests, weather, and disease.

Santayana said, “Those who cannot remember the past are condemned to repeat it.” The consequences of low crop diversity were felt during the Irish potato famine in the 1840s which caused the death or emigration of a quarter of Ireland’s citizens. A pathogen entered the potato fields and spread. Since the potatoes were genetically identical, a disease that affected one could infect them all.

Today, cost and transportation constraints benefit massive agricultural operations. The efficiency of monocultures, though, threatens our food and our health. To fight off disease in genetically-similar apples, we turn to pesticides. Apples are continually cited as worst offenders for chemical coatings (fyi, the American Chemical Society recommends a baking soda solution for washing). Today, about half of apples grown in the U.S. are Red Delicious (despite tasting like wood pulp).

Consider trying some local heritage apple varieties. Apple season starts in August!

P.S. An informative Smithsonian blog post about heritage varieties of apple includes a reference to an apple sleuth who lives just down the road from me!

Limes & Science Go Together

In 1740, an English commodore led an ill-fated squadron of ships out to sea, prepared to circumnavigate the world (and attack some Spanish holdings along the way). Of over 1800 men starting the voyage, only 500 survived. The main killer was not war or weather, but  nutrition.

Just a few years after the flotilla returned, a naval doctor conducted one of the most famous experiments in the history of science. After a few months at sea, sailors on Dr. James Lind’s ship began exhibiting signs of scurvy. The doctor treated sick sailors with random supplements to their regular diet. Some shipmen received vinegar, or sea water, or barley water. They made no improvement. Sailors who were given citrus fruits, though, made quick and full recoveries.

Unfortunately, dogma and a small sample size caused many (including Dr. Lind) to underestimate the power of citrus. It wasn’t until the mid-1790s, as scurvy-free anecdotes and experiences grew, that ships rationed out citrus juice to prevent the disease. Enjoy some lemons, limes, or oranges in celebration of science!

A Raspberry’s Worst Nightmare

With all the beautiful berries available now, I’ve been seeing more fruit flies hanging around the kitchen. Annoying? Yes. Ruining my strawberries? Nope. Fruit flies lay their eggs on damaged or rotting fruit. So they’re only interested in the pieces that are going bad. I’m ok with that.

But consider a fruit fly who lays her eggs on fresh fruit. She’d have the agricultural community freaking out. Just imagine the risk to berry crops. Actually, you don’t have to imagine because scientists have already done the calculations for you: it’s potentially $2.6 billion of risk (1).

Evolution has already dealt this stunning set of cards to Drosophila suzukii, the spotted-wing drosophila (2). The females have an ovipositor (the anatomical structure that deposits eggs) that looks like a serrated knife. Unlike the common fruit fly in your house, this species’ egg-laying parts can cut through the skins of raspberries, strawberries, blueberries, cherries, and grapes.

Want to learn more about the spotted-wing drosophila? IFAS at the University of Florida has a great info page on the little beastie (with horrifically gorgeous pictures, by Martin Hauser, of that ovipositor – if you haven’t seen fruit fly genitalia yet, you are missing out).

p.s. Thanks to Dr. Nadia Singh for introducing me to Drosophila suzukii.

1. Walsh, Douglas, M. Bolda, R. Goodhue, A. Dreves, J. Lee, D. Bruck, V. Walton, S. O’Neal, F. Zalom. 2011. Drosophila suzukii (Diptera: Drosophilidae): Invasive Pest of Ripening Soft Fruit Expanding its Geographic Range and Damage Potential. Journal of Integrated Pest Management. 2(1): G1-7.

2. Atallah, L. Teixeira, R. Salazar, G. Zaragoza, A. Kopp. 2014. The making of a pest: the evolution of a fruit-penetrating ovipositor in Drosophila suzukii and related species. Proceedings of the Royal Society B: Biological Sciences, 281 (1781)

Mocking Berries

My yard is full of Strawberries – crawling across the patio, creeping over the lawn, growing around the a/c unit. Too bad they’re all fakers.

Delicious Wild Strawberries bloom white flowers that develop drooping mini-versions of the strawberries we know and love. The Mock Strawberries (Potentilla indica) growing in my yard, in comparison, display yellow flowers and upright little red fruits so tempting to behold. It’s like the little plant begs, “Look at this beautiful, juicy berry. Don’t you want to eat it?” Unfortunately, the fruit is totally flavorless. Just a tiny little ball of seeds and water. The little jerk-plant “mocks” us.

There may be hope though. Mock Strawberries came from India or south Asia where they’re called She Mei (Snake Strawberry). Apparently, the plant is used to control mosquito larvae in China (1959 Compendium of Chinese Indigenous Pesticides). I’m not quite sure how that works, but I’ll be conducting my own experiments this summer. If successful, I won’t feel so betrayed.