An Elusive Worm: The Salinella and Its Mysterious Existence

A Journey into the Unknown

Last February, accompanied by colleagues Gert and Philipp and my daughter Francesca, I embarked on a journey to Río Cuarto, a rather unremarkable city situated to the east of the Argentinian Andes. Our mission? To hunt down a worm of exceptional distinction: the elusive Salinella.

Why Seek out a Worm?

Humans have a proclivity for favoring familiar animals. However, from the perspective of a zoologist, vertebrates such as mammals, birds, frogs, and fish are merely variations on a single theme. These species boast a head, limbs, and a backbone.

If animals were modes of transportation, vertebrates would be akin to the numerous makes and models of cars. In contrast, invertebrates—especially the myriad varieties of worms—represent a dazzling array of innovative forms: planes, submarines, unicycles, and even jetpacks.

Frenzel’s Discovery: The Little Salt Dweller

The worm we sought may be the most obscure animal ever recorded. Only Johannes Frenzel, a 19th-century German zoologist, has ever laid eyes on it. This “little salt dweller” was named salinella. Despite its rarity, its distinction lies in its simplicity. Frenzel posited that salinella is the oldest and simplest living animal, a relic from an ancient phase that bridged the gap from amoebas to more complex creatures like earthworms and butterflies.

For a zoologist interested in tracing the roots of the animal kingdom, studying salinella is akin to stepping into a time machine, offering a glimpse into a world that existed 600 million years ago when the first animals were coming into being.

The Confounding Labyrinth of Frenzel’s Documentation

The arduous nature of our expedition was exacerbated by the inscrutability of Frenzel’s own account, which is as chaotic as it is compelling. He received a sample of salty soil from his colleague, Wilhelm “Guillermo” Bodenbender. However, its exact origin was ambiguously listed as merely “from the salt pans in the Río Cuarto region.” The instructions were so convoluted, they resembled the “worst treasure map in the world.”

• Frenzel added tap water to his sample, inadvertently letting some iodine in.
• The sample, stored on a sunny windowsill, became contaminated with dust, sand, and even dead flies.

The real source of the worm remains an enigma—was it part of the salt? Did it emerge from the soil, or perhaps even float in from the nearby surroundings?

The Reality of the Quest

Armed with only a vague guide from Frenzel, our mission felt more like an act of hope than a strategic pursuit. Still, the prospect of rediscovering such an ancient creature was too alluring to resist. While Argentina’s landscapes, from glamorous Buenos Aires to its vast, flat interiors, mesmerized us, the real challenge lay in tracing the source of Bodenbender’s soil sample. In the past 130 years, the country’s once boundless pampas have transformed into widespread soy, alfalfa, and maize farmlands.

The Ongoing Pursuit

Despite this transformative landscape and the challenges it presents, the potential insights from studying the worm that eluded us are too valuable to forego. Perhaps it is in salinella where we will find crucial connections to the origins of life as we know it. Our commitment to this mission remains unwavering; we will continue our search, driven by the allure of the virtually lowliest of worms that holds the key to the past.

Max Telford, Jodrell Professor of Zoology and Comparative Anatomy at UCL, is the author of The Tree of Life, to be published by John Murray on 24 April. Between 24 March and 2 April, as part of our Invertebrate of the Year competition, we will showcase 10 invertebrates, selected by readers and wildlife writers, from over 2,500 nominations. Voting for the 2025 Invertebrate of the Year will occur from midday on 2 April to midday on 4 April, with the winner announced on 7 April.

Source: https://www.theguardian.com/environment/2025/apr/02/elusive-worm-the-salinella-is-shrouded-in-mystery