Nature and Biodiversity: 15 Fascinating Species You've Never Heard Of

The planet hosts roughly 8.7 million living species according to an estimate published in PLOS Biology in 2011, of which only about 1.5 million have been scientifically described. The rest remain unknown, and many will likely disappear before they are even named. The 2019 IPBES report estimates that one million species face short-term extinction, at a pace one hundred times faster than the natural extinction rate of the last ten million years.

Behind those troubling numbers lies a diversity of life that defies imagination. This article presents fifteen remarkable and lesser-known species, followed by a tour of the foundational concepts of biodiversity. SparkleQuiz hosts several questionnaires dedicated to the world's fauna for anyone curious about testing their knowledge of the living world.

The common octopus (Octopus vulgaris)

With its 500 million neurons (two-thirds distributed across its arms), the common octopus is probably the most intelligent invertebrate on Earth. It opens jars, solves mazes and recognizes individual human faces. Experiments in Seattle and Naples have shown that captive octopuses react differently to specific keepers. Its skin contains photoreceptor cells, which let it "see" colors even though it is technically colorblind through its eyes.

Lifespan: just one to two years. The female dies after watching over her clutch without eating for months on end.

The pistol shrimp (Alpheidae)

Small (3 to 5 cm) but devastating. Its claw snaps shut at 100 km/h, creating a cavitation bubble that briefly reaches 4,700°C: the surface temperature of the Sun. The shockwave kills prey at close range. The collective snapping of pistol shrimp colonies has disrupted military sonar since World War II.

The tardigrade

The textbook extremophile. Less than a millimeter long, the water bear survives at -272°C (near absolute zero), at 150°C, under pressures equivalent to six times those at the deepest oceanic trenches, at 1,000 times the radiation dose lethal to humans, and through ten days in the vacuum of space (ESA's FOTON-M3 experiment in 2007). It enters cryptobiosis, a dehydrated state in which its metabolism halts completely.

The axolotl (Ambystoma mexicanum)

This neotenic salamander stays in larval form its entire life while still reproducing. Endemic to the Xochimilco lakes near Mexico City, it is critically endangered in the wild (estimate: fewer than 1,000 individuals). Its regenerative ability is unique among vertebrates: it fully regrows limbs, tail, jaw, spinal cord, and even parts of the brain and heart.

Organ pipe coral (Tubipora musica)

A soft, fluorescent coral whose red skeleton resembles organ pipes. Its green fluorescence under ultraviolet light intrigues researchers: it may serve a photoprotective role for the symbiotic algae (zooxanthellae) living in its tissues. Like all corals, it suffers bleaching tied to warming oceans: Australia's Great Barrier Reef lost more than 50 percent of its coral cover between 1995 and 2017.

The Philippine eagle (Pithecophaga jefferyi)

One of the largest raptors in the world with a 2.20-meter wingspan and 8 kg of muscle. Endemic to four Philippine islands, it hunts flying lemurs, snakes and macaque monkeys. The breeding population is estimated at 400 pairs, placing it among the planet's most threatened birds. Killing a Philippine eagle is punishable by up to twelve years in prison in the Philippines.

The Amazon pink river dolphin (Inia geoffrensis)

The boto, the largest freshwater dolphin in the world (up to 185 kg and 2.5 m). Its pink color intensifies with age and excitement. Adapted to the murky waters of the Amazon basin, it hunts more than 50 fish species using a powerful sonar. Amazonian folklore claims it transforms into a handsome man, the "encantado," to seduce women at night.

The superb lyrebird (Menura novaehollandiae)

This Australian bird probably possesses the most extraordinary vocal mimicry capability in the animal kingdom. It reproduces the songs of 20 other bird species, the sound of a chainsaw, the click of a camera shutter, a car alarm, a baby's cry. The famous 1998 BBC documentary narrated by David Attenborough immortalized these performances. Its courtship song can last more than 20 minutes without a break.

The saola (Pseudoryx nghetinhensis)

Nicknamed the "Asian unicorn," this bovid was only discovered in 1992 in the Annamite mountain chain between Laos and Vietnam. No individual has survived in captivity beyond a few months. The wild population is estimated between 25 and 750 individuals. No one knows precisely how many remain: it is probably the most endangered large mammal in the world.

The okapi (Okapia johnstoni)

A cousin of the giraffe, the okapi lives in the dense rainforests of northeastern Democratic Republic of Congo. It was discovered by Western science only in 1901, although the Mbuti Pygmies had always known it. Its stripes on the hindquarters evoke a zebra, but its long neck and prehensile blue tongue (up to 30 cm) betray its giraffe lineage.

The blue-tongued skink (Tiliqua scincoides)

An Australian lizard with a stocky build and a cobalt-blue tongue that it sticks out to deter predators. That stark color, paired with the red of its mouth, functions as an aposematic signal: "I am dangerous" (even though it isn't really). It can live up to 30 years in captivity.

The immortal jellyfish (Turritopsis dohrnii)

A small jellyfish, only 4.5 mm across, originally from the Mediterranean and now found in temperate oceans worldwide. When injured, starved or stressed, it can revert to its polyp stage through a process of cellular transdifferentiation, restarting its life cycle. In theory, it can repeat this cycle indefinitely, which makes it the only known biologically immortal animal (absent predation or disease).

The kakapo (Strigops habroptilus)

A parrot from New Zealand: nocturnal, herbivorous and flightless. It can weigh up to 4 kg, making it the heaviest parrot on Earth. In 1995, only 51 individuals remained. The New Zealand conservation program, which tracks every bird individually with a name and a radio transmitter, brought the population back to 252 individuals by 2024.

The Tasmanian devil (Sarcophilus harrisii)

A carnivorous marsupial endemic to Tasmania, now threatened by a transmissible facial cancer (DFTD, devil facial tumor disease) discovered in 1996. The tumor passes directly between individuals through bites: a unique case in cancer biology. The population has dropped more than 80 percent since the disease appeared, and reintroduction programs on mainland Australia began in 2020.

The fossa (Cryptoprocta ferox)

The largest predator on Madagascar, a sort of blend of puma, mongoose and cat. It is in fact one of eight remaining endemic Madagascan carnivores, and it preys primarily on lemurs. Its unique morphology made classification difficult for biologists: it belongs to the Eupleridae family, found only on Madagascar.

Understanding biodiversity

Biodiversity is not just a species catalog. It is measured on three levels: genetic (variations within a species), specific (number of species in an ecosystem) and ecosystemic (variety of habitats).

Ecological niches

Each species occupies a niche: a precise functional role in its ecosystem, defined by what it eats, where it lives, when it is active and how it reproduces. The concept, formalized by G. Evelyn Hutchinson in 1957, shows that two species cannot indefinitely occupy the same niche in the same environment (Gause's competitive exclusion principle).

Keystone species

Some species have a disproportionate impact on their ecosystem relative to their biomass. The expression "keystone species" was coined by Robert Paine in 1969 after his experiments on the ochre sea star (Pisaster ochraceus) in California. Removing it caused the entire intertidal community to collapse. North Pacific sea otters keep sea urchin populations in check and so preserve kelp forests; the reintroduction of wolves to Yellowstone in 1995 triggered a trophic cascade observable even in the geomorphology of rivers.

Biodiversity hotspots

Norman Myers identified the hotspot concept in 1988: a region with a high concentration of endemic species and significant habitat loss. Conservation International lists 36 hotspots worldwide, covering only 2.4 percent of land surface but harboring 50 percent of endemic plant species and 43 percent of endemic terrestrial vertebrates.

The most emblematic:

• Madagascar: 90 percent of species are endemic (lemurs, baobabs, fossa)
• Western Amazon: a single hectare can hold more tree species than all of Europe
• Borneo and Sumatra: orangutans, Sumatran tigers, Sumatran rhinoceroses
• Mediterranean basin: 25,000 plant species, 13,000 of them endemic

Current threats

Five major threats, ranked by IPBES in order of severity: land-use change (deforestation, urbanization), direct exploitation (hunting, fishing, poaching), climate change, pollution, invasive species. Poaching alone reduced the African black rhinoceros population from 100,000 individuals in the 1960s to roughly 6,400 today.

A book we have read ten pages of

Telling a saola from an okapi, understanding why a tardigrade survives in space, or identifying the role of a keystone species takes regular curiosity. SparkleQuiz offers several quizzes dedicated to animals, ecosystems and threatened biodiversity: a good way to turn passive reading into active memorization.

The planet is a book we have only read about ten pages of. Each expedition to Vietnam, the Amazon or the ocean depths reveals new ones. Knowing a few emblematic species and understanding the mechanisms of biodiversity is the first step toward measuring what we are about to lose, and what remains to be found.

Put your knowledge to the test

Fifteen species, three levels of biodiversity and a handful of keystone concepts: a naturalist's memory is built exactly like an ecosystem, by repeated encounters. See which of these creatures you can still place on the map:

• Animal Kingdom: Natural Wonders: the strangest talents of the living world, from mimicry to immortality
• Extraordinary Wildlife: Endangered Species and Records: saola, kakapo and the other survivors on the brink
• Marine Life: octopus, pistol shrimp and the deep-sea unknowns
• Birds and Reptiles: from the Philippine eagle to the blue-tongued skink
• Mammals and Their Records: okapi, fossa and the champions of the class