Blue Sea Slugs (Glaucus atlanticus)

Blue Sea Slugs are shell-less gastropods with the unique ability to float upside down. Surface tension allows them to be guided by wind and ocean currents. 

These unique types of mollusks are silvery grey on the top side, while the underbelly carries dark and pale blue hues. Their bodies exhibit dark blue stripes and six finger-like projections called cerata. This form of countershading camouflaged them from would-be attackers.

Despite their average size of 1.2 inches, it's critical to understand these critters are more dangerous than they appear. The tips of their cerata are full of venom from their cnidarian-rich diet. Touching them can induce painful stings, causing symptoms such as nausea, vomiting, and allergic reactions.

Tree Snail (Partula)

Tree Snails are air-breathing arboreal mollusks. Once threatened by a biological control mishap, these snails narrowly escaped total extinction. The target was the invasive Giant African Land Dnail, but unfortunately, the introduced predator, the Florida Rosy Wolfsnail, preyed on the native Tree Snails instead.

Nearly 64 species of Tree Snails from Tahiti and its islands fell prey to this predator within ten years. Only a dozen species survived. These survivors were protected by quick-reacting scientists before they met a similar fate.

Today, programs work tirelessly to rescue these snails from the edge of extinction. For instance, the Zoological Society of London runs a successful captive-breeding initiative across the UK, France, and the US. Since 2014, they have reintroduced healthy, bred individuals back to Tahiti.

Sadly, the IUCN Red List notes numerous Tree Snail species as critically endangered. As of writing, there are 13 critically endangered, 13 extinct in the wild, and 32 extinct Partula species.

Common Octopus (Octopus vulgaris)

Common octopuses are widespread in tropical, subtropical, and temperate waters worldwide. They are also the most studied octopus species. Notably, they span 1 to 3 feet long, including arms. This is short compared to giant octopuses living under the deep sea.

Aside from their intelligence, their camouflage expertise is extraordinary, adapting color, skin texture, and posture seamlessly according to the substrate. Dive deeper into these types of marine mollusks by checking our list of octopus facts and types of octopus.

Blue-ringed Octopus (Hapalochlaena)

Blue-ringed octopuses are venomous creatures dwelling in Pacific and Indian Ocean tide pools and coral reefs. They favor hiding within crevices, showing skilled camouflage patterns.

When disturbed, they reveal their true vibrant yellow color with eye-catching blue rings, serving as a warning display. One of the four species, the Greater Blue-ringed octopus, glows blue due to light reflectors concentrated in the blue rings5, a phenomenon triggered by muscle movement.

They are small, measuring only 5 to 8 inches, but their toxin, tetrodotoxin, can kill humans swiftly. Their bites are almost unnoticeable until respiratory issues and paralysis set in.

Studies revealed that every octopus carries venom. However, only a few species, like this one, pose a substantial danger to humans.

Flamboyant Cuttlefish (Metasepia pfefferi)

The Flamboyant Cuttlefish resides in the tropical Indo-Pacific oceans. It favors sandy and muddy habitats at depths ranging from 10 to 282 feet.

This small sea creature displays a brown body, highlighted with white, yellow, and rich purple-pink. Due to chromatophores and pigment cells in its skin, it can alter colors. Its mantle is wide, oval-shaped, and arms have four lines of suckers.

A predator at heart, it feeds on crustaceans and fish. Meanwhile, it falls prey to seals, dolphins, and larger fish.

Chambered Nautilus (Nautilus pompilius)

The Chambered Nautilus, also called Pearly Nautilus, dwells in the Indo-Pacific region. Mostly found deep - up to 1640 feet - it ascends at night. 

This creature reaches 8 inches in length, sporting a smooth shell with a brown and white pattern. The shell curves above the nautilus, creating around 30 chambers for growth. It resides in the outermost chamber and has a central tube that allows buoyancy control.

Its eyes are rudimentary, lacking lenses and functioning like a pinhole camera. Instead, the nautilus relies on a keen sense of smell to catch fish and crabs, its main prey. Furthermore, it consumes carrion when necessary.

West Indian Fuzzy Chiton (Acanthopleura granulata)

The West Indian Fuzzy Chiton mainly lives from southern Florida to Panama, including Mexico and the West Indies. It thrives on high-intertidal rocks, enduring harsh and variable conditions.

This type of mollusk doesn't grow beyond 2.8 inches in length. Spiky and banded with various hues of black, its girdle encloses the creature's plates, acting as an exterior armor.

Now, the shell of chitons typically comprises eight distinct plates. The West Indian Fuzzy Chiton, though, presents an anomaly. It boasts a fifth valve, split into two symmetrical halves. These halves function independently from the other, separated by a griddle-like tissue.

Common Hippopotamus (Hippopotamus amphibius)

The Common Hippopotamus, or the River Hippopotamus, dominates the African landscape, ruling sub-Saharan Africa's lakes, rivers, and mangrove swamps. 

A male hippo can reach 3,260 lb. Despite its massive size, it is surprisingly fast, reaching up to 22 miles per hour on land on short distances. 

One of its most distinctive characteristics is the secretion of "blood sweat," which acts as a natural sunscreen and antibacterial agent. 

Male hippos reach maturity at 7.5 years old, while cows are 5 to 6 years old. After an eight-month gestation period, a female hippo isolates herself from the group. It gives birth to one calf on land or in shallow water. 

Interestingly, calves fold their ears and close their nostrils as they nurse on female hippos underwater. Moreover, this nocturnal herbivore can consume around 80 pounds of grass overnight. Adults have no known natural predators, but lions, hyenas, and crocodiles endanger young hippos.

Despite their formidable size, Common Hippos are not sociable. While they form groups, they do so primarily for protection rather than companionship.

The hippos are a vulnerable species, facing a population decline due to poaching and civil unrest1. Elephant ivory substitutes, such as hippo teeth, heighten demand in illegal markets. Conservation efforts are vital, yielding slight improvements in protected areas.

Here are five subspecies of the common hippo with differences in their skulls and geographic ranges

Pygmy Hippopotamus (Choeropsis liberiensis/Hexaprotodon liberiensis)

The Pygmy Hippopotamus is native to the dense forests and marshy swamps of West Africa. Unlike its larger relative, it is only half its height and weighs only a fraction. It measures 69 inches long and stands 39 inches tall at the shoulder. 

Moreover, the pygmy hippo lives in the water more than on land. While these animals weigh up to 606 pounds, they move with the grace and agility of a jungle ballerina.

This solitary creature spends the day hidden in cool rivers or wallows, venturing only at night to forage for food. It eats ferns, broad-leaved plants, grasses, fruits, small insects, and worms. 

Pygmy hippos are facing declining numbers due to habitat destruction from commercial plantations2, mining, and shifting agriculture. Intensified bushmeat hunting exacerbates their plight, warranting their endangered status. With fewer than 2,500 mature individuals, a 20% population decrease over two generations is projected.

North American Porcupine (Erethizon dorsatum)

The North American Porcupine, or Canadian Porcupine, is the largest porcupine species in North America. It is distributed across various habitats and can reach three feet with tails up to a foot long.

It has around 30,000 barbed, hollow quills embedded into its skin or hair and can easily detach from the porcupine's body. Additionally, North American Porcupines feed on various vegetation, making it a nuisance to foresters. Predators like the North American golden eagles also hunt them.

One peculiar habit of the porcupine is self-anointing, which involves creating a paste and meticulously applying it to its quills. Scientists still do not know the reason behind this behavior.

Blue Sea Slugs (Glaucus atlanticus)

Blue Sea Slugs are shell-less gastropods with the unique ability to float upside down. Surface tension allows them to be guided by wind and ocean currents. 

These unique types of mollusks are silvery grey on the top side, while the underbelly carries dark and pale blue hues. Their bodies exhibit dark blue stripes and six finger-like projections called cerata. This form of countershading camouflaged them from would-be attackers.

Despite their average size of 1.2 inches, it's critical to understand these critters are more dangerous than they appear. The tips of their cerata are full of venom from their cnidarian-rich diet. Touching them can induce painful stings, causing symptoms such as nausea, vomiting, and allergic reactions.

Tree Snail (Partula)

Tree Snails are air-breathing arboreal mollusks. Once threatened by a biological control mishap, these snails narrowly escaped total extinction. The target was the invasive Giant African Land Dnail, but unfortunately, the introduced predator, the Florida Rosy Wolfsnail, preyed on the native Tree Snails instead.

Nearly 64 species of Tree Snails from Tahiti and its islands fell prey to this predator within ten years. Only a dozen species survived. These survivors were protected by quick-reacting scientists before they met a similar fate.

Today, programs work tirelessly to rescue these snails from the edge of extinction. For instance, the Zoological Society of London runs a successful captive-breeding initiative across the UK, France, and the US. Since 2014, they have reintroduced healthy, bred individuals back to Tahiti.

Sadly, the IUCN Red List notes numerous Tree Snail species as critically endangered. As of writing, there are 13 critically endangered, 13 extinct in the wild, and 32 extinct Partula species.

Common Octopus (Octopus vulgaris)

Common octopuses are widespread in tropical, subtropical, and temperate waters worldwide. They are also the most studied octopus species. Notably, they span 1 to 3 feet long, including arms. This is short compared to giant octopuses living under the deep sea.

Aside from their intelligence, their camouflage expertise is extraordinary, adapting color, skin texture, and posture seamlessly according to the substrate. Dive deeper into these types of marine mollusks by checking our list of octopus facts and types of octopus.

Blue-ringed Octopus (Hapalochlaena)

Blue-ringed octopuses are venomous creatures dwelling in Pacific and Indian Ocean tide pools and coral reefs. They favor hiding within crevices, showing skilled camouflage patterns.

When disturbed, they reveal their true vibrant yellow color with eye-catching blue rings, serving as a warning display. One of the four species, the Greater Blue-ringed octopus, glows blue due to light reflectors concentrated in the blue rings5, a phenomenon triggered by muscle movement.

They are small, measuring only 5 to 8 inches, but their toxin, tetrodotoxin, can kill humans swiftly. Their bites are almost unnoticeable until respiratory issues and paralysis set in.

Studies revealed that every octopus carries venom. However, only a few species, like this one, pose a substantial danger to humans.

Flamboyant Cuttlefish (Metasepia pfefferi)

The Flamboyant Cuttlefish resides in the tropical Indo-Pacific oceans. It favors sandy and muddy habitats at depths ranging from 10 to 282 feet.

This small sea creature displays a brown body, highlighted with white, yellow, and rich purple-pink. Due to chromatophores and pigment cells in its skin, it can alter colors. Its mantle is wide, oval-shaped, and arms have four lines of suckers.

A predator at heart, it feeds on crustaceans and fish. Meanwhile, it falls prey to seals, dolphins, and larger fish.

Chambered Nautilus (Nautilus pompilius)

The Chambered Nautilus, also called Pearly Nautilus, dwells in the Indo-Pacific region. Mostly found deep - up to 1640 feet - it ascends at night. 

This creature reaches 8 inches in length, sporting a smooth shell with a brown and white pattern. The shell curves above the nautilus, creating around 30 chambers for growth. It resides in the outermost chamber and has a central tube that allows buoyancy control.

Its eyes are rudimentary, lacking lenses and functioning like a pinhole camera. Instead, the nautilus relies on a keen sense of smell to catch fish and crabs, its main prey. Furthermore, it consumes carrion when necessary.

West Indian Fuzzy Chiton (Acanthopleura granulata)

The West Indian Fuzzy Chiton mainly lives from southern Florida to Panama, including Mexico and the West Indies. It thrives on high-intertidal rocks, enduring harsh and variable conditions.

This type of mollusk doesn't grow beyond 2.8 inches in length. Spiky and banded with various hues of black, its girdle encloses the creature's plates, acting as an exterior armor.

Now, the shell of chitons typically comprises eight distinct plates. The West Indian Fuzzy Chiton, though, presents an anomaly. It boasts a fifth valve, split into two symmetrical halves. These halves function independently from the other, separated by a griddle-like tissue.

Common Hippopotamus (Hippopotamus amphibius)

The Common Hippopotamus, or the River Hippopotamus, dominates the African landscape, ruling sub-Saharan Africa's lakes, rivers, and mangrove swamps. 

A male hippo can reach 3,260 lb. Despite its massive size, it is surprisingly fast, reaching up to 22 miles per hour on land on short distances. 

One of its most distinctive characteristics is the secretion of "blood sweat," which acts as a natural sunscreen and antibacterial agent. 

Male hippos reach maturity at 7.5 years old, while cows are 5 to 6 years old. After an eight-month gestation period, a female hippo isolates herself from the group. It gives birth to one calf on land or in shallow water. 

Interestingly, calves fold their ears and close their nostrils as they nurse on female hippos underwater. Moreover, this nocturnal herbivore can consume around 80 pounds of grass overnight. Adults have no known natural predators, but lions, hyenas, and crocodiles endanger young hippos.

Despite their formidable size, Common Hippos are not sociable. While they form groups, they do so primarily for protection rather than companionship.

The hippos are a vulnerable species, facing a population decline due to poaching and civil unrest1. Elephant ivory substitutes, such as hippo teeth, heighten demand in illegal markets. Conservation efforts are vital, yielding slight improvements in protected areas.

Here are five subspecies of the common hippo with differences in their skulls and geographic ranges

Pygmy Hippopotamus (Choeropsis liberiensis/Hexaprotodon liberiensis)

The Pygmy Hippopotamus is native to the dense forests and marshy swamps of West Africa. Unlike its larger relative, it is only half its height and weighs only a fraction. It measures 69 inches long and stands 39 inches tall at the shoulder. 

Moreover, the pygmy hippo lives in the water more than on land. While these animals weigh up to 606 pounds, they move with the grace and agility of a jungle ballerina.

This solitary creature spends the day hidden in cool rivers or wallows, venturing only at night to forage for food. It eats ferns, broad-leaved plants, grasses, fruits, small insects, and worms. 

Pygmy hippos are facing declining numbers due to habitat destruction from commercial plantations2, mining, and shifting agriculture. Intensified bushmeat hunting exacerbates their plight, warranting their endangered status. With fewer than 2,500 mature individuals, a 20% population decrease over two generations is projected.

North American Porcupine (Erethizon dorsatum)

The North American Porcupine, or Canadian Porcupine, is the largest porcupine species in North America. It is distributed across various habitats and can reach three feet with tails up to a foot long.

It has around 30,000 barbed, hollow quills embedded into its skin or hair and can easily detach from the porcupine's body. Additionally, North American Porcupines feed on various vegetation, making it a nuisance to foresters. Predators like the North American golden eagles also hunt them.

One peculiar habit of the porcupine is self-anointing, which involves creating a paste and meticulously applying it to its quills. Scientists still do not know the reason behind this behavior.