The smallest cat in the world cannot escape the fate of inbreeding | Nature Trumpet

Welcome to the 51st issue of the Nature Trumpet column. In the past half month, we have collected the following natural news and research worth reading:

1) Abandoned Christmas tree becomes a new home for fish

2) The smallest cat species is inbreeding

3) Hermaphroditic bird, female on the left and male on the right

4) One millimeter small animals can absorb microplastics in the water

5) The extinct California grizzly bear was originally a vegetarian

6) Humpback whale spine deformed after being hit by ship

Christmas trees become fish habitat

What to do with abandoned Christmas trees? Make them a home for fish!

Recently, after Christmas celebrations ended, people in Stockholm gathered up dozens of Christmas trees, removed the decorations and lights , tied heavy rocks to them, and threw them into the sea .

Christmas trees were thrown into the waters of Hammarby Sjöstad, where they became a habitat for fish | References [1]

Since the 19th century, many coastal wetlands have been converted into farmland, and fish habitats have disappeared. These unwanted Christmas trees can become new hiding places for fish. The complex branches of the Christmas tree allow fish to hide in them to avoid predators, and the shadows created by the trees can also serve as camouflage for them. In addition, the Christmas tree is a perfect spawning site, where eggs can hatch in a hidden environment, and the newly born fish also have a shelter.

Throwing Christmas trees out to sea | References [1]

Fish aren't the only ones who love Christmas trees - aquatic invertebrates also love to make their homes in the trees , which in turn attract fish that love to eat insects. Studies have found that underwater trees with complex branches and limbs can greatly increase the diversity of organisms.

Fish eggs about to hatch | Silke Baron / Wikimedia Commons

This activity was initiated by the local fishing association in 2016. Over the past nine years, more than 1,000 Christmas trees have been thrown into different waters . The good news is that fish really like them - underwater video surveillance shows that gelatinous fish eggs and fry can be observed on the trees, and the discarded Christmas trees have taken on new life underwater.

Black-footed cats are inbreeding

The world's smallest but most ferocious cat species could not escape the fate of inbreeding.

The black-footed cat is only 30-50 cm long and weighs only 1-3 kg, which is smaller than an ordinary adult domestic cat. But they are good hunters, mainly preying on gerbils and small birds, and sometimes they can catch hares larger than themselves, and can kill more than 10 small animals in one night.

We just look cute, but we're actually really mean | Jonathan Kriz / Wikimedia Commons

Because of the construction of roads and farms, the habitat of black-footed cats in the wild has become fragmented , and cat groups are far away from each other. Most of the mates they can find are their close relatives. In a new study published by Shaanxi Normal University, scientists sequenced the genomes of 10 black-footed cats and found that they are inbreeding at an alarming rate.

Black-footed cat holding a mouse | Frank Vincentz / Wikimedia Commons

What is even more worrying is that inbreeding among black-footed cats is likely to make harmful gene mutations related to amyloidosis more likely to be passed on to the next generation. Amyloidosis is a rare disease that kills 70% of captive black-footed cats. Amyloidosis causes protein accumulation in the kidneys, causing inflammation and even kidney failure. Black-footed cats can also suffer from ear inflammation because of this - they use their keen hearing to catch the movements of prey, and the inner ear accounts for 25% of the skull structure. Once their ears are deaf, they will not be able to hunt.

Just a quick lick | Pierre de Chabannes / Wikimedia Commons

As the number of black-footed cats decreases, the consequences of inbreeding will become more serious. However, compared with large cats such as lions and tigers, small cats such as black-footed cats still lack sufficient research and protection .

Hermaphroditic bird

Recently, scientists discovered a hermaphroditic bird - the two sides of its body are different colors !

This is a hermaphroditic green honeycreeper | John Murillo

This is a green honeycreeper (Chlorophanes spiza). Generally, female green honeycreepers have grass-green feathers, while males have bright blue feathers. But this unique bird has green feathers on the left side and blue feathers on the right side, which is a "bilateral hermaphrodite."

A normal male green honeycreeper with blue feathers | AFP

In 2021, a bird-watching enthusiast first spotted the bird, and in 2023, researchers spotted it on the same farm. Its behavior was no different from other green honeycreepers, and no one of its kind attacked it because of its strange appearance. But it didn't seem to get along well with other birds , often standing alone by the feeder and waiting until all of its kind left before eating.

A normal female green honeycreeper, all green | AFP

In a newly published paper, researchers believe that the reason why this bird is hermaphroditic may be that an error occurred during the division of the female egg , and two nuclei appeared in one egg cell, which were fertilized by sperm separately. Previously, they dissected hermaphroditic birds of other species and found that their sexual organs were ovaries on one side and testicles on the other side, and theoretically they could still reproduce. But they are not sure whether this bird has the ability to reproduce, and they have never seen it mate with other birds.

Marine animals sucking out microplastics

This inconspicuous little animal in the ocean has a powerful filtration system that can even suck microplastics out of the water.

Cysticercus heterocystis under the microscope | University of Oregon

This species, called Oikopleura dioica, is a small filter feeder, only 1 mm in size. When eating, they secrete a mucus chamber to cover themselves, and then use their tails to inflate the mucus chamber, just like pumping up a swimming ring. There is a filtering mechanism in the mucus chamber, and when they swing their tails inside, they drive the liquid through the filter, thereby capturing food particles in the water - let alone food, this mini filter can even suck out microplastics in the water.

This slime chamber with its own filtration system is disposable, and after eating, they will slide out of the slime chamber. Heterocystis only creates slime chambers when eating, and they will create several a day.

On the left is the tail swinging pattern when filtering food, and on the right is the normal swimming pattern | Reference [4]

In a recent study, scientists believe that the filtration system of Heterocystis is based on the same principle as a peristaltic pump, but is more efficient. In industrial applications, the liquid in a peristaltic pump is moved forward by external forces, just like the contraction of the intestine squeezes food forward. However, the peristalsis of these small animals' mucus chambers does not require external forces - their tails are inside the mucus chamber, tightly attached to the chamber wall, and when they swing, pressure is generated in the sealed chamber, which allows the liquid to move forward and seals the channel for them to flow back. Scientists speculate that if we can use a similar method to design the next generation of filters, it will not only be more efficient, but also reduce wear and tear on the pump.

California Grizzlies Eat Vegetarian Food

The California grizzly bear is an extinct subspecies of brown bear. In human imagination, they are ferocious and bloodthirsty carnivores. But a new study found that California grizzly bears were originally vegetarians . It was the arrival of humans that changed their eating habits, which indirectly accelerated their extinction.

Research shows that before Europeans arrived in California in 1542, grizzly bears were primarily vegetarian, with meat accounting for only 9% of their diet. After the Europeans arrived, they brought livestock with them, and California grizzlies added human livestock to their diet , causing the meat content of their diet to surge to 26%.

A hunter poses with a bear he killed in 1916 | Forest Service, USDA

The last time a human saw a California grizzly bear was in 1924, and they quickly went extinct. Before they disappeared, newspapers portrayed them as ferocious, giant carnivores that weighed up to a ton . Hunters used poisoned bait to catch bears, and the captured bears were advertised as trophies or even sold as meat. The money and fame brought by bear hunting encouraged more people to participate in hunting, which eventually led to their extinction.

Stuffed specimen of Monarch, a California grizzly bear in captivity | Payton / Wikimedia Commons

Regardless of whether California grizzlies are really that ferocious, do they really weigh one ton? Studies have found that their average weight is only about 200 kilograms , which is about the same as today's North American grizzlies. In order to attract attention, newspapers exaggerated the size of the captured bears, and finally the rumor spread.

This also led to another tragedy - someone once captured a California grizzly bear, named it "Monarch", and kept it in a zoo. Because they believed it was a greedy carnivore, they kept feeding it raw meat , causing it to suffer from arthritis when it died. It was also very obese, weighing about 500 kilograms, twice its normal weight.

One of the Monarch's children, who died shortly after birth | Wikimedia Commons

Humpback whale spinal deformity

A humpback whale's spine was deformed after being hit by a ship.

A humpback whale with a deformed spine | Alexander Schmidt / Apex Ocean Divers

Recently, near the state of Baja California in Mexico, a drone was used to capture a humpback whale with a distinctive tail spine that was almost broken, most likely caused by a ship strike . With such a serious injury, it has to endure the pain all the time, and even swimming becomes very difficult, not to mention migration, foraging and avoiding predators. Death is almost inevitable .

Several whales with broken backs have been seen before, possibly from being hit by ships. One humpback whale, Moon, swam nearly 5,000 kilometers from Canada to Hawaii with a broken back, and last March, a 17-meter-long fin whale lingered near Spain after breaking its back, and its final fate may be a slow death from starvation.

Fin whale with a broken back near Spain, March 2023 | Oceanographic Valencia

Collisions with ships are a common cause of death for whales, with thousands of whales dying every year. In order to protect whales, the National Oceanic and Atmospheric Administration (NOAA) of the United States stipulates that the speed of ships cannot exceed the upper limit; but this does not completely solve the problem. Reducing the speed of ships can only reduce the death of whales by 25%-30% .

Author: Cat Tun

Editor: Mai Mai

Title image source: Jonathan Kriz / Wikimedia Commons