Nature Trumpet丨When the Asian river dolphin plays with the snake, an indescribable scene happens...

Welcome to the 8th issue of the Nature Trumpet column. In the past half month, we have collected these interesting natural news and research:

1) Only 10 “Giant Pandas of the Sea” left

2) Giant squid washed up on the beach

3) A tropical spider that can dive

4) The Asian pufferfish that uses snakes as toys

5) How trilobites mated

6) Tiny frogs as big as a fingernail

"Giant Panda of the Sea"

Scientists have discovered that with positive action, the vaquita, of which there are only 10 left, is expected to recover its population!

The vaquita (Phocoena sinus) is the smallest marine mammal, only 1.2 to 1.5 meters long. It lives in the Gulf of California in Mexico. It has a cute appearance, dark circles under its eyes, and a lovely "lip line", and can be called the "giant panda of the sea".

Vaquita | WWF

However, they are also the rarest cetacean. In 1997, when the species was first fully surveyed, there were about 570 vaquitas. But in the following 20 years, their numbers have dropped dramatically.

The biggest threat to the vaquita is gillnets. These extremely harmful fishing tools were originally targeted at totoaba, a fish that also lives in the Gulf of California and is fished in large quantities for its swim bladder, which is used to make fish maw. Unexpectedly, gillnets often accidentally injure vaquitas, killing many of them. In 2017, gillnet fishing was permanently banned in the area - but it was too late, and there were only 20 vaquitas left. Now, there are only 10 or fewer vaquitas left in the world.

The first vaquita captured for conservation efforts in 2017 | Vaquita CPR

Luckily, even if only a few vaquitas are left, they still have a chance to recover. Scientists have found that they have a unique advantage: a very low number of potentially harmful mutations in their genes. The small size of the vaquita population will likely force inbreeding, but they are less likely to produce harmful genetic variation when they do. Even more encouraging is that the surviving vaquitas appear to be very healthy—and are actively reproducing. If we can completely eliminate the poachers' gillnets and take positive action, the vaquita may still be here!

Giant squid stranded

Recently, a giant squid carcass was found on a beach in South Africa - its body was about 2.2 meters long, and with its tentacles, it could stretch a total of 3.5 meters.

A giant squid carcass | Alison Paulus

The giant squid is the second largest known invertebrate, living at depths of 300 to 3,000 meters in the ocean. They are huge and mysterious, and are legendary giant sea monsters in ancient times. Until now, people know very little about them, mostly from stranded bodies and remains in the stomachs of sperm whales. When they are discovered, these bodies are generally incomplete, and complete giant squid specimens are very rare.

A giant squid specimen, up to 7 meters long, is frozen in the ice and is currently kept at the Melbourne Aquarium | fir0002 / Wikimedia Commons

The giant squid corpse found this time had a long wound on its tentacles, which researchers believe was caused by the propeller of the ship. It was likely that it encountered a ship in the sea and eventually ran aground and died due to the injury. Researchers estimated that the giant squid was about 2 years old when it died. According to previous scientists' speculation, the giant squid can live up to about 5 years, and its tentacles can reach 13 meters.

Tissue samples from the giant squid have been sent to the Iziko South African Museum, where researchers will conduct DNA analysis. The museum also houses the remains of 19 other giant squids.

Spiders can dive

Spiders are better at diving than humans and can stay underwater for half an hour at a stretch!

This tropical spider that lights up the new skill tree is called Trechalea extensa. Whenever they encounter humans or predators, they hide in the water. The amazing thing is that when the spider dives, the whole body is covered with a layer of air "film", which makes it look silvery and shiny, as if it is wearing silver armor.

Trechalea extensa wrapped in a "thin film" of air in water | Lindsey Swierk

Researchers believe that this "thin film" of air is the secret of the spider's long diving. For spiders, being underwater means being damp and cold, which is no less threatening to their survival than predators. Spiders do not have gills and need to breathe with air. This "thin film" of air can prevent water from rushing into their respiratory organs, and can also reduce heat loss during diving and prevent body temperature from dropping. They are covered with hydrophobic hairs that can cleverly capture air and maintain the "thin film" of air on their bodies.

Asian pufferfish playing with snake

Last August, on the banks of a river in Bolivia, researchers captured a new and confusing behavior among cetaceans: they were playing with snakes!

Bolivian river dolphin (Inia geoffrensis boliviensis) holding a Beni anaconda (Eunectes beniensis) in its mouth | References [4]

The protagonists in the picture are several Bolivian river dolphins, which belong to the subfamily of river dolphins and belong to the freshwater dolphin family like the baiji. The snake being toyed with by them is a Beni anaconda. Anacondas are one of the largest snakes in the world, but this snake hardly moves and can only be held in the mouth of the subfamily of river dolphins.

Extended external genitalia | References [4]

According to researchers' observations, there are at least six sub-pufferfish here. They did not try to eat the snake, but were probably playing games. The adult individuals even showed off the anaconda to the minors. The researchers also captured an indescribable scene: the adult sub-pufferfish even stretched out its penis while playing with the snake, showing sexual arousal - but considering that they are cetaceans, it doesn't seem strange...

As for the anaconda, it did not move at all and was soaked in the water for a long time, so it was likely that it did not die a good death.

Trilobite mating

How did trilobites mate? This question finally had an answer recently thanks to a precious fossil.

This trilobite lived in the Cambrian period about 500 million years ago. Its scientific name is Olenoides serratus. Generally speaking, trilobite fossils rarely retain their legs, usually only the hard shell remains. Among the more than 20,000 known trilobite species, only 38 have left fossils with well-preserved appendages.

The left and right sides of a unique male trilobite fossil | Sarah R. Losso

The fossils studied by scientists this time are very unusual. It has a pair of special appendages under its abdomen. They are shorter and narrower than the front and back appendages, and there are no spines on them for processing food - what are they used for?

Scientists compared the appendages with those of various living arthropods and found that they were most likely claspers, which are organs used by male insects to hold female insects during mating. This allowed scientists to infer the mating method of trilobites: the male would climb onto the female, lie slightly behind her body, and use his claspers to grab the spines on the female's tail to stabilize his body, which would increase the probability of successful mating.

On the left, we can see the short, small appendages on the male's abdomen; on the right, a reconstruction of the trilobite Olenoides serratus mating process | Holly Sullivan

Horseshoe crabs, which are distantly related to trilobites, also have the same mating style, and even violence can occur during mating: many males may grab a female at the same time and compete for position on her body, even if their appendages are torn off. Scientists believe that such fierce competition may also occur in trilobites.

Micro frogs

In Mexico, researchers have discovered six species of tiny frogs, all about the size of a human fingernail. The smallest species, Craugastor candelariensis, is only 13 millimeters long when it is an adult male.

One of the tiny frogs, Craugastor rubinus, on a researcher's fingertips | Reference [6]

Their miniature size isn't their only feature. What's even more surprising is that they never grew up as tadpoles! Most frogs hatch from eggs as tadpoles and then gradually develop into frogs; but these micro frogs hatch as perfect frogs.

The habitat of microscopic frogs, a mountainous region in Mexico | References [6]

Scientists believe that the newly discovered micro frogs live in fallen leaves and are at the bottom of the forest food chain. They are the food source for lizards and birds and play a very important role in the ecosystem. However, the habitat of these frogs is extremely small, which makes their populations very vulnerable. Only by protecting their living environment can we avoid the extinction of these unique species.

References

[1]https://phys.org/news/2022-05-vaquita-porpoises-survive-species-doomed.html

[2]https://www.livescience.com/giant-squid-washes-ashore-south-africa

[3]https://phys.org/news/2022-05-tropical-spider-underwater-minutes.html

[4]https://esajournals.onlinelibrary.wiley.com/doi/10.1002/ecy.3724

[5]https://www.livescience.com/trilobites-mated-with-claspers

[6]https://www.cam.ac.uk/stories/tiny-frogs

Author: Maotun, Mai Mai

Editor: Mai Mai

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