Arxiu d'etiquetes: tongue

Evolution for beginners 2: coevolution

After the success of Evolution for beginners, today we’ll continue  knowing the basics of biological evolution. Why  exist insects that seem orchids and vice versa? Why gazelles and cheetahs are almost equally fast? Why your dog understands you? In other words, what is coevolution?

WHAT IS COEVOLUTION?

We know that it is inevitable that living beings establish symbiotic relationships between them. Some depend on others to survive, and at the same time, on elements of their environtment as water, light or air. These mutual pressures between species make that evolve together, and as one evolve as a species, in turn it forces the other to evolve. Let’s see some examples:

POLLINATION

The most known process of coevolution is pollination. It was actually the first co-evolutionary study (1859) by Darwin, although he didn’t use that term. The first to use the word coevolution were Ehrlich and Raven (1964).

Insects existed long before the appearance of flowering plants, but their success was due to the discovery that nectar is a good reserve of energy. In turn, the plants found in the insects another way more effectively to carry pollen to another flower. Pollination by the wind (anemophily) requires more production of pollen and a good dose of luck to at least fertilize some flowers of the same species. Many plants have developed flowers that trap insects until they are covered with pollen and then set them free. These insects have hairs in their body to enable this process. In turn some animals have developed long appendages (beaks of hummingbirds, butterflies’ proboscis…) to access the nectar.

Polilla de Darwin (Xantophan morganii praedicta). Foto de Minden Pictures/Superstock
Darwin’s moth (Xantophan morganii praedicta). Photo by Minden Pictures/Superstock

It is the famous case of the Darwin’s moth (Xanthopan morganii praedicta) of which we have already talked about. Charles Darwin, studying orchid Christmas (Angraecum sesquipedale) saw that the nectar was 29 cm inside the flower. He sensed that there should exist an animal with a proboscis of this size. Eleven years later, Alfred Russell Wallace reported him that the Morgan’s sphinxs had proboscis over 20 cm long, and a time later they were found in the same area where Darwin had studied that species of orchid (Madagascar). In honor of both it was added “praedicta” to the scientific name.

There are also bee orchids that mimic female insects to ensure their pollination. To learn more about these orchids and the Christmas one, do not miss this post by Adriel.

Anoura fistulata, murcielago, bat
The bat Anoura fistulata and its long tongue. Photo by Nathan Muchhala

But many plants not only depend on insects, also some birds (like humming birds) and mammals (such as bats) are essential to pollination. The record for the longest mammal tongue in the world is for a bat from Ecuador (Anoura fistulata); its tongue measures 8 cm (150% of the length of its body). It is the only who pollinates one plant called Centropogon nigricans, despite the existence of other species of bats in the same habitat of the plant. This raises the question of whether evolution is well defined, and occurs between pairs of species or it is diffuse due to the interaction of multiple species.

PREDATOR-PREY RELATIONSHIPS

The cheetah (Acinonyx jubatus) is the fastest vertebrate on land (up to 115 km/h). Thomson’s gazelle (Eudorcas thomsonii), the second (up to 80 km/h). Cheetahs have to be fast enough to catch a gazelle (but not all, at risk of disappearing themselves) and gazelles fast enough to escape almost once and reproduce. The fastest gaelles survive, so nature selects in turn faster cheetahs, which are who eat to survive. The pressure from predators is an important factor that determines the survival of a population and what strategies should follow the population to survive. Also, the predators will find solutions to possible new ways of life of their prey to succeed.

Guepardo persiguiendo una gacela. Foto de Federico Veronesi
Cheetah hunting a Thomson’s gazelle in Kenya. Photo by Federico Veronesi

The same applies to other predator-prey relationships, parasite-host relationships, plants-herbivores, improving their speed or other survival strategies like poison, spikes…

HUMAN AND DOGS … AND BACTERIA

Our relationship with dogs since prehistoric times, it is also a case of coevolution. This allows, for example, to create bonds with just looking at them. If you want more information, we invite you to read this post where we talk about the issue of the evolution of dogs and humans in depth.

Another example is the relationship we have established with the bacteria in our digestive system, essential for our survival. Or with pathogens: they have co-evolved with our antibiotics, so using them indiscriminately has favored these species of bacteria to develop resistance to antibiotics.

THE IMPORTANCE OF COEVOLUTION

Coevolution is one of the main processes responsible for the great biodiversity of the Earth. According to Thompson, is responsible for the millions of species that exist instead of thousands.

The interactions that have been developed with coevolution are important for the conservation of species. In cases where evolution has been very close between two species, if one become extint will lead to the extinction of the other almost certainly. Humans constantly alter ecosystems and therefore biodiversity and evolution of species. Just declining one species, we are affecting many more. This is the case of the sea otter (Enhydra lutris), which feeds on sea urchins.

Nutria marina (Enhydra lutris) comiendo erizos. Foto de Vancouver Aquarium
Sea otter (Enhydra lutris) eating sea urchins. Photo by Vancouver Aquarium

Being hunted for their fur, urchins increased number, devastated entire populations of algae (consumer of CO2, one of the responsible of global warming), seals who found refuge in the algae nonexistent now were more hunted by killer whales… the sea otter is therefore a key species for the balance of this ecosystem and the planet, as it has evolved along with urchins and algae.

Coevolutive relations between flowers and animals depend on the pollination of thousands of species, including many of agricultural interest, so we must not lose sight of the seriousness of the issue of the disappearance of a large number of bees and other insects in recent years. A complex case of coevolution that directly affects us is the reproduction of fig.

TO SUMMARIZE

As we have seen, coevolution is the evolutionary change through natural selection between two or more species that interact reciprocally.

It is needed:

  • Specificity: the evolution of each feature of a species is due  to selective pressures of the feature of the other species.
  • Reciprocity: features evolve together.
  • Simultaneity: features evolve simultaneously.

REFERENCES

MIREIA QUEROL ALL YOU NEED IS BIOLOGY

Pangolin: poaching is condemning it to extinction

Neither the tiger or elephant or rhino: the most hunted mammals by humans are pangolins, to the point of critically threaten their survival as a species. Discover the only mammal with scales, its current condition and what can we do to prevent the extinction of all species of pangolin in the world.

WHAT IS A PANGOLIN?

manis tricuspis, pangolin, árbol, tree, trepando
Tree pangolin (Phataginus tricuspis). (Photo by Bart Wursten).

The name pangolin (also known as scaly anteater or trenggiling) includes 8 different species distributed by a variety of habitats (tropical rainforests, dry forests, savanna areas, cultivated fields…) in Africa and Asia. They measure between 90 cm and 1.65 m. They are the only family in the order Pholidota: although physically similar, armadillos, sloths and anteaters are not its relatives (order Xenarthra). Most are nocturnal, solitary and shy, so there are still many questions about their biology and behavior in the wild (they don’t usually survive captivity).

MORPHOLOGY

Pangolins are the only mammals with scales: they are made of keratin (like our nails) and give them a look like a pineapple or artichoke. Scales are very sharp and they can move them voluntarily. If pangolins feel threatened hiss and puff, curl into a ball leaving the scales exposed and secrete pestilential acids to ward off predators (tigers, lions, panthers and humans).

leon, leona, pangolin, bola, lion, defensa
An impenetrable defense even to a lioness. (Photo by Holly Cheese)

The claws allow them both climb as digging: terrestrial pangolins hide and breed in underground galleries and arboreal pangolins do the same in hollows on trees. The tail of the tree pangolin is prehensile to attach to the branches. In addition, pangolins are excellent swimmers.
They are mainly bipedal animals: forepaws are so large that force them to walk on its hind legs, with a maximum speed of 5 km/h. Watch a pangolin walking and feeding:

NUTRITION

Pangolin has no teeth and is unable to chew. It feeds on ants and termites, which locates with its powerful sense of smell (the view is underdeveloped) and catch them with its sticky and long tongue (may be longer than the body itself, up to 40 cm). The stones swallowed involuntarily and corneal structures of their stomach help them to crush the exoskeletons of insects. With its powerful claws destroy their nests to access them and avoid their attack plugging his ears and nostrils, besides having an armored eyelid. It is estimated that a pangolin can consume about 70 million insects per year, which makes them important regulators of the population of ants and termites.

lengua, pangolin, tongue
The tongue of the pangolin. (Photo by Wim Vorster).

REPRODUCTION

Pangolins can reproduce at any time of the year. After pregnancy (two to five months, depending on species) only one young is born (African species) or up to three (Asian species).

pangolin, hembra, female, mamas, breast, pecho, tetas
Female pangolin. (Photo by Scott Hurd)

The pangolin is born with soft scales, which begin to harden after two days. When after a month come out of the burrow, they travel on the tail of her mother and become independent at 3-4 months. Their lifespan is unknown, although in captivity an individual lived until 20 years old.

pangolin, baby, cría, zoo bali
Female with her baby in the tail. Bali zoo. (Photo by Firdia Lisnawati)

THREATS AND CONSERVATION

In addition to habitat destruction, the main threat that pangolins face is direct hunting for human consumption. Although there are international laws to protect them, it is estimated that about 100 000 pangolins are hunted annuallyGiven the defense strategy of this animal, poachers only have to catch them of the ground. Like other species, like sharks, the food market and traditional medicine are the main causes of directing the pangolin towards extinction.

pangolin, jaulas, tráfico ilega, illegal trade, bushmeat
Illegal trade in pangolin. (Photo by Soggydan Benenovitch).

WHY PANGOLINS ARE POACHED?

  • Bushmeat is considered a delicacy and an indicator of high social status in Vietnam and China. The pangolin fetus soup is sold as an elixir to increase virility and improve breast milk production. The price of bushmeat on the black market can reach $ 300 per kilo. The price of an individual can reach $ 1,000.

sopa, feto, soup, pangolin, feto, fetus
Pangolin fetus soup. (Photo by TRAFFIC).

  • Blood is sold as a tonic to improve health and as an aphrodisiac.
  • Scales can reach $ 3000 per kilo and are used for almost anything: to cure from acne to cancer. This belief is curious, considering that the scales have the same structure as our fingernails.

pangolín, china, medicina, medicine, tradicional, cura para el cáncer
Products of traditional Chinese medicine made of pangolin. (Photo by TRAFFIC).

All these purported medicinal and magical effects have no scientific basis, making yet more nonsense pangolin smuggling.

CONSERVATION

The population trend of all species of pangolin is declining in some cases to an alarming extent. The IUCN (International Union for the Conservation of Nature) Red List of Threatened Species classifies them as it follows:

RED LIS CATEGORIES IUCN
IUCN Red List categories. (Image from iucn.org)

Because of their status, IUCN restored in 2012 a group of specialists within the Species Survival Commission (SSC) dedicated to pangolins (Pangolin Specialist Group -PangolinSG-). Its main objective are do research to increase knowledge of pangolins, the threats they face and how they can be mitigated to facilitate preservation.

The conservation projects that are being carried out include campaigns to reduce the demand of bushmeat and pangolin scales and the tightening of laws. Still, the total ignorance of populations’ state and low survival in captivity for breeding makes it difficult to design strategies for their conservation.

WHAT CAN YOU DO FOR PANGOLIN?

  • Reject any product derived from this animal, either bushmeat, scales or “miracle” products for the cure of diseases. Read the labels of any traditional remedies, especially if they are from the Asian market, and recall that its hypothetical benefits have no scientific basis, so that you can rethink their use.
  • Share information. If you own new data on pangolins, photos or videos contact with PangolinSG to cooperate with the investigation. Talk about them in your immediate environment to raise awareness and publicize this fantastic single animal.
  • Do a PhD about pangolins. Lot of research on these species is still needed, so if you are a student and you are planning to do a PhD, you can collaborate with PangolinSG with your future research.
  • Become a PangolinSG volunteer. Get involved in the development and implementation of projects and conservation programs.
  • Make a financial donation so PangolinSG can continue its work.

In conclusion, more scientific research, a change of mind and protection policies are needed to prevent the pangolin become an example of extinct species at the hands of ours, as it is about to happen to white rhino.

REFERENCES

MIREIA QUEROL ALL YOU NEED IS BIOLOGY