martes, 18 de octubre de 2016

As a total amateur, I am just wondering if the very early mammals had hedgehog-like quills rather than hair. Am I correct?

As an total amateur, I am just wondering if the very early mammals had hedgehog-like quills rather than hair. Am I correct?
Since birds developed from reptiles, feathers must have developed from scales. Between these two, there were quills giving better warmth than scales. But hedgehogs also have quills so did those quills develop entirely independantly from bird quills or did quill bearing reptiles give rise to both?

 It seems that there are three subquestions here:

- A) What was like the feature that eventually evolved into hair in mammals?
- B) Did mammal quills evolved independently from bird quills?
- C) Did quill bearing reptiles give raise to both (mammals and birds).

Mammals, birds and reptiles are all amniota*.  It is very well documented that birds derived from reptiles (sauropsida), while the clade that gave origin to mammals (synapsida) split before the aparition of reptiles. In other words, mammals don't come from reptiles:

Source of the image: Evolution | Kusumi LabKusumi Lab 

Due to their increased surface/volume ratio, smaller animals find it more difficult to internally thermoregulate because their insides are closer to their outsides. Having insulating fur when tiny would be helpful.
So the answer to question A) is probably -and only probably- like whiskers.

Following the footprints of the type of keratin present in the the skin of mammals and birds, he suggests that mammal hair comes from "hypothetical glandular integument of the first amniotes, which may have presented similarities with common day terrestrial amphibians", whileas feathers "may have evolved independently of squamate scales, each originating from the hypothetical roughened beta-keratinized integument of the first sauropsids. The avian overlapping scales, which cover the feet in some bird species, may have developed later in evolution, being secondarily derived from feathers."

I.e, hair neither comes from reptile scales nor from feathers. Also, feathers don't come from reptile scales. So the answer to question B) is yes, mammals' quills evolved independently from birds quills, and the answer to question C) is no, quill bearing reptiles didn't give rise to them both.
But...what did hair look like when it appeared for the first time?

When did hair arise?. It seems that Pelycosaurs lacked scales, and propbably also all basal therapsids.  Accordingly with wikipedia "The hairs of the fur in modern animals are all connected to nerves, and so the fur also serves as a transmitter for sensory input. Fur could have evolved from sensory hair (whiskers). The signals from this sensory apparatus is interpreted in the neocortex, a chapter of the brain that expanded markedly in animals like Morganucodon and Hadrocodium.
The more advanced therapsids could have had a combination of naked skin, whiskers, and scutes. A full pelage likely did not evolve until the therapsid-mammal transition."

Due to their increased surface/volume ratio, smaller animals find it more difficult to internally thermoregulate because their insides are closer to their outsides. Having insulating fur when tiny would be helpful.
So the answer to question A) is probably -and only probably- like whiskers.

Interesting readings:
and for not very shy readers the discussion about the first paper posted in archosaurheresies is interesting  (The origin of feathers and hair (part 2: hair) ). But, caution, the blog reflects the opinions of his author who clearly opposes to many of the views of paleontologists. So you have to read it with an analytical eye.

viernes, 14 de octubre de 2016

Why is the kakapo important?

Singularities of kakapos:
  • The ancient, flightless Kakapo is the world's rarest and strangest parrot, it only lives in New Zealand.
  • It the only flightless and nocturnal parrot.
  • It is, as well, the heaviest in the world, weighing up to 3.5 kilograms (8 lbs).

Here is a pic of an adult with two juvenile, obviously a family. You may notice how strange is to find a parrot raising their chicks in a kind of den in the ground.

Curiosities about the character of Kakapos:

The kakapo is one of the most outrageously funny, loving and strangest  birds in a land renowned for unusual creatures. Life moves very slowly  for the kakapo - it seems locked in another time.  It is slow to breed  and lives longer than any other bird. 

Why so many people in New Zealand cares about Kakapos:
  • Because they tend to identificate their "identity" with the singularities of their nation, and the many singular species New Zealand has are, without doubt, part of the gross bulk of these singularity.
  • Because New Zealand has already a sad history of loosing many singular species.

Why conserving kakapos has to do with conserving biodiversity in New Zealand:

It is a matter of conserving enough "wild" habitats for the kakapo to live in, or loosing the kakapo forever. We in Spain (and Portugal) have a very similar problem, we have our Iberian lynxes that are so madly endagered as a species. If we are not able to manage the enough territory in the conditions required for them to live in, we will only have them as a remaining captive individuals.

Why conserving kakapos is important for the rest of the world:
For two reasons:
- The people that will come after us.
- If we choose to forget endagered species, and continue growing and populate the Earth only with us and our pets and cattle, will get to a point where we won't be able to feed ourselves acording with this trend. We are just a piece of the domino that is further of the extinction point than is the kakapo today, but the falling of the rest of the pieces will reach us in a moment or other.
It is just time to think about this.

More about the kakapo:
New Zealand Ecology - Kakapo
The Fabulous Kakapo Parrot

More about extinctions in New Zealand:
List of extinct animals of New Zealand
Stephens Island wren

A vision of the extinction of the Stephen Island Wren, written by myself (Spanish):
El falso mito del gato del farero (1/3): El cuento, el pájaro y la isla

jueves, 13 de octubre de 2016

Do whales have noses?

Why shouldn't they?. Whales are mammals that have gone back to water, they can surprise us in many ways, none the less their agility and beauty of movements in the water despite of their size, but they have never refused to breath air.

They have, yes, but in a deconstructed way. It is like a child had disambled the parts of a nose and spread them in the head of whales, and them they had developed or enlogated some pieces to connect them.

What  has happened to the nasal bones and the maxilar bones is known as  telescoping, the premaxilary and maxilary bones are told as having been  extended at their rostral tips, while their caudal tips are pulled back  and up over the frontal bone.

Here is a verygood illustration comparing the anatomy of cetaceans nasal and oral cavities with other mammals'.

lunes, 10 de octubre de 2016

Why do so many huskies have heterochromia?

I'm not very proud about this one, because I don't know why, that is the genetic-development way in which the influence of one gene of albinism is inhibited in one eye and not in the other of the developing fetus, and this specific matter, factors that influence the expression or not of a given genetic character is fundamental to understand many inborn problems in newborns. 

Very interesting question. It is obviously due to a evenly distribution of melanin between the two eyes.  In huskies it always includes one eye blue (1).

The reason is that this breed was developed by inbreeding together with the standards of the breed allowing blue eyes, and also heterochromia (for example malamute's standard is brown eyes, and heterochromia is not allowed), so the condition is not restricted by those standards.

Genetically, there are four ways of getting blue eyes in dogs, three of them related to the color of the coat causing white spots, patterns or diluted patterns, and only one that it is not linked to the coat. This last form is what huskies have and hence the color of the eye doesn't interefer with the normal pattern of the breed.
Breeders say that this is caused by a single gene, but i don't see they prove it in any way, because they don't tell wether it is a dominant character, codominant or recesive. So, i just tell what they say, but i don't give it entire credit.
This is the explanation given:

Lastly, blue eyes can be inherited as a completely separate gene,  unaffected by coat colour. This gene is, however, rare. It occurs  occasionally in the Border Collie and similar breeds, but mainly it's  seen in the Siberian Husky. Huskies can have one or both blue eyes, regardless of their main coat colour,  ranging in shade from almost white to sky blue. This is particularly striking when seen on black dogs.

Now, this only explains why do they inherit blue eyes independently of the pattern of the fur, but not why they have different eye color. And this last is very important, as they have the same genes in all their body, it seems that the development of the melanin is inhibited in one eye, and not in the other. This is not that strange (2). But what factor causes this inhibition is what remains unexplained, and I have found information regarding this issue.

Here is a good site about dog genetics:
Dog Coat Colour Genetics

(1) Blue eyes are due to the Tyndall scattering of light in the eye, a phenomenon similar to that which accounts for the blueness of the sky called Rayleigh scattering. There are not blue pigments in the dogs eyes. Eye color is thus an instance of structural color and varies depending on the lighting conditions, especially for lighter-colored eyes.

(2) Heterochromia is very frequent in cats that have some form of albinism (there are various genes that lead to complete or partial inhibition of color in cats). This seems indicates that the "enviromental" factors opering during the development of both eyes are independent, although coat patterns tend to be very simmetrical.
I find this exciting to study the development of the fetus, and perhaps it could give us some ideas to understand some newborn defects such as cleft palates.
As i told it is a very-very interesting quesion and I wish I knew more about this.

viernes, 7 de octubre de 2016

Music: Do animals other than mammals and birds respond to music?

I will give two anwsers here.

1) Many pet owners share observations of how some music calms or disturbs their reptile pets. So it seems that yes, some animals respond to it. There are many forums where you can find testimonies about this. The scientific validity of these observations is not guaranteed, though.
2) Yes, in some cases. But to have a better understanding of what supposes music for many animals, we should step out from our anthropocentric concept of music.
I find this answer more difficult to explain, in spite of this what I really think. So, give me a try:

I have reading some material regarding this question for some time since you posed it. What I had in mind was that there are many animals that produce different kind of rythmic sounds for some different reasons. Cicadas and crikets males use them to attract females. Male crocs shake the waters in a very charactristic way when mating season, and the interesting thing here is that other crocs are sensible not only to the visual display but to the sound produced. Also, surprinsingly, males crocs make calls during this mating season. Frogs tend to make choirs of calls in given moments of the day. Some lizard owners like to share videos of their pogonas purring, like this one (and I dn't know wether the critter is enjoying the petting season, but it seems so):


So there is an appalling bunch of evidence that animals (other than birds and mammals) use and enjoy rythmic sounds. And as I found out, I was not the first one to notice it.

There is a new discipline called zoomusicology that  is the study of the music of non-human animals or rather the musical aspects of sound pr communication produced and received by animals. To my understanding this discipline is in its very begginings and has failed so far to produce a good definition of what is music generated by animals. However there are very interesting new views arising from it, like the reflexion of David Teie that all the music human made is directed to the specific hearing abilities of humans, and hence music directed to animals should be writing taking into account their particular characteristics. The results of one study, led by Charles T. Snowdon, indicate that the  species-specific music written by Teie was the first music that was  shown to be effective for any species other than human in a controlled  study. The most provocative implication of this research is that animals  respond to human music in remarkably human ways. Or, more accurately,  that there is something about musical stimulation that is so universal  as to include beings beyond the human.

It is important to remark that the interest of the effects of music in animals started well before our time:

Ibn al-Haytham's Treatise on the Influence of Melodies on the Souls of Animals in the 11th century was the earliest treatise dealing with the effects  of music on animals. In the treatise, he demonstrates how a camel's pace  could be hastened or retarded with the use of music, and shows other examples of how music can affect animal behaviour and animal psychology,  experimenting with horses, birds and reptiles.

As it seems animals sounds have been understimated by our science for a long period of time.

Interesting readings:

jueves, 6 de octubre de 2016

Are there any animals that create objects for recreation or is creating objects to be used in recreation something that only humans can do?

Más de Quora. Que sí, que tengo que currarme las traducciones. Pero bueno, mientras tanto es más fácil tirar de material que ya tengo escrito.

I know that dolphins invent quite complex games and partake in recreational drug use, as well as blow bubbles to amuse themselves. New Caledonean crows create tools for foraging and the complexity of those tools improves over generations and spreads like human culture. Orang-utans build umbrella like objects to keep dry, and Chimpanzees have been taught to do all kinds of things and pass that knowledge on.

I haven't seen any examples of the combination of inventive recreational activities with practical tool creation to create recreational objects, however.

The closest to a tool made by a animal with the only purpose of playing that has come to my mind are sticks used by young chimps "girls" to play with them as dolls.

Young females of the Kanyawara chimpanzee community in Kibale National Park, Uganda,  use sticks as rudimentary dolls and care for them like the group's  mother  chimps tend to their real offspring. The behavior, which was  very rarely  observed in males, has been witnessed more than a hundred  times over 14  years of study.
Chimp "Girls" Play With "Dolls" Too—First Wild Evidence

A photo of some of the sticks use by this young "mums" and carefully colected by the field investigator. Imagine them behind the chimp and thinking "drop it, drop it right now, i wanna go home", a day in a life of a scientitist. (Sounds exciting? :)).
"The  stick serves no immediate function, they just carry it—sometimes for a  few minutes, other times for hours," study leader Richard Wrangham, a biological anthropologist at Harvard University, said via email.
The article after telling about this behaviour on natire versus nurture and maternal instinct that, well, it is not exactly of my taste. But they have documented the use of these dolls, by females -what is an added point- and thus have gained my sympathy.

martes, 4 de octubre de 2016

Cymbalophora pudica, una foto

Se trata de una mariposa nocturna del Sur de Europa y Norte África. Las orugas son muy poco vistosas pero los adultos son impresionantes dentro de los 2 a 4 cm que llegan a medir.
Ésta que fotografié estaba en el suelo y era media tarde. Lo desgastado del borde de las alas me indica que ya no tenía mucho tiempo por delante, lo cual le daba aún más fuerza a esa belleza que me impulsó a captarla.