Hot answers tagged mammals
15
There is some evidence that fetal development under zero gravity conditions might be problematic.
Wakayama S, Kawahara Y, Li C, Yamagata K, Yuge L, et al. (2009) Detrimental Effects of Microgravity on Mouse Preimplantation Development In Vitro. PLoS ONE 4(8): e6753. doi:10.1371/journal.pone.0006753
The paper is here.
These authors studied aspects of ...
11
For humans, our blood and other tissues have a salinity which is less than that of sea water. There is an old chestnut that our blood has a comparable salinity to sea water - its just a classic example of textbook error.
The major reason we need to drink and excrete (sweat, breath and urine) water is to rid the system of waste- i.e. water soluble chemicals ...
7
Among the great apes, chimpanzees and gorillas live in very hierarchical, male-dominated clans that are often in violent conflict with other clans. Bonobos, on the other hand, lead very peaceful lives, and are female-dominated, using sexual contact as a manner of communication to reduce tension within and between groups. Orangutans are largely solitary ...
6
In mammals there are only two species (known, there may well be others) where males lactate. They are both species of bats and this paper discusses the evolutionary mechanisms that could underlie male lactation. I have ignored human cases because they are more of an unusual occurrence (often brought on by severe dietary stress) rather than an evolved ...
6
Well, technically yes, but most adult dolphins do not have hair:
Unlike most mammals, dolphins do not have hair, except for a few hairs around the tip of their rostrum (beak) which they lose shortly before or after birth. The only exception to this is the Boto river dolphin, which has persistent small hairs on the rostrum.
Whales do, and depending on ...
4
For what concerns amino acids, mice rapidly reject meals that are not balanced in essential amino acids and continue to look for other kind of foods. This behavior is called aversion response and it is an adaptive phenomena that can be observed already 20 minutes after exposure to the unbalanced food. The mechanism involves brain sensing of uncharged tRNAs. ...
4
I'm wondering if it is safe to assume that the approximate number of cells per unit mass in a mammal will remain fairly constant throughout its lifespan.
Not exactly. When a tissue is put under stress, it can respond in four main ways:
Hypertrophy - individual cells get larger. E.g. stressed muscle cells get bigger.
Atrophy - invidivual cells get ...
4
From Wikipedia:
Sloths go to the ground to urinate and defecate about once a week, digging a hole and covering it afterwards. They go to the same spot each time and are vulnerable to predation while doing so. The reason for this risky behaviour is unknown, although some believe that it is to avoid making noise while defecating from up high that would ...
4
At the very least, I know that male primates also have nipples like female, though they are very close relatives to human. On the other hand, in some of my dissection labs, I noticed that male pigs also have nipples just like the female ones. It seems to be the case that most male mammals have nipples, which probably has to do with mammals being ...
3
As it happens someone has just published a theory about this. To save you following the link, I reproduce the abstract below.
I must admit that I had never realised that lactose is synthesised within the organelles of the secretory pathway (β4-galactosyltransferase is a Golgi enzyme and α-lactalbumin is, of course, a whey protein, so is in transit through ...
2
I'd say that unihemispheric sleep and adaptations like it really are sleep - the brain activity on one side of the brain gives a characteristic sleep pattern. It certainly must satisfy the needs of an aquatic mammal like a dolphin or a whale since they have to be partially conscious to breathe by surfacing regularly.
It does seem to affect the brain ...
2
Bats distinguish day and night the same way that other animals do, with an internal circadian clock and by environmental cues (dawn and dusk).
Most bats (over 1000 different species total) are nocturnal, meaning that they are out of their roost and foraging at night. This includes that vast majority of bats, which also echolocate. Some bats, notably ...
2
This is not my field so I am sure there are other examples, but certain neurons will definitely be larger in adulthood than in infancy. There are motor neurons that connect the spine to, for example, the toes. These will grow in length as an animal grows. So, in a human infant they will be a few centimeters long and can reach lengths of over a meter in an ...
2
Whether using quantitative models, or "animal models", I think this is a useful quote to keep in mind:
A model is a lie that helps you see the truth.
-- Howard Skipper
As for evidence that using mice models for human nutrition is justified -- I believe there has been a good deal of research that has provided useful insight on the influence of ...
1
Actually, that is not what is discussed in the question you linked to. The following is a quote from the very comprehensive accepted answer (emphasis mine):
Polyploidy arises easily in both animals and plants, but reproductive
strategies might prevent it from propagating in certain circumstances,
rather than any reduction in fitness resulting from ...
1
My impression is that the use of mice as human models for anything is primarily the result of historical precedent. A lot of work has been done to breed different lines of mice for particular purposes, and a lot of related methodology has therefore been established. Similarly, a lot of comparative genetic/genomic work has been done to characterize ...
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