[HN Gopher] Deer don't regrow antlers the way lower animals regr...
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Deer don't regrow antlers the way lower animals regrow limbs
Author : gumby
Score : 34 points
Date : 2023-04-01 21:56 UTC (2 days ago)
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| chrisco255 wrote:
| Why did antlers evolve to be shed each year rather than semi-
| permanent structures?
| flavius29663 wrote:
| Not an expert but if I was to guess logically, it's because of
| their function in the first place: it's an immense waste of
| resources to grow them, so being able to do so proves the
| individual is a healthy male, worthy of passing on his genes.
| Growing a new set of antlers each year (and each year it's a
| larger structure) proves how many resources you can accumulate
| and then waste, kinda similar to how lawns were maintained by
| medieval English lords: just to show that they can waste
| valuable land for nothing of value.
|
| So if you think of the evolutionary pressure, there MUST have
| been some deer at some point that didn't shed their antlers.
| The question is: would a female choose a male that tries to be
| economical about it's resources and save the antlers for next
| year? Or would the female choose the male that can take that
| resource hit every year? It's kindof like asking present day
| women: do you prefer a male with a wasteful Lamborghini or a
| male with an economical VW or Toyota hybrid? I think we know
| what the answer is...
|
| Also, biology has another angle to it, but I think this could
| have been overcomed evolutionary: the antlers grow form the
| top, so in order to keep the current antlers and then still
| grow them, the deer would have had to keep the velvet healthy.
| Being such large sharp tools, used for seasonal combat, keeping
| the velvet could be hard. I think this wouldn't have been un-
| surmountable if the deer chose this strategy, but I think my
| first explanation might be the most likely one.
| jancsika wrote:
| > It's kindof like asking present day women: do you prefer a
| male with a wasteful Lamborghini or a male with an economical
| VW or Toyota hybrid? I think we know what the answer is...
|
| Would love to hear how "common knowledge" like this deals
| with circular dependencies. And since this is HN, please
| reply as quickly as possible, and only from first principles.
|
| Problem: "present day woman" turns her head to the man
| stepping out of the lambo, who is shorter than the man in the
| hybrid, so she turns her head toward the taller man, who is
| driving a hybrid, so she turns her head toward the man
| stepping out of the lambo, who is shorter...
| pazimzadeh wrote:
| So, proof of work?
| oh_sigh wrote:
| Perhaps because if the semi permanent structure gets damaged,
| the chances of mating for that animal effectively go to zero.
| ftxbro wrote:
| By the way, 'lower animals' isn't the preferred nomenclature in
| biology anymore. They have had a comparable amount of
| evolutionary time to specialize in their own things (maybe even
| effectively more if they have larger populations or smaller
| generation times), and they are more refined at some stuff while
| humans are more refined at other stuff (like advanced sweat pores
| and big brain).
|
| Humans: lose our ancestral abilities of limb regeneration
|
| Also humans: call our distant cousins who didn't lose those
| abilities as 'lower'
| GordonS wrote:
| Out of curiosity, what is the preferred nomenclature nowadays?
| tedunangst wrote:
| Regenerative limb enjoyers.
| rintakumpu wrote:
| If you want to differentiate between mammals and other
| vertebrates you could simply say "other vertebrates".
| Karawebnetwork wrote:
| Non-mammalian vertebrates also
| bloppe wrote:
| Higher
| emaginniss wrote:
| Follicly challenged species or Animals of Scales (AoS)
| [deleted]
| neom wrote:
| I can't remember if it was on here I saw it or on twitter, but a
| Moose shaking off it's antler is one of the more...
| uncomfortable... things I've seen:
|
| https://www.youtube.com/watch?v=3vT2gsJ8KbY&ab_channel=Guard...
| kayodelycaon wrote:
| I just kind of assumed antlers grew like nails. Sharks grow new
| teeth all the time. I don't see why "regeneration" would ever be
| involved in the first place.
| polishdude20 wrote:
| What's interesting with antlers is if one of them is cut or
| damaged in a certain way, when both fall off later and regrow,
| both will grow into the shape of the damaged antler.
| gumby wrote:
| Wow, that's really interesting!
| Sharlin wrote:
| Well, because your assumption was false. Antlers grow nothing
| like nails and hair which do share the same mechanism. Ruminant
| horns are a mix of the two, with a hard keratin shell covering
| living tissue.
| tomrod wrote:
| I don't understand how the hypothesis that they are the same was
| under consideration. This seems sort of obvious to me that
| fingernails, antlers, hair, and other keratin growths aren't the
| same as growing bones and limbs. But I know little about the area
| -- what am I missing in my hasty, armchair thoughts?
| LinuxBender wrote:
| I think you are right. The only difference from fingernails is
| that when the antlers fall off there is bleeding. I get drops
| of blood where I feed the deer especially when they spar cross-
| pack. When they shed their antlers and some of them have bloody
| nubs that heal then form a smooth round nub and then the cycle
| repeats.
| Sharlin wrote:
| > I think you are right. The only difference from fingernails
| is that when the antlers fall off there is bleeding.
|
| This is far from the only difference, starting from the
| material (living bone tissue vs non-living keratin), and
| process of growth (the living tissue grows and branches like
| a tree, vs. being extruded like from a 3D printer by a
| special tissue at the root of the nail).
|
| Hair and nails are the same. Antlers are very unlike those
| two. Horns are a mixture, with a keratin shell covering
| living bone tissue.
| LinuxBender wrote:
| I do not disagree with the composition. The reason I
| compare them to fingernails is that when a tip breaks off
| the tip does not regenerate. The broken tip remains broken.
| The antler may continue to grow out from the base but the
| tip will stay gone until they shed and regrow new antlers.
| Sharlin wrote:
| But the point was that I don't think they grow out from
| the base but instead from the tips! Branching wouldn't
| even be possible otherwise. A broken off antler tip may
| not regenerate, yes, but the reason is more like it
| develops scar tissue over the wound rather than just
| being made of inanimate protein like nails are.
| excalibur wrote:
| If you lose an entire fingernail, there's likely to be blood.
| LinuxBender wrote:
| Yup and since humans trim or pick at their nails they don't
| get long enough to rip out as easily. I assume people with
| the extreme cases of YNS probably bleed when those gnarly
| nails get caught on things.
|
| Deer antlers shed even when they are tiny. I have a box
| full of their tiny ones that a neighbor turns into artwork.
| causi wrote:
| _This seems sort of obvious to me that fingernails, antlers,
| hair, and other keratin growths aren 't the same_
|
| Antlers are bone, not keratin. During the growth process they
| have skin, blood vessels, and nerves.
| meindnoch wrote:
| You're confusing antlers with horns.
|
| "Each antler grows from an attachment point on the skull called
| a pedicle. While an antler is growing, it is covered with
| highly vascular skin called velvet, which supplies oxygen and
| nutrients to the growing bone. Antlers are considered one of
| the most exaggerated cases of male secondary sexual traits in
| the animal kingdom, and grow faster than any other mammal bone.
| Growth occurs at the tip, and is initially cartilage, which is
| later replaced by bone tissue. Once the antler has achieved its
| full size, the velvet is lost and the antler's bone dies. This
| dead bone structure is the mature antler. In most cases, the
| bone at the base is destroyed by osteoclasts and the antlers
| fall off at some point. As a result of their fast growth rate,
| antlers are considered a handicap since there is an immense
| nutritional demand on deer to re-grow antlers annually, and
| thus can be honest signals of metabolic efficiency and food
| gathering capability."
|
| https://en.wikipedia.org/wiki/Antler
|
| To summarize:
|
| - antlers grow from the tip, while hair/fingernails/horns grow
| from the base
|
| - antlers are living bone tissue, while hair/fingernails/horns
| are dead keratinous tissue
|
| - antlers are made from differentiated tissues (cartilage,
| bone, skin, blood vessels), while hair/fingernails/horns are
| just a keratin matrix
| klyrs wrote:
| I have no intuition here, so I read the article:
|
| > They found a group of cells - called PMCs - believed to be
| crucial for limb regeneration in frogs and salamanders - to be
| abundant in deer antlers as well as in the tips of mouse
| digits.
|
| So there's some positive evidence behind the mechanism being
| similar -- the same sort of cells are responsible for
| regeneration in deer and frogs. Which leads us to the question,
| how similar is this process? That was investigated by the
| scientists, who found that the source of PMCs to be different:
|
| > However, the researchers also discovered that the PMCs in
| antler-generating tissues were formed by a sharply different
| process to lower-order vertebrates, according to the study.
|
| The article continues in some detail as to the specific
| differences.
| gumby wrote:
| Others have responded as to how antlers are different.
|
| But FYI keratinocytes are quite mysterious too. How do hair and
| nails grow only in one direction? That's quite strange and
| nobody knows.
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