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| Questions that don't need their own topics vol.2; New and fresh | |
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| Topic Started: Jan 4 2018, 11:18 AM (26,891 Views) | |
| GreatAuk | Jan 17 2018, 01:13 PM Post #106 |
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Northern Penguin
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Why can't Cephalopoda go into fresh water? |
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| Empyreon | Jan 17 2018, 01:42 PM Post #107 |
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Are you plausible?
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From http://www.abc.net.au/science/articles/2013/01/16/3670198.htm
The article goes on to say that, because of other idiosyncrasies of cephalopod design, creatures that did attempt to venture into freshwater would likely be outcompeted by others. |
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Take a look at my exobiology subforum of the planet Nereus! COM Contributions food for thought
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| LittleLazyLass | Jan 17 2018, 04:20 PM Post #108 |
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Proud quilt in a bag
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Now inactive Heteromorph explored these constraints and possible solutions in this old thread. |
totally not British, b-baka! You like me (Unlike)I don't even really like this song that much but the title is pretty relatable sometimes, I guess. Me What, you want me to tell you what these mean? Read First Words Maybe | |
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| Sceynyos-yos | Jan 17 2018, 05:26 PM Post #109 |
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dheubewes wedor
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Why are dead red blood cells thrown out of the body, instead of dumped into the stomach and recycled? |
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| lamna | Jan 17 2018, 05:56 PM Post #110 |
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I still don't understand why cephalopods have not evolved freshwater forms. It seems to be a simple adaptation, that has happened dozens, if not hundreds of times through the evolution of life, including multiple times in molluscs. All that article says is "cephalopods can't live in freshwater because they don't have adaptations that let them live in freshwater". It then lists some unusual adaptations they have, while not mentioning how those relate. Obviously something is keeping them out of freshwater, they are a common marine animal and have been around for four hundred million years. But nowhere online seems to give an actual reason. Frustratingly, the interview that article was based on might have had it. |
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| Tartarus | Jan 17 2018, 07:20 PM Post #111 |
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Prime Specimen
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Perhaps the reason cephalopods haven't gotten into freshwater is merely coincidental. That they just happen to have not done so (unless there existed prehistoric freshwater cephalopods who never made it into the fossil record). This doesn't mean that they are unable to ever to evolve freshwater forms and I honestly see nothing that would prohibit freshwater cephalopods from ever evolving in the future. |
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| Empyreon | Jan 17 2018, 07:30 PM Post #112 |
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Are you plausible?
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Maybe a good way to think about this is to think about what the simplest series of steps from a marine to freshwater cephalopod? The environmental difference is largely about salinity, so what kind of cephalopod would benefit from the switch? The attention should likely focus on the liver, which is developed to handle marine level salinity, and would likely have some debilitating results if it's expected to function as it does in freshwater. Probably the most likely candidates would be individuals with malformed kidneys, that can't handle saltwater, and by luck happened to be in brackish areas that their malformed kidneys happen to handle better. Their offspring inherit the "bad" kidneys, and also prefer the fresher waters. Easy enough, right? But they also need to hunt and breed and survive there beyond just being able to handle water salinity, if a true "freshwater squid" is to evolve. Are they able to slip into an empty niche, or do they have to bump someone else out? Are their offspring more vulnerable to predation here than with their marine cousins? Do they have specific dietary requirements? So the article goes on to list several unique features about cephalopods, and yes, it doesn't clearly connect them to the question at hand, but they aren't irrelevant. It mentions hemocyanin, which doesn't transmit oxygen as efficiently as hemoglobin, so cephalopods have adapted a neurology to most effectively use this "slower" circulatory system. In order to be "top-order predators", as the article calls them, they've had to specialize themselves in such a way that adaptations for freshwater are less likely. Pulverizing food so that it doesn't destroy the brain as it passes through the esophagus may also limit success in freshwater settings, again, depending on other factors such as competitors. Ultimately, I don't think the article is saying that freshwater cephalopods can't happen, it's only offering some reasons as to why they haven't. |
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Take a look at my exobiology subforum of the planet Nereus! COM Contributions food for thought
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| Rodlox | Jan 17 2018, 11:50 PM Post #113 |
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Superhuman
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whether or not they can't live in fresh water...what about them conquering land...or at least doing like hermit crabs and coconut crabs? |
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| lamna | Jan 18 2018, 06:38 AM Post #114 |
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There are some cases of animals moving directly from the sea to the land, but a freshwater step is vital if you want to ever be more than a coastal animal. Given the fact that land molluscs need to remain moist, that means they need to adapt to freshwater. It's possible that cephalopods can live in freshwater but simply haven't, or that they even did at one point and we don't know about it. But it's very, very unlikely. Firstly, because aquatic environments are excellent at preserving fossils, and most cephalopods have some hard parts that can fossilise. The second is the incredible age of the group. Cephalopods evolved in the Cambrian and were already recognisable by the Ordovician. They predate fish, they have lived though 5 mass extinctions and three ice ages. They have had ample opportunity to exploit these habitats and have not. I think "X animal fills Y niche, so Z animals can't fill it" is overstated. Look how many different types of fish have adapted to live in freshwater, and how many invertebrates. |
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| Empyreon | Jan 18 2018, 12:51 PM Post #115 |
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Are you plausible?
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I'd say that's fair. It certainly seems to come up often enough that it sounds a little pat, and is likely not the whole story. You bring up excellent points about how cephalopods have survived for geologic time periods, and had ample opportunity to shift into freshwater life and havent. Could it just come down to never having the need? Maybe they do so well where they already are that there just aren't any that make the jump? After all, just because a niche is open doesn't necessarily mean anything has to fill it, let alone cephalopods. And nowhere have I seen anything about why a cephalopod couldn't move to freshwater. It could all just be chance: the right mix of creatures needing to relocate combined with a new environment, and the means to secure that niche may have just never come up in our history. Which is where future and alt history can come in!
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Take a look at my exobiology subforum of the planet Nereus! COM Contributions food for thought
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| Even | Jan 18 2018, 02:16 PM Post #116 |
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Roman Catholic theistic evolutionist
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Dead red blood cells are digested by macrophages, their globin returned into amino acids, the amino acid part of the heme removed as billirubin, and the iron core of the heme recirculated by transferrin to the liver. They're not simply thrown out of the body |
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| Lowry | Jan 18 2018, 04:03 PM Post #117 |
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ARH-WOOOOOOOOOOOOOOOOOOOO
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How much does everyone know about venom and their glands, more importantly the relocation or replication of venom glands... Do lionfish have individual venom glands for each spine? Would a venom gland be a benign enough replication without causing too much issues in the body, I know this is why simple duplication of limbs isn't possible but would venomous spurs be replicate-able over time? |
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| Rodlox | Jan 18 2018, 04:55 PM Post #118 |
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Superhuman
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pretty sure each spine has its own gland. and yes, envemonating tools arise easily enough and often in multiple lineages |
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.---------------------------------------------. Parts of the Cluster Worlds: "Marsupialless Australia" (what-if) & "Out on a Branch" (future evolution) & "The Earth under a still sun" (WIP) | |
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| Strychnos | Jan 18 2018, 05:36 PM Post #119 |
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So wait, why is replication of limbs something that messes up body structure? I know that limb duplication isn't something vertebrates can do, but I don't know why. |
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| Lowry | Jan 18 2018, 05:51 PM Post #120 |
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ARH-WOOOOOOOOOOOOOOOOOOOO
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They'd have nothing to connect to, it'd just be a horrifically deformed growth of bone that would have little to no muscle attachments and would actually cause issues. You would have to duplicate not only the bone structure but entirely rework the muscular structure of a vertebrate to implement a new limb, so a sudden change like limb duplication just isn't feasible |
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