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| [ARCHIVED] Coconut Crabs | |
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| Topic Started: May 14 2010, 01:17 AM (4,031 Views) | |
| Pando | May 14 2010, 01:17 AM Post #1 |
Obey or I'll send you to the moon
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As the Chinese swamp of 120 MYF nears its end (got a batch ready) I've been wondering about Coconut Crabs. The coconut crab is unique among arthropods that as they went on land their gills didn't turn into body tubes, but is currently in a proto-lung. In the Postozoic it goes further and turns into a real lung, allowing them to grow bigger. What is the biggest size they are able to achieve and what diversity can they have? I'm guessing that they will be able to grow as big as a lot of vertebrates as some seascorpions (including a 7 foot long one) went on land and arthropleura existed. |
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| Pando | May 14 2010, 11:58 AM Post #16 |
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Obey or I'll send you to the moon
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Wow, how did you know that? Those legs are definitely possible. All that needs to happen is that the muscles connect and thin a little. In 120 MYF all primates are carnivorous because only a species of carnivorous primates kept the primate line going, and the monkey bats don't arrive till Pangea, when Antarctica crashes with Pangea. So the monkey niche is definitely open, which coconut crabs can take. They can also take some niches from the rodent geckos, after which is what most of them do in 200 MYF. But there can also be scavengers. |
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| StinglessBee | May 14 2010, 01:00 PM Post #17 |
Adolescent
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Might it be possible for the exoskeleton to get thinner, allowing the problems to go? If not, then perhaps the exoskeleton could be hollow. I once had a few plans for land hermit crabs some time ago. Since I'm not using them, might they be of use to you? Here's the link. It was originally part of an insect dominated world that I have long since abandoned. |
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| Pando | May 14 2010, 01:20 PM Post #18 |
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Obey or I'll send you to the moon
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What kind of diversity could they achieve? |
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| MitchBeard | May 14 2010, 10:19 PM Post #19 |
proud gondwanan
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Tertiary education for the win.
Wait, what?
I would imagine you could have just as much diversity as you have in monkeys at the moment. Omnivores, frugivores, sloth like herbivores, sap specialists that are constantly wounding their feeding trees to get their precious sap, mangrove specailists that stay in the trees during high tide and come down at low tide to pick up scraps, purely terrestrial oppurtunists feeding on detritus from above. I'd imagine they wouldn't do too bad as opportunists in forests in general, not restricted to the tropics. Probably some scavengers that live in savannahs that hide in burrows like their ancestral modern coconut crabs. Edited by MitchBeard, May 14 2010, 10:20 PM.
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| Pando | May 14 2010, 11:30 PM Post #20 |
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Obey or I'll send you to the moon
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I like your ideas. But what kind of diversity could they achieve? By that I mean body shapes, not diets. The coconut crabs by 25 MYF aren't fully terrestrial, they still need to go in water every once in a while and the lung isn't completely developed, by by then they can be bigger. By 90 MYF they can have real expansion, but most will stay in the tropical Mediterranean forests that exist in the former rain forests. They survive the extinction and rapidly diversify in 120 MYF. Also, the Gympie Crab is your idea. Besides, why would Gympie even be introduced there? And I don't really focus on plants as my knowledge is nearly 0. |
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| Margaret Pye | May 15 2010, 12:56 AM Post #21 |
Adult
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Moulting. Worry about moulting. Arthropod moulting means that they have to transiently lose their skeletons in order to grow. The giant Carboniferous arthropods probably got through this stage by spending it in water, where gravity didn't matter. Your crabs could do this. Or they could evolve a continually growing exoskeleton... Mitch, do you have any idea how that could work histologically? Maybe have it in a series of plates that grew from the edges, like tetrapod bones do? But yes, the presence of lungs in some large land crabs is really interesting for speculation. |
| My speculative dinosaur project. With lots of fluff, parental care and mammalian-level intelligence, and the odd sophont. | |
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| MitchBeard | May 15 2010, 02:50 AM Post #22 |
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proud gondwanan
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No, they would not go back to the water, they would hide in burrows. If you put a modern coconut crab in water and it will drown. But they still spend their larval form in the water. You could always have crabs rock up on the Australian coast and find some gympie, seeing as they spend their larval form in the plankton they're quite good at dispersing. They could have quite diverse body forms, but to the layman they would all just look like weird crabs. It would all be in the proportions various appendages compared to each other and body size. I don't think tetrapod bone growth scheme would work for them. I have no idea how it would. But I only have a vague idea of how shedding works. I'll have another skim through my textbooks. I don't think they would have too much trouble conquering any environment that an ectotherm can dig a burrow in to be honest. |
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| Pando | May 15 2010, 02:59 AM Post #23 |
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Obey or I'll send you to the moon
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They can live in burrows, and near molting time they stock up in food. During the molting period (around a week) they live off their stored food and are growing in soft exoskeleton. |
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| MitchBeard | May 15 2010, 03:07 AM Post #24 |
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proud gondwanan
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Dude, they're ectotherms; they can go without food through the entire moulting period. They'd probably block the entrance to their burrows though. |
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| lamna | May 15 2010, 03:55 AM Post #25 |
 
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And plus they would have trouble eating if their face is squishy. On probably with them filling the monkey niche is that they can't be that active. All that armour is heavy, and being cold blooded can't help. Something more sloth-like is probably. |
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| MitchBeard | May 15 2010, 06:27 AM Post #26 |
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proud gondwanan
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Judging by where pando is putting them, I don't think being an ectotherm isn't an issue. Insects are really quite troubled with being sluggish and placated, definately  I think the largest they would get arboreally would be the size a pinapple, averaging around the size of an orange. Except for any actually slothlike ones which would be able to get bigger. I think they would actually have to get around in trees like sloths, at least on the smaller branches. Only their claws have any kind of grasping appendage on them. So hanging from them seems like the most sensible thing to do. I just had a lovely mental image of pith helmed explorers with machetes looking up into the canopy above their path watching these lovecraftian fruit skittering upside down along the highest branches at top speed and launching themselves across the gap, rotating 180 degrees so their legs face down and crashing into the trees on the otherside. |
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| Practically Uninformed | May 15 2010, 09:21 AM Post #27 |
Informed enough to care
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..."Either it's that slug I ate, or I'm having an epiphany!" Could the coconut crab develop a hard-shelled egg, like amniotes did long ago? That could be the key to their future success! |
| You may be a king or a lil' street sweeper, but sooner or later, you'll dance with the reaper! | |
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| MitchBeard | May 15 2010, 09:54 AM Post #28 |
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proud gondwanan
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They pretty much already do. from wiki
The problem more lies in the fact that they spend a month in the plankton being zoea... 
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| Ook | May 15 2010, 10:00 AM Post #29 |
not a Transhuman
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all neocaridina shrimps and many caridina shrimps carry small number (from 20-to 60) of bigger eggs,where young shrimps spend their larval stage and when they hatched,they looks like miniature adult...caridina shrimps,that have got larval stage in salt watter or fresh water have got very big number of small eggs(1000-3000) neocaridina sp.white pearl....without larval stage  caridina japonica with larval stage Edited by Ook, May 15 2010, 10:10 AM.
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| Pando | May 15 2010, 10:23 AM Post #30 |
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Obey or I'll send you to the moon
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What kind of movement would they have in the trees? Monkey niche of today is free. Primates at 120 MYF take the niche of cats. Their closest competition would be the rodent geckos. And with the world about 6 degrees hotter than today, being an ectotherm won't be an issue. |
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