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New terrestrial arthropods
Topic Started: Jul 27 2017, 07:24 PM (900 Views)
IIGSY
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I wanted to make this thread about the plausibility of various aquatic arthropod groups becoming terrestrial. There are several points I want to discuss.

Despite how massively diverse trilobites are, not a single terrestrial or amphibious one has been discovered. Not one. Hell, I don't even think there are any freshwater ones either. Why is this? Even eurypterids experimented with terrestrial forms (Hibbertopterus and Megarachne)

What are some good candidates for new lineages of terrestrial arthropods? As of now, it seems crayfish are your best bet, as a lot of crayfish spend considerable amounts of time on land and some are even effectively terrestrial. Horseshoe crabs seem like a wildcard. On one hand, they always spawn come to the shore to spawn, yet their method of feeding is heavily dependent on water.

What are some transitions that you think would be interesting? Some nice examples that come to mind are aglaspids, krill, ostracods, stomatopods, and, of course, trilobites. But what I think would be most interesting are pycnogonids. Due to how drastically reduced they are, it would be intriguing to see how they could adapt to life on land.

There are several trends that terrestrial arthropods tend to evolve. All terrestrial groups have lost biramous appendages and most breathe through spiracles.

What do you think of this? Do you have any questions or points to add?
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kusanagi
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Do any pycogonids feed on macroalgae or seagrasses? If they made the jump to herbivorous diet from sucking at sessile invertebrates, which is probably less than the jump from carnivory to herbivory in arachnids, they could probably adapt to freshwater and land habitats in such a way. (There are no sessile invertebrates on land remember so there has to be an intermediate lifestyle.) Then like certain sucking bugs they could become secondarily carnivorous but I have no idea how they would breathe on the land.

OTOH the oldest woodlice are Eocene, if there was likely a ghost lineage for reasons of vicariance they still colonised the land later than arachnids, myriapods or hexapods proving it can be done. Again OTOH but there are tracks thought to have been made by trilobites during excursions on beaches the way crabs and limulids will come out of the water. I have to wonder if trilobites were spawning in the sandmaybe or just out scavenging coastal detritus.
Edited by kusanagi, Jul 27 2017, 09:24 PM.
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IIGSY
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kusanagi
Jul 27 2017, 09:16 PM
Do any pycogonids feed on macroalgae or seagrasses? If they made the jump to herbivorous diet from sucking at sessile invertebrates, which is probably less than the jump from carnivory to herbivory in arachnids, they could probably adapt to freshwater and land habitats in such a way. (There are no sessile invertebrates on land remember so there has to be an intermediate lifestyle.) Then like certain sucking bugs they could become secondarily carnivorous but I have no idea how they would breathe on the land.

OTOH the oldest woodlice are Eocene, if there was likely a ghost lineage for reasons of vicariance they still colonised the land later than arachnids, myriapods or hexapods proving it can be done. Again OTOH but there are tracks thought to have been made by trilobites during excursions on beaches the way crabs and limulids will come out of the water. I have to wonder if trilobites were spawning in the sandmaybe or just out scavenging coastal detritus.
There are no herbivorous pycnogonids to the extant of my knowledge, but it wouldn't be that hard to evolve.


I've heard that some eurypterids may have mated like horseshoe crabs. Interesting speculation.


Oh, and what does OTOH mean?
Projects
Punga: A terraformed world with no vertebrates
Last one crawling: The last arthropod

ARTH-6810: A world without vertebrates (It's ded, but you can still read I guess)

Potential ideas-
Swamp world: A world covered in lakes, with the largest being caspian sized.
Nematozoic: After a mass extinction of ultimate proportions, a single species of nematode is the only surviving animal.
Tri-devonian: A devonian like ecosystem with holocene species on three different continents.

Quotes


Phylogeny of the arthropods and some related groups


In honor of the greatest clade of all time


More pictures


Other cool things


All African countries can fit into Brazil
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kusanagi
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OTOH is Net 1.0 for off the top of my head.
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Inceptis
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In my opinion, Talitrids are at the front of a new land colonization by arthropods. They've barely moved beyond the ocean, but they have great promise. In fact, quite a few arthropods have evolved to breathe air, but just haven't moved beyond the coastline. Coconut crabs are another interesting lead on this theme. Maybe Triops could pull it off as well in an isolated environment.

Also, terrestrial pycogonids already exist in spec if you didn't already know, courtesy of Dragonthunders in Cambrian Mars.
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IIGSY
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Inceptis
Jul 28 2017, 06:16 PM
In my opinion, Talitrids are at the front of a new land colonization by arthropods. They've barely moved beyond the ocean, but they have great promise. In fact, quite a few arthropods have evolved to breathe air, but just haven't moved beyond the coastline. Coconut crabs are another interesting lead on this theme. Maybe Triops could pull it off as well in an isolated environment.

Also, terrestrial pycogonids already exist in spec if you didn't already know, courtesy of Dragonthunders in Cambrian Mars.
Sandhoppers are cool. Squat lobsters would be funny
Projects
Punga: A terraformed world with no vertebrates
Last one crawling: The last arthropod

ARTH-6810: A world without vertebrates (It's ded, but you can still read I guess)

Potential ideas-
Swamp world: A world covered in lakes, with the largest being caspian sized.
Nematozoic: After a mass extinction of ultimate proportions, a single species of nematode is the only surviving animal.
Tri-devonian: A devonian like ecosystem with holocene species on three different continents.

Quotes


Phylogeny of the arthropods and some related groups


In honor of the greatest clade of all time


More pictures


Other cool things


All African countries can fit into Brazil
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HangingThief
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kusanagi
Jul 27 2017, 09:16 PM
Do any pycogonids feed on macroalgae or seagrasses? If they made the jump to herbivorous diet from sucking at sessile invertebrates, which is probably less than the jump from carnivory to herbivory in arachnids, they could probably adapt to freshwater and land habitats in such a way. (There are no sessile invertebrates on land remember so there has to be an intermediate lifestyle.) Then like certain sucking bugs they could become secondarily carnivorous but I have no idea how they would breathe on the land.

Why would they have to become herbivorous to become terrestrial?

Making the jump from feeding on cnidarians to feeding on marine plants is bigger than starting to feed on some animal group that's present on land, like molluscs or fellow arthropods.


Side note: the OTOH acronym is pretty confusing since it can also be interpreted as "on the other hand"
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kusanagi
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Jul 28 2017, 11:59 PM
Inceptis
Jul 28 2017, 06:16 PM
In my opinion, Talitrids are at the front of a new land colonization by arthropods. They've barely moved beyond the ocean, but they have great promise. In fact, quite a few arthropods have evolved to breathe air, but just haven't moved beyond the coastline. Coconut crabs are another interesting lead on this theme. Maybe Triops could pull it off as well in an isolated environment.

Also, terrestrial pycogonids already exist in spec if you didn't already know, courtesy of Dragonthunders in Cambrian Mars.
Sandhoppers are cool. Squat lobsters would be funny
Are you disawayre there are terrestrial squat lobsters in South America? Some amphipods are already living on land as well. As I said before the land is an extreme environment, things are pushed to the extremes all the time by competition but most have very limited successes in space and time because others got there first.

And pycogonid herbivory, cognitively the jump from recognising sessile animals as prey to finding plant prey is probably less than the leap to recognising motile animals so. Arthropods (hemipterans) have jumped from herbivory to carnivory with piercing mouthparts as a precedent.
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Flisch
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Wait, since when was Megarachne partially terrestrial?
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kusanagi
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Flisch
Jul 29 2017, 07:22 AM
Wait, since when was Megarachne partially terrestrial?
Megarachne was a hibbertonopteroid, they were amphibious to terrestrial(?).
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HangingThief
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kusanagi
Jul 29 2017, 05:03 AM


And pycogonid herbivory, cognitively the jump from recognising sessile animals as prey to finding plant prey is probably less than the leap to recognising motile animals so. Arthropods (hemipterans) have jumped from herbivory to carnivory with piercing mouthparts as a precedent.
First of all... no it isn't. Especially since there's no shortage of sessile and slow moving arthropods and mollusks.

The thing is, you mention the fact that hemipterans have jumped from herbivory to carnivory, but that's just not the same as jumping from carnivory to herbivory. Animal food sources are typically harder to obtain, but much easier to digest for something that isn't adapted for feeding on them. Many animals typically thought of as herbivorous, from caterpillars and millipedes to cows and deer, won't pass up the nutrition packed, easily digested meal that running across a little bit of animal flesh offers.
Some groups certainly have made such a jump, but it usually if not always involves parts of plants that are easier to digest and have more nutrition like seeds and fruits. That isn't really a big thing in the ocean. Sucking the fluids from marine plants would involve taking up and expelling a ton of excess carbohydrates and processing what very little protein there is to be had in such a food source.
I'm not saying a herbivorous sea spider is impossible, but it certainly isn't a necesarry step to getting them on land. There's no reason why they couldn't just feed from things like barnacles and slow moving mollusks in the intertidal zone and then gradually make the transition to preying on land animals.
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IIGSY
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kusanagi
Jul 29 2017, 05:03 AM
Insect Illuminati Get Shrekt
Jul 28 2017, 11:59 PM
Inceptis
Jul 28 2017, 06:16 PM
In my opinion, Talitrids are at the front of a new land colonization by arthropods. They've barely moved beyond the ocean, but they have great promise. In fact, quite a few arthropods have evolved to breathe air, but just haven't moved beyond the coastline. Coconut crabs are another interesting lead on this theme. Maybe Triops could pull it off as well in an isolated environment.

Also, terrestrial pycogonids already exist in spec if you didn't already know, courtesy of Dragonthunders in Cambrian Mars.
Sandhoppers are cool. Squat lobsters would be funny
Are you disawayre there are terrestrial squat lobsters in South America? Some amphipods are already living on land as well. As I said before the land is an extreme environment, things are pushed to the extremes all the time by competition but most have very limited successes in space and time because others got there first.

And pycogonid herbivory, cognitively the jump from recognising sessile animals as prey to finding plant prey is probably less than the leap to recognising motile animals so. Arthropods (hemipterans) have jumped from herbivory to carnivory with piercing mouthparts as a precedent.
Wait what? Terrestrial squat lobsters are a thing? No way.

And I dont think diet is going to be a problem for terrestrial pycnogonids. The real problem is respiration and supporting themselves.
Projects
Punga: A terraformed world with no vertebrates
Last one crawling: The last arthropod

ARTH-6810: A world without vertebrates (It's ded, but you can still read I guess)

Potential ideas-
Swamp world: A world covered in lakes, with the largest being caspian sized.
Nematozoic: After a mass extinction of ultimate proportions, a single species of nematode is the only surviving animal.
Tri-devonian: A devonian like ecosystem with holocene species on three different continents.

Quotes


Phylogeny of the arthropods and some related groups


In honor of the greatest clade of all time


More pictures


Other cool things


All African countries can fit into Brazil
Offline Profile Quote Post Goto Top
 
kusanagi
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My thoughts for stage 1 were of terrestrial spiders that went partially herbivorous by sucking plant juices. The example of sucking bugs was stage 2 should a move to raptorialism be requested. Now of sourse plants are sessile so predatory shieldbugs went overnight from herbivores to raptorials. But my understanding is most pycogonids are like most nudibranchs dietary specialists which is why they are difficult in aquaria. Then it would be easier to jump to macroalgae, and then to plants, and then whatever is ingesting the same kind of plants (happened at least 2ce in insects).
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Inceptis
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Insect Illuminati Get Shrekt
Jul 29 2017, 10:52 AM
kusanagi
Jul 29 2017, 05:03 AM
Insect Illuminati Get Shrekt
Jul 28 2017, 11:59 PM
Inceptis
Jul 28 2017, 06:16 PM
In my opinion, Talitrids are at the front of a new land colonization by arthropods. They've barely moved beyond the ocean, but they have great promise. In fact, quite a few arthropods have evolved to breathe air, but just haven't moved beyond the coastline. Coconut crabs are another interesting lead on this theme. Maybe Triops could pull it off as well in an isolated environment.

Also, terrestrial pycogonids already exist in spec if you didn't already know, courtesy of Dragonthunders in Cambrian Mars.
Sandhoppers are cool. Squat lobsters would be funny
Are you disawayre there are terrestrial squat lobsters in South America? Some amphipods are already living on land as well. As I said before the land is an extreme environment, things are pushed to the extremes all the time by competition but most have very limited successes in space and time because others got there first.

And pycogonid herbivory, cognitively the jump from recognising sessile animals as prey to finding plant prey is probably less than the leap to recognising motile animals so. Arthropods (hemipterans) have jumped from herbivory to carnivory with piercing mouthparts as a precedent.
Wait what? Terrestrial squat lobsters are a thing? No way.

And I dont think diet is going to be a problem for terrestrial pycnogonids. The real problem is respiration and supporting themselves.
1) What is this terrestrial squat lobster?

2) Support-wise, the gene that governs muscle growth just needs to be altered in some way so there's more than a single cell in each muscle, and maybe slightly thicken the exoskeleton. Then for respiration, the chelifores and palps can slightly reduce, but become gill-like before completely disappearing, while the proboscis becomes more flexible, similar to species that have already lost the former.
This was getting fairly big.
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Dragonthunders
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kusanagi
Jul 29 2017, 11:18 AM
My thoughts for stage 1 were of terrestrial spiders that went partially herbivorous by sucking plant juices. The example of sucking bugs was stage 2 should a move to raptorialism be requested. Now of sourse plants are sessile so predatory shieldbugs went overnight from herbivores to raptorials. But my understanding is most pycogonids are like most nudibranchs dietary specialists which is why they are difficult in aquaria. Then it would be easier to jump to macroalgae, and then to plants, and then whatever is ingesting the same kind of plants (happened at least 2ce in insects).
It seems a little strange, interesting to experience but does not necessarily seem to be a main path to evolve and conquer the land, I would imagine that they could already be properly established if there are already primary consumers that can provide enough food for a zoophage population.
Does that idea also work for scorpions? I ask because not only spiders have been the only one of its kind to conquer land so it could help.
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