#anomura

[alphynix]

Strange Symmetries #13: The Hermit Crab Cycle

Hermit crabs are crustaceans that first appeared at the start of the Jurassic, about 201 million years ago. Despite their common name they aren't actually true crabs, instead being a classic example of convergently evolving a crab-like body plan via carcinization.

They also have noticeably asymmetric bodies, with abdomens that coil to one side and differently-sized front claws.

Pagurus bernhardus by Arnstein Rønning | CC BY 3.0

And while modern hermit crabs are famous for inhabiting scavenged snail shells, their fossil record suggests this wasn't always the case.

Originally, they seem to have lived in ammonite shells.

Palaeopagurus vandenengeli lived in what is now northern England during the Early Cretaceous, about 130 million years ago. Around 4-5cm long (~1.6-2"), it was found preserved inside the shell of the ammonite species Simbirskites gottschei.

Its left claw was much larger than its right, and together they would have been used to block the shell opening when it was hiding away inside. And while the exact shape of its abdomen isn't known, it probably asymmetrically coiled to the side to accomodate the spiralling shape of the host shell.

Hermit crabs seem to have switched over to using gastropod shells by the Late Cretaceous, around 90-80 million years ago, possibly due to marine snails developing much stronger sturdier shells during this period in response to the increasing prevalence of specialized shell-crushing predators. The more upright snail shells would also have been much easier to drag around the seafloor than ammonite shells – and meant that they were ultimately less affected by the total disappearance of ammonites during end-Cretaceous mass extinction.

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[ketrinadrawsalot]

Decapocember Day 4: The infraorder Anomura is full of decapods called crabs that aren't actually crabs (brachyurans are true crabs). Carcinization led to many of them becoming crab-shaped. One feature common in anomurans is that two of their appendages are significantly smaller than the others, making them look like they have eight limbs.

[patheticmosasaur1]

today's invertebrate..........albunea speciosa

albunea speciosa tends to the growth, trimming it whenever it pulsates and glibling to it when needed

however if the growth starts to popumble and shape then it'll have to be measured geometrically!!

I know this is really sad, but it has to be done, for albunea speciosa's safety, and for the many winds that gumb on unwanted skin

glorpiness rating: {{★☆★♤, but really unfortunate

source

[frumpytaco]

Got out on the rocks this weekend to celebrate Tiny Crustacean Fest.

Top: the tide was really fuckin low

2nd row: A very distressed mother and the brood of babies she released from her marsupium when I put her in the water to look at. :( Absolutely refuse to make an ID on her.

3rd row, left to right: Ischyroceridae (Ischyrocerus?), Aoridae (Aoroides?), Sphaeromatidae

4th row, left to right: Melitidae, Ericthonius sp.

5th row, left to right: Petrolisthes cinctipes, Romaleon branneri, Cancer productus

6th row, left to right: Hemigrapsus nudus (I've never seen one so big in CA!), Lophopanopeus bellus, some weird orange thing without an exoskeleton idk (jk i'm pretty sure it's Triopha maculata)

[birdblues]

Three-lobed Porcelain Crab

[typhlonectes]

Aeglidae

The Aeglidae are a family of freshwater crustaceans currently restricted to South America. They are the only anomurans (hermit crabs, squat lobsters, et al.) to be found in fresh water except for a single hermit crab species, Clibanarius fonticola, on Espiritu Santo, Vanuatu. 

Aeglids resemble squat lobsters in that the abdomen is partly tucked under the thorax. The notable sexual dimorphism in the abdomen is related to the behaviour of carrying fertilised eggs on the pleopods.

Aeglids are omnivorous, preferring plant matter, but also eating adult insects, molluscs, fish and fly larvae...

Read more: https://en.wikipedia.org/wiki/Aeglidae

photograph by Jaocowiki | Wikipedia CC

[crabmeiser]

THIS IS NOT A CRAB

THIS IS AN ANOMURA AND IF I HAVE TO EXPLAIN TO ONE MORE PERSON THAT COCONUT CRABS ARENT ACTUALLY CRABS, I AM GOING TO GO INSANE.

crab of the day is...

the coconut crab (birgus latro)

fun fact: i have reoccurring nightmares about these things!

real fun fact: they are the largest known terrestrial arthropod!

[anomura]

achelata –> anomura

[forsuperbang]

I couldn't be a carcinologist, it seems too overwhelming (but awesome!)

[historicalbookimages]

🔭 Report on the Crustacea (Brachyura and Anomura) collected by the North Pacific exploring expedition, 1853-1856 City of Washington, Smithsonian Institution, 1907.

[daily-crabbys]

hello!! i have a crab fact!! (sorry if you arent taking submissions for crab facts i just thought i would supply a fact!)

the main difference between "true" and "false" crabs is how many legs they have. true crabs have eight legs, while false crabs have six!

around 250 million years ago, crab lineage split into two main groups, Brachyura (true crabs) and Anomura (false crabs)!

https://www.abc.net.au/news/science/2022-09-18/crab-convergent-evolution-crustacean-australia-marine-biology/101388282

^ this is the source i found it from by the way, i would recommend reading it since i'm not the best at explaining it! thats all from me :)

Crab Fact(summarized): The difference between true and false crabs is the number of legs that they have.

[wrmhles]

describe yourself with 10 photos already on your phone!!

tagged by @survivedthenight and @drylite lalala love u guys

tagging @medarda @anomura @pauliemartins and im double tagging @galetops but no pressure anyone heheee <3

[survivedthenight]

5 boring facts about me

thank you @onyxsboxes for the tag! 💞

i have a brown cat!

i used to play viola until i was 18 and i regret giving it up

i became inactive on here for like 3+ years but now i’m back bc of mota lmaooo

i have to be up in 4 hours for work

my favourite cocktail is a bramble

tagging @wrmhles @drylite @anomura and anyone else who wants to do this lol

[majorbuckyegan]

5 (more) boring facts about me

Thank you for the tags @caustinen and @caterina07121 🫶

I can't cook to save my life, but I can bake

I used to have a bracelet made of john taylor's (from duran duran) bass strings, but I lost it :(

I'm left handed

I've only ever lived in one house my entire life

I've worked in a hospital for the last eight years

Tagging: @swifty-fox @spaceshipkat @angelfruittree @anomura @amiserableseriesofevents @whirlpool-blogs

[typhlonectes]

Description of a new species of the Petrolisthes galathinus complex from the Caribbean Sea, and resurrection of Petrolisthes occidentalis from the East Pacific (Crustacea, Anomura, Porcellanidae)

Alexandra Hiller, Bernd Werding

Abstract The Petrolisthes galathinus complex currently consists of six American species distributed in the West Atlantic, including the amphi-American P. galathinus. All species in the complex are similar in their adult morphology but differ in colour, size, larval morphology, and shape of the adult sternal plate. The West Atlantic species have different geographic ranges, which overlap in the southern Caribbean. Previously published molecular data support the monophyly of the complex, and the reciprocal monophyly of each described species and further clades corresponding to different colour morphs. Here, the morph P. caribensis “Blue” is described as Petrolisthes coeruleus sp. nov., and Petrolisthes occidentalis is formally resurrected for the Pacific individuals of P. galathinus. By adding these two species to the P. galathinus complex, this now consists of eight species. Colour illustrations of all species and colour morphs are provided and their geographic distributions and ecological ranges are discussed and updated.

Read the paper here:

Description of a new species of the Petrolisthes galathinus complex from the Caribbean Sea, and resurrection of Petrolisthes occidentalis from the East Pacific (Crustacea, Anomura, Porcellanidae) (pensoft.net)

[n0rtist]

Could I suggest Pokemon based on the geological time periods of Earth's history, such as Paleozoic and Cenozoic?

Having a design represent a whole era might be hard to do, but my carcinization mon is taking a look at how one species evolved over time. I saw a comment or two saying how Anodukes is just a crab, but I was referencing the Anomura infraorder which are "fake crabs" including hermit crabs and squat lobsters (Anodukes more inspired by the latter).