#anomurans

[sitting-on-me-bum]

Pink Hairy Squat Lobster - (Lauriea siagiani)

Part Dr. Seuss, part arachnophobe's nightmare, this beguiling marine crustacean known as the “pink hairy squat lobster” (Lauriea siagiani) is not a lobster at all. Also called a fairy crab, the "lobster" belongs to the group of crabs called Anomurans and is just a half-inch long.

Subaluna / Shutterstock

[clannfearrunt]

Incredible. Four years later I've stumbled back into essentially the same exact general design just with 40% better understanding of the anatomy I'm working with

makes sense. I do still have the same brain after all

slightly new crabs design (?) 

[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.

[charring58]

#Hermitcrabs are anomuran decapod crustaceans of the superfamily Paguroidea that have adapted to occupy empty scavenged mollusc

[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

[lyriakisser]

idk why tumblr made me unfollow you im just trying to send you crab facts 👿 anyway.

Crabs are crustaceans, and along with shrimps and lobsters, they are called "decapods" - crustaceans with five pairs of legs. There are two major groups of animals called "crabs"- the brachyurans or "true crabs" and the anomurans or "false crabs". In general, true crabs have four pairs of legs used for walking, while false crabs have just two or three. True crabs have a short abdomen which is curled underneath their bodies; false crabs have a longer abdominal segment that is less well-protected. Hermit crabs are false crabs which use borrowed mollusk shells to house and protect their abdomens.

tge term "true crab" is so funny to me for no reason at all

[j-19zeta7]

It's ok, you can call them pillbugs, people will know what you're talking about regardless.

It's like when people call animals in the Anomuran family "crabs", even though they don't count as true crabs, people will still know what you're talking about anyway.

Pillbug spotted on the backyard. Me too, little guy. Me too.

[life-on-onarth]

4

[spacepiratedog]

MerMay 2022 Day 6

Where does it say mermaids can't be crustaceans??? Or more specifically, "anomuran decapod crustaceans of the superfamily Paguroidea"? Hermit crabs are cool, I used to love holding them in my hands (even after getting pinched once 🥲). I had a lot of fun with this one, it was a fun concept for me. 😄

[straightlightyagami]

found notes from biology when I first learned about carcinisation.

Convergent evolution to crab shape

Anomurans and brachyuran

Crab shape allows more movement and evasion of predators

Study analyzed all fossil crustaceans from mesozoic era and found increase in crab shapes. Further studies indicate that it took place during the cretaceous period.

[encyclopika]

Animal Crossing Fish - Explained #115

Brought to you by the marine biologist with the imposter!

CLICK HERE FOR THE AC FISH EXPLAINED MASTERPOST!

So, at the beginning of this crab...thing I’ve been on, I said one of these crabs was an imposter and indeed! Today’s crab is not really a true crab. Ya see, there are a ton of ocean-dwelling animals that have little pincers, and hard exoskeletons, and jointed leggies, and round, squat bodies...and although all of these features represent “CRAB” in our brains, I gotta tell ya...not all of them are. Today’s crab, the Red King Crab, is one such imposter. 

Another super-rare critter now living right off your beaches, this is another one that you’ll have to give chase to. They move FAST. My strategy with these is to trap them against the border-net, otherwise, I think it’s impossible. Good luck! It’s available now until March in the Northern Hemisphere, and that makes a lot of sense, considering the real life animal prefers the waters of the North Pacific, particularly the Gulf of Alaska, the Bering Sea, and other cold places it’s been introduced, such as the Barents Sea. Could also explain why it’s put into the cold, ice tank with the Sea Butterfly and other cold-water friends. As you can imagine, the Red King Crab is in the game because there is a HUGE market for it, and like most crabs I’ve tried, it’s delicious. 

But wait! This isn’t a crab! Even though the Red King Crab (Paralithodes camtschaticus) has all the hallmarks of being a crab, it just isn’t. Remember when we went through what a crab is when we covered the Mitten Crab? Well, if you don’t, here it is, but basically, crabs are Arthropods (Phylum), Crustaceans (SubPhylum), Malacostracans (Class), and then Decapods (Order). Decapods are so frickin’ diverse, even though the lay-person would probably put these animals in one of 4 (unofficial) “groups” - crabs, shrimp, lobsters, and crayfish. After that, it’s really hard to convince people that hermit crabs, king crabs, porcelain crabs, mole crabs, and the hairy stone crab are not true crabs under the true crab InfraOrder Brachyura (the group in which all previous crabs we’ve covered this week have been a part). Instead, all of those are in a totally different InfraOrder called Anomura, the sister group to Brachyura. So, really, these animals are just “crab-like decapods”. (And yes, I feel like an entire nerd right now, but bare with me.) 

Take a good hard look at the Red King Crab...notice how it only has 8 visible legs like a spider? This is because the very back pair of legs on Anomurans are highly reduced and are usually tucked up into the body to clean their gills. This is definitely NOT a feature of the majority of crabs (there are always exceptions), so if you see a “crab” with 8 legs, you are most likely looking at an Anomuran.  

From : https://www.saildrone.com/news/tagging-red-king-crab-acoustic-tracking

All these groups of “fake” crabs have actually all evolved this “crab-shape” independently. It seems to be a popular thing to do, to turn into a crab. It’s so popular, that we actually have a word for it in science: carcinisation. And I’ll leave you with a very good video that explains why this happens, from one of my favorite channels on YouTube, PBS Eons!

What a great way to end crab week. :3 And there you have it. Fascinating stuff, no?

[earthstory]

Life without the sun

One of the most fascinating biological environments on Earth is found on the floor of the ocean. Kilometers below the surface, no light reaches these areas, so for life to exist, it must have a different energy source. This entire ecosystem is living off the energy of the Earth. Rocks deep inside the earth contain elements in reduced form; they haven’t reacted with oxygen because there is no free oxygen inside the Earth. At places like mid-ocean ridges, the Earth itself brings these elements up to the surface and exposes them to the ocean. Life in these settings can take up some of these elements, like iron, react it with oxygen in the water, and use that energy to sustain itself. The scientist’s term for this life would be chemosynthetic – using chemistry to gain energy (contrast that term with photosynthetic, as plants are).

This entire seafloor is covered with white crabs (10 cm scalebar). There’s no reason for any of the organisms here to waste energy by coloring themselves; there’s no sunlight so nothing can be seen anyway. This is an area rich with a type of life very different from anything we’re familiar with in our lives up at the surface, almost 2500 meters above.

-JBB

"Dense mass of anomuran crab Kiwa around deep-sea hydrothermal vent" by A. D. Rogers et al. - A. D. Rogers et al. in PLoS Biology. Licensed under Creative Commons Attribution 2.5 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Dense_mass_of_anomuran_crab_Kiwa_around_deep-sea_hydrothermal_vent.jpg#mediaviewer/File:Dense_mass_of_anomuran_crab_Kiwa_around_deep-sea_hydrothermal_vent.jpg

[scissorrace]

YEAH BC FOR SOME REASON ALL THE LOBSTERS WANNA EVOLVE INTO CRAB RESEMBLING CREATURES???

there are "true crabs" (brachyurans) and crabs that aren't really crabs (anomurans). anomurans include animals like hermit crabs, and various other "crab like" creatures that have evolved that way bc the true crab body plan is just really good at surviving for some reason. it is believed since their carapace is wider and covers more area than other decapods like lobsters, that this prevents or lessens injury. there's an awesome video on this by pbs eons:

basically you could say that these crabs are "sus"

[brachyurans]

petrolisthes spp. are anomurans and that is the brachyuran crab hemigrapsus nudus meaning not only are you wrong up to the goddamn INFRAORDER you are a wildlife photographer living in oregon who can’t recognize the only intertidal crab in the entire pacific northwest with fucking polka dots you ABSOLUTE BUFFOON

[vicshush]

[Text ID:

Twitter user franz, crab content (@franzanth) writes

"Hello, artist. Nice art you have there. You know what would make it better? Crabs. But crabs are hard to draw, you say. I agree. That's why I teamed up with @jopabinia & @JaviPaleobiovto make this cheat sheet so you too, can #InsertAnInvert into your artwork with confidence."

Instructional art poster titled "How to crab"

To the left of the central image is an introduction : "A visual guide for people who want to draw crabs, but can't figure out which part goes where.

Can't blame you, really. They have too many parts and they're all over the place.

"Crabs" refers to two groups of animals, the true crabs (Brachymura) and false crabs (Anomura).

This guide covers the "typical crab" body shape from both groups.

However, there are many outliers, like the frog crab, a brachyuran, or the hermit crab and mole crab, both are anomurans.

And many others. Many, many others. Really. Crabs are weird."

The central image is a multi-colored, simplified, segmented anatomy drawing of a crab, arms arcing over its head. The main body shows a dividing line down the center with the explanatory text labeling the halves "seen from Above", where the shell hides roughly the first quarter of the legs, and "seen from Below", where all of the small, initial leg segments are fully visible.

Beneath the central image are the citations, "References : - Davie, P. J., Gguinot, D., and Ng, P. K., 2015. Anatomy and functional morphology of brachyura. In Treatise on Zoology-Anatomy, Taxonomy, Biology. The Crustacea. Volume 9 Part C (2 vol.) (pp. 11-163) [artist-added commentary on this work =] Brill. - Wolfe, J. M., Luque, J., and Bracken-Grissom, H. D., 2021. How to become a crab : Phenotypic constraints on a recurring body plan. BioEssays. DOI 10:1002/bies202100020."

To the right of the central image are the credits : "Put together by Franz Anthony, crab drawer for hire ; Dr. Jo Wolfe & Dr. Javier Luque, actual crab scientists (yes, they both have a PhD in crabs). Funding by NSF-DEB #1856679.

Version 1.0 published 2 April 2021

tweet @franzanth for updates

This guide was published as part of the #InsertAnInvert project where we encourage artists to put unsolicited crabs in their artwork. Because everything looks better with inverts in it."

Left sidebar:

"Arm parts. In a crab claw, only one finger is movable. The other, fixed finger is fused to the "palm".

[Pincing range of the claw is illustrated, with the claw closed and opened.]

These segments [two of three chunks that make up the main part of the crab's arm are highlighted in dark blue] function like our arm but without the elbow. The wrist [final chunk of the crab arm is highlighted in dark green] is flexible and helps the crab swing its arm around.

The first segment [a small gray square of a segment] attaches the whole arm to the body. Not visible from above."

Right sidebar:

"Leg parts. The first segment [a small gray square of a segment] attaches the whole leg to the body. Not visible from above.

Three segments [highlighted in red] that don't bend very much. Usually only the big one [the segments are two small squares and a rectangle roughly three times their combined length] is visible from above, like our thigh.

Two segments [highlighted in orange, visible in the central image as angling off the prior leg segment at about a 20-degree angle] that don't bend very much. Think of our lower leg.

The tip of a limb [segment highlighted in yellow] usually pointy."

Two circles below illustrate the bending of the crab's 'knee'.

"All parts of a crab's legs can bend. However, in most" typical-looking" crabs, the joint between the red and orange segments is the only one that can make acute angles like our knees. Disclaimer: there are so many exceptions to this rule, because crustaceans like to make things overly complicated."

Bottom bar:

"Body parts. The carapace or back shell comes in many shapes and forms. It's often spiky to protect the crab from predators. Having a wide, flattened carapace is one of the characteristic features of carcinized crabs. [A variety of crab shell shapes meeting this description are shown in a line.]

The pleon, which looks like a flap, is the same structure as the abdomen or "butt" in insects or shrimps. Having a pleon that's folded under the carapace is one of the characteristic features of carcinized crabs."

Bottom right sidebar:

"True or false?

True Crabs [a crab head, four short silver lines between the eyes] :

Two short pairs of antennae between the eyes.

False Crab [a crab head, two long silver lines framing the eyes, two short silver lines between the eyes] :

A pair of (usually long) antennae outside the eyes, another shorter pair between.

True Crab [four crab legs] :

Four pairs of visible walking legs.

False Crab [three crab legs and a red 'x' where a fourth isn't] :

Three pairs of visible walking legs, the fourth pair is usually tiny and hidden."

Following the art poster are two more replies from the original poster:

"If you decided to put a crab in your artwork, @ us and use the hashtag #InsertAnInvert! We're also committed to making this a month-long learning opportunity, so we'll be tweeting crab art resources throughout April 2021 a.k.a #CrabMonth. Ask us questions if you're stuck!"

"If you feel like drawing crabs, check out Crab Database for inspiration. The site has lots of photos showing all sorts of weird crabs, it's a good site for procrastination [procrastination]. https://crabdatabase.info/en/crabs"

/end text]

[literatelobstersareliterate]

Carcinisation - Wikipedia

Porcelain crabs resemble crabs, but are more closely related to squat lobsters and hermit crabs

In evolutionary biology, carcinisation (or carcinization) is a hypothesised process whereby a crustacean evolves into a crab-like form from a non-crab-like form. The term was introduced by L. A. Borradaile, who described it as "one of the many attempts of Nature to evolve a crab".[1]

Carcinisation is believed to have occurred independently in at least five groups of decapod crustaceans[2], most notably king crabs,[3][4] which most scientists believe evolved from hermit crab ancestors. The other examples are the family Porcellanidae, or porcelain crabs (which are closely related to squat lobsters),[5] the hairy stone crab Lomis hirta,[6] the coconut crab Birgus latro, and true crabs.[7] The example of king crabs (family Lithodidae) evolving from hermit crabs has been particularly well studied and, although some doubt this theory, there is considerable evidence in its favour. For example: most hermit crabs are asymmetrical, so that they fit well into spiral snail shells; the abdomens of king crabs, even though they do not use snail shells for shelter, are also asymmetrical.[8][9][10][11]

An exceptional form of carcinisation, termed "hypercarcinisation", is seen in the porcelain crab Allopetrolisthes spinifrons.[12] In addition to the shortened body form, A. spinifrons also shows similar sexual dimorphism to that seen in true crabs, where males have a shorter pleon than females.[12]

References

Jump up ^ Patsy A. McLaughlin; Rafael Lemaitre (1997). "Carcinization in the anomura – fact or fiction? I. Evidence from adult morphology". Contributions to Zoology. 67 (2): 79–123.  PDF

Jump up ^ Jonas Keiler; Christian S. Wirkner; Stefan Richter (2017). "One hundred years of carcinization – the evolution of the crab-like habitus in Anomura (Arthropoda: Crustacea)". Biological Journal of the Linnean Society. 121: 200–222. doi:10.1093/biolinnean/blw031. 

Jump up ^ Jonas Keiler; Stefan Richter; Christian S. Wirkner (2013). "Evolutionary morphology of the hemolymph vascular system in hermit and king crabs (Crustacea: Decapoda: Anomala)". Journal of Morphology. 274 (7): 759–778. doi:10.1002/jmor.20133. 

Jump up ^ Jonas Keiler; Stefan Richter; Christian S. Wirkner (2015). "The anatomy of the king crab Hapalogaster mertensii Brandt, 1850 (Anomura: Paguroidea: Hapalogastridae) – new insights into the evolutionary transformation of hermit crabs into king crabs". Contributions to Zoology. 84 (2): 149–165. 

Jump up ^ Jonas Keiler; Stefan Richter; Christian S. Wirkner (2014). "Evolutionary morphology of the organ systems in squat lobsters and porcelain crabs (Crustacea: Decapoda: Anomala): an insight into carcinization". Journal of Morphology. 276: 1. doi:10.1002/jmor.20311. 

Jump up ^ Jonas Keiler; Stefan Richter; Christian S. Wirkner (2016). "Revealing their innermost secrets: an evolutionary perspective on the disparity of the organ systems in anomuran crabs (Crustacea: Decapoda: Anomura)". Contributions to Zoology. 85 (4): 361–386. 

Jump up ^ C. L. Morrison; A. W. Harvey; S. Lavery; K. Tieu; Y. Huang; C. W. Cunningham (2001). "Mitochondrial gene rearrangements confirm the parallel evolution of the crab-like form" (PDF). Proceedings of the Royal Society B: Biological Sciences. 269 (1489): 345–350. doi:10.1098/rspb.2001.1886. PMC 1690904 . PMID 11886621. 

Jump up ^ C. W. Cunningham; N. W. Blackstone; L. W. Buss (1992). "Evolution of king crabs from hermit crab ancestors". Nature. 355 (6360): 539–542. Bibcode:1992Natur.355..539C. doi:10.1038/355539a0. PMID 1741031. 

Jump up ^ Patsy A. McLaughlin; Rafael Lemaitre; Christopher C. Tudge (2004). "Carcinization in the Anomura – fact or fiction? II. Evidence from larval, megalopal and early juvenile morphology". Contributions to Zoology. 73 (3): 165–205. 

Jump up ^ Ling Ming Tsang; Tin-Yam Chan; Shane T. Ahyong; Ka Hou Chu (2011). "Hermit to king, or hermit to all: multiple transitions to crab-like forms from hermit crab ancestors". Systematic Biology. 60 (5): 616–629. doi:10.1093/sysbio/syr063. PMID 21835822. 

Jump up ^ Rafael Lemaitre; Patsy A. McLaughlin (2009). "Recent advances and conflicts in concepts of anomuran phylogeny (Crustacea: Malacostraca)" (PDF). Arthropod Systematics & Phylogeny. 67 (2): 119–135. 

^ Jump up to: a b Alexandra Hiller; Carlos Antonio Viviana; Bernd Werding (2010). "Hypercarcinisation: an evolutionary novelty in the commensal porcellanid Allopetrolisthes spinifrons (Crustacea: Decapoda: Porcellanidae)" (PDF). Nauplius. 18 (1): 95–102. Archived from the original (PDF) on 2012-04-25.

(via Carcinisation - Wikipedia)