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Susanne Bähr @coralsandcrabs.bsky.social · Jun 18

(5) We hypothesise that gall crabs are able to offset negative effects of disturbances via increased reproductive output. Their high population turnover further suggests that they contribute to reef energy cycling by converting host-derived resources into forms accessible to higher life forms.

Susanne Bähr @coralsandcrabs.bsky.social · Jun 18

(4) By calculating turnover and mortality rates, we show that some reefs maintained reproductively active and resilient populations despite extensive bleaching, while compounded stressors at one site led to a population collapse.

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Susanne Bähr @coralsandcrabs.bsky.social · Jun 18

(3) Fate-tracking revealed surprisingly high population turnover with steady colonisation and extinction events as well as settlement preferences for already inhabited hosts.

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Susanne Bähr @coralsandcrabs.bsky.social · Jun 18

(2) We fate-tracked nearly 800 crabs for 2 years, capturing the 2023 Red Sea bleaching event. In addition, we performed belt transect surveys for comparison. These surveys showed that reef-specific effects drive gall crab abundance and prevalence over cross-shelf gradients.

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Susanne Bähr @coralsandcrabs.bsky.social · Jun 18

Stoked to share the publication of another of my PhD chapters! This time we investigated the temporal dynamics of gall crab populations, representing the first data set of its kind for any coral-associated invert. (1) 🦀 🧪🪸
onlinelibrary.wiley.com/doi/10.1002/...

Temporal Dynamics and Disturbance Responses in Coral‐Dwelling Decapods Provide a Novel Perspective on Their Ecological Role in Coral Reef Systems

Our study investigates the temporal dynamics and disturbance responses of coral-dwelling gall crabs (Cryptochiridae), an overlooked yet ecologically significant group of obligate coral symbionts. By ....

onlinelibrary.wiley.com

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Reposted by Susanne Bähr

Prof. Stefan Rahmstorf @rahmstorf.bsky.social · Jun 5

Read the story behind our new study published yesterday in Nature, unfiltered straight from the scientists: 🌊
theconversation.com/unprecedente...

Unprecedented heat in the North Atlantic Ocean kickstarted Europe’s hellish 2023 summer. Now we know what caused it

Parts of the Atlantic Ocean are again much warmer than normal, priming Europe for more extreme heat this summer.

theconversation.com

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Susanne Bähr @coralsandcrabs.bsky.social · Jun 4

Super excited that my PhD research made it on the national news of my chosen home for the past four years! @royalsocietypublishing.org 🦀🧪🪸🌍
arab.news/bvtne

Saudi Arabia’s KAUST study finds gall crabs use fluorescence to blend into coral homes

JEDDAH: Marine researchers from the King Abdullah University of Science and Technology have discovered that gall crabs use highly evolved fluorescence to help conceal themselves within coral hideouts....

arab.news

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Susanne Bähr @coralsandcrabs.bsky.social · Apr 22

(4) Our findings emphasize the need to better understand the ecological roles of cryptic symbionts on coral reefs, as these invertebrates are integral parts of multisymbiotic systems, yet their contributions to reef functioning remain largely unquantified. Huge thanks to everyone involved!

Susanne Bähr @coralsandcrabs.bsky.social · Apr 22

(3)The results were surprising: no consistent negative impact of gall crabs on photosynthetic efficiency.
In some cases, we even observed slight increases.
These findings suggest that crabs take a neutral role toward the algal symbionts of stony corals.

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Susanne Bähr @coralsandcrabs.bsky.social · Apr 22

(2) Here we applied this technique—a method typically used to assess stress responses in coral algal symbionts—to coral-crab associations for the first time. This allowed us to look for potentially concealed local effects the crabs might have on the zooxanthellae in their hosts' tissue.

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Susanne Bähr @coralsandcrabs.bsky.social · Apr 22

What would a PhD be without a side quest? 🦀🪸
Super excited our study is out in Frontiers in Marine Science!
We tested if gall crabs affect coral algal symbionts using Imaging PAM fluorometry.
Turns out—these tiny tenants don’t stress out the algae.
🔗 doi.org/10.3389/fmar... (1)

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Susanne Bähr @coralsandcrabs.bsky.social · Mar 12

(6) Differences in fluorescence expression may be linked to variations in their microhabitats. Crabs living in enclosed galls don't fluoresce, while others inhabiting more open dwellings show vivid fluorescence. Fluorescence may play a role in camouflage on the fluorescent coral host background.

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Susanne Bähr @coralsandcrabs.bsky.social · Mar 12

(5) By performing ancestral state reconstruction and combining the morphology results with a phylogenomic reconstruction, we show that fluorescence is phylogenetically widespread in the family. It evolved once in the genus Opecarcinus and was subsequently retained with varying expression levels.

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Susanne Bähr @coralsandcrabs.bsky.social · Mar 12

(4) This analysis revealed four distinct fluorescent morphologies (Fluotypes). Each of these fluotypes has distinct characteristics, such as cheliped or abdominal fluorescence.

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Susanne Bähr @coralsandcrabs.bsky.social · Mar 12

(3) We developed a fluorescent imaging technique for a multivariate trait analysis based on 27 morphological characters.

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Susanne Bähr @coralsandcrabs.bsky.social · Mar 12

(2) We found gall crabs to display a vivid orange fluorescence that is visible without an excitation light source (A). Based on these observations, we hypothesised that it may be an adaptive trait for this family of decapods.

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Susanne Bähr @coralsandcrabs.bsky.social · Mar 12

Proud PhD Moment 🦀 My third PhD chapter is finally released to the world, and the cherry on the cake: My photo made the cover of the current #ProcB issue @royalsocietypublishing.org 🪸 check it out here: doi.org/10.1098/rspb...

#CoralReefs #Biodiversity #Fluorescence #Symbiosis #Decapods

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Susanne Bähr @coralsandcrabs.bsky.social · Feb 17

Dissertation writing break well spent although Red Sea February water temps are 🥶 #coralsky

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Susanne Bähr @coralsandcrabs.bsky.social · Feb 3

Hey, never apologize for asking random questions about crabs! This is literally my career haha

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Susanne Bähr @coralsandcrabs.bsky.social · Feb 3

the crabs perish. They can not survive long without a living host. They feed on coral mucus, so their food source disappears... I'm currently preparing the results of a long-term study on their response to bleaching for publication so stay tuned!

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Susanne Bähr @coralsandcrabs.bsky.social · Feb 3

Hello Erick, *almost Dr :) Thanks for your interest in these critters. They can not leave their hosts; the females, especially, are almost forced to stay within their dwellings. When the coral bleaches they can persist, I found them to be actually quite resilient. However, if the host dies

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Susanne Bähr @coralsandcrabs.bsky.social · Dec 18

Currently there are nearly 60 described gall crab species that settle on a really diverse set on host families. They are host specific though, to varying degrees. Some species settle on a single host species only, some others are a bit more flexible.

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Susanne Bähr @coralsandcrabs.bsky.social · Dec 18

So far we have no strong evidence that their presence has any significant negative effects on their hosts but stay tuned for more research about this soon! 🦀
They do feed on coral mucus but since thats continously produced by the coral it doesn‘t seem to be very energy draining.

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Reposted by Susanne Bähr

Wally Rich @reefwally.bsky.social · Dec 15

I started surveying the shallow reef flats in front of KAUST for my PhD in 2020. I was impressed that corals could live in such extreme conditions - the water hits 38ºC in the summer! However, heatwaves in '23 and '24 were too much even for these corals. Today's survey had nearly 100% mortality 😞 🌊🦑

A shallow reef flat in August 2023 covered with branching corals. About half of them are live and yellow, while the rest are dead from natural mortality over the years.

A few bright white coral colonies in the reef flat that are undergoing bleaching in August 2024.

The same reef flat after the bleaching event. Photo taken December 2024. All colonies are grey and dead.

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Susanne Bähr @coralsandcrabs.bsky.social · Dec 10

Wow it looks like it's fluorescent and red fluorescence is not very common in decapods :O

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