Wondering if there's a crab you can't eat? Yes there is says Carys Matthews. Xanthid crabs, belonging to the family Xanthidae, are a diverse group of brightly coloured toxic crustaceans commonly found in tropical and subtropical marine environments.
Often referred to as “mud crabs” or “gorilla crabs,” they are known for their striking appearance and fascinating, albeit dangerous, biological traits.
What does the xanthid crab look like?
Xanthid crabs are small to medium-sized and exhibit a wide range of colours, including vibrant yellows, reds, oranges, and blacks. Their vivid hues serve as a warning sign, as many species are highly toxic. They typically have robust claws, a square or oval carapace, and a spiny texture, giving them a distinctive and somewhat rugged appearance.
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Where does the xanthid crab live?
Found in Indonesia, Australia, Japan, Australia, Taiwan, and the Philippines, Xanthid crabs inhabit coral reefs, rocky substrates, and mangrove forests, where they play an essential role in maintaining the ecosystem. They are omnivorous scavengers, feeding on algae, detritus, and small invertebrates. Their powerful claws make them adept at cracking shells and manipulating food.
These crabs are typically nocturnal and use their cryptic coloration to blend into their surroundings, avoiding detection during the day. While not aggressive, they will defend themselves vigorously if threatened.
Why is it so deadly?
Despite their deadly reputation, xanthid crabs are not aggressive toward humans. Their striking appearance and cryptic habits make them a fascinating creature to observe.
The xanthid crab’s vibrant colours and toxic traits have enabled them to survive in marine environments.
Just how toxic is the xanthid crab?
One of the most remarkable features of xanthid crabs is their toxicity. Unlike many toxic animals that produce their own poisons, xanthid crabs acquire toxins from the bacteria in their diet, such as Pseudomonas and Vibrio.
These toxins, including saxitoxins and tetrodotoxins, are potent neurotoxins that can be lethal to predators and humans. Cooking does not neutralise the toxins, making the crabs dangerous to consume. There is no known antidote.
Can the xanthid crab poison itself?
Interestingly, xanthid crabs themselves are immune to the effects of these toxins, allowing them to store and use them as a powerful defence mechanism.
The potent toxins found in xanthid crabs have drawn interest from researchers studying their potential applications in medicine, particularly in neuroscience and pharmacology. Tetrodotoxins, for instance, are being investigated for their use as painkillers and in the treatment of neurological disorders.
Is it endangered?
Xanthid crabs as a family (Xanthidae) are not currently classified as endangered. However, specific species within this family may face localised threats due to habitat destruction, pollution, and climate change.
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Main image: Pebble crabs are a member of the Xanthidae family © Getty Images