Urchin Mantis Shrimp
21:55One of our favourite sites around Sharm el-Sheikh is Shark’s Bay. At first glance it seems little more than a vast tundra of rocks and sand. On closer inspection though it has a lot to offer, especially if you enjoy macro. One of the most exciting discoveries we have made there recently is a small colony of urchin mantis shrimps. Admittedly we didn’t know what creature we’d stumbled upon until we’d compared our photos to others on the Internet but even before we were able to positively identify the shrimps, we knew we’d spotted something a little rare and unusual. The shrimp has a telson (in laymans terms, it’s arse) that resembles a rock-boring urchin which it blocks the entrance to its cavity (lair) to avoid detection (both from predators and divers). We only initially noticed the shrimps because one just happened to move whilst we were photographing the coral it inhabits. On the same day we saw an eagle ray which is enough to make most divers happy, yet this 30mm shrimp was the highlight of the dive.
Common name: Urchin Mantis Shrimp
Functional type: Smasher
Range: Central Pacific and Hawaii to Western Indian Ocean
Habitat: Coral reefs, reef walls
Depth: 10–50 m
Home: Cavities in hard substrates, often large worm tubes; juveniles in coral rubble
Diet: Unknown; has been found eating crabs, gastropods and other species of mantis shrimp
Size: 8–80 mm
Color: Yellow, orange or more typically red with while spots, while spots form band running across carapace and raptorial meri, no prominent meral spot; telson spines white
Distinguishing Characters: Bilobed eyes; spined telson that mimics an echinometrid urchin
Activity: Crepuscular, rarely leaves cavity; often seen blocking entrance with telson
Aquarium Requirements:
Temperature: 22–28° C
Salinity: 33–35 PSU
Cohabitants: Unknown; will eat small prey, almost never leaves cavity
Aquarium size (adult): 20 l
Aquarium substrate: Requires tight-fitting, long narrow cavity, either pvc pipe or in rubble
Suitability for Aquarium: Good; needs stable water parameters; not active but usually can be seen looking out of cavity entrance; use of unusual telson that mimics urchin is interesting
Availability: Rare; occasionally can be specially ordered from collectors in Hawaii; while common at 20–30 m, because of the nature of their cavities, E. guerinii are extremely difficult to collect alive.


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