The pale white Ghost Boxer Shrimp (Stenopus pyrsonotus) is a small (+/- 2.5cm/1 inch), shy crustacean belonging to the Stenopodidea, a group of shrimp-like crustaceans. Due to their combination of crawling and swimming characteristics, they are not considered real shrimps.
These pale shellfish prefer to venture around in dark habitats (deep water or inside caves, caverns, or crevices). For an unknown reason, the ones we encountered were almost the same size as the Soldierfish in the first shot of the video, which is four times the size described in different reference books and scientific websites.
What causes this small local population of Ghost Boxer Shrimp to grow almost four times bigger than the species encountered elsewhere? One can only speculate, but let’s look at some facts. These Ghost Boxer Shrimp live in a cavern on Mauritius’ West coast where the water temperature varies from a pleasantly warm 27°C/81°F in the summer to a cool 21°C/70°F in winter. However, inside this cave, due to its isolation from almost all outside elements, the temperature remains constant, measuring around 25°C/77°F. Besides the presence of a rather small population of Red Banded Lobsters (Justitia longimanus) in the same cave, the Ghost Boxer Shrimp are shielded from any potential predatory fish. Whitetip Reefsharks (Triaenodon obesus) used to rest a few meters/several feet inside this cave, but the sharks unfortunately have long since disappeared. Could it be that the absence of predators, the constant pleasant water temperature, and the isolation from the outside reef and open ocean provide the perfect conditions for growing larger than normal? Specimens living in the deeper parts of tropical reefs, where these light-fearing crustaceans reside, are exposed to seasonal temperature changes and fluctuations, as well as encountering predators on a daily basis. Unless an extensive study on this phenomenon is conducted, we can only speculate why these supposedly small pale critters have grown to a gigantic size inside this underwater cave.
Filming in a restricted space comes with its own challenges. Inside this particular cave, there is no significant water movement, causing debris and detritus resulting from the activities of its inhabitants to settle in the form of super-fine dust on the cave floor, walls, and rocks. The slightest movement of a diver, an underwater photographer or a videographer with their camera rig could generate dust clouds, making underwater photography and filming very difficult. One must move slowly inside the cave and ensure that his/her fins stay well above the cavern’s surface to avoid stirring up dust which can become potential life-threatening. Once the dust has been stirred up, the damage is done, and the cavern has now turned into a hazardous place. No need to tell you that filming or taking pictures is now finished for the rest of the day as it may take several hours for the dust to settle and for the visibility in the cave to return.
To create a more complete and realistic experience for our viewers, we added an "empty room" sound effect. The hollow sounds, combined with a suitable musical style, created a dark cavern-like atmosphere reminiscent of the submerged cave on Mauritius's West coast.
This short underwater videoclip has been filmed in Mauritius 🇲🇺
For more information on the other denizen that inhabit this cave please go to vlog posts 95 or click this link https://www.beyondscuba.com/post/red-banded-lobster-justitia-longimanus
and vlog post 45 https://www.beyondscuba.com/post/the-variable-thorny-oyster
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