Ancylomenes pedersoni is a small and colorful shrimp that belongs to the order Decapoda, family Palaemonidae, within the subphylum of crustaceans. This family consists of 149 different genera, among which we find the genus Ancylomenes, formed by Ancylomenes pedersoni along with 21 other species. It is distributed in the waters of the western Atlantic Ocean and the Caribbean Sea, where it lives in waters up to 35 meters deep.
The body of Ancylomenes pedersoni does not exceed 3 cm in total length and has an abrupt shape in which the head tends to be erect, and the final part of the body is smaller in diameter than the central part, and is directed downwards. That is, the body adopts a shape somewhat reminiscent of a sideways ‘S’. It is curious to observe the specimens of Ancylomenes pedersoni, since its body is practically translucent, with numerous small white dots on its surface and spots on the upper part of blue-purple color. Also prominent are fine white longitudinal lines, and a pair of long white antennae. Specimens of this species also have two pairs of long pincers (the first more developed than the second) which also have blue-purple bands, as well as 3 pairs of long, slender legs.
It is very common to find specimens of Ancylomenes pedersoni living in association with anemones, especially Bartholomea annulata, Bartholomea lucida, Condylactis gigantea and Stichodactyla haddoni, or with certain species of corals such as Plerogyra sinuosa and Physogyra lichtensteini. From this association the shrimp benefits from the protection against predators provided by the stinging tentacles of the anemone, while the anemones are spotless, as the shrimp will clean them of any debris that may accumulate.
The diet of Ancylomenes pedersoni is omnivorous, and is based mainly on parasites and dead tissues of certain fish which they clean, as well as occasionally some organic debris.
Ancylomenes pedersoni is a dioecious species, in which one specimen of each of the sexes maintains a mating ritual for the male to transfer the sperm to the female just when it has just shed its skin. The eggs formed after fertilization are carried by the female on the lower part of her abdomen, clinging to appendages called pleopods that keep them grouped together. The female usually carries about 100-150 eggs under her abdomen, which are of a milky white semi-translucent color.
Photos:
from