Use of sponges in the decoration of Inachus phalangium (Decapoda, Majidae) from the Adriatic Sea

The sponge species used for decoration of a population of Inachus phalangium (Fabricius 1755) from the Conero Riviera (coast of Adriatic Sea) were studied. Sponges are one of the most important sources of material used in the decoration of this species. Fourteen species of sponges were recorded on this crab and the most abundant were Haliclona palmata (Ellis & Solander 1791), Aplysina aerophoba Schmidt, 1862 and Tedania anhelans (Lieberkuhn 1859). The SEM analysis of sponge fragments showed that they are fully functional with evident incurrent and excurrent opening of the aquiferous system. Aquarium observations confirm that crabs actively cut sponges and place fragments on the exoskeleton, fixing them on hooked setae. The lateral zones of the carapace are the areas most decorated with sponge and females show a percentage of covering significantly greater than males. A comparison of the sponges present in the environment with those observed on crabs indicates that L phalangium generally uses the most common present in its habitat with the exception of those whose mechanical properties prevent manipulation.