On the association between the crab <i>Hapalonotus reticulatus</i> (Crustacea, Brachyura, Eumedonidae) and the sea cucumber <i>Holothuria (Metriatyla) scabra</i> (Echinodermata, Holothuridae)
A study of the fauna associated with holothurians from Hansa Bay (Papua New Guinea) reveals a new symbiotic association between the holothuroid Holothuria (Metriatyla) scabra and the crab Hapalonotus reticulatus. All the collected holothurians were infested, but with only one crab per holothurian, always in the right respiratory tree near the cloaca. Because of its size, H. reticulatus considerably expands the wall of the respiratory tree forming a membranaceous cyst. This association, therefore, appears to be parasitic. However, the crab does not feed upon host tissue but seems to filter its food from water passing through the respiratory tree of its host. The description of two males allows to comment upon the taxonomical position of H. reticulatus. We classify H. reticulatus in the recently re-established family Eumedonidae. This is the first record of a species of Eumedonia living in association with a holothurian
