Cancrion khanhensis sp. nov. (Crustacea: Isopoda: Entoniscidae) infesting Monomia haanii (Stimpson, 1858) (Crustacea: Brachyura: Portunidae) from Nha Trang Bay, Khanh Hoa, Vietnam, with remarks on larval stages of entoniscids and description of a new family, genus and two new species of hyperparasites infesting entoniscids.

An undescribed entoniscid isopod was found to parasitize Monomia haani, a common portunid crab in Khanh Hoa province of Vietnam. The new species is the eighth in the genus Cancrion, the second species of Cancrion found parasitizing hosts in the family Portunidae, and the first member of the family Entoniscidae to be described from southeast Asia. The cryptoniscius larva of a species of Cancrion is described for the first time. The new entoniscid infests hosts with a prevalence of 10.1% and intensity of 1 or 2 females per host. A new family, genus and species of cryptoniscoid hyperparasite with novel female and cryptoniscus body morphology is also described; this is the first record of a hyperparasite found infesting an entoniscid isopod. The purported cryptoniscus larva of Tiarinion texopallium Shields Ward, 1998 is shown to be that of a hyperparasitic cryptoniscoid isopod closely allied to the new Vietnamese hyperparasite and is described as a new species belonging to the new family and genus.

Comatulids (Crinoidea, Comatulida) chemically defend against coral fish by themselves, without assistance from their symbionts.

Symbiotic associations between small animals and relatively large sessile invertebrates that use taste deterrents for protection are widespread in the marine environment. To determine whether the symbionts are involved in the chemical protection of their hosts, the palatability of ten species of comatulids and six species of their symbionts was evaluated. Taste attractiveness was determined by offering agar pellets flavoured with extracts of comatulids and their symbionts for four coral reef fish species. Five species of symbiont were highly palatable, and one was indifferent to the taste. Almost all comatulids were distasteful, while their aversiveness was different for different fish. These findings indicate that comatulids chemically defend themselves without assistance from symbionts, and the taste deterrents are not universal and can only be effective against particular predators. The presence of tasteful symbionts reduces the security of their hosts by provoking attacks of predators and may impact on the individual and population fitness of comatulids. However, the chemical protection of comatulids is useful for symbionts and undoubtedly increases their survival. Obtained results allows the relationship between comatulids and their symbionts considered commensalism. Most likely, similar relationships can be established in many other associations, where symbionts inhabit chemically defended coral reef invertebrates.