Introduction Host-parasite associations provide very useful models to study adaptive processes. We investigated the interaction between carnivorous marine gastropods, the Ovulidae or egg-cowries, and their cnidarian food targets. Ovulidae (Fleming, 1828), is a family of specialized carnivorous caenogastropods that feed by browsing on octocorals (Anthozoa: Octocorallia: Malacalcyonacea and Scleralcyonacea) or, to a much lesser degree, on antipatharians (Anthozoa: Hexacorallia: Antipatharia) and Stylasteridae (Hydrozoa: Hydroidolina: Anthoathecata). Very scanty information is available on the phylogenetic relationships and the degree of specificity of the relationship with the cnidarians of this corallivorous lineage, especially for deep-water taxa. Methods To assess taxonomic identifications and investigate cnidarian/ovulid relationships in the context of their evolution, we generated an extensive molecular dataset comprising two mitochondrial ( cox1 and 16S rDNA ) and one nuclear gene ( 28S rDNA ) from 524 specimens collected worldwide. The coral hosts of the ovulid species have been identified by integrating literature data with new records, employing morphological and/or molecular (the mitochondrial 16S rDNA and mtMSH , and the nuclear ITS2) markers. Results We obtained a molecular phylogenetic framework for the Ovulidae, time-calibrated with nine reliable fossil records. An ancestral state reconstruction allowed to identify Hexacorallia or Hydroidolina as the most likely ancestral cnidarian host for the Ovulidae. Discussion Our phylogenetic hypothesis revealed the existence of groups that do not completely correspond to the currently employed subfamilial arrangement. Concerning trophic ecology, while only pediculariines ( Pedicularia and allied) are associated with hydrozoans (Stylasteridae), our results suggest that some ovulid lineages shifted independently between octocorals and hexacorals.

ATIMO VATAE, AURORA 2007, BIOMAGLO, CORSICABENTHOS 1, CORSICABENTHOS 2, CORSICABENTHOS 3, EBISCO, EXBODI, KANACONO, KANADEEP, KARUBENTHOS 2, KAVIENG 2014, KOUMAC 2.3, MADEEP, MADIBENTHOS, MAINBAZA, MIRIKY, NORFOLK 2, NanHai 2014, PAKAIHI I TE MOANA, PANGLAO 2004, PAPUA NIUGINI, SALOMONBOA 3, SANTO 2006, SPANBIOS, ZhongSha 2015

MUSORSTOM 4

The type, size, shape and distribution of nematocysts represent important taxonomic characters that help to identify many hydrozoan species. The Stylasteridae is one of the most species-rich hydroid families. Nevertheless, information about the soft tissue and especially data about the nematocysts are still very scant. Scattered data about nematocysts are available in several taxonomic papers, but unfortunately without the type identification or shape description, this information is not very useful. Therefore, several questions still need answers. What types of nematocysts are present in the stylasterid family? Do nematocysts have a particular distribution in the soft tissue? Could they be considered a useful taxonomic character for the family? Is it possible to hypothesize their functions? In order to answer these questions, we analysed 15 stylasterid species belonging to seven genera. Euryteles, desmonemes, isorhizas and probably also mastigophores were identified. All examined species have euryteles and desmonemes, while isorhizas are recorded in two genera and mastigophores in only one genus. Moreover, the shape of the nematocysts in some species is very distinct. The distribution of nematocysts shows that each species contains, in the coenosarc, all nematocysts of its cnidome, while in the polyps there are only euryteles and desmonemes. Our study showed that in integrating the information about nematocyst type, size, shape and distribution, each species investigated herein has a specific cnidome. Therefore, nematocysts have a taxonomic value for stylasterids and, whenever possible, nematocysts should be included in the species descriptions. Moreover, the possible functions of stylasterid nematocysts are given in relation to their type and distribution.

CHALCAL 2, MUSORSTOM 4

Abstract Barnacles that fit morphologically into the description of the pyrgomatid genus Cantellius were retrieved from hydrozoan Stylasteridae. The use of molecular markers also confirmed the assignment of these barnacles to the genus Cantellius. Hitherto, stylasterids have not been recorded as hosts of pyrgomatids. This finding conflicts with and refutes the statement that scleractinans (Hexacorallia) are obligatory hosts of pyrgomatids. These are the first unequivocal records of living pyrgomatids in stylasterids, thus documenting a new type of habitat for this group of barnacles. Further inspections of stylasterids will probably reveal more new host records and, possibly, new pyrgomatids.

BENTHEDI