This website illustrates mushroom corals (Fungiidae), and the endo- and ecto-parasitic gastropods (Epitoniidae, Coralliophilidae) and boring mussels (Mytilidae) that live associated with them. In addition Actiniarian hosts of wentletraps (Epitoniidae) are shown. The photographs were taken as part of a PhD-project (funded by WOTRO) at the National Museum of Natural History, Naturalis, Leiden, the Netherlands...
"A biogeographical study of parasitic gastropods and their coral hosts in the Indo-West Pacific" (PDF):

Little is known of the cause and maintenance of the high level of biodiversity at the central Indo-Pacific. Two main factors have been distinguished:

(1) Many Indo-West Pacific species have vast wide-spread distributions that overlap in the Indo-Malayan centre of maximum diversity.
(2) Many species have complex symbiotic relationships.

Mushroom corals (Fungiidae) and their parasitic gastropod snails (Epitoniidae and Coralliophilidae) are ideal model taxa to study these aspects.

Understanding the population genetics and evolutionary history of the animals will reveal:
(1) whether gene flow and the integrity of widespread species are maintained across the Indo-Pacific.
(2) to what degree the snails and their coral hosts are co-evolving, and
(3) whether the historical biogeography and geologic timing of reconstructed speciation events can shed light on the evolutionary mechanisms that have led to the present diversity.

We are sequencing multiple DNA markers for these mushroom corals and their gastropod parasites so as to understand the population genetics of widespread species.