Gymnodinioides kozloffi n. sp. is described from the eelgrass broken-back shrimp Hippolyte zostericola. The species is distinct from others in the apostome genus Gymnodinioides in that the trophont ciliature has a small group of kinetosomes located to the right of Kinety 9a, and Kinety 1 and 2 are divided. Other apostome morphologies are described from many decapod crustaceans from St. Andrew Bay, Florida, including Gymnodinioides inkystans, Hyalophysa chattoni, and variants of both H. chattoni and G. kozloffi. All of these apostome ciliates are exuviotrophic, found feeding on exuvial fluid within the exoskeleton of the host after ecdysis. The hosts surveyed for this study are the following: Callinectes sapidus, Eurypanopeus depressus, Hippolyte zostericola, Farfantepenaeus spp., Palaemonetes intermedius, Palaemon floridanus, Portunus spp., Tozeuma carolinense, and Sicyonia laevigata, which revealed a number of new host-apostome records.