Of all the crustaceans, Isopods are one the most specious orders. Members of the order are globally distributed, diverse and abundant, playing a vital ecological role in many terrestrial and benthic habitats. The genus Cymodoce of the Sphaeromatidae isopods, span a size range from 5-25mm length with large variability in morphologies. Despite their small size and cryptic life history, these are enigmatic animals, are well deserving of further study.

The species Cymodoce pelsarti (Tattersall, 1922) occurs in Western Australia and Queensland, with occurrences reported from Heron Island. It is entirely possible that some of the isopods at Heron Island are a similar but undescribed species. Due to small variations in morphology of collected specimens than those from the taxonomic description, Cymodoce cf. pelsarti will be adopted for this collection. This study describes in detail the morphology and ecology of isopods collected from Heron Island. Detailed also are novel observations of chromatophore fluorescence under UV light and chromatophore controlled variability in colouration.