Abstract Amplification of diagnostic genomic DNA sequences using the highly sensitive polymerase chain reaction (PCR) technique provides a fast, sensitive and relatively inexpensive approach to species identification where there is a lack of diagnostic morphological characters. This applies particularly to the early life-history stages of marine invertebrates. Using PCR primers designed to amplify diagnostic length variants within phylogenetically widespread genes (in this case an expansion segment within the 28S rRNA gene), a first attempt is presented to produce a DNA database for use in the identification of hydrothermal vent larvae. In addition, a scanning electron microscopy study of particulates recovered from the neutrally buoyant plumes of hydrothermal vents on the Mid-Atlantic Ridge revealed evidence of biological material derived both from the vent environment and from the sea surface as marine ‘snow’. This investigation represents the first stage in the development of a bottom-mounted recorder to study the spatial and temporal aspects of larval dispersal in the hydrothermal vent environment. Larval dispersal processes are fundamental to the biogeography, genetics and evolution of the hydrothermal vent fauna.