The Palolo Spot
    Palolo Science

Fig 4 - Palola viridis Click for Higher Resolution

Palolo worms from the South Pacific are relatively well studied, because the annual risings are not only major festivities for the locals, but have also attracted the attention of biologists and anthropologists since the 18th century. It was noted that the swarming worms were headless. For a long time, it was a mystery where the heads were. Gray’s (1847) first scientific description of a Samoan Palolo worm was based on the headless portion only, later called the epitoke. He called the species Palola viridis, the genus name being derived from the Samoan name, and the species name meaning green. At the end of the 19th century, Friedländer (1898) and Krämer (1899) independently discovered that the worms spend most of their lifetime burrowing in hard substrate. Only once a year, their hind ends break off and swim spiralling to the surface to shed eggs and sperm. This reproductive frenzy only lasts for a few hours. Over the course of the next year, the head ends (or atokes) regenerate and eventually produce new epitokes.

In parts of the world where Palolos do not rise or where the rising is not of cultural importance, they received less scientific attention than Palola viridis from the South Pacific. Yet Palola species have been recorded from all major oceans (see map/Fig. 5 and Table 1).

Palolo worms belong to the phylum Annelida, class Polychaeta, family Eunicidae. The family includes a number of different genera, but Palola is easily recognizable. See Table 2, Fig. 6 for distinguishing characteristics. The genus comprises 14 nominal species (Table 3). , but some may be synonyms and others may comprise several species. The species are difficult to identify because they are lacking many of the features that are taxonomically important in related eunicid genera. Gills, for example, if present, are usually single filaments, whereas in Eunice the branching pattern of the gills is a character to distinguish species. Subacicular hooks, which in Eunice are of variable colour and shape, depending on species, are absent in Palola. As morphological features are limited in their use for taxonomy of Palola, we are currently working on a sequence analysis of mitochondrial genes to define species boundaries in this group more clearly.