Summary

Myrianida pachycera (Augener, 1913) is a small errant polychaete with beautiful colouration, an extraordinarily wide distribution and a fascinating reproductive and evolutionary history. The distinctive yellow and blue coloration and pattern is most likely the defining feature of the species, though other anatomical features inform its wider taxonomic placement.

M. pachycera can be found on the benthos in shallow coastal waters on hard substrates, and probably regularly frequents biofouling communities. It is commonly associated with sedentary or sessile coastal species, probably utilising them for shelter and sustenance.

M. pachycera is one of the few species that undergoes gemmiparitous stolonisation, a fascinating strategy that confers the reproductive responsibility, not on the mature adult, but on the clone-like individuals that the adult generates from its own body. The internal anatomy of these clone-like individuals, stolons, was investigated here, to discern where gametes originated and where they were distributed within the stolon’s body.

The gemmiparitous reproductive strategy is one of many among the family Syllidae, and this reproductive diversity offers a unique opportunity to delineate high-resolution phylogenetic relationships. M. pachycera’s taxonomic placement seems well resolved: It is part of the genus Myrianida Milne Edwards, 1845, which is part of the sub-family Autolytinae Langerhans, 1879, which is included in the family Syllidae Grube, 1850.  

The images used throughout are of a single individual that was collected from a settlement plate in Moreton Bay’s Manly Boat Harbour. This individual will be referred to hereafter as the project specimen.

Figure 1 Part of a chain of stolons of Myrianida pachycera.