Methodology:

Egg samples were collected on 2021-04-22 from Troval dive site, Ryder Bay, using SCUBA. Specimens were maintained in ambient water temperature during transit from the dive site to the Aquarium. Egg samples were transferred into a through-flow aquarium tank where they remained for seven months.

Specimens were checked each week and photographed upon noticeable changes in their development. In the Bonner Laboratory aquarium, a subsample of the egg mass was pipetted from the mucus mass and transferred to a petri dish. A portable dissection microscope (Meiji EMZ-TR) was temporarily installed in the aquarium.

Photographs were collected using a simple system of aligning an Olympus TG4 camera in the lens viewer, in the absence of a suitable aquarium microscope with a fitted camera.

Samples were quickly returned to the aquarium tank.

Molecular barcoding using the 18SrRNA gene was performed to identify the larvae. Briefly DNA was extracted from the larvae using the DNeasy Blood and Tissue kit (Qiagen) according to manufacturer's instructions. Amplification of a 560bp fragment of the 18S rRNA was performed using the primers NSF4 (CTGGTTGATYCTGCCAGT) and NSR581 (ATTACCGCGGCTGCTGGC) and 2x MyTaq HS Readymix (Meridian Biosciences) according to manufacturer's instructions. PCR cycling conditions were as follows: 95 degrees C for 5 mins, the 35 cycles of 95 degrees C for 20 secs; 60 degrees C for 20 secs; 72 degrees C for 30 secs and a final extension of 72 degrees C for 10 mins. The PCR product was Sanger sequenced by Source Bioscience (UK). Blast sequence similarity searching revealed that it was highly likely that these larvae were an uncharacterised Terebellidae species. In the absence of any associated adults for detailed taxonomy, more detailed identification to species level was not possible. The 18SrRNA sequence is available from NCBI under Accession number PP908343.