Our expedition colleagues from the Australian Museum would absolutely agree that good things coming in small packages - or in tiny lifeforms! A lot of what we’ve shared with you so far has focused on the larger marine life that we’ve come across on this expedition like the impressive sharks on the BRUV cams but some of the most mesmerising finds are much, much smaller and harder to spot.

One of the focuses for our invertebrates experts Anna Murray and Stephen Keable is marine worms.

These worms are scientifically known as ‘Polychaeta', meaning many chaetae (or bristles), referring to the hairs that are conspicuous along the edges of the segments making up the body. Marine worms are typically known to most people for use as fishing bait, and while significant in food chains, they also play a variety of essential roles in ecosystems by providing services such as aerating sediments, and can also be commercially important fouling organisms.

Polychaetes are particularly abundant and diverse in tropical areas and one of our favourite finds so far on this expedition is the “Christmas tree worm”. The Christmas tree worm or Spirobranchus sp is striking because of its spectacularly colourful feeding fan, which forms a pine-tree like shape - we found this one at our last stop in Ono-I-Lau, one of the islands in the Lau group.

If you’ve spent any time around coral reefs you may be familiar with this type of polychaete worm as it forms tubes within the living coral. However it is also one of a number of very similar species, all belonging to the genus Spirobranchus, which have been misidentified and confused in the past.

Which is why Stephen and Anna's work in identifying these worms is important. Genetic samples, coupled with fine scale study of morphological features, are proving to be a key to unlocking this complex of species.

The Australian Museum holds an extensive collection of polychaete worms from across the Indo-Pacific area, which is used for reference in identifying species and understanding their distributions. The samples obtained during the current expedition will complement this and provide new information for a variety of projects examining worm relationships and population connectivity.

The worms are usually collected using SCUBA diving to hand-sample coral rubble, sediments and other substrates, such as sponges, that polychaetes occupy - and the team has already found several good examples of the worms they're searching for including specimens of Spirobranchus.

In terms of a progress report, we’re now back at sea after a few days of paperwork and preparations for our second leg. We have made a couple of tweaks to our expedition itinerary and we’re currently working our way through the islands in the Lau group including Namuka, Ono-i-lau, Vatoa, Ogea, Yagasa and Oneata. We’ve decided not to visit Ata Island in Tonga, as it’s a little bit out of our way, but will instead make a brief return to Suva at the end of next week before we head for Minerva Reefs and Rangiahua Kermadec Islands.