We were exploring the critters at St Helens boat ramp recently when Seth discovered many of these worms next to the ramp. We hadn’t seen them before so Seth caught one in a net to get a closer look. I was concerned about it being out of the water for too long so only got a couple of photos.
I waited a while before putting them on Facebook, as I get concerned about asking too many questions. Being anxious and an amateur can make things interesting! It turns out is a type of polychaete worm in the nereididae family. I tried to do some Googling to help me identify species from this family…. and I think I ended up more confused than before.
According to this website
Nereidids are long and slender worms of medium size found among algae, gravel and shells on hard substrates, or digging into soft substrates. They are characterised, among other features, by well-developed parapodia, and an eversible pharynx with two prominent black jaws and small sclerotised teeth on the surface of the pharynx. During reproduction, many species leave the sea-bed and swarm towards the surface
The important features are the parapodia and pharynx. I tried looking up where the pharynx is with these worms, but had trouble finding any basic resources on where the pharynx is. According to one of the marine research group guides, it’s important to collect and photograph with pharynx everted.
In one of the photos, it looked like the worm had filiform branchiae, or gills. This meant that it could belong to the Marphysa genus. In 2018, the species in the genus were under review. A new paper came out in 2020, but I’m struggling to make sense of the current information let alone any new information. A lot of these papers aren’t accessible to the super newbie.
Another person commented that the worm was also an epitoke. According to Wikipedia,
Epitoky is a process that occurs in many species of polychaete marine worms wherein a sexually immature worm (the atoke) is modified or transformed into a sexually mature worm (the epitoke)
They swim towards to the surface during reproduction, so it makes sense that we would see sexually mature worms. The aforementioned pink branchiae were apparently ‘the additional lamellae of the epitoke’s modified parapodia.’
I’ve put pause on trying to learn more about these worms. I’m in waaaay over my head here. I’d rather focus on flatworms 🙂