It never ceases to amaze me how different every swim can be. Today I dropped in on the fossil-beach side of the Beaumaris Motor Yacht Squadron and headed out to where it’s about 2m deep. Visibility wasn’t great but I was able to find not one but three species of sapsucker. These seas slugs have a very interesting life history as they effectively absorb the essence of plants into their bodies to become plant-like. Unlike nudibranchs, which are carnivorous, they are strictly vegetarian. Their numbers come and go as the various Caulerpa species grow and die each year. Caulerpa are the moss-like species that seasonally carpet the seafloor in this region. The sea slugs can chew through huge amounts very quickly, as was demonstrated last month at Ricketts Point, with an incredible emergence of another species.
Sea slugs
Here is a list of sapsucking sea slugs of Port Phillip Bay from iNaturalist. The ones I saw today were two Bubble-snails, Oxynoe viridis, and Roburnella wilsoni. The latter was described from this region. I initially overlooked it, thinking it was the fruiting body of the weed. It’s very small! The Oxynoe’s were abundant in places. Also, mixed among them, were small Elysia maoria. I am thinking that I probably overlooked two or three other species as they are all rather cryptic.
Seahorse
A single Bigbelly seahorse in the shallows on the way back in was a nice treat. It was only in about 30cm of water. There are often seahorses along this stretch between the Motor Yacht Squadron and Sea Scouts Hut.
