Marine Biodiversity of Southern Sydney Harbour's Journal

Congratulations to the "Goby Whisperer" Erik Schlogl for his Photo Observation(s) of the Month of October of the Broad-banded Shrimpgoby (Amblyeleotris periophthalmus) from Parsley Bay in southern Sydney Harbour, and the Redspotted Shrimpgoby (Amblyeleotris ogasawarensis) from Camp Cove. The former Broad-banded Shrimpgoby represents the very first record from Sydney Harbour, and a southern range extension from South West Solitary Island in NSW. This is also only the 34th record of this species for all of Australia. Given the time of the year (spring) and size of this photographed fish, this tropical species may have even survived the unseasonably warm 2023 Sydney winter. For the latter Redspotted Shrimpgoby, this represents only the second observation from Sydney Harbour, ever, and only the 16th record for all of Australia. The other Sydney Harbour observation was also in Camp Cove, and no surprise, also by Erik Schlogl.

Shrimpgobies are curious beasts in that they form mutualistic relationships with alpheid shrimps, even sharing the same burrows. The shrimp has poor eyesight and so it perpetually builds the burrow while the able-eyed goby serves as a sentry at the burrow entrance. Each time the shrimp emerges from the burrow entrance, it rests one of its antennae on the body of the goby. If the goby detects danger its body quivers to alert the shrimp. If the threat escalates, the goby darts straight back into the burrow. The shrimpgobies on the other hand, feed by filtering mouthfuls of sand through their gill rakers at points near their burrows in search of benthic invertebrates.

This journal post was written by project leader and iNaturalist member, Dr Joseph DiBattista.

Congratulations to Karolyn Landat for their Photo Observation(s) of the Month of November of the sea slug from the Elysia genus at Camp Cove in southern Sydney Harbour, also observed on the same day here. This genus of colourful sea slugs is nested within the Plakobranchidae family, but do not be fooled! Even though they superficially resemble nudibranchs, they are not closely related to them at all. Instead they are sacoglossans, sometimes referred to as the solar-powered sea slugs.

At least some species of Elysia sea slugs have extraordinary feeding strategies. When nibbling on their primary food source of algae, they often retain the associated chloroplasts in the lining of their digestive tract, enabling them to survive solely by photosynthesis (without further feeding) for several months at a time. Other species of this genus can be stressed to sadistic extremes. Indeed, some Elysia are capable of regenerating their entire body anew from a severed head (gasp!!!). The observation by Karolyn Landat may be the elusive Elysia australis, but this will require a few more experts providing identification suggestions on iNaturalist given that there are over 100 species in the genus, many with ambiguous taxonomy.

This journal post was written by project leader and iNaturalist member, Dr Joseph DiBattista.