I posted several sightings of Tenagodus australis on iNaturalist during September 2025. Tenagodus australis is a member of “Cerith Snails and Allies Superfamily Cerithioidea”
One of my sightings from 6th September was posted at https://inaturalist.ala.org.au/observations/313054913 . I described the sighting as follows; –
“Common on this outing. Mostly on lower beach at low tide, and anecdotally becoming a more common molluscan species washup as the duration of this prolonged, severe harmful algal bloom (HAB) increases. I note, for what it is worth, that I hadn’t posted this species to iNat until this year (apart from one in 2023), despite being interested in marine life generally for years, and having been an iNat enthusiast since about 2016. I also note that nearly all the Tenagodus australis specimens I’ve seen washed up have had brown macroalgae attached, so they are presumably relatively long lived snails that can usually cope with major storms and related natural events without being pulled out of the substrate (the wave energy acting on the tall fucoid brown algal plants that they usually have anchored to them perhaps is rarely enough to dislodge a healthy Tenagodus australis, but it’s enough to dislodge a dead or dying one. Another likely contributor to any such tendency, during an HAB, would be the reduced protection from high wave energy resulting from the HAB having killed or thinned out other benthic lifeforms such as razor clams and mussels sharing similar habitats. All mere speculation on my part.”
“Further to the above Notes, I should add that since posting this observation I’ve read in a decades-old publication, that Tenagodus australis tends to associate with a certain type of sponge, being found buried in the sponge with only the ostia of the casings visible on the surface of the sponges. So the brown macroalgae stipes are probably attached to both sponge and Tenagodus australis therein/thereupon, for what it is worth. Speculation mainly since I have not read any recent information on the biology of this gastropod mollusc.”
I posted another sighting (from Myponga) on 7th September at https://inaturalist.ala.org.au/observations/312336886
I posted another sighting on 10th September at https://inaturalist.ala.org.au/observations/313014046
I posted another sighting on 13th September at https://inaturalist.ala.org.au/observations/313687330 . My comments here were “Another example from the lower beach at the mouth of the Bungala River, showing the remaining benthic habitat dislodged along with the subject snail casings. The common Kelp plant, now also dead, has probably been the victim of the HAB and major storm events combination that has caused such damage to SA’S marine and estuarine ecosystems and infrastructure. A pending observation has some very dark bluish black sponge washups as subject, and I have recently read that Tenagodus australis usually associates with such a sponge, apparently being largely buried within such sponges when alive, normally. This information was in an old (several decades) mollusc ID handbook by the Malacological Society of South Australia, and I haven’t yet read any more recent descriptions of this wormlike snail’s biology. However, I am struck by the coincidence of the increasing numbers of dead Tenagodus australis casing washups lately and the increasing numbers of dark, irregular forms of sponge washups, matching the sort of sponge referred to in the old handbook above.
For what it is worth, in the upper L field of images 1 and 4, there’s a small blob of very dark sponge, separate from the main Tenagodus australis tubes. Whether it is a type of sponge representing a preferred microhabitat for Tenagodus australis, I’ve no idea, and I also note that the main Tenagodus australis tubes have some remnants of much paler mauve to purple-bluish sponge around them, along with the “roots ” of the Common Kelp holdfast. Just saying…:)”
(The above photos are not in any particular order.)