#australian seashell

I’ve covered the adults elsewhere but here’s one laying eggs. The Baler glues them to solid substrate and lays them down layer by layer with regularly spaced holes and ridges to ensure good water flow. 

Aka the  ridged lucine. 

Native to SE Australian shores, but for some reason all but two of the records at ALA are limited to the New South Wales coastline.

Lucinid bivalves live in muddy sand or gravel at or below low tide mark, and like this example have rounded shells with forward-facing projections, etched with concentric rings. They do not have siphons, but the extremely long foot makes a slime-lined channel for the intake and expulsion of water.

Lucinids are also remarkable for their symbiosis with sulphur-reducing bacteria, hosted in specialized gill cells called bacteriocytes. The bivalve pumps sulfide-rich water over its gills and the bacteria use the sulphur to carbon into organic compounds, which are then transferred to the host as food.

Lucinid bivalves originated in the Silurian but did not diversify until the late Cretaceous, when seagrasses and mangroves evolved and provided much larger areas of sulphur-rich sediment. They’re pretty good for the seagrasses, too, since the lucinid-symbiont holobiont removes toxic sulfide from the sediment, and the seagrass roots provide oxygen to the bivalve-symbiont system.

In at least two species of Lucinid, the symbionts are also able to fix nitrogen gas into organic nitrogen.

Photos by @gemfyre.

A very large carnivorous sea snail that we found at Point Peron the other day, where it was engrossed with devouring a Turban Shell (Turbo torquatus).

Balers have been used to scoop water out of canoes, which is how they got the common name, and while ‘melo’ means ‘apple-shaped’ it’s also been applied to the Latin for watermelons, eggplants, and other large oval objects.

Balers are generally nocturnal, burying themselves in the sand during the day, and feed on other molluscs including scallops, turban shells, tritons and even other volutes. They seize it with their large colourful foot and plugs the prey’s aperture, essentially smothering it. This one clearly found itself too far from open ground to bury itself and eat in peace, and was resting upside down on the rock platform just offshore.

Another slit-limpet, this time with the hole in the shell shifted towards the rear, and a rectangular ridge at the front.

Found along the western and southern coastlines, although the Atlas of Living Australia also places a few sighting in the vicinity of Ayres Rock. Methinks somebody goofed (or, more likely, just had ‘Australia’ as the locality data.)

Fairly common across much of Southern Australia. Not the only limpet with a cross-shaped pattern, but it is the most common over here, apparently.

One of Australia’s five Batillariids - and one of those was accidentally introduced from New Zealand.

That said, B. australis is out-of-place too - it’s native to the east coast of Australia. There used to be a South Australian population, now extinct. And about 60 years ago they turned up in the Swan River here in Perth, and they’ve completely taken over. Estimates suggest 3.6 billion of the little buggers in the Swan Canning Riverpark, and they’re out in Cockburn Sound too, which is where I found these two. At the beach beside UWA, they were literally piled up in their hundreds.

To add further notoriety, they’re a host of the parasitic fluke Austrobilharzia. The larvae of these trematodes are ejected from the snail, and they have to find the legs of a wading bird to drill into. But since they are animals of very little brain, they apparently think that humans are actually wading birds, drill in, and are promptly killed. The ongoing immune reaction as your body try to destroy the dead invader produces the condition known as ‘Swimmer’s Itch’.

They aggregate on mud or muddy sand in well-sheltered areas such as mangrove swamps and in the mouths of coastal lakes, where organic detritus settles easily. They prefer areas above mid-tide, where they leave a maze of feeding tracks crawling over the surface. They were an important seafood for native peoples of the east coast, and the shells are common in middens.

The Volutes are yet another family of large predatory snails, and which happily come near the end of the alphabet since I found this one after starting the gastropod posts. Some species are under a centimeter long, but the Balers can be around 50. They live in clean sandy areas, and some are thought to burrow during the day.

Some species are particularly ornate and popular with collectors, but this one had been rolling around in the surf at Woodman Point for some time, and if it had any sharp corners or decoration they’ve been worn off. It does still show the braided columella that is diagnostic of the family, on the other hand. It’s probably A. grayi.

Volute eggs hatch directly into little snails - this means populations on nearby islands remain genetically distinct, if there’s a deepwater channel to stop the snails mixing. This can produce wide differences in markings even within one species.