Up to 16 cm (6+1⁄4 in) long with distinctive leopard-like dark markings on its dorsal side, the smooth toadfish has a rounded front and tapers to a narrow tail at the back.

Often an unwanted catch by anglers, the smooth toadfish is highly poisonous because of the tetrodotoxin present in its body, and eating it may result in death.

[5] French naturalist Auguste Duméril erected a new genus in publishing the species as Aphanacanthe reticulatus in 1855 from a description authored by his countryman Gabriel Bibron,[6] who had died suddenly.

However, it is a nomen nudum as it does not provide enough detail or information to diagnose or properly describe the species,[7] since Duméril had only written a (French) translation of the genus name—αφανης qui nе parait pas, ἃκανθα, épine ("with no thorns").

[6] British ichthyologist Charles Tate Regan described Spheroides liosomus in 1909 from specimens collected in Melbourne, Hobart, Flinders Island and Port Phillip.

[3] The smooth toadfish was assigned to several other genera after it became clear that it fell outside a more restricted definition of Tetr(a)odon,[3] including Torquigener.

The smooth toadfish has tiny spines that are entirely within the skin layer; these run along its back from the nasal organs almost to the dorsal fin, and along its sides from the eye to the pectoral fine, and along its underparts from behind its mouth to its vent.

[20] A South Australian field study on wrack and associated fauna found that the smooth toadfish was associated with larger volumes and aggregations containing green algae.

[22] Its large range, abundance and stable population mean the smooth toadfish is classified as Least Concern on the IUCN Red List.

[17] Its diet includes molluscs such as black mussels, pipis,[16] white sunset shells (Soletellina alba) and oysters (Crassostrea),[17] crustaceans such as semaphore crabs and shrimp, and brown algae.

Raised levels of arsenic, cobalt, cadmium and lead in gills suggested the fish absorbed these from the surrounding water.

[16] A study of asymmetry of fish bones in smooth toadfish in various parts of Sydney and Hawkesbury River estuaries showed a relationship between exposure to organochlorine pesticides but not heavy metals, indicating the finding may correlate to stress from organic toxicity.

[27] Notorious for taking bait from fish hooks, the smooth toadfish is an unwanted catch for anglers as its flesh is highly poisonous and unfit for human consumption.

[15] A man named John Buff was fatally poisoned after catching and eating toadfish in Duck River in 1821 near Parramatta; his case and subsequent coroner's inquest were published in The Sydney Gazette.

The smooth toadfish was responsible for the deaths of the wife and two children of Captain Bell of New Town near Hobart in a widely publicised case in March 1831.

[9] Colonial surgeon James Scott wrote, The melancholy and dreadful effect produced by eating it was lately instanced in the neighbourhood of Hobart town ...

The family's three servants, one of whom appeared to have been poisoned as well and was ill, were placed in custody separately to stop them communicating with each other while the investigation proceeded.

The inquest concluded with a finding of accidental death, with some deliberation over whether Speed should have been charged with manslaughter or even murder after hearing the warning.

The symptoms of poisoning, which are predominantly neurological, include ataxia, in addition to numbness and/or paraesthesia (tingling) around the mouth, lips, and limb extremities.