Some species are known the way a rumor is known. Hapalochlaena nierstraszi was described by William Adam in 1938 from a single specimen taken in the Bay of Bengal. For most of a century that was the whole public file: one animal, one name, and a place on the list. In 2013 a second specimen was reported from the Chennai coast, and the name stepped, just slightly, out of the archive.
Two animals is not a natural history. It is a start. Size figures that get repeated, roughly eight to sixteen centimeters and a weight of a few to about eighteen grams, come from that very small sample and should be carried lightly. Range maps that paint a confident swath of Indian Ocean around this name are guessing. The honest sentence is that a blue-ringed octopus lives, or lived, in the Bay of Bengal, and that we do not yet know the population.
That scarcity changes the tone of the other essays in this journal. The greater and southern species are common enough to have been filmed, kept, and argued over. Nierstraszi is a reminder that “blue-ringed octopus” is a genus, and that parts of a genus can be almost unknown while the famous members are on posters. Rarity is not the same thing as safety, and fame is not the same thing as a finished taxonomy.
If a later revision moves this name, or folds it into another, the field note still stands. The Indian Ocean side of the story is thinner than the Australian side, and anyone writing as if all four species were equally well studied is smoothing over a real gap.