#predatory snail

[onenicebugperday]

New Zealand predatory snail, Powelliphanta hochstetteri, Rhytididae

This species, found on the South Island of New Zealand, is a carnivore that preys primarily on earthworms.

Photo 1 by samuelpurdiewildlife, 2-4 by absoluteandy, 5-6 by paddy18, and 7-8 (for scale) by conservatreenz

[drhoz]

A video that answers two questions, both of which never occurred to me - how do mussels actually produce the byssus threads that hold them down? And how can a now immobile bivalve protect itself from predatory snails?

[drhoz]

#899 - Dicathais orbita - Cart-rut Shell

AKA Cart-rut Murex. A large predatory, cannibal and scavenger snail, common on Australia’s southern coastlines - over here around Perth they’ve been seen killing Turban Snails (Turbo (Ninella) torquata), which are several times their size.

An interesting example on a clime species, too - on the east coast it has deep angular grooves in the shell, but as you move anti-clockwise around the coast it becomes smoother, with irregular grooves (and was called Dicathais textilosa), and by the time to get to WA it has no grooves at all, but does have bumps and nodules (and was named D. aegrota).

As it happens, i stopped by that Halls Head beach again, once I was back in Perth. The tide was very low, exposing limestone rock platforms I hadn’t even known were there. And they were thick with small Cart-rut shells, of the smoother kind found over here.

It couldn’t have been very pleasant for the other molluscs on these rocks, being outnumbered by your predators.

Phillips, Campbell and Wilson (1973) concluded that the variation is the result of water temperature, diet, substrate and degree of exposure to wave action.

Little Bay, Sydney

[drhoz]

Conus marmoreus (ex Zanzibar) attacks Littorina littorea. Injection of poison at 01:35. It takes about 15 min until the venom is affecting the snail and the cone can eat it. It eats the snail in one piece and leaves the empty shell behind. Every week the cone eats 1 or 2 Littorina.

It makes sense that a venom used against other molluscs doesn’t work as quickly as the the venom of species that hunt fish - the snails can’t run away afterwards. They’re still going to by paralysed, of course, but a dying fish could still swim off a good distance before succumbing, which is no good to the cone shell.

[drhoz]

A Conus catus harpooning and swallowing its prey. This video really shows how fast the prey is paralysed after it has been harpooned by the snail.