Brechites australis (Australia watering pot)

The “Australian Watering Pot” is a fascinating bivalve native to Australia. It is member of the peculiar watering pot family Penicillidae, members of which grow a normal shell with two valves like other clams in earlier stages of life but at one stage suddenly switches over to growing a calcareous tube made of highly organised aragonite crystals instead. This is secreted by a thin organic film covering the tube, and the animal is capable of repairing damaged tube. The early shell is not lost but still attached to the tube in opened position (see center image), proving its Bivalvia identity. It gains the common name from the fact that the bottom end (pointing downwards in life) of the calcareous tube has many pores just like a gardener’s watering pot, and it can actually function like one if you put water through the top end (where siphon exits, pointing upwards in life). Debris around the tube is often caught as it grows and fuses as part of the shell, like many empty mollusc shells in the specimen depicted. It is a rather common filter feeding species living on soft bottoms of shallow water around -2~10m deep. Average tube length 170~180mm, large specimens may exceed 200mm. – Adapted from Chong Chen’s post