CRITTER CONFIDENTIAL
Netted dog-whelk
Marine biologist Paul Naylor unearths new mysteries in the private life of an overlooked marine creature
Tritia reticulata
Busy aggregation of netted dogwhelks on a dead spider crab
If you ’ re not already an admirer of these busy little molluscs , have a good look at the next dead crab or fish you come across and , also , at the surrounding seabed . Netted dog-whelks are avid scavengers , and while there might already be a hungry congregation of them on the carcass itself , I
This hermit crab in a heavily sponge-encrusted shell appeared to be considering moving to a lighter model
14 find the sight of latecomers hurrying to the feast especially eye-catching .
With their long siphon held aloft , even if much of the rest of them is submerged in the sediment , they are drawing in water to detect chemicals released by the food and are heading straight for it . If the snails ’ trails are visible on the seabed behind them , as they so often are , it is obvious they are homing in from several metres away , which is an impressive distance relative to their size .
The netted dog-whelk is distinguishable from the dog-whelk ( Nucella lapillus ) by the grid-like pattern of ridges and grooves on its shell , which is reflected in both the English and scientific names . There is also a habitat difference , with netted dog-whelks being most readily spotted on sandy and muddy seabeds , while dog-whelks are common among shallow rocks where they prey on live animals such as barnacles , limpets and mussels .
The egg capsules of netted dog-whelks can be found laid on seaweed , seagrass or rocks and are very distinctive , looking like tiny flattened transparent vases with the individual eggs visible inside . The eggs hatch into free-swimming larvae that spend several weeks in the plankton before settling , instead of immediately developing into miniature crawling snails like the eggs of dog-whelks and the large common whelk . It ’ s another example of how very similar molluscs can have startlingly different life histories .
Talking of mystery … while sponges often