Netted dog whelks (Nassarius reticulatus) at Falckenstein Beach

Netted dog whelks (Nassarius reticulatus, LINNAEUS 1758) are named after the structure of their shell. This is comparatively thick and criss-crossed with longitudinal and spiral ridges forming a typical reticulated pattern. The shell itself is pointed and oval / egg-shaped with up to 10 spirals, reaching a maximum length of ca. 3cm.

Netted dog whelks are scavengers and predators with a long, protractible siphon. They detect their food by chemosensors, i.e. the respiration water flow pumped in via the siphon is checked for chemical stimuli from prey objects. Distribution of the netted dog whelk in the Kiel Bight is, in contrary to adjacent regions in the Belt Sea, confined to the lower sublitoral below 5m depth. There, the animal predominantly inhabits sandy and muddy bottom. The compared to the aforementioned areas deeper occurrence in the Kiel bight (so called brackish-water submergence) is related to the minimum salinity of 15 required by the netted dog whelk. In the (western) Baltic, an according salinity is restricted to deeper areas. During winter, the whelk migrates into deeper water. In the Mecklenburg Bight, Nassarius reticulatus is rather rare and until a few years ago was regarded as extinct or missing respectively. A more frequent appearance in that area can at least partly be related to increased inflows of high saline through the Belt Sea into the western Baltic. In spite of their minimum salinity requirements, netted dog whelks are comparatively insensitive to oxygen depletion situations.

If you happen to discover one of the often buried and due to their coloration highly camouflaged animals, a closer look may be worth risked: Often netted dog whelks are associated with symbiontic hydrozoans (Podocoryne carnea) that settle on their shells (see picture in this report).

Further information on biology and distribution of netted dog whelks in the Baltic Sea (in German) can be found here.

Characteristics

• Shell length: 25 to 30mm
• Color: brown, yellowish-brown, greyish-brown
• Shape: Characteristic reticulated pattern on shell surface. Shell pointed, oval to egg-shaped. Aperture oval and small, with short siphonal canal
• Distribution: Lower sublitoral beyond 5m depth.
  Atlantic from Norway to Morocco; North Sea, Mediterranean, Black Sea.
• Taxonomy:

look up in "European register of marine species" (ERMS).