Hi Wes, Well I don't have an in-depth understanding of this pnenomenon, but I can mention a few observations. First, our "splash zone" is relatively devoid of molluscan life. Our mollusks stay in the ocean where they belong. No Siphonaria clinging to the rocks above high tide level, no Neritina scooting up tree roots, or Littorina doing arboreal gymnastics. Just about everything lives below mean high tide level. If you go to the beach at high tide, you generally won't find a living mollusk exposed. Therefore, every mollusk gets submerged for at least a few hours every day. Although I never really thought it out before, I suspect your question is a key to why this is so. In winter, the splash zone above the high tide level can be covered by a thick layer of dense ice, which would entomb anything living there. However, the intertidal area never develops any appreciable ice buildup because it is submerged several hours a day in sea water which is, obviously, higher in temperature than the freezing point of sea water. The salt in sea water has some protective value, reducing the freezing point from 0 degrees C (the freezing point of fresh water) to about -2 degrees C (from +32 degrees F to about +28 degrees F), and some intertidal mollusks can have higher salt concentrations in their tissues than in the surrounding water. Also, some intertidal gastropods tend to stay low on the sides of rocks, close to the substrate in winter, rather than crawling on top of them; or they congregate in deep fissures or tidal pools; and some may migrate to a lower area of the intertidal zone. Presumably all these bahaviors are aimed at having a longer total time of submersion. Also, some of them remain under dense growths of rockweed. Whether that has any insulative value, I have no idea. So there are some mechanisms that help such animals survive harsh winter conditions. Still, when there is a sudden drop to unusually cold conditions, especially sub-zero conditions (that's sub-zero Fahrenheit, about -18 Celcius), many intertidal mollusks do in fact die. Sometimes there are massive localized kills of various species. One time after a freeze, I saw a drift line about 4 feet wide, several inches deep, and a quarter of a mile long, composed almost entirely of Crepidula fornicata (slipper limpet) shells. Another time, hundreds of thousands of Mytilus edulis (blue mussel) washed in. And another time, a beach was completely covered with Pecten irradians (bay scallops), all gaping open with the frozen soft parts still inside, and every one of them with its hinged side facing into the wind, which was substantial! Yes, we do have a fair number of species here, if you know where to look. But nothing comparable to the tropical zones. The number of species, diversity of form, and range of colors of mollusks in the tropics far outweighs what we have here. Rhode Island isn't exactly Arctic conditions (thank goodness!). We usually have snow only three months or so. Maybe one of our more northern correspondents could add something to this. Ross - are you there? Regards, Paul