Subzero temperature adaptations in arthropods from the summit of Mauna Kea, Hawaii

A preliminary study of subzero temperature adaptations was made of arthropods from the summit (4,200 m) of Mauna Kea, Hawaii. This barren, alpine stone desert aeolian habitat commonly experiences snow and nightly subzero temperatures in spite of its subtropical location. In mid-December, collections were made of a wolf spider (Lycosa sp.). the lygaeid bug (Nysius wekiuicola), and a noctuid caterpillar (Agrotis sp.). The Agrotis caterpillars were freeze tolerant. They had quite high supercooling points (SCP = −4.8°C) and survived a 24 hr frozen exposure at −6.2°C. The site of nucleation is apparently not the hemolymph, as the hemolymph SCP was −15.1°C. The spiders and wekiu bugs were not freeze tolerant. The SCPs of the spiders (X = −5.8°C) were not particularly low, but these highly mobile arthropods may be able to seek thermally buffered microhabitats when the need arises. The wekiu bugs showed greater supercooling abilities, with some individuals supercooling to −18°C, although the SCPs were quite variable. The subzero temperature adaptations of the arthropods from such an isolated subtropical site are remarkable adaptive capabilities.