How does the intertidal spider Desis marina (Hector) remain under water for such a long time?

Abstract

Desis marina (Araneae: Desidae) was found on the Kaikoura coastline, living in hollows under the holdfasts of the bull kelp, Durvillaea antarctica. Field surveys showed that they were distributed down to 77 cm below MSL and that spiders living at such depths are required to survive up to 19 days of tide-induced submergence. Although D. marina is a terrestrial animal, no special respiratory adaptations were required to enable them to live in this unusual aquatic habitat. To determine the mechanisms that made this possible, a series of laboratory experiments was run to measure the amount of air that was required to ensure the survival of animals of various weights (all at 17.5°C). These data were then compared to field measurements of air space available, tide-determined submergence times, and spider size. It was concluded that in the field, the available air space in and around the nest always provided sufficient air to ensure survival, even during the most extreme periods of submergence. The distribution of the spiders that were living in association with D. antarctica appeared to be controlled by the factors which limit the distribution of the kelp.

Keywords:

• Desis marina
• Desidae
• spiders
• intertidal environment
• respiration
• oxygen demand
• habitat