Pearse Resurgence: Cave divers discover three new species

December 04, 2016

New Zealand (Bernd F. Laeschke – June 2012): Cave divers discovered several new species - a transparent amphipod, a worm, and a small snail -in the Pearse Resurgence, a system in the remote Motueka Valley on the South island of New Zealand near Nelson. Pearse Resurgence is connected to the Nettlebed Cave, a deep, extensive cave system in the Mount Arthur Range. It was thought to be the deepest cave system in the southern hemisphere until divers pushed deeper in the nearby Ellis Basin cave system during an expedition in April 2010.

"It's not easy to get inside the caves, and we want to know about the very specific life in them," says Dr. Graham Fenwick, a scientist at New Zealand’s National Institute of Water and Atmospheric Research (NIWA). "It's important to do an inventory of life in New Zealand, and in this case, it's a pretty special type of environment, and we don't have many limestone karst systems that are readily explored."

Worldwide, these aquifer studies are yielding rich troves of biodiversity. The importance of the stygofauna is twofold - they contribute to the health of the aquifer by bio-filtration and in turn they may represent an important marker of the health of the water.

The bio-survey in the Pearse Resurgence was performed using two techniques. Firstly, any invertebrates observed free swimming in the cave were captured by hand using a tube with a bulb on the end. The second technique involved the deployment of baited fauna traps in the cave at depths from 16 to 377 feet (5 to 115 meters) below the surface. Small plastic jars baited with a small shrimp were filled with nylon gauze and secured in various places in the cave, in crevices and amongst sediments.

One species of amphipod crustacean new to science dominated the stygofauna collected from the Pearse Resurgence. This species is completely colorless. "It is 6-8mm long, the divers could see it crawling over rocks, it really is a beautiful animal. It belongs to the poorly known genus Paraleptamphopus, one of two genera within the New Zealand endemic Family Paraleptamphopidae," says Fenwick.

Originally described from Canterbury's deep alluvial aquifers, this family is represented by species inhabiting groundwater and marginally subterranean habitats throughout New Zealand. Within the Pearse Resurgence, this amphipod was found most commonly within the main shaft, where the expedition's divers stalked it on rock faces or caught it in small traps baited with shrimp.

It appears to live on the water-worn rock surfaces from within 6.56 feet (2 meters) of the surface of the main shaft's air bell, to depths of more than 131 feet (40 meters) where they were taken amongst gravel and finer sediments.

The two other stygofaunal invertebrates discovered in the system were a minute gastropod snail (about 0.06 inches or 1.5 millimeter in diameter) and an oligochaete worm (about 0.31 inches or 8 millimeter long). Both were taken from rare deposits of fine sandy sediments within the main shaft at depths from 49 to 112 feet (15-34 meters). "All these new finds are endemic to this area," says Fenwick.