Marine leeches provide clues on climate change

Mr Kolb diving for leeches in the Arctic Ocean
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Marine leeches provide clues on climate change

Elusive marine leeches in Antarctica are the focus of study on how climate change is affecting vulnerable fish species.

German-born doctoral researcher Juergen Kolb says it is proven that leeches transmit viruses and bacteria into host bodies, and that new strains are currently arriving in Antarctica.

“The situation is potentially quite dangerous. If conditions become warmer, we’ll get new types of pathogens being transmitted into fish. Not only can this cause harm or death of individual fish but lead to the collapse of entire fish populations,” says Mr Kolb. “Eventually this could threaten commercial fishing industries and the food sources that humans depend on.”

Based at Massey’s Institute of Natural Resources in Auckland, he is one of a handful of biologists world wide studying marine leeches.

The bloodsuckers have generally been ignored by scientists because they are so hard to find and collect, he says. But gaining a better understanding of their biology and ecological importance could provide vital clues about the impact of climate change on fragile ecological systems and the survival of less adaptive animal species.

Although little is known about marine leeches in extreme environments such as Antarctica, their physiology is thought to be similar to fresh water and terrestrial leeches in warmer habitats.

Based on his earlier research on Arctic marine leeches, Mr Kolb says it is highly likely leeches will survive any rise in water temperature from global warming that would threaten other extreme cold water-adapted species more sensitive to change.

Mr Kolb began his studies at the University of Freiburg. In 2006 he sailed on a Norwegian scientific research vessel to Svalbard Archipelago – halfway between Norway and the North Pole – where he dived up to 35 metres deep in freezing waters. But difficult conditions meant he was able to collect only seven leeches, which were attached to seaweed, algae, fish and crabs. He then decided to continue his research from New Zealand because of its accessibility to Antarctica. He hopes to gather a much greater quantity of leeches, this time by an easier method of catching leech-covered fish off the Antarctic coast. He will carry out genetic analysis on the leeches to determine how closely they are related to other leech species.

Leeches, or Hirudinea, are a class of Phylum Annelida or segmented worms - most widely represented by the common earthworm. Leeches are divided into sections like an earthworm but with suckers at both ends. A leech is a thin tube of muscles around a cavity containing a gut and reproductive systems. It can flatten its body to avoid being removed from a host and, if necessary, swim in an undulating movement for kilometres.

“I’ve always been fascinated by parasites,” says Mr Kolb. “They are extreme in terms of their physiology and adaptation to their parasitic lifestyle. They are, by nature, ultimate survivors – if you are a fish you have a hard time killing a leech.”

ENDS

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