Invertebrate Spotlight: Protulophila Hydroids

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It was just announced a couple months ago that researchers in New Zealand found a specimen of the hydroid Protulophila that was previously believed to be extinct for 4 million years.  Before this discovery, these organisms had only been found in fossil records in the Middle East and Europe, some of which dated back 170 million years.

Awesome discovery, right? But to take a step back now, what exactly is a hydroid?

It’s a Cnidarian, which is a phylum of aquatic invertebrates; other cnidarians include corals, sea anemones, and jellyfish.  Through their lifecycle, cnidarians have two basic forms: (1) a polyp that is sessile and attached to a substrate, and (2) a free-swimming medusa.

 

This is the lifecycle of Obeila sp., a hydroid with a global distribution. Photo at: http://www.njscuba.net

 

The fossilized symbiotic hydroid was found inhabiting the tube of a one-million year old serpulid tube worm fossil in Wanganui, New Zealand.  Because they are found within fossilized rocks, these cnidarians have been deemed “living fossils.”  This finding gave the researchers an idea: maybe the hydroid could be found alive somewhere in New Zealand waters.

An artist’s rendition of the symbiotic relationship between Protulophila hydroids and serpulid tube worms. Image credit: Dennis Gordon/Erika MacKay/NIWA.

Sure enough, the scientists examined samples taken from Picton, NZ that were collected in 2008 and found preserved Protulophila specimens.  Dr. Dennis Gordon, one of the scientists involved in the finding, says, “Finding living Protulophila is a rare example of how knowledge of fossils has led to the discovery of living biodiversity.”

A scanning electron microscope image of a resin cast of Protulophila polyp chambers and connections in a serpulid worm tune. Photo by: Paul Taylor, Natural History Museum, London.

He also said that “Our detective work has also suggested the possibility that Protulophila may be the missing polyp stage of a hydroid in which only the tiny planktonic jellyfish stage is known. Many hydroid species have a two-stage life cycle and often the two stages have never been matched. Our discovery may thus mean that we are solving two puzzles at once.”

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