New Amphipod Species Discovered On Museum Shelves

In October 2010, Dr. José Manuel Guerra-Garcia, a colleague from the University of Seville, was visiting to examine our collection of caprellid amphipods. After discovering two particularly unusual specimens, he called me over to his microscope. The specimens came from a submerged cave nine metres deep on Santa Catalina Island, off the coast of California. They were collected in 1970 and placed in our collections, and not seen until now. Could they be something new? They were very tiny—only two to three millimetres long. They also had tiny bumps on the sides of their bodies that were very unusual for the genus Liropus. To the layperson, these specimens would be indistinguishable from all the rest, but for an expert like José, they stood out. The combination of peculiar characteristics and unique location led us to make it official. In 2013, José and I formally published the new amphipod in the journal Zootaxa as Liropus minusculus, aptly named for its tiny size.

A skeletal, shrimp-like animal. — *Liropus minusculus*. Although this male caprellid amphipod is the smallest of the genus, it still looks quite fearsome! The large, sharp claws of the pair of legs on the body posterior to the head are used for fighting other males during mating and also likely to capture small animals in the water. It uses the last pair of legs with the impressive claws to grab onto algae or other substrates.

It is very common for collections to wait for decades in a museum before an expert comes to examine them. But finding new species is so exciting that some don’t have to wait that long. Museum scientists and their colleagues find and describe new species in publications every year. By doing so, we add to the world’s known biodiversity and document it through time and changing climates. In this way, we are fulfilling one of our fundamental roles as a museum.

In my career at the museum, my colleagues and I have described and named about 100 species of amphipods, including one deep-sea species Macroarthrus victoriae, named in honour of my daughter, Victoria. Now that’s something really special!

Line drawings of a shrimp-like animal. — A scientific drawing depicting the unique characteristics that define *Macroarthrus victoriae*.

Amphipods are distantly related to the common crustaceans that most of us know and love to eat, such as shrimps, lobsters, and crabs. However, caprellids—or skeleton shrimp—are a very odd group of amphipods that get their name from their extremely elongated and slender bodies.

While other Liropus species have been described from Mediterranean, African, and Japanese waters, this was the first record from the North-East Pacific. Caprellid amphipods are very poor swimmers as they have lost the pleopods—structures which grant other amphipods superior swimming abilities. They get around either by violent contractions of their bodies or more commonly, by grabbing with the front legs and releasing the back ones, similar to how an inchworm moves.

A shrimp-like animal against a black background. — *Ischyrocerus latipes*. This male was collected from the Beaufort Sea in 2004. Its enlarged second pair of legs (gnathopod 2) are used for cleaning, grooming, collecting bits of food, and for fighting off other males while mate guarding a female.

After our big discovery, we received a special surprise! I was contacted by a colleague who exclaimed: “Ed, you have a new species in the top 10 new species of 2014 list!”.

Liropus minusculus was chosen by the International Institute for Species Exploration (IISE) at the SUNY College of Environmental Science and Forestry from about 18,000 other new species identified that year. I later found out that this list is an homage to the many scientists around the world who are working to uncover the vast biodiversity of our planet.

So, not only had José and I published a new species, but we had the honour of being included with nine other species in this special top 10 list. Priceless.