Student researchers help discover world's smallest frog

Mar 30, 2012 By Krishna Ramanujan
Paedophryne amauensis, the world's smallest frog species, on a dime. Rittmeyer et al. 2012

When two Cornell undergraduates and a recent graduate went on a field research trip to Papua New Guinea in 2008, little did they know it would lead to entries in the Guinness Book of World Records and a groundbreaking research paper.

The paper, published in January in One (), describes the discovery of two diminutive , Paedophryne swiftorum and Paedophryne amanuensis -- the two smallest frog species in the world. The latter is arguably the smallest known vertebrate species.

Michael Grundler '10 discovered P. swiftorum while exploring a stream at the biological field station near Kamiali, Papua New Guinea, where the students stayed for six weeks between June and August 2008. The work involved transects to explore how frog and changes with elevation.

On his knees poking at a millipede, Grundler heard a clicking sound he and others had previously assumed was crickets, but turning his head, he saw a tiny frog inflating its vocal sack.

"When we got back to camp, [Grundler] handed us a bag with a little frog," said paper lead author Eric Rittmeyer '08, a graduate student at Louisiana State University's (LSU) Museum of Natural Sciences. "None of us believed it was an adult, but in frogs, the calls are mating calls, and only vocalize, so we knew it was an adult."

Rittmeyer, Grundler and study co-author and classmate Derrick Thompson '09 then collected more specimens, which were identified as a new species. The reach an average size of 8.5 millimeters.

In 2009, Rittmeyer returned to as a graduate student with Christopher Austin, LSU associate professor of biological sciences and curator of herpetology at the LSU Museum of Natural Science and the paper's senior author. This time, near Amau Village, they heard the clicks of another frog and collected specimens of P. amanuensis for the first time. While P. swiftorum makes a series of double clicks, P. amanuensis has "regular single clicks faster than one per second; you could almost set a metronome by it," Rittmeyer said.

P. amanuensis, a close relative of P. swiftorum, is disputably the smallest in the world, with adult males averaging 7.7 millimeters in length. There's a dispute as to the actual titleholder of world's smallest: males of an anglerfish species, Photocorynus spiniceps, reach a maximum size of 6.2 millimeters. "However, these male anglerfish lack stomachs are not free living at maturity; instead, they are obligate parasites on the much larger females, which reach a size of over 50 millimeters," Rittmeyer said. Comparing the fish and the frog are not valid, he said.

P. amanuensis is listed in the as the smallest frog and smallest amphibian, and noted as the smallest vertebrate, though there is no such official category.

In the paper, the researchers examine how 29 extremely small species with a maximum size below 13 millimeters are distributed among all frog families. They found several of the largest families, such as Hylidae (tree frogs) and Bufonidae, do not have extremely small species, while the Microhylidae family has many species on the list, representing seven different genera (evolutionarily distinct groupings of organisms having common characteristics). "This suggests that small body size evolved multiple times within Microhylidae," Rittmeyer said.

They also found that the majority of the smallest frogs have direct development, meaning they hatch from eggs as mini-adults, rather than as tadpoles, and most of them live in leaf litter that stays moist year-round in tropical rainforests. This could represent a previously unrecognized ecological guild.

Explore further: New camera sheds light on mate choice of swordtail fish

add to favorites email to friend print save as pdf

Related Stories

New frog species is world's smallest vertebrate

Jan 11, 2012

LSU's Chris Austin recently discovered two new species of frogs in New Guinea, one of which is now the world's tiniest known vertebrate, averaging only 7.7 millimeters in size – less than one-third of ...

World's smallest frogs discovered in New Guinea

Dec 12, 2011

Field work by researcher Fred Kraus from Bishop Museum, Honolulu has found the world's smallest frogs in southeastern New Guinea. This also makes them the world's smallest tetrapods (non-fish vertebrates). ...

Frogs use calls to find mates with matching chromosomes

Dec 27, 2011

When it comes to love songs, female tree frogs are pretty picky. According to a new study from the University of Missouri, certain female tree frogs may be remarkably attuned to the songs of mates who share the same number ...

Micro-frog springs toxic surprise

Nov 03, 2010

A "robber frog" whose body is just 10 millimetres (three-eighths of an inch) long eats toxic mites and exudes their poison on its skin to deter predators, scientists reported on Wednesday.

Laos said to harbor many new frog species

Apr 20, 2006

The Wildlife Conservation Society in New York says new species of frogs -- and lots of them -- are being discovered in the Southeast Asia nation of Laos.

Recommended for you

Meteorite that doomed dinosaurs remade forests

16 hours ago

The meteorite impact that spelled doom for the dinosaurs 66 million years ago decimated the evergreens among the flowering plants to a much greater extent than their deciduous peers, according to a study ...

New camera sheds light on mate choice of swordtail fish

17 hours ago

We have all seen a peacock show its extravagant, colorful tail feathers in courtship of a peahen. Now, a group of researchers have used a special camera developed by an engineer at Washington University in ...

App helps homeowners identify spiders

20 hours ago

Each autumn the number of spiders seen indoors suddenly increases as males go on the hunt for a mate. The Society of Biology is launching a new app to help the public learn more about the spiders that will ...

User comments : 0