Photo courtesy of Hendrik Freitag, Ph.D

AMID THREATS to biodiversity in the Philippines, four new crab species have recently been found in Palawan by a research team led by Hendrik Freitag, PhD, an associate professor of the Biology Department.

The crabs were discovered in the freshwater inlands of the island province. They have distinct purple and reddish brown colorations.

The newly discovered endemic species, together with the previously known Insulamon unicorn discovered by Japanese and Singaporean researchers in 1982, make for a revision of the entire Insulamon genus.

The genus is not found elsewhere than Palawan. “You cannot even find it here in Luzon [island], in Mindoro or Mindanao,” said Freitag.

The discovery is part of the Aqua Palawana Program initiated by Freitag and Manfred Jäch, PhD of the Natural History Museum in Vienna. Researchers who are part of the program seek to investigate the macro invertebrate fauna of Palawan and other bio-diverse areas.

Freitag published a paper about the four new species in the National University of Singapore’s Raffles Bulletin of Zoology.

Distinct characteristics

Freitag said that the most important distinction of these species is the unique structure of their pleopods, the fork limbs of crustaceans that hold the eggs in females and are copulatory organs in males. These structures are usually adapted for swimming.

Besides the structure, the crabs are also distinct in color from other species. “Some [have a] really nice purple color. Others are rather brownish. It probably depends on their diet and social position,” said Freitag.

He hypothesized that colors are meant for the crabs to distinguish status or sex, saying that orange and reddish colors might mean dominance while purple ones pointed to the females and smaller males.

“These crabs were thought to be of the same species,” said Freitag. In 2000, however, he already noticed that there were more than one species of the genus.

According to Freitag, he got the idea of the new species in a biological survey he conducted around the area of the Puerto Princesa Underground River, a national heritage site and one of the New7Wonders of Nature.

The crabs are edible, but no common name has been given to the species in spite of locals being acquainted with the crabs.

Endangered species

According to Freitag, these species are considered endangered because of their endemism and limitedness to small areas, in contrast to widely distributed genera. The most widely distributed Insulamon palawanense are the least endangered of them.

“These freshwater crabs cannot disperse anymore to the ocean or real land, so they really depend on rivers and other [freshwater ways],” he said. However, he added that a lot of these places are polluted, destroyed or dried up because of deforestation.

The Insulamon palawanense is mostly seen on mainland Palawan. The Insulamon magnum, the largest among the species in the genus, and the Insulamon johannchristiani are only native to northern Palawan. The Insulamon porculum, which has certain structures similar to a pig’s tail, is limited to small areas in central Palawan.

Freitag sees the ancestral practice of kaingin as the most serious threat to the habitats of the species since they dwell on forest rivers.

In an email interview, Jäch said, “Mining, illegal logging and establishing of oil palm plantations may be considered serious threats.” He added that these practices lead to the destruction of rainforests and bodies of water near it.

“These are the key habitats of the very large majority of endemic species. Everything that affects these habitats is a threat to the unique biodiversity.”

To help protect these endangered species, Freitag works with Katala Foundation, a local non-government organization active in the conservation of endemic wildlife species.

Biodiversity hotspot

“These [crab species] are quite rare but [they] show the high rate of endemism and biodiversity richness in the Philippines,” said Freitag. “It is well-known already that the Philippines is a biodiversity hotspot in a worldwide scale.”

According to Conservation International, an environmental organization based in the United States, the Philippines is distinguished as one of the 17 mega-diverse countries that are sanctuary to most of the earth’s flora and fauna.

Freitag also recognized the rich biodiversity of Mindoro and will be conducting another research in the area. He has also involved students in his research expeditions.

“That’s what I try [to do] because it will be best if local experts will deal with this description of species and biodiversity in general, as it also helps [if] any common [person] will appreciate the rich biodiversity of the country.”

Life sciences majors Arielle Vidal and Kimberly Go are Freitag’s thesis advisees, and are involved in the research of species under the Hydraena genus—water beetles found in Mindoro and Palawan.