The first case of a Portuguese beetle living exclusively in groundwater

New to science, the species was named after Pluto, the ruler of the underworld in Greek mythology

A diving beetle demonstrating various adaptations to the life underground, including depigmentation and evolutionary loss of eyes, was discovered at the bottom of a clay pound in the cave Soprador do Carvalho, Portugal. The species turned out to be the very first in the whole order of beetles (Coleoptera) to be known exclusively from the underground waters of the country.

The Soprador do Carvalho cave (Portugal) is the type locality of the newly described species Iberoporus pluto. Photo by Ignacio Ribera.

Despite not being able to find any other specimens during their study – save for the single female, the team of Dr Ignacio Ribera, Institute of Evolutionary Biology (Spain) and Prof Ana Sofia P. S. Reboleira, University of Copenhagen (Denmark) identified the beetle as new to science, thanks to its unambiguous morphology in combination with molecular data.

Profile view of the newly described species Iberoporus pluto. Photo by Ignacio Ribera.

Aptly named Iberoporus pluto in reference to the ruler of the underworld in Greek mythology Pluto, the species was recently described in the open-access journal ZooKeys.

With a uniformly pale orange body measuring 2.8 mm in length and 1.1 mm in its widest part, the beetle is larger than the rest species known in its genus, and its appendages are longer and more slender. While blindness and depigmentation are clear adaptation to life away from sunlight, the elongated limbs and antennae reflect poor swimming abilities needed in a subterranean habitat. Going for 4 km in horizontal direction, Soprador do Carvalho is the largest in the Dueça cave system, located in the north-eastern part of the Sicó karst area in central Portugal. In recent years, the cave is being explored for tourism.

“The knowledge of the subterranean fauna from Portugal has significantly increased over the last decade, with the description of a high number of obligate subterranean species (tripling their number) and the establishment of new biogeographic patterns,” explain the authors of the study. “A high number of these species are stygobiont (i.e. confined to groundwater), mostly from wells in the north of the country, where evapotranspiration is higher.”


Original source:

Ribera I, Reboleira ASPS (2019) The first stygobiont species of Coleoptera from Portugal, with a molecular phylogeny of the Siettitia group of genera (Dytiscidae, Hydroporinae, Hydroporini, Siettitiina). ZooKeys 813: 21-38.

Saving the Underworld: Clarifying the subterranean fauna classification for improved conservation

Inevitably, many habitats, including the particularly vulnerable subterranean ones, will continue being erased from our planet as a result of human activities and interests. The challenge is to protect the ones that are the sole habitats to certain organisms, so that their species are safe from extinction. Hence, it is essential that the distribution of every each one of them is clearly defined.

Brazilian scientists Prof. Eleonora Trajano, Universidade Federal de São Carlos, and Prof. Dr. Marcelo Rodrigues de Carvalho, Universidade de São Paulo, discuss the current classification system, its application and complexities in a paper published in the open access Subterranean Biology.

9759_Image 2Nowadays, there are three categories of subterranean fauna accepted. Troglobites live exclusively underground and are usually characterised with reduced or lacking eyes and pale or transparent colors; troglophiles may live both in caves and on the surface, with individuals commuting between these habitats and promoting genetic interchange between subterranean and surface populations; trogloxenes use caves regularly, but must leave them periodically in order to complete their life cycle.

Throughout the years, many alterations and subdivisions have been applied to the classification used when determining whether a cave organism belongs exclusively to the subterranean habitat, or not, before concluding these three groups, also known as the Schiner-Racovitza system. It is important to separate them properly, since the destruction of a habitat to an endemic troglobite, for instance, would immediately wipe out its whole species, as it would be impossible for the animals to move away.

However, many historic publications do not feature enough details about the described species’ distribution, nor identification of the used classification, so that the information is unreliable. Furthermore, there have been times, when people have been even afraid to survey the underground habitats, led by beliefs and associations linking caves to the “World of the Dead”.

In their paper, the authors conclude that the only way to define the species status of subterranean organisms with certainty is to study each species’ dynamics over a period of at least three years, since animals may migrate on a seasonal and/or non-seasonal basis. Also, scientists need to study thoroughly the area outside the surveyed cave, while testing for sampling sufficiency at all times.oo_124566

“When employing classifications of subterranean organisms, especially for conservation purposes, these conditions should be checked for reliability of the status attributed to them,” say the authors. “Misplacing these organisms within the Schiner-Racovitza categories impairs the efficiency of such policies.”


Original source:

Trajano E, Carvalho MR (2017) Towards a biologically meaningful classification of subterranean organisms: a critical analysis of the Schiner-Racovitza system from a historical perspective, difficulties of its application and implications for conservation. Subterranean Biology 22: 1-26.