Sciency Thoughts: La Paz

Thursday, 7 February 2019

Bolivian landslide kills at least fifteen.

Fifteen people, including at least five children, have now been confirmed dead and more than fifty have been injured following a pair of landslides that hit the La Paz-Caranavi highway near El Choro in La Paz Department on Saturday 2 February 2019. The first incident is reported to have buried several vehicles, and blocked the road, with the second incident hitting rescue teams and vehicles held up by the original blockage shortly after, and causing part of the road to collapse down the hillside.

The scene of a landslide in which several people died in La Paz Department, Bolivia, on 2 February 2019. The Guardian.

The incident happened amid torrential rains associated with the Bolivian Rainy Season, which typically lasts from November to March, driven by high evaporation over the Pacific Ocean during the southern summer, which falls as rain when air currents coming from the ocean are pushed upwards as they encounter the Andes Mountains, causing the air to cool and lose its moisture, with peak rainfall in January and February. Landslides are a common problem after severe weather events, as excess pore water pressure can overcome cohesion in soil and sediments, allowing them to flow like liquids. Approximately 90% of all landslides are caused by heavy rainfall.

Dolichothele mottai & Dolichothele camargorum: Two new species of Tarantula from Brazil and Bolivia.

Tarantulas, Theraphosidae, are large and usually hairy Mygalomorph Spiders, the group that also includes Trapdoor and Baboon Spiders, and which is noted for features such as non-oposable fangs and only having two pairs of book-lungs. Most Tarantula species are found in the Americas, and while members of this group are found on every continent, most Old World species referred to as 'Tarantulas' are in fact large members of other groups, usually other Mygalomorphs or Wolf Spiders. Tarantulas seldom bite defensively, instead defending themselves with a dense covering of irritating 'urticating hairs' on their abdomens, which can be loosed by brushing with the hind legs and wafted at potential predators, causing irritation to the eyes and nose.

In a paper published in the journal ZooKeys on 21 December 2017, Irene Soliz Revollo of the Instituto de Biociências at the Universidade Estadual Paulista Júlio de Mesquita Filho, and the Laboratório de Ecologia e Evolução at the Instituto Butantan, Pedro Ismael da Silva Júnior of the Laboratório Especial de Toxinologia Aplicada, also at the Instituto Butantan, and Rogério Bertani, again of the Laboratório de Ecologia e Evolução at the Instituto Butantan, describe two new species of Tarantula from Brazil, both of which are placed in the ground-dwelling genus Dolichothele.

The first new species described is named Dolichothele mottai, in honour of the arachnologist Paulo Cesar Motta, for his work on the Mygalomorph Spiders of the Brazilian Cerrado. The species is described from two specimens, a female with a body length of 9.4 cm and a male with a body length of 8.1 cm. Both sexes are covered in iridescent red hairs. The species was found in Cerrado (savanna) environments in the Distrito Federal and state of Goiás, where they build silk tunnels under rocks and logs, males were seen roaming in search of mates in September to November.

Dolichothele mottai, male specimen. Paulo Cesar Motta in Seliz Revollo et al. (2017).

The second new species is named Dolichothele camargorum, in honour of Erney Plessmann de Camargo and Luis Marcelo Aranha Camargo, for their work on medical and biological research in the state of Rondônia, Brazil. The species is described from two specimens, a male with a body length of 5.6 cm and a female with a body length of 10.9 cm, both are black and brown with brown hairs. The species was found in Cerrado fragments in Rondônia State in Brazil and the department of La Paz in Bolivia.