El Hierro 2025
 

Animals and plants that colonize islands often undergo remarkable adaptive radiations, giving rise to numerous endemic species. This pattern is also evident in the Canary Islands, where—among many other groups—two pholcid spider genera, Pholcus and Spermophora, have diversified extensively across most of the islands. In addition to these, a third pholcid genus occurs in the Canary Islands, but in stark contrast it is represented by a single species, Ossinissa justoi, restricted to a small system of lava tubes in southern El Hierro. Ossinissa remains one of the very few pholcid genera absent from the family’s molecular phylogeny, as old material proved unsuitable for DNA extraction. In September 2025, I was finally able to visit El Hierro to collect fresh material for molecular analyses. The results should provide new insights into the relationships and evolutionary origin of this enigmatic species.

With the generous help of Joerg Foest, a leading expert on El Hierro’s caves, I explored several cave systems across the island. However, Ossinissa was found only in Cueva de los Pocitos (below left), one of the two caves where it had already been recorded decades ago. This lave tube is very close to (and possibly connected with) the type locality, Cueva de Don Justo, but that cave is locked and we were unable to obtain a permit for entry.

Above: Male and female with egg sac of Ossinissa justoi. The spiders live in total darkness but still have tiny eyes with pigment.

I am deeply grateful to Joerg Foest for his enthusiastic support, for sharing his extensive knowledge of El Hierro’s caves and natural history, and for guiding me safely in and out of each cave. I also thank Pedro Oromí for his assistance in preparing the trip, and Nuria Macías Hernández (Universidad de La Laguna) for her invaluable help in securing permits.