Sarax timorensis is a new species of arachnid discovered by biologist Ana Sofia Reboleira during the first expedition of the project Fatuk Kuak hosi Timor Lorosa’e 2016. In this month-long expedition, a Portuguese team of speleologists led by the scientist explored the caves of Timor-Leste, carrying out biological exploration works in search of new species from that particular habitat.
The expedition was organised by four Portuguese speleology groups, with the support of the Oriente Foundation, the National University of Timor Lorosa’e, and the Timorese speleology group Juventude Hadomi Natureza. It was in a grotto in the eastern province of Lautém that the cave-dwelling arachnid — exclusive to Timor-Leste — was found.
What Is Sarax timorensis?
Sarax timorensis is an arachnid of the order Amblypygi — a group of typically tropical and subtropical animals found in hot, humid environments. Arachnids include spiders, ticks, and scorpions, but amblypygids form their own distinct order.
Notably, Sarax timorensis is not a spider. Spiders are arachnids, but so are scorpions and amblypygids. The distinction matters:
- Amblypygids do not bite or attack humans
- They have no venomous glands
- They produce no silk and build no webs
- When threatened, they may grip with their pedipalps — pincer-like appendages near the mouth — causing only minor surface injuries
Adaptations to Cave Life
The species shows clear signs of adaptation to subterranean environments:
| Trait | Description |
|---|---|
| Eyes | Tiny; poor vision |
| Pigmentation | Greatly reduced |
| Body size | Exceptionally large for its family |
| Eye pairs | Two pairs of lateral eyes (unusual — most have three or none) |
The lack of sunlight in cave habitats explains the poor vision and pigmentation. It is also common for subterranean arthropods to trend toward gigantism in atrophic (low solar input) and oligotrophic (nutrient-poor) ecosystems. Sarax timorensis is, in fact, the second largest species in the Charinidae family, with the discovered specimen measuring a total length of 18.82 mm.
Movement and Hunting Behaviour
Although amblypygids have eight legs, they walk primarily on six, moving in a crab-like lateral style. The two front legs serve a sensory function — acting like antennae to detect the environment.
Because they produce no silk, amblypygids use a different hunting strategy. They are often described as “sit and wait” predators: after sensing prey with their front legs, they wait until it is within short range, then leap and crush it.
A Living Laboratory
According to a January 2019 publication in the journal ZooKeys, Southwest Asia had until then been considered an area poor in amblypygid biodiversity. Ana Sofia Reboleira argues that island cave systems are, in reality, “living laboratories” for evolutionary studies — the isolation of island organisms makes it easier to observe and study evolutionary processes.
The expedition covered the provinces of Baucau, Lautém, and Viqueque. Field work was demanding: high temperatures combined with extreme humidity inside and outside the caves created conditions described as “at the limit of human survival.” Despite this, the team succeeded both in discovering a new species and in producing the first systematic survey of cave species across South-East Asia.
Ana Sofia Reboleira’s Scientific Record
Sarax timorensis is one of many contributions by Ana Sofia Reboleira to science. The biologist and speleologist, who is also Professor of Natural History at the University of Copenhagen in Denmark, has identified 59 new species and 6 new genera in the past decade alone. Notable discoveries include:
- Iberoporus pluto — an underground beetle found in Serra do Sicó, Portugal
- Lusoblothrus aenigmaticus — a rare pseudo-scorpion discovered in the Algarve, Portugal
- Heterocaucaseuma deprofundum — an eyeless, unpigmented millipede found in the Krubera-Voronya cave in Georgia, one of the deepest known caves in the world
The formal description of Sarax timorensis in ZooKeys was co-authored with postdoctoral researcher Gustavo Silva de Miranda of the Smithsonian Institution, USA. At the University of Copenhagen, Reboleira also coordinates a laboratory dedicated to the global study of speleological systems.