Algar do Carvão cave spider

This species was described based on males only. This is a pale spider with long legs and large eyes. Male pedipalpus: tibia with single trichobothrium, paracymbium with tooth-shaped distal hook, embolus basally wide (Borges and Wunderlich 2008) (Figs 1, 2)

Figure 1.

Male of Turinyphia cavernicola from Algar do Carvão (Terceira, Azores) (Credit: Paulo Henrique Silva).

Figure 2.

Female of Turinyphia cavernicola from Algar do Carvão (Terceira, Azores) (Credit: Pedro Cardoso)

Relatively intensive searches have located the spider in Algar do Carvão, Gruta da Malha and Furna de Santa Maria, all in Terceira Island (Pereira et al. 2015) (Figs 3, 4)

Figure 4.

The volcanic pit Algar do Carvão (Terceira, Azores), the main location of the species Turinyphia cavernicola.

This is a single island endemic restricted to the Island of Terceira, Azores, Portugal. The species was originally described from a single cave, the volcanic show pit Algar do Carvão, and later also found in two lava tubes: Gruta da Malha and Furna de Santa Maria, that are located nearby.

The species is a specialized troglobite living in constant humidity conditions. Many caves in Terceira Island are being impacted by pollution due to the intensive cattle production in the island of Terceira, with the changes in ecological conditions of caves in the last 50 years, namely the change of the N,P abiotic cycles and changes in the water pH (Hathaway et al. 2014). The addition of fences around the cave will be an important mitigation measure.

In Terceira Island there are 15 well-surveyed caves and we found subpopulations in only three. The trend of decline is partly based on the assumption that this species can occur in all these caves and that the absence is due not only to biological reasons (type of cave; age of the lava flow) but mainly to anthropogenic disturbance on caves during the last 50 years. Most of the caves were in the past covered by dense humid native forest, and forest clearence promoted changes in humidity and resource availability in cave environment.

After a detailed survey of 15 caves in Terceira island the species was only found at Algar do Carvão, Gruta da Malha and Furna de Santa Maria. Each is affected by different threats, mainly touristic pressure in the first and cattle production with consequent deforestation and nutrient input into caves in the latter two.

After a detailed survey of 15 caves in Terceira island the species was only found at Algar do Carvão, Gruta da Malha and Furna de Santa Maria, which is a small number of locations for a predictably larger range (up to 5 times larger) just 50 years ago.

Inferred from decrease in AOO and habitat quality.

Three subpopulations are known in the island, but two of them are very small and located in disturbed lava tubes. The single large subpopulation is located in the show cave Algar do Carvão, which is under intensive pressure due to increasing levels of visitation in the last ten years.

The species original distribution was potentially 70 km², probably including most of the 15 caves surveyed in the Terceira Island, the current range representing a reduction of 93%. However considerable searching efforts around the current caves where the species occurs have failed to find additional subpopulations.

The large system of lava tubes in Terceira island is fragmented both naturally and artificially. Natural fragmentation is due to the occurence of several independent historical lava-flows in the island. Artificial fragmentation is due to recent destruction of caves for road construction and intensive pasture implementation. Two out of thee subpopulations are considered non-sustainable.

The species is a troglobite specialist occuring only in humid lava tubes and volcanic pits. The sheet webs are built in small holes and crevices in the lateral walls of the caves.

The intensive cattle production in the island of Terceira increased a lot in the last twenty years and creates high disturbance and pollution in cave systems. This might be the cause for inferred recent reduction in AOO. Touristic pressure might also be a threat in the single show-cave within its geographic range, through reduction in habitat quality.

The species builds sheet-webs across small holes in volcanic basaltic rock. Usually occurs from twilight conditions near cave openings to deep parts of the caves (Borges and Wunderlich 2008, Martín et al. 2008, Martín et al. 2010). In the main pit-cave of Algar do Carvão the contruction of the lateral walls of the stairs with stones from the cave allowed the creation of additional supports for the webs.

An area of 40.5ha around Algar do Carvão was classified as “Regional Natural Monument” by the Regional Decree nr 9/2004/A, of March 23^rd 2004, due to its unique volcanic features and its environmental importance. Since pasture intensification is one main threat, this might be important to safeguard the species survival in the future and should be extended beyond the current area, possibly allowing the recovery of other caves to original conditions where the species might be reintroduced.