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Description |
Geographic Range [top]
Range Description: Philippines: Cabayugan River, Puerto Princesa, Palawan. The Cabayugan River catchment (10°09N, 118°51E) is approx. 3,683 ha and the catchment is surrounded by mountains 1,028 m high. This species was discovered during an extensive ecological survey in 2000-2001 of the river systems of St. Paul’s Subterranean River National Park in Palawan, Philippines, that included the Cabayugan / Underground River.
Countries occurrence:
Native:
Philippines
Additional data:
? Estimated area of occupancy (AOO) - km2: <37
Range Map: Click here to open the map viewer and explore range.
Population [top]
Population: High abundance in undisturbed first to 3rd order headwaters, lower abundance in middle river course. It is
possible that the absence or low abundance of P. cabayugan in the middle parts of the river may be due to natural physical/environmental variables. However, the use of pesticides and fertilizers in the nearby paddy fields may also have played a part. The highest abundance of P. cabayugan was found in undisturbed first to third order headwaters with moderate to low turbidity (> 120 cm light penetration).
Current Population Trend: Stable
Additional data:
? Population severely fragmented: No
Habitat and Ecology [top]
Habitat and Ecology: This species is found in lowland waters surrounded by mountains. The soils in the upper river are alluvial shale and sandstone, while in the lower and underground levels they are limestone. Specimens were collected from different micro-habitats such as under small falls, in riffles and in pools, and also in caves. Individuals were not found in paddy fields or their drainage channels. No specimens were found in other river stretches, in the subterranean course, or the estuary. This species may leave the water body for short times at least. This species is primarily aquatic. The specimens were found in the permanent tributaries, which are lowland waters, with a basic pH of 7.1 to 8.7 and a high conductivity (140-170 uS/cm). Influenced by anthropogenic activities (paddy fields, settlements, increased temperature fluctuations 26°C +/- 3°C and raised turbidity).
The Cabayugan River catchment (10 09 N, 118 51 E), has an area of approximately 3,683 ha. The catchment is surrounded by mountains up to 1,028 m high, but all permanent tributaries and sites sampled are lowland waters. The soils drained are yellowish to deep red clays on ultrabasic subsoils at the peripheral headwaters; alluvial soils on shale and sandstone at the upper to middle river course; and karst soils on limestone at the lower and subterranean course of Cabayugan/Underground River. The pH was generally basic, ranging from 7.1 to 8.7, and the conductivity relatively high, ranging from 140 to 740 mS/cm. The specimens were collected from the river bed and in colonization baskets situated between stony and course organic substrates. Crabs were found in different micro-habitats such as under small falls, in riffles, and in pools. Applying drift nets at all sites, several specimens were caught only at a spring brook running out off limestone rocks. Dissolved oxygen was occasionally found decreasing to 60% saturation in this site. All other sites sampled had generally higher values. Lower abundance of P. cabayugan was found in the middle river course that is influenced by anthropogenic activities (paddy fields, settlements). Those result in higher temperature fluctuations (26°C +/- 3°C), raised turbidity and slightly increased BOD2+5 (max: 2.6 mg/l, n=5). In paddy fields and their draining channels, no individuals of the species were found. This is in contrast to other parathelphusid crabs such as members of Sayamia, Esanthelphusa and Somanniathelphusa that occur in rice fields in many parts of Indochina and China (see Ng and Naiyanetr 1993, Naiyanetr 1994, Ng 1995, Dai 1999, Yeo and Nguyen 1999). Not found in the subterranean course of the river and the estuary. The species is primarily aquatic but actively leaves the water body for short times. Juvenile stages (<5 by 4.5 mm) occur throughout the year at the same stream courses as the adults. One female (26.4 by 21.6 mm) was found carrying 54 juveniles of 2.0 by 1.9 mm size. Juveniles of the same size were detected as smallest among the released free living ones. P. cabayugan has an affinity for small and undisturbed headwater streams, with clear and unpolluted water. The preferred habitats overlap in parts with those of the potamid genus Insulamon Ng & Takeda, 1992.
Systems: Freshwater
Threats [top]
Major Threat(s): Pesticides and fertilizers from paddy fields.
Conservation Actions [top]
Conservation Actions: No conservation measures are known to be in place for this species and it is not found in a protected area.
Citation: Esser, L. and Cumberlidge, N. 2008. Parathelphusa cabayugan. The IUCN Red List of Threatened Species 2008: e.T134129A3907037. http://dx.doi.org/10.2305/IUCN.UK.2008.RLTS.T134129A3907037.en. Downloaded on 16 May 2018.
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