Rediscovery and conservation status of Philippine endemic freshwater crabs, Mainitia mainitensis Balss, 1937 and Amarinus wolterecki Balss, 1934 from Lake Mainit, Mindanao Island, Philippines

Author(s): Nickel Jean Lagare
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Institution or organization of origin: Davao del Norte State College
Country: Philippines


The decline in freshwater biodiversity demands the urgency for faunal inventory and conservation. Lake Mainit being the deepest and the fourth largest lake in the Philippines, is a home of diverse flora and fauna; however, the majority have been neglected and underrepresented. The study seeks to trace the taxonomic history and provide notes on the conservation status of the Philippine endemic freshwater crabs, Mainitia mainitensis, and Amarinus wolterecki. These species are only found in Lake Mainit and were described by Balss in 1934 and 1936, respectively. Since then, no further encounters have been reported. This is the first documentation and rediscovery of M. mainitensis and A. wolterecki that were successfully captured during the sampling period in 2019. Locals mentioned that M. mainitensis are commonly found along the lakeshore, while A. wolterecki are only found within the lake. The presence of ovigerous females establishes that these freshwater crab species are in successful recruitment despite of environmental degradation and pressures. According to IUCN Red List, M. mainitensis is listed under the category Vulnerable (VU) while A. wolterecki is not evaluated (NE). For now, the extent of occurrence cannot be calculated, but the area of occupancy is estimated to be 8km2 and species are provisionally considered as “Endangered”. Among the most urgent environmental concerns are the decline of water quality and water pollution, which inevitably threatened the sustainability of the lake’s biodiversity. Further studies are needed to completely provide a comprehensive assessment and distributional data, particularly in the unexplored areas in Lake Mainit.

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