Aquatic biota of the middle basin of the Lacantun River, Chiapas and the importance of long-term monitoring

A list of aquatic species belonging to 6 phyla (Platyhelminthes, Acanthocephala, Nematoda, Arthropoda, Mollusca, Chordata) sampled in the basin of the Lacantun River, in the region known as "Selva Lacandona", Chiapas, Mexico, is presented. The list represents a 10-year sampling program (2010-2020) conducted over a network of 13 permanent stations which covered a 74 km river section in the Lacantun River. A total of 236 species was registered, 220 (93.2%) are native, 25 (10.6%) endemic to the region and 16 (6.8%) introduced. The number of species per sampling station ranged from 41 in the Lacanja River to 112 in the Lacantun River. Twenty-three new distribution records and 123 new host records for platyhelminths, acanthocephalans and nematodes are presented. The conservation status analysis shows that most of the recorded species lack a first assessment. The increment in the number of species recorded through time shows the importance of long-term studies. Despite the degradation of the aquatic ecosystems due to high deforestation rates in the Marques de Comillas region, the pollution produced by the non-sustainable agricultural systems, and the introduction of invasive aquatic species, most of the studied aquatic species have maintained a healthy condition.