The unusual biology of marine file snakes with a perspective for the conservation of Acrochordus granulatus

Abstract

Biodiversity and the function of tropical shallow-water marine environments are threatened by numerous anthropogenic factors, especially climate change, overharvesting of resources, and destruction of habitat. Marine snakes are important components of coastal shallow-water systems and should be considered as indicators of the health of coastal ecosystems such as mangroves. Acrochordid snakes (Acrochordidae: Acrochordus) represent a highly distinct evolutionary lineage with unusual adaptations to shallow water habitats and importance to biodiversity of tropical coastal regions. One of three congeneric species, Acrochordus granulatus (file snake), is an interesting and common inhabitant of coastal estuaries and mangroves in the Philippines. This paper reviews unusual attributes of A. granulatus and provides a perspective for its conservation in coastal habitats. Morphological, physiological, and behavioral characters of this snake are specialized for life in shallow-water marine environments such as mangroves. Unusual and specialized features confer abilities for prolonged submergence and include low metabolic rate, large capacity for oxygen storage, cutaneous gas exchange, nearly complete utilization of oxygen stores during aerobic submergence, intracardiac and cutaneous shunts for regulating blood flow, and reclusive behavior. Fresh water is required for water balance, and file snakes are dependent on rainfall in many habitats where they drink from freshwater lenses formed by precipitation on the surfaces of marine water. File snakes feed largely on fishes and are candidates as bio-indicators of the health of shallow-water coastal habitats. Attention should be given to threatening insults on coastal environments including climate change, habitat destruction, harvesting of resources, and other factors in need of research, monitoring, and plans for abatement. Importantly, conservation can be promoted by educating people about the docile behavior, unusual traits, and interesting ecology of A. granulatus. KEYWORDS: mangrove, shallow water, Acrochordidae, little file snake, conservation physiology, ecophysiology