Feeding Strategies of Mangrove Leaf-Eating Crabs for Meeting Their Nitrogen Needs on a Low-Nutrient Diet

Sesarmid crabs play an important role in mangrove biogeochemical processes due to their leaf-eating and burrowing activities. How meet nitrogen (N) needs remains a puzzle, as N-poor leaf litter (<1% dry weight) cannot support the growth of most macrofauna. Several strategies for overcoming this challenge have been proposed, but actual mechanisms remain unknown. We identified two categories according feeding habits (1): species active outside burrows during low tide - we hypothesize that they N through consuming microphytobenthos (MPB) (hypothesis H1); (2) spending time inside N-fixation by associated microbes (H2). To test H1, conducted series experiments on sesarmid crab Parasesarma affine (model category 1) with 13 C- 15 N-enriched MPB leaves. P. relied mainly leaves C source source, supporting H1. Two Neosarmatium smithi 2) showed limitation could be ameliorated selecting seasonally available higher-quality food items such floral parts, or supplements from nitrogen-fixing bacteria, genomic analysis. The strategy which may make significant contribution both ecosystem functions regulating cycling nutrient elements. stoichiometric regulations needs, selection, can enhance trophic efficiency transfer rate at community level ultimately increase turnover level.