A role of a herbivorous crab, <i>Neosarmatium smithi</i>, in dissolved iron elution from mangrove ecosystems

Abstract

Iron solubilization in mangrove soils associated with polyphenols leached out from leaf-litter can improve iron bioavailability. In this context, the leaf-removing process by mangrove crabs would increase reacting frequency of the polyphenols in mangrove leaves with iron in the soils. In this study, we investigated ecological roles of a leaf-removing crab, Neosarmatium smithi, on the iron solubilization process. After the fallen leaves carried by the crabs to their burrows and eaten by them, polyphenols may be remained in their feces. If so, contact of polyphenols in the feces with mangrove soils could promote elution of dissolved iron from the soils. In order to demonstrate this hypothesis, we firstly surveyed the appearance ratio of the black part in crab burrows and measured total phenolic content in feces of N. smithi as well as in the black part soil. Then, we examined influences of the crab feces on dissolved iron elution from mangrove soils. As the results, the appearance ratio of the black part in the burrow was 67 % and the phenolic content in the feces, the black part, and the yellow part in crab burrows were 9.93, 0.49, and 0.12 mg g 1 , respectively. Dissolved iron content in the solution (soil water extract from feces) was 0.65 g g 1 and this content was 4.5 times higher than the control (soil distilled water). We suggest that the polyphenols remained in the feces affect to solubilize insoluble forms of iron by iron reduction and chelating properties.

Assessing mangrove restoration practices using species‐interaction networks

“…Ninety‐eight percent of the video recordings captured ground‐dwelling decapod species, mostly small Parasesarma crabs, important omnivores and detritivores in mangrove systems (Cannicci et al 2008; Diele et al 2013; Cannicci et al 2021), which were often recorded feeding on senescent leaves or manipulating and feeding on sediment. Video recordings of the sediment also proved effective in capturing animal‐sediment interactions of particularly shy but functionally important species, such as; Thalassina anomala whose burrowing activity is a major agent of soil turnover, but is usually difficult to survey (Nickell & Atkinson 1995), and the presence and behavior of the key nutrient cycling species Neosarmatium smithi (Giddins et al 1986; Nakanishi et al 2020). The behavior and interactions of the functionally important decapod species would have been missed in our bipartite ecological network without the inclusion of video‐surveying.…”