Photo credit: Wikipedia and Ariff Aziz
Little do we know that mangrove forests, which grow in coastal areas where seawater and freshwater meet, playing a crucial role in protecting the shore from erosion and capable of storing up CO2 for millennia, has a kind of creature that is responsible for maintaining and improving the ecosystem. Referred to as “ecosystem engineers,” mud lobsters help aerate the soil, recycle nutrients, and enhance the retention of organic substances in the mangrove ecosystem, especially through their soil excavation.
“This animal, the mud lobster, looks like a mix of shrimp and crab. In Thailand, we know them as Mae Hob. Our team’s focus is on investigating factors contributing to the density of mud lobsters and their mounds, which serve as their homes,” said Associate Professor Dr. Krisanadej Jaroensutasinee, a researcher and the Director of Center of Excellence for Ecoinformatics, and Assistant Dean at School of Science, Walailak University.
The team went to Kampuan mangrove forest, situated in the Thai Southern province of Ranong, to conduct research. They found a total of 11 plant species with the dominance of Rhizophora apiculata, Rhizophora mucronata, and Bruguiera cylindrica; and four species of mud lobsters: Thalassina anomala, Thalassina spinosa, Thalassina krempfi, and Thalassina squamifera, with Thalassina anomala and Thalassina spinosa being the most prevalent.
“We used three transect lines, covering 5x350 square meters, spanning from 100 meters from the river’s edge to 350 meters into the mangrove forest. We measured soil characteristics, the nearest plants to the mounds, and mound characteristics to see the connections and understand how these factors contribute to the density of mud lobsters and the mounds,” explained Dr. Krisanadej.
According to the study, as the distance from the river's edge to the mound increases, the mound density rises. This is evidenced by the number of mounds increasing from 267 mounds/ hectare at 100 meters from the river’s edge to approximately 1,700 mounds/ hectare at 350 meters. This is because mud lobsters prefer drier sand to build their homes, particularly fine sand with particle sizes less than 250 micrometers. Another reason is that the greater distance from the river’s edge reduces risks that mud lobsters could face from the tide, which could affect their excavation activities during burrow construction.
The finding also suggests that in areas with high population density where there are numerous mounds, the mound basal area decreases while the mound height increases. This demonstrates that Mae Hob have resource partitioning and conserve their space. Instead of building wider mounds, they build taller ones. “This is just like how we build condominiums or tall buildings in big cities. This strategy reduces competition among Mae Hob and helps them coexist with each other,” he said.
The research team noticed a link between plants’ prop roots and mound height. They found that the closer the distance from the prop roots to the mound, the higher the mound. This evidence suggests that prop roots provide support in mud lobsters’ mound construction. However, in areas with many prop roots, they have a negative effect as they limit space for burrow construction.
This research, part of a senior project by Mr. Songprat Detrattanawichai, a student at WU School of Science, in collaboration with Professor Dr. Elena Sparrow from the University of Alaska Fairbanks, USA, was funded by the Development and Promotion of Science and Technology Talents Project (DPST) scholarship and Walailak University Center for Excellence for Ecoinformatics. It is scheduled to be published in Emerging Science Journal, Scopus Q1, in its first issue of 2024. The project also has a future outlook: to understand how prop roots affect Mud Lobsters' characteristics and their burrowing activities, as well as how the structure of prop roots plays a role in mangrove ecosystems.
Research team: Associate Professor Dr. Krisanadej Jaroensutasinee, Associate Professor Dr. Mullica Jaroensutasinee, Mr. Songprat Detrattanawichai, and Professor Dr. Elena Sparrow (photos from left to right)