Florida State University, FAMU-FSU College of Engineering, Department of Mechanical Engineering, 2525 Pottsdamer St., Tallahassee, FL 32310, USA.
Florida State University, FAMU-FSU College of Engineering, Department of Mechanical Engineering, 2525 Pottsdamer St., Tallahassee, FL 32310, USA.
J Theor Biol. 2021 Oct 21;527:110823. doi: 10.1016/j.jtbi.2021.110823. Epub 2021 Jul 1.
Mound structures that soil termites build have diverse morphologies. Previous observational studies documented that mounds are built to provide regulated environments for the termites that live within them and their structures are formed in ways to support this purpose under the influence of the mounds' immediate environment. The objective of this study is to provide a methodology and a predictive computational model to investigate the reason behind the different but systematic shapes of termite mounds, considering all the relevant forces imposed on them and their thermoregulatory and gas-exchange functions. The gas-exchange function accounts for the capacity of the mound to diffuse metabolic gases generated in the mound's underground nest, while the thermoregulatory function satisfies the connection between the underground nest and deep ground temperatures. The proposed predictive model is based on the principles of heat transfer and thermodynamics and allows optimized mechanically stable structures to freely emerge. The results indicate that, while the model is free to generate any mechanically stable structure, under the relevant environmental and metabolic conditions, it produces structures with forms and geometrical characteristics similar to those of natural mounds. Investigation of the connection between the local environment and the mound shapes indicated that the Sun and wind play an important role in the mound structural form. Mounds exposed to stronger solar irradiance exhibit cone-shaped structures that are pointed towards the Sun, while shaded mounds are observed to be vertical domes. The local wind is observed to affect the external shape of the mound by preventing them to grow tall while controlling the features of the internal structure. By investigating the similarities between structures in different regions (i.e., India, Namibia, and Brazil), it is revealed that, unlike mounds with a strong need for gas-exchange, mounds with a significant demand for thermoregulation exhibit deeper nests, thicker external walls, and well-defined cone- (as opposed to the dome-) shaped structures. Overall, the form of termite mounds is strongly correlated to both regulatory functions and local environments, and the resulting mound shape arises as a combination of these factors.
土白蚁建造的土丘结构具有多种形态。先前的观察研究记录表明，土丘的建造是为了为生活在其中的白蚁提供受调节的环境，并且它们的结构是在土丘周围环境的影响下以支持这一目的的方式形成的。本研究的目的是提供一种方法和预测计算模型，以研究不同但系统的白蚁土丘形状背后的原因，同时考虑到施加在它们身上的所有相关力及其气体交换和体温调节功能。气体交换功能考虑了土丘扩散在土丘地下巢穴中产生的代谢气体的能力，而体温调节功能则满足了地下巢穴与深部土壤温度之间的联系。所提出的预测模型基于传热和热力学原理，并允许优化的机械稳定结构自由出现。结果表明，虽然该模型可以自由生成任何机械稳定的结构，但在相关的环境和代谢条件下，它会生成与自然土丘相似的形状和几何特征的结构。对局部环境与土丘形状之间的关系的研究表明，太阳风和风在土丘结构形式中起着重要作用。暴露在更强太阳辐射下的土丘呈现出指向太阳的锥形结构，而被遮蔽的土丘则呈现出垂直的圆顶形状。局部风通过防止土丘长高并控制内部结构的特征，对土丘的外部形状产生影响。通过研究不同地区（即印度、纳米比亚和巴西）结构之间的相似性，发现与具有强烈气体交换需求的土丘不同，具有显著体温调节需求的土丘具有更深的巢穴、更厚的外壁和定义明确的锥形（而非圆顶）结构。总的来说，白蚁土丘的形状与调节功能和局部环境密切相关，而形成的土丘形状则是这些因素的综合作用。
