Physiological evaluation of the behavior and epidermis of freshwater planarians ( Girardia tigrina and Girardia sp.) exposed to stressors

• Published in: Biology open 2018-06, Vol.7 (6), p.bio029595-bio029595
• Main Authors: de Oliveira, Matheus Salgado, Lopes, Karla Andressa Ruiz, Leite, Priscila Maria Sarmeiro Corrêa Marciano, Morais, Flavia Villaça, de Campos Velho, Nádia Maria Rodrigues
• Format: Article
• Language: English
• Subjects: Animals; Environmental changes; Epidermis; Evaluation; Exposure; Flatworms; Girardia tigrina; Hydrogen ion concentration; Hydrogen ions; Ion concentration; New species; pH effects; Physiology; Platyhelminthes; Pluripotency; Regeneration; Regeneration (physiology); Scanning electron microscopy; Scanning transmission electron microscopy; Stem cells; Stressors; Temperature; Temperature effects; Temperature tolerance; Thermal stress; Tissue engineering; Turbellaria; Water temperature
• ISSN: 2046-6390; 2046-6390
• DOI: 10.1242/bio.029595

Planarians are metazoan freshwater flatworms which are free-living organisms. Their body has pluripotent stem cell promoters of tissue regeneration capacity. The water temperature and the potential of hydrogen (pH) of lentic ecosystems are important factors involved in the distribution and abundance of these animals. Although the pH factor is directly related to the physiology and behavior of planarians, their adaptive and regenerating capacities still remain unknown. The Critical Thermal Maximum (CTM) is a very widespread method used in the evaluation of thermal tolerance. In this study, (Girard, 1850) and sp., a species found in Brazil, which is under study as a new species, had their epidermis assessed by scanning electron microscopy (SEM) to analyze their physiological structures before and after exposure to different stressors. SEM was used as a method to evaluate the planarians' epidermis as a result of the increasing temperature (CTM) and pH alterations, the latter with the use of a new methodology defined as Critical Hydrogen ion concentration Maximum (CHM). In increasing temperatures from 20°C to 37°C, both and sp. proved to be adaptable to thermal stress. sp. was shown to be more resistant to higher temperatures. However, was more resistant to extreme pH conditions (4.0 to 10.0). SEM analysis showed morphological differences among planarian species, such as the arrangement of the structures and cell types of the dorsal epidermis. Moreover, planarians demonstrated the ability to change the surrounding pH of their external environment in order to maintain the function of their physiological mechanisms, suggesting that these animals have a complex survival system, possibly related to protonephridia, flame cells and excretory pores.This article has an associated First Person interview with the first author of the paper.