Optimization of computed tomography method applied to obtain gastropod shell internal volume

• Grant number: 16/22759-7
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: August 01, 2017
• End date: June 30, 2018
• Field of knowledge: Biological Sciences - Ecology - Applied Ecology
• Principal Investigator: Alexander Turra
• Grantee: Andreza Caroline Caiero
• Host Institution: Instituto Oceanográfico (IO). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

Gastropod shells provide protection against biotic and abiotic factor to hermit crab and improper shells may reduce the individual fitness. The shell internal volume (SIV) is an important selection factor for hermit crabs and, therefore many ecological studies evaluate this parameter. Generally, the methods used to estimate SIV consist in filling the shells with water or sand, although this might generate errors related to the possibility of air spaces due to shell features and material. The use of accurate and precise methodologies such as computed tomography (CT) may be used in these studies, however may also have estimative errors. In CT method, SIV is estimated by the volume of air that fills the internal cavity of shells, in addition, level and width window parameters enable us to obtain several SIV values. Those parameters are connect to distinguish contrast and density of analyzed object and different combinations could estimate imprecise SIV values considering, shell structure as air or the inverse. Therefore, it is important to investigate how the combination of these parameters interfere in SIV values, so CT may be applied in studies in hermit crabs ecology. Consequentely, the current work is looking for the optimization of this parameters or a range of them to obtain the SIV in CT technic, and to investigate if the use of free software Osirix Lite allows equivalents estimations to the standard software of the CT machine to obtain the SIVs. Also, we will investigate if using the free software Osirix Lite provide equivalent estimations to the standard CT software to obtain the SIV values. For this purpose, 9 gastropods shells will be analyzed in the restrict use software of the CT machine. After, the set of combination or range of the parameters will be applied for 30 each species shells to obtain the SIV values. Finally, the same CT images will be analyzed in the free software Osirix Lite, comparing the results with the obtained from CT software. This study intends to identify the parameters that may be applied independent from type and size shell so precise and exact of free software's use, adding for improve the use of CT in VIC studies. (AU)