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ARS Home » Southeast Area » Stoneville, Mississippi » Warmwater Aquaculture Research Unit » Research » Publications at this Location » Publication #395843

Research Project: Biophotonics - The Application of Novel Imaging Methodologies to Livestock Production Research

Location: Warmwater Aquaculture Research Unit

Title: Near-infrared spectroscopy (NIRS) as a method for biological sex discrimination in the endangered Houston toad (Anaxyrus houstonensis)

item CHEN, LI-DUNN - Mississippi State University
item SANTOS-RIVERA, MARIANA - Mississippi State University
item BURGER, ISABELLA - Mississippi State University
item KOUBA, ANDREW - Mississippi State University
item VANCE, CARRIE - Mississippi State University
item BARBER, DIANE - Fort Worth Zoo

Submitted to: Methods and Protocols
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/28/2021
Publication Date: 12/30/2021
Citation: Chen, L., Santos-Rivera, M., Burger, I., Kouba, A.J., Vance, C.K., Barber, D. 2021. Near-infrared spectroscopy (NIRS) as a method for biological sex discrimination in the endangered Houston toad (Anaxyrus houstonensis). Methods and Protocols. 5(1):4-16.

Interpretive Summary: In this study, we have demonstrated the potential of NIRS as a biophotonic technique to capture chemical signals in living amphibians to effectively discriminate biological sex and gravidity. These findings can be further applied to other threatened amphibians whose sex is ambiguous and difficult to discern (e.g., juveniles and monomorphic species) or for evaluating the sexual maturation of females. Considering that amphibians represent the most threatened class of vertebrates, methods to detect and assess crucial physiological information are needed to effectively inform the management decisions concerning at-risk populations. As NIRS is a non-invasive, cost-effective tool capable of generating a robust throughput of chemical information, it may benefit wildlife conservation managers to partner with experts in specific management situations where knowledge of physiological factors (e.g., biological sex) is needed to make reliable, on-the-ground decisions.

Technical Abstract: Biological sex is one of the more critically important physiological parameters needed for managing threatened animal species because it is crucial for informing several of the management decisions surrounding conservation breeding programs. Near-infrared spectroscopy (NIRS) is a non-invasive technology that has been recently applied in the field of wildlife science to evaluate various aspects of animal physiology and may have potential as an in vivo technique for determining biological sex in live amphibian species. This study investigated whether NIRS could be used as a rapid and non-invasive method for discriminating biological sex in the endangered Houston toad (Anaxyrus houstonensis). NIR spectra (N = 396) were collected from live A. houstonensis individuals (N = 132), and distinct spectral patterns between males and females were identified using chemometrics. Linear discriminant analysis (PCA-LDA) classified the spectra from each biological sex with accuracy = 98% in the calibration and internal validation datasets and 94% in the external validation process. Through the use of NIRS, we have determined that unique spectral signatures can be holistically captured in the skin of male and female anurans, bringing to light the possibility of further application of this technique for juveniles and sexually monomorphic species, whose sex designation is important for breeding-related decisions.