18 Histomorphometric comparison of right and left oviduct structure from alpaca (Vicugna pacos)

One of the phenomena that occurs during pregnancy in camelids is that nearly all fetuses occupy the left uterine horn, even though both ovaries ovulate with equal frequency. However, there are no reports on morphometric differences between the alpaca left and right oviducts, which could indicate an effect on gamete transport. The present study was carried out to measure and compare inner and outer measurements of the left and right oviduct regions from alpaca. One hundred twenty transverse sections (5µm) of oviducts were studied from 5 adult females, all with dominant ovarian follicle collected in the slaughterhouse. The oviducts were divided into 5 regions: tubal uterus junction (UTJ), isthmus (Is), ampullary isthmus junction (AIJ), ampulla (A), and infundibulum (In), processed and stained with haematoxylin and eosin. Stained slides were studied under the trinocular microscope at 40× magnification, and the images obtained under the microscope were transferred to a computer. The luminal area, number of primary folds, height of primary folds, height of epithelium, thickness of the muscular layer, inner diameter of circular muscular layer, and thickness of the serosa layer were measured using the Motic Images Plus 2.0 software. These measurements for each 5 regions were compared between left and right oviducts using ANOVA test and the association of the parameters with Pearson correlation analysis using SPSS vs.22 software (IBM Corp.). Ampulla luminal area (399 553.5±152 551.2µm2), thickness of the muscular layer of the region UTJ (280.9±55.0µm), thickness of the muscular layer of the Isthmus region (175.4±28.9µm), and inner diameter of circular muscular layer of the UTJ region (1003.4±102.9µm) of the right side were larger (P<0.05) than those on left side. On the left side, we observed the opposite (P<0.05) in the AIJ region, with a greater height of epithelium (9.9±2.6µm) and thickness of the serosa layer (106.5±52.7µm) compared with the right side. Also, we observed a negative correlation between the thickness of the muscular layer and number of primary folds (r=−0.63; P<0.001) and between thickness of the muscular layer and height of primary folds (r=−0.18; P=0.007). In conclusion, the regions of the right and left oviductal structure present some different morphometrics that could influence the transport of gametes and embryos in South American camelids. It is necessary to carry out secretomic and gene expression studies at the oviduct level, and to expand the number of replicates to correlate the ovary with the presence of a dominant follicle and the reported measurements.