Tracking of the hormonally induced maturation of female eels by computed tomography

Ultrasound as a noninvasive tool for monitoring reproductive physiology in male Atlantic salmon (Salmo salar)

We examined the potential for ultrasound as a noninvasive tool for maturation monitoring in Atlantic salmon (Salmo salar) males. Ultrasound examination and measurements were compared to common practices for maturation monitoring such as gonadosomatic index (GSI), sex hormone analysis, and histological analysis of spermatogenesis. There were significant correlations (R² = 0.68, P < 0.01) between ultrasound‐based measurements of the left testis and total testes weight and GSI, and ultrasound could be used for noninvasive GSI measurements. Echogenicity of ultrasound images corresponded to the histological stages observed, which added nuance to ultrasound‐based GSI measurements during final weeks preceding stripping. We propose that ultrasound can be used as an alternative to more invasive methods for sexual maturation monitoring in wild and farmed Atlantic salmon males. Using ultrasound technology, we have established a quick and noninvasive method that could reduce the number of stressful handlings and unwanted sacrifice of broodfish required for maturation monitoring in Atlantic salmon males.

In vivo tracking of maturation in male European eel, Anguilla anguilla (L.), by computed tomography

The present study aimed in vivo tracking of maturation of male eel by computed tomography (CT). Additionally, individually monitored testes sizes were correlated with the conventionally used external maturity indicators (i.e. eye and nose indexes) in order to test and improve their usefulness at individual level. Testes could be clearly identified with the CT from the end of the third week of hCG administration routinely used to induce maturation in fish. The volume of testes increased exponentially during hormone treatment, and by the end of the sixth week of maturation procedure all males produced motilable spermatozoa. Present results prove that testes size can noninvasively be monitored with CT from maturity level where testes size rich 3000 mm3 volume. Eye and nose indexes are in close correlation with testes volume and thus can also be effectively used to monitor maturity level of male eel, but preferably only at stock level. However, due to their high individual variability, these indexes can be applied only with caution at individual level and should be supplemented with other noninvasive techniques such as CT.

Validation of multi-detector computed tomography as a non-invasive method for measuring ovarian volume in macaques (Macaca fascicularis)

The purpose of this study was to validate low radiation dose, contrast-enhanced, multi-detector computed tomography (MDCT) as a non-invasive method for measuring ovarian volume in macaques. Computed tomography scans of four known-volume phantoms and nine mature female cynomolgus macaques were acquired using a previously described, low radiation dose scanning protocol, intravenous contrast enhancement, and a 32-slice MDCT scanner. Immediately following MDCT, ovaries were surgically removed and the ovarian weights were measured. The ovarian volumes were determined using water displacement. A veterinary radiologist who was unaware of actual volumes measured ovarian CT volumes three times, using a laptop computer, pen display tablet, hand-traced regions of interest, and free image analysis software. A statistician selected and performed all tests comparing the actual and CT data. Ovaries were successfully located in all MDCT scans. The iliac arteries and veins, uterus, fallopian tubes, cervix, ureters, urinary bladder, rectum, and colon were also consistently visualized. Large antral follicles were detected in six ovaries. Phantom mean CT volume was 0.702+/-SD 0.504 cc and the mean actual volume was 0.743+/-SD 0.526 cc. Ovary mean CT volume was 0.258+/-SD 0.159 cc and mean water displacement volume was 0.257+/-SD 0.145 cc. For phantoms, the mean coefficient of variation for CT volumes was 2.5%. For ovaries, the least squares mean coefficient of variation for CT volumes was 5.4%. The ovarian CT volume was significantly associated with actual ovarian volume (ICC coefficient 0.79, regression coefficient 0.5, P=0.0006) and the actual ovarian weight (ICC coefficient 0.62, regression coefficient 0.6, P=0.015). There was no association between the CT volume accuracy and mean ovarian CT density (degree of intravenous contrast enhancement), and there was no proportional or fixed bias in the CT volume measurements. Findings from this study indicate that MDCT is a valid non-invasive technique for measuring the ovarian volume in macaques.