Giant Panda

The Berlin Zoo

By the time Berlin Zoo acquired female SB 378 in 1995, the male SB 208 was already 16 years old, so it was deemed appropriate to monitor testicular integrity frequently via ultrasound. The genital tract schematic (Fig. 17.8) indicates regions where ultrasound images were generated. The sonogram in Figure 17.9a is a midsegment view of the testis during the breeding season (April). The testes were larger in size, and the parenchyma was less echoic at this time, as compared to other times of the year, presumably because of increased spermatogenic activity. Compared to other bear species (Knauf et al., 2003), the rete testis system in the giant panda appeared more pronounced, especially during the breeding season. Although SB 208 always exhibited seasonal changes in testicular activity, there were indications of age-related parenchymal degeneration. A cystic structure (see Fig. 17.9b) and the presence of two echogenic spots close to the caput epididymis as the result of apoptosis and scar tissue replacement (testicular degeneration) in the parenchyma (see Fig. 17.9c) were observed in the ultrasound examination conducted in 2002. A lesion in the left testis caused by an accidental dart injection while attempting immobilisation can also be seen in Figure 17.9d. The lesion was still detectable near the rete testis one year later, although it was reduced in size by half and presumably had little effect on overall testicular function.

of an inactive ovary (Ov, arrow heads); (g) sonogram of an ovary (Ov, arrow heads) containing at least three active corpora lutea (Cl); (h) degeneration of endometrial cysts (Cy) in the cranial part of the uterus (Ut, arrow heads) as a result of foetal resorption. (See also Plate XXV.)

Figure 17.7. Transrectal ultrasound of the uterus (between the arrows) of the adult giant panda SB 371 during a pre-breeding evaluation at the San Diego Zoo. b, bladder; u, uterus.

The sonogram in Figure 17.9e depicts the right scent gland during the breeding season (April). Scent glands, visualised transrectally about 2 cm cranial to the anal sphincter, contain a creamy, yellowish secretion used for scent marking, which can easily be collected by manual palpation. There was a size difference between the left and right gland in this male.

The classical anatomical study of Davis (1964) suggested that the giant panda does not have a prostate gland. However, transrectal ultrasound evaluations clearly revealed that this male had a distinctive prostate comprised of two lobes laterally situated to the urethra with a central dorsal isthmus above the urethra (see Fig. 17.9f). It was located 2 to 4 cm caudal to the neck of the urinary bladder. The prostate parenchyma was less echoic than that of the scent glands and had a homogeneous appearance. Dorsal to the urinary bladder and lying in parallel were the cigar-shaped, ductal glands of the ductus deferens (see Fig. 17.9g; central aspect of the left gland). They were moderately

Figure 17.8. Modified drawing (Davis, 1964) of the male urogenital tract showing the regions where the images in Figures 17.9 and 17.10 were generated.

echogenic and had a solid parenchyma and a distinctive echogenic gland capsule approximately 1.5 mm thick. The ductus deferens entered the cranial end of a ductal gland, was slightly coiled and situated partly above the urinary bladder (see Fig. 17.9h). Although easily imaged by transrectal ultrasound (7.5 MHz) during the breeding season (March to May) and presumably because of increased spermatogenic

Figure 17.9. Ultrasonographic images of the male giant panda SB 208 at the Berlin Zoo. (a) Middle segment of the testis during the breeding season showing a pronounced rete testis (RT) and testicular parenchyma (TP); (b) cystic alteration (Ca) of the testicular parenchyma; (c) echogenic spots close to the caput epididymis associated with testicular degeneration (TD); (d) lesion in the left testis (Te), near the rete testis (RT), caused by an accidental dart injection (DI); (e) right scent gland (SG) in a male panda during breeding season; (f) transrectal sonogram (7.5 MHz) of

Figure 17.9. Ultrasonographic images of the male giant panda SB 208 at the Berlin Zoo. (a) Middle segment of the testis during the breeding season showing a pronounced rete testis (RT) and testicular parenchyma (TP); (b) cystic alteration (Ca) of the testicular parenchyma; (c) echogenic spots close to the caput epididymis associated with testicular degeneration (TD); (d) lesion in the left testis (Te), near the rete testis (RT), caused by an accidental dart injection (DI); (e) right scent gland (SG) in a male panda during breeding season; (f) transrectal sonogram (7.5 MHz) of activity, the ductus deferens were nearly undetectable outside this time of year.

The San Diego Zoo

Transcutaneous ultrasound was used to evaluate the testicles of both males at San Diego Zoo. Several hyperechoic foci were noted consistently in the testes of SB 381 (Fig. 17.10). Because these same foci were observed over a five-year time-span with no change, we presumed that they represented permanent fibrotic areas. However, there was no apparent adverse impact on male testis function as viable sperm were collected via electroejaculation at times when the foci were obvious.

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